Analysis of aortic area/height ratio in patients with thoracic aortic aneurysm and Type A dissection

Analysis of aortic area/height ratio in patients with thoracic aortic aneurysm and Type A dissection Abstract OBJECTIVES Significant proportions of aortic dissections occur at aortic diameters <5.5 cm. By indexing aortic area to height and correlating with absolute aortic diameter, we sought to identify those aneurysm patients with aortic diameters <5.5 cm who do not meet current size thresholds for surgery, yet with corresponding abnormal indexed aortic areas (IAAs) >10 cm2/m, are at increased risk of aortic complications. METHODS IAAs were calculated at 3 aortic locations in 187 aneurysm and 66 dissection patients operated on between 2010 and 2016 at our tertiary aortic centre. Proportions of patients with IAA >10 cm2/m, mean IAAs corresponding to aortic diameters <4.0 cm, 4.0–4.5 cm, 4.5–5.0 cm, 5.0–5.5 cm and >5.5 cm, and mean aortic diameters corresponding to IAAs 10–12 cm2/m, 12–14 cm2/m and >14 cm2/m were determined. RESULTS Proportions of patients with abnormal IAAs were similar in both groups. In all, 49.1% of aneurysm patients with aortic diameters 4.5–5.0 cm, and 98.5% with aortic diameters 5.0–5.5 cm had abnormal IAAs. Out of 207 separate aneurysms with IAAs >10 cm2/m between the mid-sinus and mid-ascending aorta, only 139 (69.5%) would warrant surgery according to existing guidelines. CONCLUSIONS Using the IAA, we identified a significant proportion of patients with thoracic aortic aneurysms who are at increased risk of aortic complications, despite current aortic guidelines not endorsing surgical intervention in this group. Our data suggests the IAA may be useful in preoperative risk evaluation and as a criterion for surgery. Aneurysm , Aortic dissection , Aorta INTRODUCTION The aortic cross-sectional area/patient height ratio (πr2/h, cm2/m) has been validated in the stratification of mortality risk in patients with a tricuspid aortic valve and dilated aorta [1]. First proposed by Svensson et al. [2], this indexed measurement accounts for the greater risk of aortic complications associated with larger aortic dimensions in shorter patients, whilst incorporating the exponential risk of dissection or rupture with increasing aortic size. Indexed aortic root area >10 cm2/m has been shown to have significant independent prognostic value in patients with tricuspid aortic valve and concomitant aortopathy, compared to a non-indexed aortic diameter [1]. The same study showed that a significant proportion (44% of 771 patients) with aortic root diameter 4.5–5.5 cm had an abnormally high aortic root/height ratio; 78% of patients in this subgroup died, although mortality could not be directly attributed to aortic dissection or rupture [1]. These findings highlight that the cohort of patients with aortic size less than the thresholds mandating surgery in current established guidelines, and in whom the cross-sectional aortic area/height ratio exceeds 10 cm2/m, represents an opportunity for early, proactive intervention to prevent potentially fatal aortic dissection. This strategy would theoretically prevent 95% of acute aortic dissections in a Marfan population [2]. The relationship between aortic diameter and indexed cross-sectional aortic area has not been fully ascertained in patients presenting with isolated thoracic aortic aneurysms and those with acute Type A aortic dissection. In this study, we sought to determine (i) the indexed aortic area (IAA) in patients with thoracic aortic aneurysms and acute Type A aortic dissection at different aortic locations, (ii) the proportion of at-risk aneurysm patients with IAAs >10 cm2/m and (iii) the relationship between IAAs >10 cm2/m and corresponding aortic diameters in aneurysm patients. MATERIALS AND METHODS Definitions For the purpose of this study, an aortic root or ascending aortic diameter ≥4 cm was considered aneurysmal. Postoperative renal dysfunction was defined as a new requirement for haemofiltration or haemodialysis following surgery. In-hospital mortality was defined as death during the same hospital admission. Study populations We performed a retrospective observational study on all consecutive adult patients undergoing first-time surgery for thoracic aortic aneurysm (aneurysm group) or acute Type A aortic dissection (dissection group) between 2010 and 2016 at St George’s Hospital, London, UK. Patients were assigned to the aneurysm group based on echocardiographic, contrast-enhanced computed tomography (CT) or contrast-enhanced magnetic resonance imaging (MRI) demonstrating an aortic root or ascending aorta ≥4 cm in diameter. Patients with an aortic root/ascending aorta approaching 4 cm in dimension and coexisting connective tissue disease were also included in the aneurysm group. Patients admitted to our service with acute Type A dissection, confirmed on contrast-enhanced CT, comprised the dissection group. Patients for whom relevant preoperative imaging had not been performed within the preceding year, and in whom aortic root/ascending aortic replacement was performed for procedural complications in the absence of preoperative aortic aneurysm or dissection, were excluded. Other variables considered included cardiovascular risk factors (hypertension, hypercholesterolaemia, diabetes mellitus, smoking), as well as pulmonary disease, peripheral vascular disease, chronic kidney disease, connective tissue disease, previous transient ischaemic attack/stroke, ventricular function, aortic valve cusp configuration and aortic valvular regurgitation. Prospectively-collected demographic, clinical and operative data was manually retrieved from our institution’s computer database and cross-referenced with medical records. Local ethical approval (equivalent to institutional review board) was granted for this retrospective study. Imaging review The most recent preoperative aortic scans were retrospectively reviewed in multiplanar CT and/or MRI modalities for each patient. Maximum cross-sectional aortic diameters were measured using the inner edge-to-inner edge method in coronal and sagittal views in a plane perpendicular to the direction of blood flow at 3 aortic locations: the mid-point of the sinuses of Valsalva, the sinotubular junction and the mid-ascending aorta (at the level of the pulmonary artery bifurcation) [3]. The largest aortic diameter was used for analysis when multiple measurements were generated. For patients presenting with dissection, diameter measurements included both true and false aortic lumens. All imaging was reviewed by a single clinician with cross-checking of a randomly-selected 10% sample by 2 experienced cardiovascular radiologists to ensure concurrence in measurement technique and reproducibility. Outcome measures Cross-sectional area at each aortic location was calculated using the formula π × r2, where r represents the aortic radius, for patients in aneurysm and dissection groups. This was divided by patient height to determine a ratio of the aortic cross-sectional area to height (IAA). The median IAA at each of the 3 aortic locations was calculated for both groups, and the proportion of at-risk patients with IAA >10 cm2/m identified for each aortic location. IAAs at the mid-sinus, sinotubular junction and mid-ascending aortic locations were categorised into 3 subgroups (10–12 cm2/m, 12–14 cm2/m and >14 cm2/m) and the mean aortic diameter corresponding to each range was calculated. In addition, patients in the aneurysm group were assigned to 1 of 5 subgroups (<4.0 cm, 4.0–4.5 cm, 4.5–5.0 cm, 5.0–5.5 cm or >5.5 cm) depending on aortic diameter at mid-sinus, sinotubular junction and mid-ascending aortic locations. IAAs were analysed for all patients within the subgroups to calculate the mean IAA at each aortic location for each size subgroup. Statistical analysis Statistical analysis was performed using SPSS software (SPSS Inc., Chicago, IL, USA). Summary statistics are presented as percentages for categorical variables, and medians and interquartile ranges, or means ± standard deviations, for continuous variables. Univariable analyses of categorical and continuous variables were performed using χ2 and Fisher’s exact tests. The distribution of continuous variables was assessed for normality with the Shapiro–Wilk Test, and continuous variables were compared between groups using the Mann–Whitney U-test. A P-value <0.05 was considered statistically significant. RESULTS Study populations Out of 218 aneurysm patients and 75 dissection patients undergoing surgical repair between 2010 and 2016 at our institution, 187 patients and 66 patients, respectively, were eligible for analysis. The preoperative characteristics of both groups are shown in Table 1. Twenty-five of 187 (13.4%) patients in the aneurysm group were diagnosed with MRI scanning, whereas all patients with dissection underwent CT imaging. Being a tertiary aortic centre, patients with inherited aortopathies are closely monitored within established surveillance programmes and offered early prophylactic surgery. Within the aneurysm group, 20 (10.7%) patients had Marfan syndrome, with an additional 5 (2.67%) having other connective tissue diseases. The dissection group included 6 (9.09%) patients with Marfan syndrome and 1 (1.52%) patient with other connective tissue disease. Patients in the aneurysm and dissection groups were followed up for a median 337 and 470 days, respectively. Table 1: Preoperative patient characteristics Characteristics  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Age (years)  63 (52–73)  66 (51–73)  0.77  Male  127 (67.9)  45 (68.2)  0.97  BMI  27 (24–30)  27 (25–29)  0.67  Logistic EuroSCORE  5.58 (2.17–9.17)  8.86 (4.23–14.0)  0.001  NYHA class      <0.001   I  75 (40.1)  50 (75.8)     II  79 (42.2)  8 (12.1)     III  33 (17.6)  8 (12.1)    Hypertension  109 (58.3)  35 (53.0)  0.46  Hypercholesterolaemia  60 (32.1)  11 (16.7)  0.017  Smoking  84 (44.9)  18 (27.3)  0.022  Pulmonary disease  14 (7.49)  6 (9.09)  0.68  CKD stage      <0.001   1  75 (40.1)  15 (22.7)     2  89 (47.6)  28 (42.2)     3  20 (10.7)  21 (31.8)     4  2 (1.07)  1 (1.52)     5  1 (0.53)  0 (0.00)    Preoperative dialysis  1 (0.53)  1 (1.52)  0.45  TIA/CVA  19 (10.2)  9 (13.6)  0.40  Previous MI  13 (6.95)  5 (7.58)  0.79  Peripheral vascular disease  11 (5.88)  0 (0.00)  0.07  LV function      0.10   Good  153 (81.8)  61 (92.4)     Moderate  30 (16.0)  5 (7.58)     Poor  4 (2.14)  0 (0.00)    RV function      <0.001   Good  176 (94.1)  50 (75.8)     Moderate  9 (4.81)  15 (22.7)     Poor  1 (0.53)  0 (0.00)    Aortic valve cuspidity      <0.001   Unicuspid  3 (1.60)  0 (0.00)     Bicuspid  70 (37.4)  1 (1.52)     Tricuspid  113 (60.4)  65 (98.5)     Quadricuspid  1 (0.53)  0 (0.00)    Marfan syndrome  20 (10.7)  6 (9.09)  0.71  Other connective tissue disease  5 (2.67)  1 (1.52)  0.59  Aortic regurgitation  133 (71.1)  45 (68.2)  0.65  Pericardial effusion  4 (2.14)  21 (31.8)  <0.001  Cardiac tamponade  0 (0.00)  8 (12.1)  <0.001  Aortic rupture  0 (0.00)  3 (4.55)  0.017  Preoperative ventilation  0 (0.00)  2 (3.03)  0.07  Cardiogenic shock  0 (0.00)  4 (6.06)  0.004  Mesenteric ischaemia  0 (0.00)  1 (1.52)  0.26  Site of intimal tear         Aortic root    28 (42.4)     Sinotubular junction    3 (4.55)     Ascending aorta    21 (31.8)     Other    13 (19.7)    Characteristics  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Age (years)  63 (52–73)  66 (51–73)  0.77  Male  127 (67.9)  45 (68.2)  0.97  BMI  27 (24–30)  27 (25–29)  0.67  Logistic EuroSCORE  5.58 (2.17–9.17)  8.86 (4.23–14.0)  0.001  NYHA class      <0.001   I  75 (40.1)  50 (75.8)     II  79 (42.2)  8 (12.1)     III  33 (17.6)  8 (12.1)    Hypertension  109 (58.3)  35 (53.0)  0.46  Hypercholesterolaemia  60 (32.1)  11 (16.7)  0.017  Smoking  84 (44.9)  18 (27.3)  0.022  Pulmonary disease  14 (7.49)  6 (9.09)  0.68  CKD stage      <0.001   1  75 (40.1)  15 (22.7)     2  89 (47.6)  28 (42.2)     3  20 (10.7)  21 (31.8)     4  2 (1.07)  1 (1.52)     5  1 (0.53)  0 (0.00)    Preoperative dialysis  1 (0.53)  1 (1.52)  0.45  TIA/CVA  19 (10.2)  9 (13.6)  0.40  Previous MI  13 (6.95)  5 (7.58)  0.79  Peripheral vascular disease  11 (5.88)  0 (0.00)  0.07  LV function      0.10   Good  153 (81.8)  61 (92.4)     Moderate  30 (16.0)  5 (7.58)     Poor  4 (2.14)  0 (0.00)    RV function      <0.001   Good  176 (94.1)  50 (75.8)     Moderate  9 (4.81)  15 (22.7)     Poor  1 (0.53)  0 (0.00)    Aortic valve cuspidity      <0.001   Unicuspid  3 (1.60)  0 (0.00)     Bicuspid  70 (37.4)  1 (1.52)     Tricuspid  113 (60.4)  65 (98.5)     Quadricuspid  1 (0.53)  0 (0.00)    Marfan syndrome  20 (10.7)  6 (9.09)  0.71  Other connective tissue disease  5 (2.67)  1 (1.52)  0.59  Aortic regurgitation  133 (71.1)  45 (68.2)  0.65  Pericardial effusion  4 (2.14)  21 (31.8)  <0.001  Cardiac tamponade  0 (0.00)  8 (12.1)  <0.001  Aortic rupture  0 (0.00)  3 (4.55)  0.017  Preoperative ventilation  0 (0.00)  2 (3.03)  0.07  Cardiogenic shock  0 (0.00)  4 (6.06)  0.004  Mesenteric ischaemia  0 (0.00)  1 (1.52)  0.26  Site of intimal tear         Aortic root    28 (42.4)     Sinotubular junction    3 (4.55)     Ascending aorta    21 (31.8)     Other    13 (19.7)    Values are n (%) or median (interquartile range). BMI: body mass index; CKD: chronic kidney disease; CVA: cerebrovascular accident; LV: left ventricle; MI: myocardial infarction; NYHA: New York Heart Association; RV: right ventricle; TIA: transient ischaemic attack. Table 1: Preoperative patient characteristics Characteristics  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Age (years)  63 (52–73)  66 (51–73)  0.77  Male  127 (67.9)  45 (68.2)  0.97  BMI  27 (24–30)  27 (25–29)  0.67  Logistic EuroSCORE  5.58 (2.17–9.17)  8.86 (4.23–14.0)  0.001  NYHA class      <0.001   I  75 (40.1)  50 (75.8)     II  79 (42.2)  8 (12.1)     III  33 (17.6)  8 (12.1)    Hypertension  109 (58.3)  35 (53.0)  0.46  Hypercholesterolaemia  60 (32.1)  11 (16.7)  0.017  Smoking  84 (44.9)  18 (27.3)  0.022  Pulmonary disease  14 (7.49)  6 (9.09)  0.68  CKD stage      <0.001   1  75 (40.1)  15 (22.7)     2  89 (47.6)  28 (42.2)     3  20 (10.7)  21 (31.8)     4  2 (1.07)  1 (1.52)     5  1 (0.53)  0 (0.00)    Preoperative dialysis  1 (0.53)  1 (1.52)  0.45  TIA/CVA  19 (10.2)  9 (13.6)  0.40  Previous MI  13 (6.95)  5 (7.58)  0.79  Peripheral vascular disease  11 (5.88)  0 (0.00)  0.07  LV function      0.10   Good  153 (81.8)  61 (92.4)     Moderate  30 (16.0)  5 (7.58)     Poor  4 (2.14)  0 (0.00)    RV function      <0.001   Good  176 (94.1)  50 (75.8)     Moderate  9 (4.81)  15 (22.7)     Poor  1 (0.53)  0 (0.00)    Aortic valve cuspidity      <0.001   Unicuspid  3 (1.60)  0 (0.00)     Bicuspid  70 (37.4)  1 (1.52)     Tricuspid  113 (60.4)  65 (98.5)     Quadricuspid  1 (0.53)  0 (0.00)    Marfan syndrome  20 (10.7)  6 (9.09)  0.71  Other connective tissue disease  5 (2.67)  1 (1.52)  0.59  Aortic regurgitation  133 (71.1)  45 (68.2)  0.65  Pericardial effusion  4 (2.14)  21 (31.8)  <0.001  Cardiac tamponade  0 (0.00)  8 (12.1)  <0.001  Aortic rupture  0 (0.00)  3 (4.55)  0.017  Preoperative ventilation  0 (0.00)  2 (3.03)  0.07  Cardiogenic shock  0 (0.00)  4 (6.06)  0.004  Mesenteric ischaemia  0 (0.00)  1 (1.52)  0.26  Site of intimal tear         Aortic root    28 (42.4)     Sinotubular junction    3 (4.55)     Ascending aorta    21 (31.8)     Other    13 (19.7)    Characteristics  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Age (years)  63 (52–73)  66 (51–73)  0.77  Male  127 (67.9)  45 (68.2)  0.97  BMI  27 (24–30)  27 (25–29)  0.67  Logistic EuroSCORE  5.58 (2.17–9.17)  8.86 (4.23–14.0)  0.001  NYHA class      <0.001   I  75 (40.1)  50 (75.8)     II  79 (42.2)  8 (12.1)     III  33 (17.6)  8 (12.1)    Hypertension  109 (58.3)  35 (53.0)  0.46  Hypercholesterolaemia  60 (32.1)  11 (16.7)  0.017  Smoking  84 (44.9)  18 (27.3)  0.022  Pulmonary disease  14 (7.49)  6 (9.09)  0.68  CKD stage      <0.001   1  75 (40.1)  15 (22.7)     2  89 (47.6)  28 (42.2)     3  20 (10.7)  21 (31.8)     4  2 (1.07)  1 (1.52)     5  1 (0.53)  0 (0.00)    Preoperative dialysis  1 (0.53)  1 (1.52)  0.45  TIA/CVA  19 (10.2)  9 (13.6)  0.40  Previous MI  13 (6.95)  5 (7.58)  0.79  Peripheral vascular disease  11 (5.88)  0 (0.00)  0.07  LV function      0.10   Good  153 (81.8)  61 (92.4)     Moderate  30 (16.0)  5 (7.58)     Poor  4 (2.14)  0 (0.00)    RV function      <0.001   Good  176 (94.1)  50 (75.8)     Moderate  9 (4.81)  15 (22.7)     Poor  1 (0.53)  0 (0.00)    Aortic valve cuspidity      <0.001   Unicuspid  3 (1.60)  0 (0.00)     Bicuspid  70 (37.4)  1 (1.52)     Tricuspid  113 (60.4)  65 (98.5)     Quadricuspid  1 (0.53)  0 (0.00)    Marfan syndrome  20 (10.7)  6 (9.09)  0.71  Other connective tissue disease  5 (2.67)  1 (1.52)  0.59  Aortic regurgitation  133 (71.1)  45 (68.2)  0.65  Pericardial effusion  4 (2.14)  21 (31.8)  <0.001  Cardiac tamponade  0 (0.00)  8 (12.1)  <0.001  Aortic rupture  0 (0.00)  3 (4.55)  0.017  Preoperative ventilation  0 (0.00)  2 (3.03)  0.07  Cardiogenic shock  0 (0.00)  4 (6.06)  0.004  Mesenteric ischaemia  0 (0.00)  1 (1.52)  0.26  Site of intimal tear         Aortic root    28 (42.4)     Sinotubular junction    3 (4.55)     Ascending aorta    21 (31.8)     Other    13 (19.7)    Values are n (%) or median (interquartile range). BMI: body mass index; CKD: chronic kidney disease; CVA: cerebrovascular accident; LV: left ventricle; MI: myocardial infarction; NYHA: New York Heart Association; RV: right ventricle; TIA: transient ischaemic attack. Mortality There was no significant difference in mortality between the aneurysm (10/187, 5.3%) and dissection (7/66, 10.6%) groups (P = 0.139) during the follow-up period. Mean aortic diameter Table 2 shows the mean aortic diameter for aneurysm and dissection groups according to aortic location. All acute Type A aortic dissections occurred at mean aortic diameters <5.5 cm between the aortic root and mid-ascending aorta. Table 2: Mean aortic diameter according to aortic location Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  P-value  Mid-sinus  4.53 ± 0.78  4.42 ± 0.82  0.13  Sinotubular junction  3.87 ± 0.79  4.05 ± 1.18  0.70  Mid-ascending  4.97 ± 1.12  5.20 ± 1.26  0.31  Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  P-value  Mid-sinus  4.53 ± 0.78  4.42 ± 0.82  0.13  Sinotubular junction  3.87 ± 0.79  4.05 ± 1.18  0.70  Mid-ascending  4.97 ± 1.12  5.20 ± 1.26  0.31  Values are mean ± standard deviation. Table 2: Mean aortic diameter according to aortic location Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  P-value  Mid-sinus  4.53 ± 0.78  4.42 ± 0.82  0.13  Sinotubular junction  3.87 ± 0.79  4.05 ± 1.18  0.70  Mid-ascending  4.97 ± 1.12  5.20 ± 1.26  0.31  Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  P-value  Mid-sinus  4.53 ± 0.78  4.42 ± 0.82  0.13  Sinotubular junction  3.87 ± 0.79  4.05 ± 1.18  0.70  Mid-ascending  4.97 ± 1.12  5.20 ± 1.26  0.31  Values are mean ± standard deviation. Indexed aortic areas Table 3 shows the median IAAs, and Fig. 1 the overall distribution of IAAs, for aneurysm and dissection groups categorised according to aortic location. These were largest at the mid-ascending aorta, where the 10 cm2/m cut-off was exceeded, followed by those at the mid-sinus level where values approached abnormal levels. Median IAAs were not significantly different between groups at any aortic location. Table 3: Median indexed aortic areas (cm2/m) according to aortic location Aortic location  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Mid-sinus  9.37 (2.67–21.2)  8.01 (4.04–24.7)  0.09  Sinotubular junction  6.49 (2.03–20.6)  6.69 (2.77–35.6)  0.68  Mid-ascending  10.6 (3.07–41.9)  11.2 (3.37–36.5)  0.32  Aortic location  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Mid-sinus  9.37 (2.67–21.2)  8.01 (4.04–24.7)  0.09  Sinotubular junction  6.49 (2.03–20.6)  6.69 (2.77–35.6)  0.68  Mid-ascending  10.6 (3.07–41.9)  11.2 (3.37–36.5)  0.32  Values are median (range). Table 3: Median indexed aortic areas (cm2/m) according to aortic location Aortic location  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Mid-sinus  9.37 (2.67–21.2)  8.01 (4.04–24.7)  0.09  Sinotubular junction  6.49 (2.03–20.6)  6.69 (2.77–35.6)  0.68  Mid-ascending  10.6 (3.07–41.9)  11.2 (3.37–36.5)  0.32  Aortic location  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Mid-sinus  9.37 (2.67–21.2)  8.01 (4.04–24.7)  0.09  Sinotubular junction  6.49 (2.03–20.6)  6.69 (2.77–35.6)  0.68  Mid-ascending  10.6 (3.07–41.9)  11.2 (3.37–36.5)  0.32  Values are median (range). Figure 1: View largeDownload slide Distribution of indexed aortic areas in aneurysm group (left-sided bars) and dissection group (right-sided bars) according to aortic location. Asc: ascending aorta; STJ: sinotubular junction. Figure 1: View largeDownload slide Distribution of indexed aortic areas in aneurysm group (left-sided bars) and dissection group (right-sided bars) according to aortic location. Asc: ascending aorta; STJ: sinotubular junction. Indexed aortic areas >10 cm2/m Numbers of patients with IAAs exceeding 10 cm2/m are shown in Table 4. The results reflect the fact that the IAA can exceed 10 cm2/m at several aortic locations in a given patient. The highest IAA was found at the mid-ascending aorta location, where 56.7% of aneurysm group patients, and 60.6% of dissection group patients, had abnormally high IAAs. At the mid-sinuses, 39.6% of aneurysm group patients and 25.8% of dissection group patients had IAAs >10 cm2/m. Table 4: Patients with indexed aortic area >10 cm2/ma Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  Mid-sinus  74 (39.6)  17 (25.8)  Sinotubular junction  20 (10.7)  13 (19.7)  Mid-ascending  106 (56.7)  40 (60.6)  Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  Mid-sinus  74 (39.6)  17 (25.8)  Sinotubular junction  20 (10.7)  13 (19.7)  Mid-ascending  106 (56.7)  40 (60.6)  a Indexed aortic area >10 cm2/m can occur at ≥1 aortic location in the same patient. Table 4: Patients with indexed aortic area >10 cm2/ma Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  Mid-sinus  74 (39.6)  17 (25.8)  Sinotubular junction  20 (10.7)  13 (19.7)  Mid-ascending  106 (56.7)  40 (60.6)  Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  Mid-sinus  74 (39.6)  17 (25.8)  Sinotubular junction  20 (10.7)  13 (19.7)  Mid-ascending  106 (56.7)  40 (60.6)  a Indexed aortic area >10 cm2/m can occur at ≥1 aortic location in the same patient. Mean indexed aortic areas corresponding to aortic diameter in aneurysms Figure 2 demonstrates the mean IAA for patients with aortic diameters <4.0 cm, 4.0–4.5 cm, 4.5–5.0 cm, 5.0–5.5 cm and >5.5 cm at mid-sinus, sinotubular junction and mid-ascending aortic locations. The mean IAA is shown to increase linearly with increasing aortic diameter as expected. Importantly, abnormally high mean IAAs first emerge at aortic diameters of 4.5–5.0 cm. The mean IAA is 11.9 cm2/m at an aortic diameter of 5.0–5.5 cm and 17.3 cm2/m at >5.5 cm. Figure 2: View largeDownload slide Mean indexed aortic area corresponding to aortic diameter in aneurysms. Figure 2: View largeDownload slide Mean indexed aortic area corresponding to aortic diameter in aneurysms. Table 5 shows the proportion of patients with IAAs >10 cm2/m according to aortic diameter. No patients with aortic diameters <4.0 cm had an abnormal IAA exceeding 10 cm2/m. Within the 4.0–4.5 cm subgroup, only 1 of 108 (0.9%) patients had an abnormal IAA. Abnormal IAAs were noted in 57 of 116 (49.1%) patients in the 4.5–5.0 cm subgroup, rising to 67 of 68 (98.5%) patients in the 5.0–5.5 cm subgroup and 72 of 72 (100%) patients in the >5.5 cm subgroups. Table 5: Proportion of aneurysm patients with indexed aortic area >10 cm2/m according to aortic diameters Aortic diameter (cm)  Indexed aortic areas >10 cm2/m, N/n (%)  <4.0  0/212 (0.0)  4.0–4.5  1/108 (0.9)  4.5–5.0  57/116 (49.1)  5.0–5.5  67/68 (98.5)  >5.5  72/72 (100)  Aortic diameter (cm)  Indexed aortic areas >10 cm2/m, N/n (%)  <4.0  0/212 (0.0)  4.0–4.5  1/108 (0.9)  4.5–5.0  57/116 (49.1)  5.0–5.5  67/68 (98.5)  >5.5  72/72 (100)  Table 5: Proportion of aneurysm patients with indexed aortic area >10 cm2/m according to aortic diameters Aortic diameter (cm)  Indexed aortic areas >10 cm2/m, N/n (%)  <4.0  0/212 (0.0)  4.0–4.5  1/108 (0.9)  4.5–5.0  57/116 (49.1)  5.0–5.5  67/68 (98.5)  >5.5  72/72 (100)  Aortic diameter (cm)  Indexed aortic areas >10 cm2/m, N/n (%)  <4.0  0/212 (0.0)  4.0–4.5  1/108 (0.9)  4.5–5.0  57/116 (49.1)  5.0–5.5  67/68 (98.5)  >5.5  72/72 (100)  Relationship between indexed aortic areas and aortic diameter in aneurysms Patients with an IAA >10 cm2/m (the at-risk population) at mid-sinus, sinotubular junction and mid-ascending aortic locations, were categorised into groups with IAA ranges 10–12 cm2/m, 12–14 cm2/m and >14 cm2/m. There were 74 patients, 20 patients and 106 patients who at mid-sinus, sinotubular junction and mid-ascending aorta location, respectively, had IAAs >10 cm2/m. The mean of the corresponding aortic diameters for each range was then calculated (Table 6). Table 6: Relationship between mean aortic diameters and indexed aortic area ranges in aneurysms   Mean aortic diameter (cm) according to aortic location (n, % of all patients with indexed aortic area >10 cm2/m per aortic location)   Indexed aortic area (cm2/m)  Mid-sinus  Sinotubular junction  Mid-ascending  N = 74  N = 20  N =106  10–12  4.98 (45, 60.0)  5.04 (9, 42.9)  4.92 (46, 43.4)  12–14  5.46 (18, 24.3)  5.35 (4, 20.0)  5.37 (17, 15.4)  >14  6.25 (11, 14.7)  6.19 (7, 33.3)  6.54 (43, 40.6)    Mean aortic diameter (cm) according to aortic location (n, % of all patients with indexed aortic area >10 cm2/m per aortic location)   Indexed aortic area (cm2/m)  Mid-sinus  Sinotubular junction  Mid-ascending  N = 74  N = 20  N =106  10–12  4.98 (45, 60.0)  5.04 (9, 42.9)  4.92 (46, 43.4)  12–14  5.46 (18, 24.3)  5.35 (4, 20.0)  5.37 (17, 15.4)  >14  6.25 (11, 14.7)  6.19 (7, 33.3)  6.54 (43, 40.6)  Table 6: Relationship between mean aortic diameters and indexed aortic area ranges in aneurysms   Mean aortic diameter (cm) according to aortic location (n, % of all patients with indexed aortic area >10 cm2/m per aortic location)   Indexed aortic area (cm2/m)  Mid-sinus  Sinotubular junction  Mid-ascending  N = 74  N = 20  N =106  10–12  4.98 (45, 60.0)  5.04 (9, 42.9)  4.92 (46, 43.4)  12–14  5.46 (18, 24.3)  5.35 (4, 20.0)  5.37 (17, 15.4)  >14  6.25 (11, 14.7)  6.19 (7, 33.3)  6.54 (43, 40.6)    Mean aortic diameter (cm) according to aortic location (n, % of all patients with indexed aortic area >10 cm2/m per aortic location)   Indexed aortic area (cm2/m)  Mid-sinus  Sinotubular junction  Mid-ascending  N = 74  N = 20  N =106  10–12  4.98 (45, 60.0)  5.04 (9, 42.9)  4.92 (46, 43.4)  12–14  5.46 (18, 24.3)  5.35 (4, 20.0)  5.37 (17, 15.4)  >14  6.25 (11, 14.7)  6.19 (7, 33.3)  6.54 (43, 40.6)  A considerable 84.3% of patients with an IAA >10 cm2/m based on mid-sinus measurements had a mean aortic diameter below the current 5.5 cm threshold for surgical intervention. Similarly, at the sinotubular junction, some 62.9% of patients with an abnormal IAA had a mean aortic diameter <5.5 cm. At the mid-ascending aortic location, 58.8% of the at-risk patients with an abnormally high IAA had a mean aortic diameter <5.5 cm. Only 139 (69.5%) patients out of the entire cohort of 200 patients who have an IAA >10 cm2/m between the mid-sinus of Valsalva and mid-ascending aorta would be eligible for surgical intervention for the aortic root/ascending aorta on the basis of existing guidelines. DISCUSSION We performed a retrospective observational study to assess the correlation between aortic diameter and IAA in 187 patients with thoracic aortic aneurysm and 66 patients with acute Type A dissection. Our study population was limited solely to those patients presenting to us for surgical management of diseased aortas. Of course, there may be a very large group of patients undergoing surveillance for mild proximal aortic dilatation, in whom the IAA may exceed 10 cm2/m, but who have not yet been selected for surgical intervention based on traditional aortic size criteria, or who have not undergone acute dissection. We noted that dissected aortas had mean aortic root/mid-ascending diameters <5.5 cm on presentation (Table 2). Considering that the diameter of an acutely dissected aorta will likely increase compared to its predissected state, with haematoma expansion and resultant separation of the aortic wall layers, this suggests that the <5.5 cm mean diameter of the dissected aortas seen in our group would have been even smaller prior to the dissection event [4]. Current guidelines advocate prophylactic aortic replacement at absolute aortic diameters of 4.5–5.5 cm in tricuspid and bicuspid aortic valves, or 4.0–4.5 cm with inherited aortopathies, such as Marfan and Ehlers–Danlos syndromes [3]. However, 40% of patients presenting with Type A aortic dissection have an aortic diameter <5 cm, at which size 15% of patients with Marfan syndrome, who have the highest lifetime risk of aortic dissection, will undergo dissection or rupture [4–6]. Loss of aortic elastic tissue in bicuspid-valve related aneurysms means dissection risk in this patient population is not dissimilar to those with Marfan syndrome [2, 7]. This questions the true prognostic value of the absolute aortic diameter, and emphasises the need for optimal timing of surgical intervention, especially in those patients under surveillance who do not meet established size criteria for