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Anaortic coronary surgery using the Π-circuit is associated with a low incidence of perioperative neurological complications

Anaortic coronary surgery using the Π-circuit is associated with a low incidence of perioperative... Abstract OBJECTIVES Our goal was to compare the observed and the expected rates of postoperative cerebrovascular accidents (CVA) in a large cohort of consecutive patients undergoing off-pump coronary artery bypass grafting (CABG) using the ∏-circuit as a no-touch technique. METHODS From January 2001 to May 2016, 3081 patients were consecutively submitted to an off-pump CABG operation using the ∏-circuit. A CVA was defined as a neurological deficit, lasting less (transient ischaemic attack) or more (stroke) than 24 h, diagnosed by a neurologist and confirmed by a computed tomography or magnetic resonance imaging scan of the brain. The primary end point was to compare the observed and the expected rates of CVAs; the latter was obtained using the Society of Thoracic Surgeons’ calculator. The secondary end point was to compare the observed and the expected mortality rates using the Society of Thoracic Surgeons’ calculator and the prevalence of postoperative complications. Moreover, we identified some subgroups at higher risk. RESULTS The postoperative rate of CVAs was 0.5% (14 cases): 2 (0.1%) were transient ischaemic attacks and 12 (0.4%) were strokes. The mean expected CVA rate (1.6%) was significantly higher than the observed rate (P < 0.001). None of patients who experienced postoperative CVAs died. The observed mortality was 1.3% (40 patients) vs the expected mortality (2.6%), which was significantly higher (P < 0.001). Multivariable analysis identified age >70 years old, diabetes, extracardiac vasculopathy and chronic renal failure as risk factors for postoperative CVAs. However, in all the subgroups of risk, except for those with chronic renal failure, the use of the ∏-circuit was associated with a low rate of CVAs. CONCLUSIONS The ∏-circuit should be included as a possible choice among no-touch techniques. The observed rate of CVAs of 75% is lower than the expected rate. Coronary artery bypass grafting, No-touch aorta, Anaortic, Arterial revascularization INTRODUCTION Coronary artery bypass grafting (CABG) is still considered the gold standard of treatment for 3-vessel and left main coronary artery disease, both in the general population and in patients with diabetes, as confirmed by the SYNTAX (Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery) and FREEDOM (Strategies for Multivessel Revascularization in Patients with Diabetes) trials [1, 2]. One of the drawbacks of CABG compared with percutaneous coronary intervention is the high risk of having a cerebrovascular accident (CVA) [3]. A postoperative CVA in the population having CABG is an uncommon but harmful complication, ranging from 0.4% to 3.5% [4–15]. Off-pump coronary artery bypass (OPCAB) per se failed to reduce the postoperative occurrence of CVAs, because a proximal anastomosis has to be done with the aid of a partial clamp in most cases [16–18]. Hence, different anaortic strategies were developed to minimize the risk of postoperative strokes: ‘no-touch’ techniques [use of bilateral internal mammary artery (IMA) in situ or as a composite graft, a Y or T graft, or use of the left or right IMA as a source of blood for the saphenous vein (SV) or radial artery] and the use of proximal anastomotic devices (PADs) to perform proximal anastomoses, either automatically or hand-sewn, on the aorta without partial clamping. Researchers, in recent meta-analyses, compared all these strategies to OPCAB with partial clamping and to on-pump CABG, reporting a significant reduction of stroke, especially when ‘no-touch’ techniques were used [19, 20]. Among the ‘no-touch’ techniques, we proposed the use of the ∏-circuit, which foresees the use of different conduits, either arterial or venous, grafted together, having 1 or 2 mammary arteries as the blood source [21]. Hence, we sought to compare the observed and the expected rates of postoperative CVAs in a large cohort of consecutive patients undergoing CABG using the ∏-circuit as a no-touch technique. METHODS Study population From January 2001 to May 2016, the ∏-circuit was used in all 3081 patients with coronary artery disease admitted for CABG at the Henry Durant Hospital. The institutional review board approved this retrospective observational study. Pre- and operative data are summarized in Table 1. Table 1: Preoperative and operative data Variables n = 3081 Age (years; continuous), mean ± SD 66 ± 10 Age class (years), n (%)  ≤60 942 (31)  61–70 1049 (34)  >70 1090 (35) Gender, n (%)  Female 412 (13)  Male 2669 (87) Emergency, n (%) 255 (8) Ejection fraction (%), n (%)  >50 2068 (67)  31–50 812 (26)  ≤30 201 (7) BMI (kg/m2), mean ± SD 28 ± 5 Obese, n (%) 919 (29.8) Diabetes, n (%) 1034 (34) Hypercholesterolaemia, n (%) 1654 (54) Hypertension, n (%) 1655 (54) Chronic pulmonary disease, n (%) 221 (7) CRF (creatinine >200 μmol/l), n (%) 61 (2) Preoperative AF, n (%) 185 (4) ECV, n (%) 281 (9) Previous CVA, n (%) 124 (4)  Stroke 75  TIA 49 Preoperative IABP, n (%) 64 (2) Previous cardiac operation, n (%) 149 (5) Off-pump conversion to on-pump, n (%) 4 (0.1) Mean number of anastomoses, mean ± SD 2.8 ± 0.9 Mean number of arterial anastomoses, mean ± SD 2.6 ± 1.0 Conduits grafted to coronary bed, n (%)  LIMA 3027 (98)  RIMA 2178 (71)  RA 807 (26)  SVG 536 (17) Variables n = 3081 Age (years; continuous), mean ± SD 66 ± 10 Age class (years), n (%)  ≤60 942 (31)  61–70 1049 (34)  >70 1090 (35) Gender, n (%)  Female 412 (13)  Male 2669 (87) Emergency, n (%) 255 (8) Ejection fraction (%), n (%)  >50 2068 (67)  31–50 812 (26)  ≤30 201 (7) BMI (kg/m2), mean ± SD 28 ± 5 Obese, n (%) 919 (29.8) Diabetes, n (%) 1034 (34) Hypercholesterolaemia, n (%) 1654 (54) Hypertension, n (%) 1655 (54) Chronic pulmonary disease, n (%) 221 (7) CRF (creatinine >200 μmol/l), n (%) 61 (2) Preoperative AF, n (%) 185 (4) ECV, n (%) 281 (9) Previous CVA, n (%) 124 (4)  Stroke 75  TIA 49 Preoperative IABP, n (%) 64 (2) Previous cardiac operation, n (%) 149 (5) Off-pump conversion to on-pump, n (%) 4 (0.1) Mean number of anastomoses, mean ± SD 2.8 ± 0.9 Mean number of arterial anastomoses, mean ± SD 2.6 ± 1.0 Conduits grafted to coronary bed, n (%)  LIMA 3027 (98)  RIMA 2178 (71)  RA 807 (26)  SVG 536 (17) AF: atrial fibrillation; BMI: body mass