surgery, but may still be at significant risk of dissection. Additionally, utilization of absolute aortic diameter in existing guidelines fails to account for size, height and gender differences in aortic dimensions, as well as the irregular elliptical shape of the aorta. More recently, there has been greater emphasis on indexing aortic cross-sectional area to patient height for dissection and mortality risk stratification in dilated aortas with both bicuspid and trileaflet aortic valves [1, 2, 5]. An IAA >10 cm2/m has been determined as a cut-off value after which prophylactic aortic root with or without ascending aortic replacement is advocated for curative potential and thus to improve long-term survival [1]. In the present study, we found that median IAAs were comparable between groups from the mid-sinus to the mid-ascending aorta (Table 3). Median IAAs exceeded the critical 10 cm2/m point at the ascending aortic location, suggesting that aneurysm patients may be at risk of dissection once an IAA of 10 cm2/m is exceeded. Based on measurements at the mid-ascending aorta, over half of the patients (106/187) in the aneurysm group were shown to be at risk with IAAs >10 cm2/m; the same was true for over a third (74/187) of aneurysm patients based on mid-sinus measurements (Table 4). We showed that between 57.8–84.3% (Table 6) of our study population (depending on the aortic location considered) who were at increased risk of aortic complications according to IAAs, would not have been eligible for aortic surgery according to contemporary guidelines. A previous observational study found an abnormally high IAA in 44% of patients with aortic root diameters at 4.5–5.5 cm [1]. In our study, 124 of 184 (67.4%) patients with aortic diameters 4.5–5.5 cm were found to have abnormally high IAAs (Table 5). Thus, the present study confirms that a significant proportion of patients with aortic diameters that do not reach the size criteria recommended for elective aortic aneurysm surgery have an abnormal IAA, indicating their increased risk of aortic complications. Emergency surgery for acute Type A dissection aims to prevent the potentially fatal complications of aortic rupture, acute aortic regurgitation, pericardial tamponade, acute coronary occlusion, stroke and limb and organ ischaemia. With improving understanding of the underlying pathophysiology, enhanced recognition with modern imaging modalities, prompt referral to cardiothoracic services and accruing surgical experience, survival rates in acute aortic syndrome have gradually improved in recent years. Hospital mortality has been reported at 10–25% in the current era across all ages [5, 8]. Elective aortic root and/or ascending aortic replacement carries an even lower operative risk at experienced centres with a high-volume case output [9]. This emphasises the importance of accurately identifying at-risk individuals with thoracic aortic aneurysms for prophylactic surgery. The purpose of this isolated retrospective observational study was not to determine a novel size threshold for the selection of patients for aortic surgical intervention. Rather, we aimed to elucidate the less well-studied association between absolute aortic diameter and IAA. It is now well-recognised that aortic dissection may occur in a significant cohort of patients at aortic diameters less than the 5.5 cm proposed for surgical repair [2, 5, 6]. Considering this, and in conjunction with the present study’s findings that IAA is abnormally increased in 67.4% of patients with aortic diameter 4.5–5.5 cm (Table 5), rendering them at higher risk of aortic complications, we suggest that an IAA >10 cm2/m should be considered as a potential risk factor in thoracic aortic disease, and be further evaluated as a criterion for aortic surgery. Large-scale prospective multicentre registries with accurate long-term follow-up of outcomes are needed to clarify the prognostic value of the IAA in varied surgical populations, including bicuspid and trileaflet aortic valves, as well as Marfan’s syndrome, which confers the greatest dissection risk. This would ideally afford patients at risk of aneurysm-related dissection or rupture the chance for potentially curative surgery, and at lower operative risk when performed at dedicated, high-volume aortic centres [9–12]. Limitations This is a retrospective observational study with inherent potential for associated selection bias. However, since our tertiary institution is a referral centre for acute Type A aortic dissection, patients submitted to aortic surgery at other tertiary cardiac centres would share similar characteristics, namely aortic diameter and IAA, to those in our population. Despite examining all-comers submitted to thoracic aortic aneurysm or dissection surgery over a predefined time period, our study population did not comprise large numbers of patients with inherited aortopathies or bicuspid aortic valves, since these are monitored closely in established surveillance programmes and selected for early surgery. Thus the results of our analysis may be transferable to other major aortic centres in non-aortopathy populations. We utilized the formula π × r2 for aortic area calculations which may be less suitable for eccentric aortic shapes where a planimetry technique may be more appropriate [1]. Finally, whilst the results of the present study suggest IAA >10 cm2/m may be useful as a risk factor in thoracic aortic disease, validation of the IAA in comparative analyses would be required prior to its adoption in preoperative risk evaluation. CONCLUSIONS This study confirms that a large proportion of patients with thoracic aortic aneurysms have IAAs >10 cm2/m corresponding to absolute aortic dimensions that do not satisfy contemporary guideline criteria for aortic surgical intervention, despite being at increased risk of aortic complications. This cohort of patients may benefit from undergoing earlier surgery performed at high-volume centres with special aortic expertise, and at more conservative aortic size ranges, which need verification in larger prospective studies with extended follow-up. Conflict of interest: none declared. REFERENCES 1 Masri A, Kalahasti V, Svensson LG, Roselli EE, Johnston D, Hammer D et al.   Aortic cross-sectional area/height ratio and outcomes in patients with a trileaflet aortic valve and a dilated aorta. Circulation  2016; 134: 1724– 37. Google Scholar CrossRef Search ADS PubMed  2 Svensson LG, Kim KH, Lytle BW, Cosgrove DM. Relationship of aortic cross-sectional area to height ratio and the risk of aortic dissection in patients with bicuspid aortic valves. J Thorac Cardiovasc Surg  2003; 126: 892– 3. Google Scholar CrossRef Search ADS PubMed  3 Hiratzka LF, Bakris GL, Beckman JA, Bersin RM, Carr VF, Casey DEJr et al.   2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with Thoracic Aortic Disease: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines, American Association for Thoracic Surgery, American College of Radiology, American Stroke Association, Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society of Thoracic Surgeons, and Society for Vascular Medicine. Circulation  2010; 121: e266– 369. Google Scholar CrossRef Search ADS PubMed  4 Pape LA, Tsai TT, Isselbacher EM, Oh JK, O'Gara PT, Evangelista A et al.   Aortic diameter >or = 5.5 cm is not a good predictor of type A aortic dissection: observations from the International Registry of Acute Aortic Dissection (IRAD). Circulation  2007; 116: 1120– 7. Google Scholar CrossRef Search ADS PubMed  5 Svensson LG, Khitin L. Aortic cross-sectional area/height ratio timing of aortic surgery in asymptomatic patients with Marfan syndrome. J Thorac Cardiovasc Surg  2002; 123: 360– 1. Google Scholar CrossRef Search ADS PubMed  6 Gott VL, Greene PS, Alejo DE, Cameron DE, Naftel DC, Miller DC et al.   Replacement of the aortic root in patients with Marfan’s syndrome. N Engl J Med  1999; 340: 1307– 13. Google Scholar CrossRef Search ADS PubMed  7 Isselbacher EM, Lino Cardenas CL, Lindsay ME. Hereditary influence in thoracic aortic aneurysm and dissection. Circulation  2016; 133: 2516– 28. Google Scholar CrossRef Search ADS PubMed  8 Rylski B, Hoffman I, Beyersdorf F, Suedkamp M, Siepe M, Nitsch B et al.   Acute aortic dissection type A: age-related management and outcomes reported in the German Registry for Acute Aortic Dissection Type A (GERAADA) of over 2000 patients. Ann Surg  2014; 259: 598– 604. Google Scholar CrossRef Search ADS PubMed  9 Bilkhu R, Youssefi P, Soppa G, Sharma R, Child A, Edsell M et al.   Aortic root surgery: does high surgical volume and a consistent perioperative approach improve outcome? Semin Thorac Cardiovasc Surg  2016; 28: 302– 9. Google Scholar CrossRef Search ADS PubMed  10 Svensson LG, Pillai ST, Rajeswaran J, Desai MY, Griffin B, Grimm R et al.   Long-term survival, valve durability, and reoperation for 4 aortic root procedures combined with ascending aorta replacement. J Thorac Cardiovasc Surg  2016; 151: 764– 74. Google Scholar CrossRef Search ADS PubMed  11 Caceres M, Ma Y, Rankin JS, Saha-Chaudhuri P, Englum BR, Gammie JS et al.   Mortality characteristics of aortic root surgery in North America. Eur J Cardiothorac Surg  2014; 46: 887– 93. Google Scholar CrossRef Search ADS PubMed  12 Masri A, Kalahasti V, Alkharabsheh S, Svensson LG, Sabik JF, Roselli EE et al.   Characteristics and long-term outcomes of contemporary patients with bicuspid aortic valves. J Thorac Cardiovasc Surg  2016; 151: 1650– 9. Google Scholar CrossRef Search ADS PubMed  © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png European Journal of Cardio-Thoracic Surgery Oxford University Press

Analysis of aortic area/height ratio in patients with thoracic aortic aneurysm and Type A dissection

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
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1010-7940