index; CRF: chronic renal failure; CVA: cerebrovascular accident; ECV: extracardiac vasculopathy; IABP: intra-aortic balloon pump; LIMA: left internal mammary artery; RA: radial artery; RIMA: right internal mammary artery; SD: standard deviation; SVG: saphenous vein graft; TIA: transient ischaemic attack. Table 1: Preoperative and operative data Variables n = 3081 Age (years; continuous), mean ± SD 66 ± 10 Age class (years), n (%)  ≤60 942 (31)  61–70 1049 (34)  >70 1090 (35) Gender, n (%)  Female 412 (13)  Male 2669 (87) Emergency, n (%) 255 (8) Ejection fraction (%), n (%)  >50 2068 (67)  31–50 812 (26)  ≤30 201 (7) BMI (kg/m2), mean ± SD 28 ± 5 Obese, n (%) 919 (29.8) Diabetes, n (%) 1034 (34) Hypercholesterolaemia, n (%) 1654 (54) Hypertension, n (%) 1655 (54) Chronic pulmonary disease, n (%) 221 (7) CRF (creatinine >200 μmol/l), n (%) 61 (2) Preoperative AF, n (%) 185 (4) ECV, n (%) 281 (9) Previous CVA, n (%) 124 (4)  Stroke 75  TIA 49 Preoperative IABP, n (%) 64 (2) Previous cardiac operation, n (%) 149 (5) Off-pump conversion to on-pump, n (%) 4 (0.1) Mean number of anastomoses, mean ± SD 2.8 ± 0.9 Mean number of arterial anastomoses, mean ± SD 2.6 ± 1.0 Conduits grafted to coronary bed, n (%)  LIMA 3027 (98)  RIMA 2178 (71)  RA 807 (26)  SVG 536 (17) Variables n = 3081 Age (years; continuous), mean ± SD 66 ± 10 Age class (years), n (%)  ≤60 942 (31)  61–70 1049 (34)  >70 1090 (35) Gender, n (%)  Female 412 (13)  Male 2669 (87) Emergency, n (%) 255 (8) Ejection fraction (%), n (%)  >50 2068 (67)  31–50 812 (26)  ≤30 201 (7) BMI (kg/m2), mean ± SD 28 ± 5 Obese, n (%) 919 (29.8) Diabetes, n (%) 1034 (34) Hypercholesterolaemia, n (%) 1654 (54) Hypertension, n (%) 1655 (54) Chronic pulmonary disease, n (%) 221 (7) CRF (creatinine >200 μmol/l), n (%) 61 (2) Preoperative AF, n (%) 185 (4) ECV, n (%) 281 (9) Previous CVA, n (%) 124 (4)  Stroke 75  TIA 49 Preoperative IABP, n (%) 64 (2) Previous cardiac operation, n (%) 149 (5) Off-pump conversion to on-pump, n (%) 4 (0.1) Mean number of anastomoses, mean ± SD 2.8 ± 0.9 Mean number of arterial anastomoses, mean ± SD 2.6 ± 1.0 Conduits grafted to coronary bed, n (%)  LIMA 3027 (98)  RIMA 2178 (71)  RA 807 (26)  SVG 536 (17) AF: atrial fibrillation; BMI: body mass index; CRF: chronic renal failure; CVA: cerebrovascular accident; ECV: extracardiac vasculopathy; IABP: intra-aortic balloon pump; LIMA: left internal mammary artery; RA: radial artery; RIMA: right internal mammary artery; SD: standard deviation; SVG: saphenous vein graft; TIA: transient ischaemic attack. Surgery The technical details of the ∏-circuit were reported previously [21]. Briefly, the ∏-circuit represents a net that is built using 1 mammary artery (in general the left IMA) or both IMAs for the inflow. A radial artery or an SV or segments of the left or the right IMA can be used as an elongation or a side branch of the main conduit, depending on what is needed (Figs 1–3). The composite graft(s) is (are) preformed before the procedure starts and is (are) used to graft all the stenosed coronary vessels. The ∏-circuit is completely flexible, and the arrangements of its components can vary according to the needs of the individual patient. The aorta is never touched. Figure 1: View largeDownload slide Coronary angiogram taken 1 year after surgery. The Π-circuit between the left and the proximal segments of the right internal mammary artery (RIMA) (Y graft) and between the LIMA and the distal segment of the RIMA (E graft). The arrow head indicates end-to-end anastomosis between the LIMA and the proximal segment of the free RIMA. fRIMAd: free right internal mammary artery, distal segment; fRIMAp: free right internal mammary artery, proximal segment; lad: left anterior descending artery; LIMA: left internal mammary artery; om: obtuse marginal artery; pda: posterior descending artery. Figure 1: View largeDownload slide Coronary angiogram taken 1 year after surgery. The Π-circuit between the left and the proximal segments of the right internal mammary artery (RIMA) (Y graft) and between the LIMA and the distal segment of the RIMA (E graft). The arrow head indicates end-to-end anastomosis between the LIMA and the proximal segment of the free RIMA. fRIMAd: free right internal mammary artery, distal segment; fRIMAp: free right internal mammary artery, proximal segment; lad: left anterior descending artery; LIMA: left internal mammary artery; om: obtuse marginal artery; pda: posterior descending artery. Figure 2: View largeDownload slide Computed tomography angiography 12 years after surgery showing the Π-circuit between the LIMA and the right internal mammary artery (Y graft) and the right internal mammary artery and the distal segment of the LIMA. CX: circumflex artery; diag: diagonal branch; fLIMAd: free left internal mammary artery, distal segment; fRIMA: free right internal mammary artery; lad: left anterior descending artery; LIMA: left internal mammary artery; Mg: marginal branch. Figure 2: View largeDownload slide Computed tomography angiography 12 years after surgery showing the Π-circuit between the LIMA and the right internal mammary artery (Y graft) and the right internal mammary artery and the distal segment of the LIMA. CX: circumflex artery; diag: diagonal branch; fLIMAd: free left internal mammary artery, distal segment; fRIMA: free right internal mammary artery; lad: left anterior descending artery; LIMA: left internal mammary artery; Mg: marginal branch. Figure 3: View largeDownload slide Coronary angiography 12 years after surgery. The Π-circuit between the RIMA and an SVG. lad: left anterior descending artery; pda: posterior descending artery; RIMA: right internal mammary artery; SVG: saphenous vein graft. Figure 3: View largeDownload slide Coronary angiography 12 years after surgery. The Π-circuit between the RIMA and an SVG. lad: left anterior descending artery; pda: posterior descending artery; RIMA: right internal mammary artery; SVG: saphenous vein graft. Definitions, end points and statistics A CVA was defined as a global or focal neurological deficit, lasting less [transient ischaemic attack] or more (stroke) than 24 h after surgery, diagnosed by a neurologist and confirmed by a brain computed tomography (CT) or magnetic resonance imaging scan. A stroke was defined as a focal or global cerebral dysfunction of presumed vascular origin lasting more than 24 h. A transient ischaemic attack was defined as a focal cerebral dysfunction of presumed vascular origin that resolved completely within 24 h [3]. The primary end point was to compare the observed stroke rate with the expected rate obtained using the Society of Thoracic Surgeons’ calculator. The secondary end point was to compare the expected and the observed mortality rates using the Society of Thoracic Surgeons’ calculator (www.sts.org). Categorical data were reported as numbers and percentages, and continuous data were reported as the mean and standard deviation in the case of normal distribution or as the median and quartiles in the case of non-normal distribution. The χ2 goodness-of-fit test was used to compare the observed and the expected rates of events. Comparisons between subgroups were tested using the χ2 test in case of categorical variables, and the independent t-test or the Mann–Whitney U-test was used for normally and non-normally distributed continuous variables, respectively. Logistic binary regression was used to identify risk factors for postoperative CVA. All variables reported in Table 1 were tested using univariable analysis, and those with a P-value of <0.2 were initially included in the multivariable model. The backward conditional probability was used. Calibration and discrimination of the final model were tested using the Hosmer–Lemeshow test and the C-index, respectively. Two-sided statistics were performed with a significance level of 0.05. For all analyses, the R 3.4.1 software was used (released by R Development Core Team. R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing, 2011. ISBN 3-900051-07-0, URL: http://www.R-project.org/). RESULTS Cerebrovascular accident The postoperative rate of CVAs was 0.5% (14 cases): 2 (0.1%) were transient ischaemic attacks and 12 (0.4%) were strokes. The mean expected stroke rate (1.6%) was significantly higher than the observed rate (P < 0.001) with the observed-to-expected (O/E) mortality ratio equal to 0.25. None of the patients who experienced a postoperative CVA died. The incidence of postoperative CVA increased with the age of patients: in 941 patients aged ≤60 years, it was 0.1% (1 case); in 1049 patients aged 61–70 years, it was 0.4% (4 cases); and in 1090 patients aged >70, it was 0.8% (9 cases) (P = 0.048). Other risk factors for postoperative CVA at univariable analysis were diabetes, extracardiac vasculopathy, previous CVA and chronic renal failure. Multivariable analysis confirmed age >70 years old, diabetes, extracardiac vasculopathy and chronic renal failure as independent variables of risk for postoperative CVA (Table 2). However, in all the subgroups of risk except for those with chronic renal failure, the use of the ∏-circuit was associated with a low rate of CVAs. Table 2: Risk factors for a postoperative cerebrovascular accident Variables Univariable analysis OR (95% CI) Multivariable analysis OR (95% CI) Age class  ≤60 (942 patients) Reference Reference  61–70 (1049 patients) 3.6 (1.4–12.1) 3.8 (0.8–9.6)  >70 (1090 patients) 7.8 (1.9–17.4) 5.8 (1.7–13.2) Diabetes (1034 patients) 4.9 (1.6–14.9) 4.0 (1.3–13.1) ECV (281 patients) 4.0 (1.3–10.1) 2.7 (1.1–7.8) Previous CVA (124 patients) 4.1 (1.1–9.3) Previous CRF (61 patients) 8.4 (1.9–18.3) 5.3 (1.1–15.3) Variables Univariable analysis OR (95% CI) Multivariable analysis OR (95% CI) Age class  ≤60 (942 patients) Reference Reference  61–70 (1049 patients) 3.6 (1.4–12.1) 3.8 (0.8–9.6)  >70 (1090 patients) 7.8 (1.9–17.4) 5.8 (1.7–13.2) Diabetes (1034 patients) 4.9 (1.6–14.9) 4.0 (1.3–13.1) ECV (281 patients) 4.0 (1.3–10.1) 2.7 (1.1–7.8) Previous CVA (124 patients) 4.1 (1.1–9.3) Previous CRF (61 patients) 8.4 (1.9–18.3) 5.3 (1.1–15.3) Hosmer–Lemeshow test P-value 0.83, C-statistic 0.82. CI: confidence interval; CRF: chronic renal failure; CVA: cerebrovascular accident; ECV: extracardiac vasculopathy; OR: odds ratio. Table 2: Risk factors for a postoperative cerebrovascular accident Variables Univariable analysis OR (95% CI) Multivariable analysis OR (95% CI) Age class  ≤60 (942 patients) Reference Reference  61–70 (1049 patients) 3.6 (1.4–12.1) 3.8 (0.8–9.6)  >70 (1090 patients) 7.8 (1.9–17.4) 5.8 (1.7–13.2) Diabetes (1034 patients) 4.9 (1.6–14.9) 4.0 (1.3–13.1) ECV (281 patients) 4.0 (1.3–10.1) 2.7 (1.1–7.8) Previous CVA (124 patients) 4.1 (1.1–9.3) Previous CRF (61 patients) 8.4 (1.9–18.3) 5.3 (1.1–15.3) Variables Univariable analysis OR (95% CI) Multivariable analysis OR (95% CI) Age class  ≤60 (942 patients) Reference Reference  61–70 (1049 patients) 3.6 (1.4–12.1) 3.8 (0.8–9.6)  >70 (1090 patients) 7.8 (1.9–17.4) 5.8 (1.7–13.2) Diabetes (1034 patients) 4.9 (1.6–14.9) 4.0 (1.3–13.1) ECV (281 patients) 4.0 (1.3–10.1) 2.7 (1.1–7.8) Previous CVA (124 patients) 4.1 (1.1–9.3) Previous CRF (61 patients) 8.4 (1.9–18.3) 5.3 (1.1–15.3) Hosmer–Lemeshow test P-value 0.83, C-statistic 0.82. CI: confidence interval; CRF: chronic renal failure; CVA: cerebrovascular accident; ECV: extracardiac vasculopathy; OR: odds ratio. Mortality Forty patients died within the first postoperative month, 28 of cardiac causes and 12 of non-cardiac causes (observed mortality, 1.3%). The mean expected mortality rate (2.6%) was significantly higher than the observed rate (P < 0.001) with an O/E mortality ratio equal to 0.5. Other complications and length of stay The main postoperative complications are listed in Table 3. In particular, postoperative onset of atrial fibrillation occurred in 601 patients (19.5%) without any impact on the prevalence of CVA. Table 3: Postoperative complications Complication n (%) Acute kidney injury 119 (3.9)  Dialysis 2 (0) Acute respiratory failure/pneumonia 191 (6.2) Acute myocardial infarction 7 (0.2) Low-output syndrome 34 (1.1) Gastroenteric complications 56 (1.8) Atrial fibrillation 601 (19.5) Sternal wound complications 20 (0.6) Complication n (%) Acute kidney injury 119 (3.9)  Dialysis 2 (0) Acute respiratory failure/pneumonia 191 (6.2) Acute myocardial infarction 7 (0.2) Low-output syndrome 34 (1.1) Gastroenteric complications 56 (1.8) Atrial fibrillation 601 (19.5) Sternal wound complications 20 (0.6) Table 3: Postoperative complications Complication n (%) Acute kidney injury 119 (3.9)  Dialysis 2 (0) Acute respiratory failure/pneumonia 191 (6.2) Acute myocardial infarction 7 (0.2) Low-output syndrome 34 (1.1) Gastroenteric complications 56 (1.8) Atrial fibrillation 601 (19.5) Sternal wound complications 20 (0.6) Complication n (%) Acute kidney injury 119 (3.9)  Dialysis 2 (0) Acute respiratory failure/pneumonia 191 (6.2) Acute myocardial