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1873-734X
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10.1093/ejcts/ezy110
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Abstract

Abstract OBJECTIVES Significant proportions of aortic dissections occur at aortic diameters <5.5 cm. By indexing aortic area to height and correlating with absolute aortic diameter, we sought to identify those aneurysm patients with aortic diameters <5.5 cm who do not meet current size thresholds for surgery, yet with corresponding abnormal indexed aortic areas (IAAs) >10 cm2/m, are at increased risk of aortic complications. METHODS IAAs were calculated at 3 aortic locations in 187 aneurysm and 66 dissection patients operated on between 2010 and 2016 at our tertiary aortic centre. Proportions of patients with IAA >10 cm2/m, mean IAAs corresponding to aortic diameters <4.0 cm, 4.0–4.5 cm, 4.5–5.0 cm, 5.0–5.5 cm and >5.5 cm, and mean aortic diameters corresponding to IAAs 10–12 cm2/m, 12–14 cm2/m and >14 cm2/m were determined. RESULTS Proportions of patients with abnormal IAAs were similar in both groups. In all, 49.1% of aneurysm patients with aortic diameters 4.5–5.0 cm, and 98.5% with aortic diameters 5.0–5.5 cm had abnormal IAAs. Out of 207 separate aneurysms with IAAs >10 cm2/m between the mid-sinus and mid-ascending aorta, only 139 (69.5%) would warrant surgery according to existing guidelines. CONCLUSIONS Using the IAA, we identified a significant proportion of patients with thoracic aortic aneurysms who are at increased risk of aortic complications, despite current aortic guidelines not endorsing surgical intervention in this group. Our data suggests the IAA may be useful in preoperative risk evaluation and as a criterion for surgery. Aneurysm , Aortic dissection , Aorta INTRODUCTION The aortic cross-sectional area/patient height ratio (πr2/h, cm2/m) has been validated in the stratification of mortality risk in patients with a tricuspid aortic valve and dilated aorta [1]. First proposed by Svensson et al. [2], this indexed measurement accounts for the greater risk of aortic complications associated with larger aortic dimensions in shorter patients, whilst incorporating the exponential risk of dissection or rupture with increasing aortic size. Indexed aortic root area >10 cm2/m has been shown to have significant independent prognostic value in patients with tricuspid aortic valve and concomitant aortopathy, compared to a non-indexed aortic diameter [1]. The same study showed that a significant proportion (44% of 771 patients) with aortic root diameter 4.5–5.5 cm had an abnormally high aortic root/height ratio; 78% of patients in this subgroup died, although mortality could not be directly attributed to aortic dissection or rupture [1]. These findings highlight that the cohort of patients with aortic size less than the thresholds mandating surgery in current established guidelines, and in whom the cross-sectional aortic area/height ratio exceeds 10 cm2/m, represents an opportunity for early, proactive intervention to prevent potentially fatal aortic dissection. This strategy would theoretically prevent 95% of acute aortic dissections in a Marfan population [2]. The relationship between aortic diameter and indexed cross-sectional aortic area has not been fully ascertained in patients presenting with isolated thoracic aortic aneurysms and those with acute Type A aortic dissection. In this study, we sought to determine (i) the indexed aortic area (IAA) in patients with thoracic aortic aneurysms and acute Type A aortic dissection at different aortic locations, (ii) the proportion of at-risk aneurysm patients with IAAs >10 cm2/m and (iii) the relationship between IAAs >10 cm2/m and corresponding aortic diameters in aneurysm patients. MATERIALS AND METHODS Definitions For the purpose of this study, an aortic root or ascending aortic diameter ≥4 cm was considered aneurysmal. Postoperative renal dysfunction was defined as a new requirement for haemofiltration or haemodialysis following surgery. In-hospital mortality was defined as death during the same hospital admission. Study populations We performed a retrospective observational study on all consecutive adult patients undergoing first-time surgery for thoracic aortic aneurysm (aneurysm group) or acute Type A aortic dissection (dissection group) between 2010 and 2016 at St George’s Hospital, London, UK. Patients were assigned to the aneurysm group based on echocardiographic, contrast-enhanced computed tomography (CT) or contrast-enhanced magnetic resonance imaging (MRI) demonstrating an aortic root or ascending aorta ≥4 cm in diameter. Patients with an aortic root/ascending aorta approaching 4 cm in dimension and coexisting connective tissue disease were also included in the aneurysm group. Patients admitted to our service with acute Type A dissection, confirmed on contrast-enhanced CT, comprised the dissection group. Patients for whom relevant preoperative imaging had not been performed within the preceding year, and in whom aortic root/ascending aortic replacement was performed for procedural complications in the absence of preoperative aortic aneurysm or dissection, were excluded. Other variables considered included cardiovascular risk factors (hypertension, hypercholesterolaemia, diabetes mellitus, smoking), as well as pulmonary disease, peripheral vascular disease, chronic kidney disease, connective tissue disease, previous transient ischaemic attack/stroke, ventricular function, aortic valve cusp configuration and aortic valvular regurgitation. Prospectively-collected demographic, clinical and operative data was manually retrieved from our institution’s computer database and cross-referenced with medical records. Local ethical approval (equivalent to institutional review board) was granted for this retrospective study. Imaging review The most recent preoperative aortic scans were retrospectively reviewed in multiplanar CT and/or MRI modalities for each patient. Maximum cross-sectional aortic diameters were measured using the inner edge-to-inner edge method in coronal and sagittal views in a plane perpendicular to the direction of blood flow at 3 aortic locations: the mid-point of the sinuses of Valsalva, the sinotubular junction and the mid-ascending aorta (at the level of the pulmonary artery bifurcation) [3]. The largest aortic diameter was used for analysis when multiple measurements were generated. For patients presenting with dissection, diameter measurements included both true and false aortic lumens. All imaging was reviewed by a single clinician with cross-checking of a randomly-selected 10% sample by 2 experienced cardiovascular radiologists to ensure concurrence in measurement technique and reproducibility. Outcome measures Cross-sectional area at each aortic location was calculated using the formula π × r2, where r represents the aortic radius, for patients in aneurysm and dissection groups. This was divided by patient height to determine a ratio of the aortic cross-sectional area to height (IAA). The median IAA at each of the 3 aortic locations was calculated for both groups, and the proportion of at-risk patients with IAA >10 cm2/m identified for each aortic location. IAAs at the mid-sinus, sinotubular junction and mid-ascending aortic locations were categorised into 3 subgroups (10–12 cm2/m, 12–14 cm2/m and >14 cm2/m) and the mean aortic diameter corresponding to each range was calculated. In addition, patients in the aneurysm group were assigned to 1 of 5 subgroups (<4.0 cm, 4.0–4.5 cm, 4.5–5.0 cm, 5.0–5.5 cm or >5.5 cm) depending on aortic diameter at mid-sinus, sinotubular junction and mid-ascending aortic locations. IAAs were analysed for all patients within the subgroups to calculate the mean IAA at each aortic location for each size subgroup. Statistical analysis Statistical analysis was performed using SPSS software (SPSS Inc., Chicago, IL, USA). Summary statistics are presented as percentages for categorical variables, and medians and interquartile ranges, or means ± standard deviations, for continuous variables. Univariable analyses of categorical and continuous variables were performed using χ2 and Fisher’s exact tests. The distribution of continuous variables was assessed for normality with the Shapiro–Wilk Test, and continuous variables were compared between groups using the Mann–Whitney U-test. A P-value <0.05 was considered statistically significant. RESULTS Study populations Out of 218 aneurysm patients and 75 dissection patients undergoing surgical repair between 2010 and 2016 at our institution, 187 patients and 66 patients, respectively, were eligible for analysis. The preoperative characteristics of both groups are shown in Table 1. Twenty-five of 187 (13.4%) patients in the aneurysm group were diagnosed with MRI scanning, whereas all patients with dissection underwent CT imaging. Being a tertiary aortic centre, patients with inherited aortopathies are closely monitored within established surveillance programmes and offered early prophylactic surgery. Within the aneurysm group, 20 (10.7%) patients had Marfan syndrome, with an additional 5 (2.67%) having other connective tissue diseases. The dissection group included 6 (9.09%) patients with Marfan syndrome and 1 (1.52%) patient with other connective tissue disease. Patients in the aneurysm and dissection groups were followed up for a median 337 and 470 days, respectively. Table 1: Preoperative patient characteristics Characteristics  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Age (years)  63 (52–73)  66 (51–73)  0.77  Male  127 (67.9)  45 (68.2)  0.97  BMI  27 (24–30)  27 (25–29)  0.67  Logistic EuroSCORE  5.58 (2.17–9.17)  8.86 (4.23–14.0)  0.001  NYHA class      <0.001   I  75 (40.1)  50 (75.8)     II  79 (42.2)  8 (12.1)     III  33 (17.6)  8 (12.1)    Hypertension  109 (58.3)  35 (53.0)  0.46  Hypercholesterolaemia  60 (32.1)  11 (16.7)  0.017  Smoking  84 (44.9)  18 (27.3)  0.022  Pulmonary disease  14 (7.49)  6 (9.09)  0.68  CKD stage      <0.001   1  75 (40.1)  15 (22.7)     2  89 (47.6)  28 (42.2)     3  20 (10.7)  21 (31.8)     4  2 (1.07)  1 (1.52)     5  1 (0.53)  0 (0.00)    Preoperative dialysis  1 (0.53)  1 (1.52)  0.45  TIA/CVA  19 (10.2)  9 (13.6)  0.40  Previous MI  13 (6.95)  5 (7.58)  0.79  Peripheral vascular disease  11 (5.88)  0 (0.00)  0.07  LV function      0.10   Good  153 (81.8)  61 (92.4)     Moderate  30 (16.0)  5 (7.58)     Poor  4 (2.14)  0 (0.00)    RV function      <0.001   Good  176 (94.1)  50 (75.8)     Moderate  9 (4.81)  15 (22.7)     Poor  1 (0.53)  0 (0.00)    Aortic valve cuspidity      <0.001   Unicuspid  3 (1.60)  0 (0.00)     Bicuspid  70 (37.4)  1 (1.52)     Tricuspid  113 (60.4)  65 (98.5)     Quadricuspid  1 (0.53)  0 (0.00)    Marfan syndrome  20 (10.7)  6 (9.09)  0.71  Other connective tissue disease  5 (2.67)  1 (1.52)  0.59  Aortic regurgitation  133 (71.1)  45 (68.2)  0.65  Pericardial effusion  4 (2.14)  21 (31.8)  <0.001  Cardiac tamponade  0 (0.00)  8 (12.1)  <0.001  Aortic rupture  0 (0.00)  3 (4.55)  0.017  Preoperative ventilation  0 (0.00)  2 (3.03)  0.07  Cardiogenic shock  0 (0.00)  4 (6.06)  0.004  Mesenteric ischaemia  0 (0.00)  1 (1.52)  0.26  Site of intimal tear         Aortic root    28 (42.4)     Sinotubular junction    3 (4.55)     Ascending aorta    21 (31.8)     Other    13 (19.7)    Characteristics  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Age (years)  63 (52–73)  66 (51–73)  0.77  Male  127 (67.9)  45 (68.2)  0.97  BMI  27 (24–30)  27 (25–29)  0.67  Logistic EuroSCORE  5.58 (2.17–9.17)  8.86 (4.23–14.0)  0.001  NYHA class      <0.001   I  75 (40.1)  50 (75.8)     II  79 (42.2)  8 (12.1)     III  33 (17.6)  8 (12.1)    Hypertension  109 (58.3)  35 (53.0)  0.46  Hypercholesterolaemia  60 (32.1)  11 (16.7)  0.017  Smoking  84 (44.9)  18 (27.3)  0.022  Pulmonary disease  14 (7.49)  6 (9.09)  0.68  CKD stage      <0.001   1  75 (40.1)  15 (22.7)     2  89 (47.6)  28 (42.2)     3  20 (10.7)  21 (31.8)     4  2 (1.07)  1 (1.52)     5  1 (0.53)  0 (0.00)    Preoperative dialysis  1 (0.53)  1 (1.52)  0.45  TIA/CVA  19 (10.2)  9 (13.6)  0.40  Previous MI  13 (6.95)  5 (7.58)  0.79  Peripheral vascular disease  11 (5.88)  0 (0.00)  0.07  LV function      0.10   Good  153 (81.8)  61 (92.4)     Moderate  30 (16.0)  5 (7.58)     Poor  4 (2.14)  0 (0.00)    RV function      <0.001   Good  176 (94.1)  50 (75.8)     Moderate  9 (4.81)  15 (22.7)     Poor  1 (0.53)  0 (0.00)    Aortic valve cuspidity      <0.001   Unicuspid  3 (1.60)  0 (0.00)     Bicuspid  70 (37.4)  1 (1.52)     Tricuspid  113 (60.4)  65 (98.5)     Quadricuspid  1 (0.53)  0 (0.00)    Marfan syndrome  20 (10.7)  6 (9.09)  0.71  Other connective tissue disease  5 (2.67)  1 (1.52)  0.59  Aortic regurgitation  133 (71.1)  45 (68.2)  0.65  Pericardial effusion  4 (2.14)  21 (31.8)  <0.001  Cardiac tamponade  0 (0.00)  8 (12.1)  <0.001  Aortic rupture  0 (0.00)  3 (4.55)  0.017  Preoperative ventilation  0 (0.00)  2 (3.03)  0.07  Cardiogenic shock  0 (0.00)  4 (6.06)  0.004  Mesenteric ischaemia  0 (0.00)  1 (1.52)  0.26  Site of intimal tear         Aortic root    28 (42.4)     Sinotubular junction    3 (4.55)     Ascending aorta    21 (31.8)     Other    13 (19.7)    Values are n (%) or median (interquartile range). BMI: body mass index; CKD: chronic kidney disease; CVA: cerebrovascular accident; LV: left ventricle; MI: myocardial infarction; NYHA: New York Heart Association; RV: right ventricle; TIA: transient ischaemic attack. Table 1: Preoperative patient characteristics Characteristics  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Age (years)  63 (52–73)  66 (51–73)  0.77  Male  127 (67.9)  45 (68.2)  0.97  BMI  27 (24–30)  27 (25–29)  0.67  Logistic EuroSCORE  5.58 (2.17–9.17)  8.86 (4.23–14.0)  0.001  NYHA class      <0.001   I  75 (40.1)  50 (75.8)     II  79 (42.2)  8 (12.1)     III  33 (17.6)  8 (12.1)    Hypertension  109 (58.3)  35 (53.0)  0.46  Hypercholesterolaemia  60 (32.1)  11 (16.7)  0.017  Smoking  84 (44.9)  18 (27.3)  0.022  Pulmonary disease  14 (7.49)  6 (9.09)  0.68  CKD stage      <0.001   1  75 (40.1)  15 (22.7)     2  89 (47.6)  28 (42.2)     3  20 (10.7)  21 (31.8)     4  2 (1.07)  1 (1.52)     5  1 (0.53)  0 (0.00)    Preoperative dialysis  1 (0.53)  1 (1.52)  0.45  TIA/CVA  19 (10.2)  9 (13.6)  0.40  Previous MI  13 (6.95)  5 (7.58)  0.79  Peripheral vascular disease  11 (5.88)  0 (0.00)  0.07  LV function      0.10   Good  153 (81.8)  61 (92.4)     Moderate  30 (16.0)  5 (7.58)     Poor  4 (2.14)  0 (0.00)    RV function      <0.001   Good  176 (94.1)  50 (75.8)     Moderate  9 (4.81)  15 (22.7)     Poor  1 (0.53)  0 (0.00)    Aortic valve cuspidity      <0.001   Unicuspid  3 (1.60)  0 (0.00)     Bicuspid  70 (37.4)  1 (1.52)     Tricuspid  113 (60.4)  65 (98.5)     Quadricuspid  1 (0.53)  0 (0.00)    Marfan syndrome  20 (10.7)  6 (9.09)  0.71  Other connective tissue disease  5 (2.67)  1 (1.52)  0.59  Aortic regurgitation  133 (71.1)  45 (68.2)  0.65  Pericardial effusion  4 (2.14)  21 (31.8)  <0.001  Cardiac tamponade  0 (0.00)  8 (12.1)  <0.001  Aortic rupture  0 (0.00)  3 (4.55)  0.017  Preoperative ventilation  0 (0.00)  2 (3.03)  0.07  Cardiogenic shock  0 (0.00)  4 (6.06)  0.004  Mesenteric ischaemia  0 (0.00)  1 (1.52)  0.26  Site of intimal tear         Aortic root    28 (42.4)     Sinotubular junction    3 (4.55)     Ascending aorta    21 (31.8)     Other    13 (19.7)    Characteristics  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Age (years)  63 (52–73)  66 (51–73)  0.77  Male  127 (67.9)  45 (68.2)  0.97  BMI  27 (24–30)  27 (25–29)  0.67  Logistic EuroSCORE  5.58 (2.17–9.17)  8.86 (4.23–14.0)  0.001  NYHA class      <0.001   I  75 (40.1)  50 (75.8)     II  79 (42.2)  8 (12.1)     III  33 (17.6)  8 (12.1)    Hypertension  109 (58.3)  35 (53.0)  0.46  Hypercholesterolaemia  60 (32.1)  11 (16.7)  0.017  Smoking  84 (44.9)  18 (27.3)  0.022  Pulmonary disease  14 (7.49)  6 (9.09)  0.68  CKD stage      <0.001   1  75 (40.1)  15 (22.7)     2  89 (47.6)  28 (42.2)     3  20 (10.7)  21 (31.8)     4  2 (1.07)  1 (1.52)     5  1 (0.53)  0 (0.00)    Preoperative dialysis  1 (0.53)  1 (1.52)  0.45  TIA/CVA  19 (10.2)  9 (13.6)  0.40  Previous MI  13 (6.95)  5 (7.58)  0.79  Peripheral vascular disease  11 (5.88)  0 (0.00)  0.07  LV function      0.10   Good  153 (81.8)  61 (92.4)     Moderate  30 (16.0)  5 (7.58)     Poor  4 (2.14)  0 (0.00)    RV function      <0.001   Good  176 (94.1)  50 (75.8)     Moderate  9 (4.81)  15 (22.7)     Poor  1 (0.53)  0 (0.00)    Aortic valve cuspidity      <0.001   Unicuspid  3 (1.60)  0 (0.00)     Bicuspid  70 (37.4)  1 (1.52)     Tricuspid  113 (60.4)  65 (98.5)     Quadricuspid  1 (0.53)  0 (0.00)    Marfan syndrome  20 (10.7)  6 (9.09)  0.71  Other connective tissue disease  5 (2.67)  1 (1.52)  0.59  Aortic regurgitation  133 (71.1)  45 (68.2)  0.65  Pericardial effusion  4 (2.14)  21 (31.8)  <0.001  Cardiac tamponade  0 (0.00)  8 (12.1)  <0.001  Aortic rupture  0 (0.00)  3 (4.55)  0.017  Preoperative ventilation  0 (0.00)  2 (3.03)  0.07  Cardiogenic shock  0 (0.00)  4 (6.06)  0.004  Mesenteric ischaemia  0 (0.00)  1 (1.52)  0.26  Site of intimal tear         Aortic root    28 (42.4)     Sinotubular junction    3 (4.55)     Ascending aorta    21 (31.8)     Other    13 (19.7)    Values are n (%) or median (interquartile range). BMI: body mass index; CKD: chronic kidney disease; CVA: cerebrovascular accident; LV: left ventricle; MI: myocardial infarction; NYHA: New York Heart Association; RV: right ventricle; TIA: transient ischaemic attack. Mortality There was no significant difference in mortality between the aneurysm (10/187, 5.3%) and dissection (7/66, 10.6%) groups (P = 0.139) during the follow-up period. Mean aortic diameter Table 2 shows the mean aortic diameter for aneurysm and dissection groups according to aortic location. All acute Type A aortic dissections occurred at mean aortic diameters <5.5 cm between the aortic root and mid-ascending aorta. Table 2: Mean aortic diameter according to aortic location Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  P-value  Mid-sinus  4.53 ± 0.78  4.42 ± 0.82  0.13  Sinotubular junction  3.87 ± 0.79  4.05 ± 1.18  0.70  Mid-ascending  4.97 ± 1.12  5.20 ± 1.26  0.31  Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  P-value  Mid-sinus  4.53 ± 0.78  4.42 ± 0.82  0.13  Sinotubular junction  3.87 ± 0.79  4.05 ± 1.18  0.70  Mid-ascending  4.97 ± 1.12  5.20 ± 1.26  0.31  Values are mean ± standard deviation. Table 2: Mean aortic diameter according to aortic location Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  P-value  Mid-sinus  4.53 ± 0.78  4.42 ± 0.82  0.13  Sinotubular junction  3.87 ± 0.79  4.05 ± 1.18  0.70  Mid-ascending  4.97 ± 1.12  5.20 ± 1.26  0.31  Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  P-value  Mid-sinus  4.53 ± 0.78  4.42 ± 0.82  0.13  Sinotubular junction  3.87 ± 0.79  4.05 ± 1.18  0.70  Mid-ascending  4.97 ± 1.12  5.20 ± 1.26  0.31  Values are mean ± standard deviation. Indexed aortic areas Table 3 shows the median IAAs, and Fig. 1 the overall distribution of IAAs, for aneurysm and dissection groups categorised according to aortic location. These were largest at the mid-ascending aorta, where the 10 cm2/m cut-off was exceeded, followed by those at the mid-sinus level where values approached abnormal levels. Median IAAs were not significantly different between groups at any aortic location. Table 3: Median indexed aortic areas (cm2/m) according to aortic location Aortic location  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Mid-sinus  9.37 (2.67–21.2)  8.01 (4.04–24.7)  0.09  Sinotubular junction  6.49 (2.03–20.6)  6.69 (2.77–35.6)  0.68  Mid-ascending  