infarction 7 (0.2) Low-output syndrome 34 (1.1) Gastroenteric complications 56 (1.8) Atrial fibrillation 601 (19.5) Sternal wound complications 20 (0.6) Twenty patients had sternal wound complications (0.6%). The impact of diabetes (0.6% vs 1.0%, P = 0.083) and obesity (0.6% vs 1.1%, P = 0.87) was minimal, whereas chronic lung disease (0.6% vs 1.4%, P = 0.0174) was shown to be a risk factor for wound complications. The median postoperative length of stay was 7 days (6–8), significantly longer in 14 patients with postoperative CVA: 8 days (7–11) vs 7 days (6–8) (P = 0.006). DISCUSSION CABG represents the gold standard in the treatment of complex coronary artery disease [22], but it is burdened by a higher rate of major complications that make surgery still too invasive compared to percutaneous coronary intervention. Among the complications, a CVA, in particular a stroke, is considered the most worrisome because, although uncommon, a CVA increases mortality, prolongs the length of hospital stay and causes heavy permanent disability with great clinical and economic implications for patients and health care systems [23]. The Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery trial [1] reported an estimated rate of stroke in patients undergoing percutaneous coronary interventions of 0.6%, significantly lower than that in patients having CABG (2.2%), but this gap could likely be justified because only 15% of patients underwent OPCAB. However, OPCAB per se failed to reduce the incidence of postoperative CVAs as confirmed by some randomized controlled trials comparing OPCAB to on-pump CABG (ONCAB) [16–18]. Stroke incidence was 1.3% in the ROOBY trial [16], 1.5% in the CORONARY trial [17] and 2.2% in the GOPCABE trial [18]. In fact, avoiding the pump can reduce systemic inflammation, but the main cause underlying postoperative CVA is thromboembolisms from the aorta. Partial clamping to perform proximal anastomoses on the aorta explains why the rate of CVA in OPCAB is similar to that in ONCAB, as shown by Calafiore et al. [3], who reported rates of CVAs in patients undergoing ONCAB and OPCAB with partial clamping that were similar, 1.2% and 1.1%, respectively. The rate dropped to 0.2% in patients undergoing OPCAB without aortic manipulation. This finding has been confirmed by recent meta-analyses [19, 20]. Zhao et al. [20] carried out a network meta-analysis including 13 studies with 37 720 patients, divided into 4 groups: 7098 had no-touch techniques, 12 512 had OPCAB with partial clamping, 2997 had OPCAB with PADs and 15 113 had ONCAB. In the group undergoing no-touch techniques, the percentage reduction of postoperative CVAs was 78% compared to the ONCAB group, 66% compared to the OPCAB group with partial clamping and 52% compared to the group with OPCAB with PAD. A comparison between PAD and OPCAB with partial clamping failed to show any significant difference (odds ratio 0.71, 0.44–1.11), demonstrating that the no-touch technique represents the best tool to reduce significantly the burden of stroke after CABG. Pawliszak et al. [19] included 18 studies in a meta-analysis comprising 25 163 patients. The no-touch technique was associated with a reduction in CVAs of 70%. The main finding of the present retrospective single-centre study is that the use of the ∏-circuit is associated with a lower rate of CVA after CABG compared to the expected rate according to the Society of Thoracic Surgery risk model. Herein, the O/E mortality ratio for a CVA was 0.25 (percentage reduction 75%). This ratio is inferior to the ones reported by Moss et al. [4]; in 12 079 patients, the O/E mortality ratio was 0.48 in patients undergoing a no-touch technique, 0.61 in patients in whom a PAD was used as a clampless tool and 0.95 in patients undergoing OPCAB with partial clamping. The observed CVA rate reported herein is extremely low, falling close to the lower limit of the range (0.2–3.5%) reported in the literature [4–15]. In our series, as in others [3, 19, 24, 25], some subgroups of patients at higher risk have been identified as the elderly and as patients with diabetes, diffuse vasculopathy or chronic renal disease. In all these cases, avoiding aortic manipulation can be useful to reduce postoperative CVAs even if the rates of CVA were higher than those in the general population; this result is likely due to a higher grade of atherosclerosis in the cerebral artery system, which can be the cause of cerebral complications even in the absence of an aortic embolism. One of the criticisms of the ∏-circuit is the use of composite arteriovenous grafts with suboptimal flow in the short term, which is influenced by runoff and native flow competition [26]. However, a recent study demonstrated that at the 1-year follow-up, SV graft connected to the left IMA had a reduced luminal diameter but no abnormal internal intima-media thickness [27]. Moreover, a randomized study (SAVE right internal thoracic artery (RITA) Trial) reported a 1-year patency rate of 97.1% for the SV composite grafts, which was not inferior to that of the RITA composite grafts (97.1%) with a 95% lower confidence limit of −2.6% (P < 0.001 for non-inferiority) [28]. Unfortunately, data on the patency rates of these subsets of conduits are not available in this series. LIMITATIONS AND CONCLUSIONS The retrospective nature of the studies leads to some important missing information: no direct (angiographic or coronary CT imaging) or indirect (follow-up freedom from myocardial infarction or repeat revascularization) data regarding the patency of the grafts are available, and completeness of revascularization could not be reported. We did not have a control group because of the plan to submit all the patients having CABG to this procedure, which is an important limitation. Another important limitation of the study is the small number of events (only 14). A stepwise regression model was used, so we were unable to follow the usual rule of thumb of a minimum of 10 outcome events per predictor variable. In conclusion, the ∏-circuit should be included as a possible choice among the no-touch techniques because it is associated with a low rate of perioperative CVAs. Conflict of interest: none declared. 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A randomized comparison of the Saphenous Vein Versus Right Internal Thoracic Artery as a Y-Composite Graft (SAVE RITA) trial: one-year angiographic results and mid-term clinical outcomes . J Thorac Cardiovasc Surg 2014 ; 148 : 901 – 7 . 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

Anaortic coronary surgery using the Π-circuit is associated with a low incidence of perioperative neurological complications

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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/ezy224
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Abstract

Abstract OBJECTIVES Our goal was to compare the observed and the expected rates of postoperative cerebrovascular accidents (CVA) in a large cohort of consecutive patients undergoing off-pump coronary artery bypass grafting (CABG) using the ∏-circuit as a no-touch technique. METHODS From January 2001 to May 2016, 3081 patients were consecutively submitted to an off-pump CABG operation using the ∏-circuit. A CVA was defined as a neurological deficit, lasting less (transient ischaemic attack) or more (stroke) than 24 h, diagnosed by a neurologist and confirmed by a computed tomography or magnetic resonance imaging scan of the brain. The primary end point was to compare the observed and the expected rates of CVAs; the latter was obtained using the Society of Thoracic Surgeons’ calculator. The secondary end point was to compare the observed and the expected mortality rates using the Society of Thoracic Surgeons’ calculator and the prevalence of postoperative complications. Moreover, we identified some subgroups at higher risk. RESULTS The postoperative rate of CVAs was 0.5% (14 cases): 2 (0.1%) were transient ischaemic attacks and 12 (0.4%) were strokes. The mean expected CVA rate (1.6%) was significantly higher than the observed rate (P < 0.001). None of patients who experienced postoperative CVAs died. The observed mortality was 1.3% (40 patients) vs the expected mortality (2.6%), which was significantly higher (P < 0.001). Multivariable analysis identified age >70 years old, diabetes, extracardiac vasculopathy and chronic renal failure as risk factors for postoperative CVAs. However, in all the subgroups of risk, except for those with chronic renal failure, the use of the ∏-circuit was associated with a low rate of CVAs. CONCLUSIONS The ∏-circuit should be included as a possible choice among no-touch techniques. The observed rate of CVAs of 75% is lower than the expected rate. Coronary artery bypass grafting, No-touch aorta, Anaortic, Arterial revascularization INTRODUCTION Coronary artery bypass grafting (CABG) is still considered the gold standard of treatment for 3-vessel and left main coronary artery disease, both in the general population and in patients with diabetes, as confirmed by the SYNTAX (Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery) and FREEDOM (Strategies for Multivessel Revascularization in Patients with Diabetes) trials [1, 2]. One of the drawbacks of CABG compared with percutaneous coronary intervention is the high risk of having a cerebrovascular accident (CVA) [3]. A postoperative CVA in the population having CABG is an uncommon but harmful complication, ranging from 0.4% to 3.5% [4–15]. Off-pump coronary artery bypass (OPCAB) per se failed to reduce the postoperative occurrence of CVAs, because a proximal anastomosis has to be done with the aid of a partial clamp in most cases [16–18]. Hence, different anaortic strategies were developed to minimize the risk of postoperative strokes: ‘no-touch’ techniques [use of bilateral internal mammary artery (IMA) in situ or as a composite graft, a Y or T graft, or use of the left or right IMA as a source of blood for the saphenous vein (SV) or radial artery] and the use of proximal anastomotic devices (PADs) to perform proximal anastomoses, either automatically or hand-sewn, on the aorta without partial clamping. Researchers, in recent meta-analyses, compared all these strategies to OPCAB with partial clamping and to on-pump CABG, reporting a significant reduction of stroke, especially when ‘no-touch’ techniques were used [19, 20]. Among the ‘no-touch’ techniques, we proposed the use of the ∏-circuit, which foresees the use of different conduits, either arterial or venous, grafted together, having 1 or 2 mammary arteries as the blood source [21]. Hence, we sought to compare the observed and the expected rates of postoperative CVAs in a large cohort of consecutive patients undergoing CABG using the ∏-circuit as a no-touch technique. METHODS Study population From January 2001 to May 2016, the ∏-circuit was used in all 3081 patients with coronary artery disease admitted for CABG at the Henry Durant Hospital. The institutional review board approved this retrospective observational study. Pre- and operative data are summarized in Table 1. Table 1: Preoperative and operative data Variables n = 3081 Age (years; continuous), mean ± SD 66 ± 10 Age class (years), n (%)  ≤60 942 (31)  61–70 1049 (34)  >70 1090 (35) Gender, n (%)  Female 412 (13)  Male 2669 (87) Emergency, n (%) 255 (8) Ejection fraction (%), n (%)  >50 2068 (67)  31–50 812 (26)  ≤30 201 (7) BMI (kg/m2), mean ± SD 28 ± 5 Obese, n (%) 919 (29.8) Diabetes, n (%) 1034 (34) Hypercholesterolaemia, n (%) 1654 (54) Hypertension, n (%) 1655 (54) Chronic pulmonary disease, n (%) 221 (7) CRF (creatinine >200 μmol/l), n (%) 61 (2) Preoperative AF, n (%) 185 (4) ECV, n (%) 281 (9) Previous CVA, n (%) 124 (4)  Stroke 75  TIA 49 Preoperative IABP, n (%) 64 (2) Previous cardiac operation, n (%) 149 (5) Off-pump conversion to on-pump, n (%) 4 (0.1) Mean number of anastomoses, mean ± SD 2.8 ± 0.9 Mean number of arterial anastomoses, mean ± SD 2.6 ± 1.0 Conduits grafted to coronary bed, n (%)  LIMA 3027 (98)  RIMA 2178 (71)  RA 807 (26)  SVG 536 (17) Variables n = 3081 Age (years; continuous), mean ± SD 66 ± 10 Age class (years), n (%)  ≤60 942 (31)  61–70 1049 (34)  >70 1090 (35) Gender, n (%)  Female 412 (13)  Male 2669 (87) Emergency, n (%) 255 (8) Ejection fraction (%), n (%)  >50 2068 (67)  31–50 812 (26)  ≤30 201 (7) BMI (kg/m2), mean ± SD 28 ± 5 Obese, n (%) 919 (29.8) Diabetes, n (%) 1034 (34) Hypercholesterolaemia, n (%) 1654 (54) Hypertension, n (%) 1655 (54) Chronic pulmonary disease, n (%) 221 (7) CRF (creatinine >200 μmol/l), n (%) 61 (2) Preoperative AF, n (%) 185 (4) ECV, n (%) 281 (9) Previous CVA, n (%) 124 (4)  Stroke 75  TIA 49 Preoperative IABP, n (%) 64 (2) Previous cardiac operation, n (%) 149 (5) Off-pump conversion to on-pump, n (%) 4 (0.1) Mean number of anastomoses, mean ± SD 2.8 ± 0.9 Mean number of arterial anastomoses, mean ± SD 2.6 ± 1.0 Conduits grafted to coronary bed, n (%)  LIMA 3027 (98)  RIMA 2178 (71)  RA 807 (26)  SVG 536 (17) AF: atrial fibrillation; BMI: body mass index; CRF: chronic renal failure; CVA: cerebrovascular accident; ECV: extracardiac vasculopathy; IABP: intra-aortic balloon pump; LIMA: left internal mammary artery; RA: radial artery; RIMA: right internal mammary artery; SD: standard deviation; SVG: saphenous vein graft; TIA: transient ischaemic attack. Table 1: Preoperative and operative data Variables n = 3081 Age (years; continuous), mean ± SD 66 ± 10 Age class (years), n (%)  ≤60 942 (31)  61–70 1049 (34)  >70 1090 (35) Gender, n (%)  Female 412 (13)  Male 2669 (87) Emergency, n (%) 255 (8) Ejection fraction (%), n (%)  >50 2068 (67)  31–50 812 (26)  ≤30 201 (7) BMI (kg/m2), mean ± SD 28 ± 5 Obese, n (%) 919 (29.8) Diabetes, n (%) 1034 (34) Hypercholesterolaemia, n (%) 1654 (54) Hypertension, n (%) 1655 (54) Chronic pulmonary disease, n (%) 221 (7) CRF (creatinine >200 μmol/l), n (%) 61 (2) Preoperative AF, n (%) 185 (4) ECV, n (%) 281 (9) Previous CVA, n (%) 124 (4)  Stroke 75  TIA 49 Preoperative IABP, n (%) 64 (2) Previous cardiac operation, n (%) 149 (5) Off-pump conversion to on-pump, n (%) 4 (0.1) Mean number of anastomoses, mean ± SD 2.8 ± 0.9 Mean number of arterial anastomoses, mean ± SD 2.6 ± 1.0 Conduits grafted to coronary bed, n (%)  LIMA 3027 (98)  RIMA 2178 (71)  RA 807 (26)  SVG 536 (17) Variables n = 3081 Age (years; continuous), mean ± SD 66 ± 10 Age class (years), n (%)  ≤60 942 (31)  61–70 1049 (34)  >70 1090 (35) Gender, n (%)  Female 412 (13)  Male 2669 (87) Emergency, n (%) 255 (8) Ejection fraction (%), n (%)  >50 2068 (67)  31–50 812 (26)  ≤30 201 (7) BMI (kg/m2), mean ± SD 28 ± 5 Obese, n (%) 919 (29.8) Diabetes, n (%) 1034 (34) Hypercholesterolaemia, n (%) 1654 (54) Hypertension, n (%) 1655 (54) Chronic pulmonary disease, n (%) 221 (7) CRF (creatinine >200 μmol/l), n (%) 61 (2) Preoperative AF, n (%) 185 (4) ECV, n (%) 281 (9) Previous CVA, n (%) 124 (4)  Stroke 75  TIA 49 Preoperative IABP, n (%) 64 (2) Previous cardiac operation, n (%) 149 (5) Off-pump conversion to on-pump, n (%) 4 (0.1) Mean number of anastomoses, mean ± SD 2.8 ± 0.9 Mean number of arterial anastomoses, mean ± SD 2.6 ± 1.0 Conduits grafted to coronary bed, n (%)  LIMA 3027 (98)  RIMA 2178 (71)  RA 807 (26)  SVG 536 (17) AF: atrial fibrillation; BMI: body mass index; CRF: chronic renal failure; CVA: cerebrovascular accident; ECV: extracardiac vasculopathy; IABP: intra-aortic balloon pump; LIMA: left internal mammary artery; RA: radial artery; RIMA: right internal mammary artery; SD: standard deviation; SVG: saphenous vein graft; TIA: transient ischaemic attack. Surgery The technical details of the ∏-circuit were reported previously [21]. Briefly, the ∏-circuit represents a net that is built using 1 mammary artery (in general the left IMA) or both IMAs for the inflow. A radial artery or an SV or segments of the left or the right IMA can be used as an elongation or a side branch of the main conduit, depending on what is needed (Figs 1–3). The composite graft(s) is (are) preformed before the procedure starts and is (are) used to graft all the stenosed coronary vessels. The ∏-circuit is completely flexible, and the arrangements of its components can vary according to the needs of the individual patient. The aorta is never touched. Figure 1: View largeDownload slide Coronary angiogram taken 1 year after surgery. The Π-circuit between the left and the proximal segments of the right internal mammary artery (RIMA) (Y graft) and between the LIMA and the distal segment of the RIMA (E graft). The arrow head indicates end-to-end anastomosis between the LIMA and the proximal segment of the free RIMA. fRIMAd: free right internal mammary artery, distal segment; fRIMAp: free right internal mammary artery, proximal segment; lad: left anterior descending artery; LIMA: left internal mammary artery; om: obtuse marginal artery; pda: posterior descending artery. Figure 1: View largeDownload slide Coronary angiogram taken 1 year after surgery. The Π-circuit between the left and the proximal segments of the right internal mammary artery (RIMA) (Y graft) and between the LIMA and the distal segment of the RIMA (E graft). The arrow head indicates end-to-end anastomosis between the LIMA and the proximal segment of the free RIMA. fRIMAd: free right internal mammary artery, distal segment; fRIMAp: free right internal mammary artery, proximal segment; lad: left anterior descending artery; LIMA: left internal mammary artery; om: obtuse marginal artery; pda: posterior descending artery. Figure 2: View largeDownload slide Computed tomography angiography 12 years after surgery showing the Π-circuit between the LIMA and the right internal mammary artery (Y graft) and the right internal mammary artery and the distal segment of the LIMA. CX: circumflex artery; diag: diagonal branch; fLIMAd: free left internal mammary artery, distal segment; fRIMA: free right internal mammary artery; lad: left anterior descending artery; LIMA: left internal mammary artery; Mg: marginal branch. Figure 2: View largeDownload slide Computed tomography angiography 12 years after surgery showing the Π-circuit between the LIMA and the right internal mammary artery (Y graft) and the right internal mammary artery and the distal segment of the LIMA. CX: circumflex artery; diag: diagonal branch; fLIMAd: free left internal mammary artery, distal segment; fRIMA: free right internal mammary artery; lad: left anterior descending artery; LIMA: left internal mammary artery; Mg: marginal branch. Figure 3: View largeDownload slide Coronary angiography 12 years after surgery. The Π-circuit between the RIMA and an SVG. lad: left anterior descending artery; pda: posterior descending artery; RIMA: right internal mammary artery; SVG: saphenous vein graft. Figure 3: View largeDownload slide Coronary angiography 12 years after surgery. The Π-circuit between the RIMA and an SVG. lad: left anterior descending artery; pda: posterior descending artery; RIMA: right internal mammary artery; SVG: saphenous vein graft. Definitions, end points and statistics A CVA was defined as a global or focal neurological deficit, lasting less [transient ischaemic attack] or more (stroke) than 24 h after surgery, diagnosed by a neurologist and confirmed by a brain computed tomography (CT) or magnetic resonance imaging scan. A stroke was defined as a focal or global cerebral dysfunction of presumed vascular origin lasting more than 24 