10.6 (3.07–41.9)  11.2 (3.37–36.5)  0.32  Aortic location  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Mid-sinus  9.37 (2.67–21.2)  8.01 (4.04–24.7)  0.09  Sinotubular junction  6.49 (2.03–20.6)  6.69 (2.77–35.6)  0.68  Mid-ascending  10.6 (3.07–41.9)  11.2 (3.37–36.5)  0.32  Values are median (range). Table 3: Median indexed aortic areas (cm2/m) according to aortic location Aortic location  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Mid-sinus  9.37 (2.67–21.2)  8.01 (4.04–24.7)  0.09  Sinotubular junction  6.49 (2.03–20.6)  6.69 (2.77–35.6)  0.68  Mid-ascending  10.6 (3.07–41.9)  11.2 (3.37–36.5)  0.32  Aortic location  Aneurysm group (n = 187)  Dissection group (n = 66)  P-value  Mid-sinus  9.37 (2.67–21.2)  8.01 (4.04–24.7)  0.09  Sinotubular junction  6.49 (2.03–20.6)  6.69 (2.77–35.6)  0.68  Mid-ascending  10.6 (3.07–41.9)  11.2 (3.37–36.5)  0.32  Values are median (range). Figure 1: View largeDownload slide Distribution of indexed aortic areas in aneurysm group (left-sided bars) and dissection group (right-sided bars) according to aortic location. Asc: ascending aorta; STJ: sinotubular junction. Figure 1: View largeDownload slide Distribution of indexed aortic areas in aneurysm group (left-sided bars) and dissection group (right-sided bars) according to aortic location. Asc: ascending aorta; STJ: sinotubular junction. Indexed aortic areas >10 cm2/m Numbers of patients with IAAs exceeding 10 cm2/m are shown in Table 4. The results reflect the fact that the IAA can exceed 10 cm2/m at several aortic locations in a given patient. The highest IAA was found at the mid-ascending aorta location, where 56.7% of aneurysm group patients, and 60.6% of dissection group patients, had abnormally high IAAs. At the mid-sinuses, 39.6% of aneurysm group patients and 25.8% of dissection group patients had IAAs >10 cm2/m. Table 4: Patients with indexed aortic area >10 cm2/ma Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  Mid-sinus  74 (39.6)  17 (25.8)  Sinotubular junction  20 (10.7)  13 (19.7)  Mid-ascending  106 (56.7)  40 (60.6)  Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  Mid-sinus  74 (39.6)  17 (25.8)  Sinotubular junction  20 (10.7)  13 (19.7)  Mid-ascending  106 (56.7)  40 (60.6)  a Indexed aortic area >10 cm2/m can occur at ≥1 aortic location in the same patient. Table 4: Patients with indexed aortic area >10 cm2/ma Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  Mid-sinus  74 (39.6)  17 (25.8)  Sinotubular junction  20 (10.7)  13 (19.7)  Mid-ascending  106 (56.7)  40 (60.6)  Aortic location  Aneurysm group (n = 187), n (%)  Dissection group (n = 66), n (%)  Mid-sinus  74 (39.6)  17 (25.8)  Sinotubular junction  20 (10.7)  13 (19.7)  Mid-ascending  106 (56.7)  40 (60.6)  a Indexed aortic area >10 cm2/m can occur at ≥1 aortic location in the same patient. Mean indexed aortic areas corresponding to aortic diameter in aneurysms Figure 2 demonstrates the mean IAA for patients with aortic diameters <4.0 cm, 4.0–4.5 cm, 4.5–5.0 cm, 5.0–5.5 cm and >5.5 cm at mid-sinus, sinotubular junction and mid-ascending aortic locations. The mean IAA is shown to increase linearly with increasing aortic diameter as expected. Importantly, abnormally high mean IAAs first emerge at aortic diameters of 4.5–5.0 cm. The mean IAA is 11.9 cm2/m at an aortic diameter of 5.0–5.5 cm and 17.3 cm2/m at >5.5 cm. Figure 2: View largeDownload slide Mean indexed aortic area corresponding to aortic diameter in aneurysms. Figure 2: View largeDownload slide Mean indexed aortic area corresponding to aortic diameter in aneurysms. Table 5 shows the proportion of patients with IAAs >10 cm2/m according to aortic diameter. No patients with aortic diameters <4.0 cm had an abnormal IAA exceeding 10 cm2/m. Within the 4.0–4.5 cm subgroup, only 1 of 108 (0.9%) patients had an abnormal IAA. Abnormal IAAs were noted in 57 of 116 (49.1%) patients in the 4.5–5.0 cm subgroup, rising to 67 of 68 (98.5%) patients in the 5.0–5.5 cm subgroup and 72 of 72 (100%) patients in the >5.5 cm subgroups. Table 5: Proportion of aneurysm patients with indexed aortic area >10 cm2/m according to aortic diameters Aortic diameter (cm)  Indexed aortic areas >10 cm2/m, N/n (%)  <4.0  0/212 (0.0)  4.0–4.5  1/108 (0.9)  4.5–5.0  57/116 (49.1)  5.0–5.5  67/68 (98.5)  >5.5  72/72 (100)  Aortic diameter (cm)  Indexed aortic areas >10 cm2/m, N/n (%)  <4.0  0/212 (0.0)  4.0–4.5  1/108 (0.9)  4.5–5.0  57/116 (49.1)  5.0–5.5  67/68 (98.5)  >5.5  72/72 (100)  Table 5: Proportion of aneurysm patients with indexed aortic area >10 cm2/m according to aortic diameters Aortic diameter (cm)  Indexed aortic areas >10 cm2/m, N/n (%)  <4.0  0/212 (0.0)  4.0–4.5  1/108 (0.9)  4.5–5.0  57/116 (49.1)  5.0–5.5  67/68 (98.5)  >5.5  72/72 (100)  Aortic diameter (cm)  Indexed aortic areas >10 cm2/m, N/n (%)  <4.0  0/212 (0.0)  4.0–4.5  1/108 (0.9)  4.5–5.0  57/116 (49.1)  5.0–5.5  67/68 (98.5)  >5.5  72/72 (100)  Relationship between indexed aortic areas and aortic diameter in aneurysms Patients with an IAA >10 cm2/m (the at-risk population) at mid-sinus, sinotubular junction and mid-ascending aortic locations, were categorised into groups with IAA ranges 10–12 cm2/m, 12–14 cm2/m and >14 cm2/m. There were 74 patients, 20 patients and 106 patients who at mid-sinus, sinotubular junction and mid-ascending aorta location, respectively, had IAAs >10 cm2/m. The mean of the corresponding aortic diameters for each range was then calculated (Table 6). Table 6: Relationship between mean aortic diameters and indexed aortic area ranges in aneurysms   Mean aortic diameter (cm) according to aortic location (n, % of all patients with indexed aortic area >10 cm2/m per aortic location)   Indexed aortic area (cm2/m)  Mid-sinus  Sinotubular junction  Mid-ascending  N = 74  N = 20  N =106  10–12  4.98 (45, 60.0)  5.04 (9, 42.9)  4.92 (46, 43.4)  12–14  5.46 (18, 24.3)  5.35 (4, 20.0)  5.37 (17, 15.4)  >14  6.25 (11, 14.7)  6.19 (7, 33.3)  6.54 (43, 40.6)    Mean aortic diameter (cm) according to aortic location (n, % of all patients with indexed aortic area >10 cm2/m per aortic location)   Indexed aortic area (cm2/m)  Mid-sinus  Sinotubular junction  Mid-ascending  N = 74  N = 20  N =106  10–12  4.98 (45, 60.0)  5.04 (9, 42.9)  4.92 (46, 43.4)  12–14  5.46 (18, 24.3)  5.35 (4, 20.0)  5.37 (17, 15.4)  >14  6.25 (11, 14.7)  6.19 (7, 33.3)  6.54 (43, 40.6)  Table 6: Relationship between mean aortic diameters and indexed aortic area ranges in aneurysms   Mean aortic diameter (cm) according to aortic location (n, % of all patients with indexed aortic area >10 cm2/m per aortic location)   Indexed aortic area (cm2/m)  Mid-sinus  Sinotubular junction  Mid-ascending  N = 74  N = 20  N =106  10–12  4.98 (45, 60.0)  5.04 (9, 42.9)  4.92 (46, 43.4)  12–14  5.46 (18, 24.3)  5.35 (4, 20.0)  5.37 (17, 15.4)  >14  6.25 (11, 14.7)  6.19 (7, 33.3)  6.54 (43, 40.6)    Mean aortic diameter (cm) according to aortic location (n, % of all patients with indexed aortic area >10 cm2/m per aortic location)   Indexed aortic area (cm2/m)  Mid-sinus  Sinotubular junction  Mid-ascending  N = 74  N = 20  N =106  10–12  4.98 (45, 60.0)  5.04 (9, 42.9)  4.92 (46, 43.4)  12–14  5.46 (18, 24.3)  5.35 (4, 20.0)  5.37 (17, 15.4)  >14  6.25 (11, 14.7)  6.19 (7, 33.3)  6.54 (43, 40.6)  A considerable 84.3% of patients with an IAA >10 cm2/m based on mid-sinus measurements had a mean aortic diameter below the current 5.5 cm threshold for surgical intervention. Similarly, at the sinotubular junction, some 62.9% of patients with an abnormal IAA had a mean aortic diameter <5.5 cm. At the mid-ascending aortic location, 58.8% of the at-risk patients with an abnormally high IAA had a mean aortic diameter <5.5 cm. Only 139 (69.5%) patients out of the entire cohort of 200 patients who have an IAA >10 cm2/m between the mid-sinus of Valsalva and mid-ascending aorta would be eligible for surgical intervention for the aortic root/ascending aorta on the basis of existing guidelines. DISCUSSION We performed a retrospective observational study to assess the correlation between aortic diameter and IAA in 187 patients with thoracic aortic aneurysm and 66 patients with acute Type A dissection. Our study population was limited solely to those patients presenting to us for surgical management of diseased aortas. Of course, there may be a very large group of patients undergoing surveillance for mild proximal aortic dilatation, in whom the IAA may exceed 10 cm2/m, but who have not yet been selected for surgical intervention based on traditional aortic size criteria, or who have not undergone acute dissection. We noted that dissected aortas had mean aortic root/mid-ascending diameters <5.5 cm on presentation (Table 2). Considering that the diameter of an acutely dissected aorta will likely increase compared to its predissected state, with haematoma expansion and resultant separation of the aortic wall layers, this suggests that the <5.5 cm mean diameter of the dissected aortas seen in our group would have been even smaller prior to the dissection event [4]. Current guidelines advocate prophylactic aortic replacement at absolute aortic diameters of 4.5–5.5 cm in tricuspid and bicuspid aortic valves, or 4.0–4.5 cm with inherited aortopathies, such as Marfan and Ehlers–Danlos syndromes [3]. However, 40% of patients presenting with Type A aortic dissection have an aortic diameter <5 cm, at which size 15% of patients with Marfan syndrome, who have the highest lifetime risk of aortic dissection, will undergo dissection or rupture [4–6]. Loss of aortic elastic tissue in bicuspid-valve related aneurysms means dissection risk in this patient population is not dissimilar to those with Marfan syndrome [2, 7]. This questions the true prognostic value of the absolute aortic diameter, and emphasises the need for optimal timing of surgical intervention, especially in those patients