h. A transient ischaemic attack was defined as a focal cerebral dysfunction of presumed vascular origin that resolved completely within 24 h [3]. The primary end point was to compare the observed stroke rate with the expected rate obtained using the Society of Thoracic Surgeons’ calculator. The secondary end point was to compare the expected and the observed mortality rates using the Society of Thoracic Surgeons’ calculator (www.sts.org). Categorical data were reported as numbers and percentages, and continuous data were reported as the mean and standard deviation in the case of normal distribution or as the median and quartiles in the case of non-normal distribution. The χ2 goodness-of-fit test was used to compare the observed and the expected rates of events. Comparisons between subgroups were tested using the χ2 test in case of categorical variables, and the independent t-test or the Mann–Whitney U-test was used for normally and non-normally distributed continuous variables, respectively. Logistic binary regression was used to identify risk factors for postoperative CVA. All variables reported in Table 1 were tested using univariable analysis, and those with a P-value of <0.2 were initially included in the multivariable model. The backward conditional probability was used. Calibration and discrimination of the final model were tested using the Hosmer–Lemeshow test and the C-index, respectively. Two-sided statistics were performed with a significance level of 0.05. For all analyses, the R 3.4.1 software was used (released by R Development Core Team. R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing, 2011. ISBN 3-900051-07-0, URL: http://www.R-project.org/). RESULTS Cerebrovascular accident The postoperative rate of CVAs was 0.5% (14 cases): 2 (0.1%) were transient ischaemic attacks and 12 (0.4%) were strokes. The mean expected stroke rate (1.6%) was significantly higher than the observed rate (P < 0.001) with the observed-to-expected (O/E) mortality ratio equal to 0.25. None of the patients who experienced a postoperative CVA died. The incidence of postoperative CVA increased with the age of patients: in 941 patients aged ≤60 years, it was 0.1% (1 case); in 1049 patients aged 61–70 years, it was 0.4% (4 cases); and in 1090 patients aged >70, it was 0.8% (9 cases) (P = 0.048). Other risk factors for postoperative CVA at univariable analysis were diabetes, extracardiac vasculopathy, previous CVA and chronic renal failure. Multivariable analysis confirmed age >70 years old, diabetes, extracardiac vasculopathy and chronic renal failure as independent variables of risk for postoperative CVA (Table 2). However, in all the subgroups of risk except for those with chronic renal failure, the use of the ∏-circuit was associated with a low rate of CVAs. Table 2: Risk factors for a postoperative cerebrovascular accident Variables Univariable analysis OR (95% CI) Multivariable analysis OR (95% CI) Age class  ≤60 (942 patients) Reference Reference  61–70 (1049 patients) 3.6 (1.4–12.1) 3.8 (0.8–9.6)  >70 (1090 patients) 7.8 (1.9–17.4) 5.8 (1.7–13.2) Diabetes (1034 patients) 4.9 (1.6–14.9) 4.0 (1.3–13.1) ECV (281 patients) 4.0 (1.3–10.1) 2.7 (1.1–7.8) Previous CVA (124 patients) 4.1 (1.1–9.3) Previous CRF (61 patients) 8.4 (1.9–18.3) 5.3 (1.1–15.3) Variables Univariable analysis OR (95% CI) Multivariable analysis OR (95% CI) Age class  ≤60 (942 patients) Reference Reference  61–70 (1049 patients) 3.6 (1.4–12.1) 3.8 (0.8–9.6)  >70 (1090 patients) 7.8 (1.9–17.4) 5.8 (1.7–13.2) Diabetes (1034 patients) 4.9 (1.6–14.9) 4.0 (1.3–13.1) ECV (281 patients) 4.0 (1.3–10.1) 2.7 (1.1–7.8) Previous CVA (124 patients) 4.1 (1.1–9.3) Previous CRF (61 patients) 8.4 (1.9–18.3) 5.3 (1.1–15.3) Hosmer–Lemeshow test P-value 0.83, C-statistic 0.82. CI: confidence interval; CRF: chronic renal failure; CVA: cerebrovascular accident; ECV: extracardiac vasculopathy; OR: odds ratio. Table 2: Risk factors for a postoperative cerebrovascular accident Variables Univariable analysis OR (95% CI) Multivariable analysis OR (95% CI) Age class  ≤60 (942 patients) Reference Reference  61–70 (1049 patients) 3.6 (1.4–12.1) 3.8 (0.8–9.6)  >70 (1090 patients) 7.8 (1.9–17.4) 5.8 (1.7–13.2) Diabetes (1034 patients) 4.9 (1.6–14.9) 4.0 (1.3–13.1) ECV (281 patients) 4.0 (1.3–10.1) 2.7 (1.1–7.8) Previous CVA (124 patients) 4.1 (1.1–9.3) Previous CRF (61 patients) 8.4 (1.9–18.3) 5.3 (1.1–15.3) Variables Univariable analysis OR (95% CI) Multivariable analysis OR (95% CI) Age class  ≤60 (942 patients) Reference Reference  61–70 (1049 patients) 3.6 (1.4–12.1) 3.8 (0.8–9.6)  >70 (1090 patients) 7.8 (1.9–17.4) 5.8 (1.7–13.2) Diabetes (1034 patients) 4.9 (1.6–14.9) 4.0 (1.3–13.1) ECV (281 patients) 4.0 (1.3–10.1) 2.7 (1.1–7.8) Previous CVA (124 patients) 4.1 (1.1–9.3) Previous CRF (61 patients) 8.4 (1.9–18.3) 5.3 (1.1–15.3) Hosmer–Lemeshow test P-value 0.83, C-statistic 0.82. CI: confidence interval; CRF: chronic renal failure; CVA: cerebrovascular accident; ECV: extracardiac vasculopathy; OR: odds ratio. Mortality Forty patients died within the first postoperative month, 28 of cardiac causes and 12 of non-cardiac causes (observed mortality, 1.3%). The mean expected mortality rate (2.6%) was significantly higher than the observed rate (P < 0.001) with an O/E mortality ratio equal to 0.5. Other complications and length of stay The main postoperative complications are listed in Table 3. In particular, postoperative onset of atrial fibrillation occurred in 601 patients (19.5%) without any impact on the prevalence of CVA. Table 3: Postoperative complications Complication n (%) Acute kidney injury 119 (3.9)  Dialysis 2 (0) Acute respiratory failure/pneumonia 191 (6.2) Acute myocardial infarction 7 (0.2) Low-output syndrome 34 (1.1) Gastroenteric complications 56 (1.8) Atrial fibrillation 601 (19.5) Sternal wound complications 20 (0.6) Complication n (%) Acute kidney injury 119 (3.9)  Dialysis 2 (0) Acute respiratory failure/pneumonia 191 (6.2) Acute myocardial infarction 7 (0.2) Low-output syndrome 34 (1.1) Gastroenteric complications 56 (1.8) Atrial fibrillation 601 (19.5) Sternal wound complications 20 (0.6) Table 3: Postoperative complications Complication n (%) Acute kidney injury 119 (3.9)  Dialysis 2 (0) Acute respiratory failure/pneumonia 191 (6.2) Acute myocardial infarction 7 (0.2) Low-output syndrome 34 (1.1) Gastroenteric complications 56 (1.8) Atrial fibrillation 601 (19.5) Sternal wound complications 20 (0.6) Complication n (%) Acute kidney injury 119 (3.9)  Dialysis 2 (0) Acute respiratory failure/pneumonia 191 (6.2) Acute myocardial infarction 7 (0.2) Low-output syndrome 34 (1.1) Gastroenteric complications 56 (1.8) Atrial fibrillation 601 (19.5) Sternal wound complications 20 (0.6) Twenty patients had sternal wound complications (0.6%). The impact of diabetes (0.6% vs 1.0%, P = 0.083) and obesity (0.6% vs 1.1%, P = 0.87) was minimal, whereas chronic lung disease (0.6% vs 1.4%, P = 0.0174) was shown to be a risk factor for wound complications. The median postoperative length of stay was 7 days (6–8), significantly longer in 14 patients with postoperative CVA: 8 days (7–11) vs 7 days (6–8) (P = 0.006). DISCUSSION CABG represents the gold standard in the treatment of complex coronary artery disease [22], but it is burdened by a higher rate of major complications that make surgery still too invasive compared to percutaneous coronary intervention. Among the complications, a CVA, in particular a stroke, is considered the most worrisome because, although uncommon, a CVA increases mortality, prolongs the length of hospital stay and causes heavy permanent disability with great clinical and economic implications for patients and health care systems [23]. The Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery trial [1] reported an estimated rate of stroke in patients undergoing percutaneous coronary interventions of 0.6%, significantly lower than that in patients having CABG (2.2%), but this gap could likely be justified because only 15% of patients underwent OPCAB. However, OPCAB per se failed to reduce the incidence of postoperative CVAs as confirmed by some randomized controlled trials comparing OPCAB to on-pump CABG (ONCAB) [16–18]. Stroke incidence was 1.3% in the ROOBY trial [16], 1.5% in the CORONARY trial [17] and 2.2% in the GOPCABE trial [18]. In fact, avoiding the pump can reduce systemic inflammation, but the main cause underlying postoperative CVA is thromboembolisms from the aorta. Partial clamping to perform proximal anastomoses on the aorta explains why the rate of CVA in OPCAB is similar to that in ONCAB, as shown by Calafiore et al. [3], who reported rates of CVAs in patients undergoing ONCAB and OPCAB with partial clamping that were similar, 1.2% and 1.1%, respectively. The rate dropped to 0.2% in patients undergoing OPCAB without aortic manipulation. This finding has been confirmed by recent meta-analyses [19, 20]. Zhao et al. [20] carried out a network meta-analysis including 13 studies with 37 720 patients, divided into 4 groups: 7098 had no-touch techniques, 12 512 had OPCAB with partial clamping, 2997 had OPCAB with PADs and 15 113 had ONCAB. In the group undergoing no-touch techniques, the percentage reduction of postoperative CVAs was 78% compared to the ONCAB group, 66% compared to the OPCAB group with partial clamping and 52% compared to the group with OPCAB with PAD. A comparison between PAD and OPCAB with partial clamping failed to show any significant difference (odds ratio 0.71, 0.44–1.11), demonstrating that the no-touch technique represents the best tool to reduce significantly the burden of stroke after CABG. Pawliszak et al. [19] included 18 studies in a meta-analysis comprising 25 163 patients. The no-touch technique was associated with a reduction in CVAs of 70%. The main finding of the present retrospective single-centre study is that the use of the ∏-circuit is associated with a lower rate of CVA after CABG compared to the expected rate according to the Society of Thoracic Surgery risk model. Herein, the O/E mortality ratio for a CVA was 0.25 (percentage reduction 75%). This ratio is inferior to the ones reported by Moss et al. [4]; in 12 079 patients, the O/E mortality ratio was 0.48 in patients undergoing a no-touch technique, 0.61 in patients in whom a PAD was used as a clampless tool and 0.95 in patients undergoing OPCAB with partial clamping. The observed CVA rate reported herein is extremely low, falling close to the lower limit of the range (0.2–3.5%) reported in the literature [4–15]. In our series, as in others [3, 19, 24, 25], some subgroups of patients at higher risk have been identified as the elderly and as patients with diabetes, diffuse vasculopathy or chronic renal disease. In all these cases, avoiding aortic manipulation can be useful to reduce postoperative CVAs even if the rates of CVA were higher than those in the general population; this result is likely due to a higher grade of atherosclerosis in the cerebral artery system, which can be the cause of cerebral complications even in the absence of an aortic embolism. One of the criticisms of the ∏-circuit is the use of composite arteriovenous grafts with suboptimal flow in the short term, which is influenced by runoff and native flow competition [26]. However, a recent study demonstrated that at the 1-year follow-up, SV graft connected to the left IMA had a reduced luminal diameter but no abnormal internal intima-media thickness [27]. Moreover, a randomized study (SAVE right internal thoracic artery (RITA) Trial) reported a 1-year patency rate of 97.1% for the SV composite grafts, which was not inferior to that of the RITA composite grafts (97.1%) with a 95% lower confidence limit of −2.6% (P < 0.001 for non-inferiority) [28]. Unfortunately, data on the patency rates of these subsets of conduits are not available in this series. LIMITATIONS AND CONCLUSIONS The retrospective nature of the studies leads to some important missing information: no direct (angiographic or coronary CT imaging) or indirect (follow-up freedom from myocardial infarction or repeat revascularization) data regarding the patency of the grafts are available, and completeness of revascularization could not be reported. We did not have a control group because of the plan to submit all the patients having CABG to this procedure, which is an important limitation. Another important limitation of the study is the small number of events (only 14). A stepwise regression model was used, so we were unable to follow the usual rule of thumb of a minimum of 10 outcome events per predictor variable. In conclusion, the ∏-circuit should be included as a possible choice among the no-touch techniques because it is associated with a low rate of perioperative CVAs. Conflict of interest: none declared. 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Journal

European Journal of Cardio-Thoracic SurgeryOxford University Press

Published: Jun 11, 2018

References