under surveillance who do not meet established size criteria for surgery, but may still be at significant risk of dissection. Additionally, utilization of absolute aortic diameter in existing guidelines fails to account for size, height and gender differences in aortic dimensions, as well as the irregular elliptical shape of the aorta. More recently, there has been greater emphasis on indexing aortic cross-sectional area to patient height for dissection and mortality risk stratification in dilated aortas with both bicuspid and trileaflet aortic valves [1, 2, 5]. An IAA >10 cm2/m has been determined as a cut-off value after which prophylactic aortic root with or without ascending aortic replacement is advocated for curative potential and thus to improve long-term survival [1]. In the present study, we found that median IAAs were comparable between groups from the mid-sinus to the mid-ascending aorta (Table 3). Median IAAs exceeded the critical 10 cm2/m point at the ascending aortic location, suggesting that aneurysm patients may be at risk of dissection once an IAA of 10 cm2/m is exceeded. Based on measurements at the mid-ascending aorta, over half of the patients (106/187) in the aneurysm group were shown to be at risk with IAAs >10 cm2/m; the same was true for over a third (74/187) of aneurysm patients based on mid-sinus measurements (Table 4). We showed that between 57.8–84.3% (Table 6) of our study population (depending on the aortic location considered) who were at increased risk of aortic complications according to IAAs, would not have been eligible for aortic surgery according to contemporary guidelines. A previous observational study found an abnormally high IAA in 44% of patients with aortic root diameters at 4.5–5.5 cm [1]. In our study, 124 of 184 (67.4%) patients with aortic diameters 4.5–5.5 cm were found to have abnormally high IAAs (Table 5). Thus, the present study confirms that a significant proportion of patients with aortic diameters that do not reach the size criteria recommended for elective aortic aneurysm surgery have an abnormal IAA, indicating their increased risk of aortic complications. Emergency surgery for acute Type A dissection aims to prevent the potentially fatal complications of aortic rupture, acute aortic regurgitation, pericardial tamponade, acute coronary occlusion, stroke and limb and organ ischaemia. With improving understanding of the underlying pathophysiology, enhanced recognition with modern imaging modalities, prompt referral to cardiothoracic services and accruing surgical experience, survival rates in acute aortic syndrome have gradually improved in recent years. Hospital mortality has been reported at 10–25% in the current era across all ages [5, 8]. Elective aortic root and/or ascending aortic replacement carries an even lower operative risk at experienced centres with a high-volume case output [9]. This emphasises the importance of accurately identifying at-risk individuals with thoracic aortic aneurysms for prophylactic surgery. The purpose of this isolated retrospective observational study was not to determine a novel size threshold for the selection of patients for aortic surgical intervention. Rather, we aimed to elucidate the less well-studied association between absolute aortic diameter and IAA. It is now well-recognised that aortic dissection may occur in a significant cohort of patients at aortic diameters less than the 5.5 cm proposed for surgical repair [2, 5, 6]. Considering this, and in conjunction with the present study’s findings that IAA is abnormally increased in 67.4% of patients with aortic diameter 4.5–5.5 cm (Table 5), rendering them at higher risk of aortic complications, we suggest that an IAA >10 cm2/m should be considered as a potential risk factor in thoracic aortic disease, and be further evaluated as a criterion for aortic surgery. Large-scale prospective multicentre registries with accurate long-term follow-up of outcomes are needed to clarify the prognostic value of the IAA in varied surgical populations, including bicuspid and trileaflet aortic valves, as well as Marfan’s syndrome, which confers the greatest dissection risk. This would ideally afford patients at risk of aneurysm-related dissection or rupture the chance for potentially curative surgery, and at lower operative risk when performed at dedicated, high-volume aortic centres [9–12]. Limitations This is a retrospective observational study with inherent potential for associated selection bias. However, since our tertiary institution is a referral centre for acute Type A aortic dissection, patients submitted to aortic surgery at other tertiary cardiac centres would share similar characteristics, namely aortic diameter and IAA, to those in our population. Despite examining all-comers submitted to thoracic aortic aneurysm or dissection surgery over a predefined time period, our study population did not comprise large numbers of patients with inherited aortopathies or bicuspid aortic valves, since these are monitored closely in established surveillance programmes and selected for early surgery. Thus the results of our analysis may be transferable to other major aortic centres in non-aortopathy populations. We utilized the formula π × r2 for aortic area calculations which may be less suitable for eccentric aortic shapes where a planimetry technique may be more appropriate [1]. Finally, whilst the results of the present study suggest IAA >10 cm2/m may be useful as a risk factor in thoracic aortic disease, validation of the IAA in comparative analyses would be required prior to its adoption in preoperative risk evaluation. CONCLUSIONS This study confirms that a large proportion of patients with thoracic aortic aneurysms have IAAs >10 cm2/m corresponding to absolute aortic dimensions that do not satisfy contemporary guideline criteria for aortic surgical intervention, despite being at increased risk of aortic complications. This cohort of patients may benefit from undergoing earlier surgery performed at high-volume centres with special aortic expertise, and at more conservative aortic size ranges, which need verification in larger prospective studies with extended follow-up. Conflict of interest: none declared. REFERENCES 1 Masri A, Kalahasti V, Svensson LG, Roselli EE, Johnston D, Hammer D et al.   Aortic cross-sectional area/height ratio and outcomes in patients with a trileaflet aortic valve and a dilated aorta. Circulation  2016; 134: 1724– 37. Google Scholar CrossRef Search ADS PubMed  2 Svensson LG, Kim KH, Lytle BW, Cosgrove DM. Relationship of aortic cross-sectional area to height ratio and the risk of aortic dissection in patients with bicuspid aortic valves. J Thorac Cardiovasc Surg  2003; 126: 892– 3. Google Scholar CrossRef Search ADS PubMed  3 Hiratzka LF, Bakris GL, Beckman JA, Bersin RM, Carr VF, Casey DEJr et al.   2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with Thoracic Aortic Disease: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines, American Association for Thoracic Surgery, American College of Radiology, American Stroke Association, Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society of Thoracic Surgeons, and Society for Vascular Medicine. Circulation  2010; 121: e266– 369. Google Scholar CrossRef Search ADS PubMed  4 Pape LA, Tsai TT, Isselbacher EM, Oh JK, O'Gara PT, Evangelista A et al.   Aortic diameter >or = 5.5 cm is not a good predictor of type A aortic dissection: observations from the International Registry of Acute Aortic Dissection (IRAD). Circulation  2007; 116: 1120– 7. Google Scholar CrossRef Search ADS PubMed  5 Svensson LG, Khitin L. Aortic cross-sectional area/height ratio timing of aortic surgery in asymptomatic patients with Marfan syndrome. J Thorac Cardiovasc Surg  2002; 123: 360– 1. Google Scholar CrossRef Search ADS PubMed  6 Gott VL, Greene PS, Alejo DE, Cameron DE, Naftel DC, Miller DC et al.   Replacement of the aortic root in patients with Marfan’s syndrome. N Engl J Med  1999; 340: 1307– 13. Google Scholar CrossRef Search ADS PubMed  7 Isselbacher EM, Lino Cardenas CL, Lindsay ME. Hereditary influence in thoracic aortic aneurysm and dissection. Circulation  2016; 133: 2516– 28. Google Scholar CrossRef Search ADS PubMed  8 Rylski B, Hoffman I, Beyersdorf F, Suedkamp M, Siepe M, Nitsch B et al.   Acute aortic dissection type A: age-related management and outcomes reported in the German Registry for Acute Aortic Dissection Type A (GERAADA) of over 2000 patients. Ann Surg  2014; 259: 598– 604. Google Scholar CrossRef Search ADS PubMed  9 Bilkhu R, Youssefi P, Soppa G, Sharma R, Child A, Edsell M et al.   Aortic root surgery: does high surgical volume and a consistent perioperative approach improve outcome? Semin Thorac Cardiovasc Surg  2016; 28: 302– 9. Google Scholar CrossRef Search ADS PubMed  10 Svensson LG, Pillai ST, Rajeswaran J, Desai MY, Griffin B, Grimm R et al.   Long-term survival, valve durability, and reoperation for 4 aortic root procedures combined with ascending aorta replacement. J Thorac Cardiovasc Surg  2016; 151: 764– 74. Google Scholar CrossRef Search ADS PubMed  11 Caceres M, Ma Y, Rankin JS, Saha-Chaudhuri P, Englum BR, Gammie JS et al.   Mortality characteristics of aortic root surgery in North America. Eur J Cardiothorac Surg  2014; 46: 887– 93. Google Scholar CrossRef Search ADS PubMed  12 Masri A, Kalahasti V, Alkharabsheh S, Svensson LG, Sabik JF, Roselli EE et al.   Characteristics and long-term outcomes of contemporary patients with bicuspid aortic valves. J Thorac Cardiovasc Surg  2016; 151: 1650– 9. Google Scholar CrossRef Search ADS PubMed  © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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European Journal of Cardio-Thoracic SurgeryOxford University Press

Published: Mar 15, 2018

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