Individualized surgical strategies for left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

Individualized surgical strategies for left ventricular outflow tract obstruction in hypertrophic... Abstract OBJECTIVES Surgical strategies to treat drug refractory left ventricular outflow tract obstruction (LVOTO) in hypertrophic cardiomyopathy include septal myectomy (SM) and, less frequently, mitral valve (MV) repair or replacement. The primary aim of this study was to report the surgical technique and management outcomes in a consecutive group of patients with variable phenotypes of hypertrophic cardiomyopathy in a broad national specialist practice. METHODS A total of 203 consecutive patients, 132 men (mean age 48.6 ± 14.6 years) underwent surgery for the management of LVOTO. Surgical approaches included SM (n = 159), SM with MV repair (n = 25), SM with MV replacement (n = 9) and MV replacement alone (n = 10). Specific surgical approaches were performed based on the underlying mechanism of obstruction. Eleven (5.4%) patients had previous alcohol septal ablation for the management of LVOTO. Concomitant non-mitral cardiac procedures were carried out in 22 (10.8%) patients. RESULTS Operative survival rate was 99.0% with 2 deaths within 30 days. The mean bypass time was 92.9 ± 47.8 min, with a mean length of hospital stay of 10.5 ± 7.8 days. Surgical complications included 3 ventricular septal defects requiring repair (1.5%), 1 Gerbode defect surgically repaired, 2 aortic valve repairs (1.0%), 2 transient ischaemic attacks (1.0%) and 4 strokes (2.0%). Thirty-nine (19.2%) patients had perioperative new-onset atrial fibrillation and 8 (3.9%) patients had unexpected atrioventricular block requiring a permanent pacemaker. Mean resting left ventricular outflow tract gradient improved from 70.6 ± 40.3 mmHg preoperatively to 11.0 ± 10.5 mmHg at 1 year postoperatively (P < 0.001). Mean New York Heart Association class improved from 2.6 ± 0.5 preoperatively to 1.6 ± 0.6 at 1 year after the procedure. CONCLUSIONS In variable phenotypes of LVOTO in hypertrophic cardiomyopathy, an individualized surgical approach provided effective reductions in left ventricular outflow tract gradients and good symptomatic relief with acceptable mortality and morbidity. Septal myectomy, Mitral valve intervention, Left ventricular outflow tract obstruction, Hypertrophic cardiomyopathy INTRODUCTION Hypertrophic cardiomyopathy (HCM) is the commonest genetically inherited cardiac condition affecting 1 in 500 of the population. Complications include left ventricular outflow tract obstruction (LVOTO), atrial fibrillation (AF), ventricular arrhythmias, sudden cardiac death and heart failure [1–4]. Severe drug refractory symptoms can persist in up to one-third of cases. Expert consensus indicates surgical intervention to be the gold standard in the management of these patients [2]. Septal myectomy (SM) alone is the preferred surgical technique in the majority of patients with HCM, providing excellent outcomes [5–11]. The mechanism of LVOTO is often complex, with a variety of non-classical phenotypes seen in HCM. This includes limited septal hypertrophy, angulation of the aorta, elongation of the mitral leaflets and abnormalities of the submitral apparatus. Abnormal mitral attachments include thickened or anteriorly displaced papillary muscles, direct insertion of the papillary muscle into the anterior mitral valve (MV) leaflet or fibrotic chordal attachments [12]. These non-classical phenotypes may, in individual circumstances, dictate a different surgical approach. With an improved understanding of the mechanism of obstruction, an increasing number of MV repairs and replacements are being performed concomitantly with SM or alone. The primary aim of this study is to evaluate the early outcomes following individualized surgical strategies for the management of LVOTO in a wide spectrum of HCM patients. METHODS Study Between 2003 and 2015, 203 consecutive patients underwent surgical intervention for the management of LVOTO in HCM in a national specialized cardiomyopathy unit at the Heart Hospital, University College London Hospital. No patients were excluded. All patients were operated on by 1 of 2 surgeons (C.G.A.McG. and V.T.). Clinical assessment All patients were assessed in a clinic specializing in cardiomyopathy. Baseline demographic data including age, gender, medical and family history were documented, as was preoperative and postoperative New York Heart Association (NYHA) functional class. Variables from transthoracic echocardiography, including interventricular septal wall thickness, posterior wall thickness, left ventricular end-diastolic diameter, left atrial diameter, left ventricular ejection fraction, resting and provoked LVOT gradients and severity of mitral and aortic regurgitation, were collected. Drug refractory symptomatic LVOTO with an LVOT gradient >50 mmHg was the principal indication for surgery according to the international guidelines [2]. The conditions of all patients and the most suitable surgical approach that could be performed were discussed at a joint medical and surgical cardiac conference. Particular attention was paid to the MV on multimodality imaging preoperatively to decide whether an MV intervention might be required at the time of surgery. Surgical technique After median sternotomy and before cardiopulmonary bypass, direct simultaneous pressure measurements were performed with needles in the aorta and the left ventricle. Provocation was measured following a bolus of isoproterenol (5 μg) intravenously and repeated if an increase in the heart rate and/or reduction in the blood pressure was not attained. During the study period, the surgical technique of SM evolved from the classical Morrow myectomy to the Danielson modification of the classical Morrow myectomy [13, 14]. After the initial planned surgery and cessation of cardiopulmonary bypass, transoesophageal echocardiography was performed to assess the LVOT and the MV. Direct simultaneous pressure measurements were repeated with and without provocation as done pre-bypass. Indications to resume bypass and perform further surgery at this point were principally a significant residual gradient and/or persistent systolic anterior motion (SAM) related mitral regurgitation (MR). MV repairs included transatrial Alfieri edge-to-edge repair, transaortic mitral plication, cleft repair, division of papillary muscles or artificial chordal repair. Mitral annuloplasty was avoided in all patients. MV replacement was done at the time of SM using the standard techniques, and MV replacement was done alone without SM again using the standard techniques. Perioperative complications were defined as those occurring within the first 30 days following surgery. Follow-up All patients were followed up clinically at regular annual visits or more frequent intervals based on their clinical status. At the 1-year follow-up, postoperative echocardiographic data were available in 83.7% of patients. The remainder of the patients were followed up by their local cardiologist. Statistical analysis Variables were collected and assessed using the SPSS software, version 24 (IBM, Chicago, IL, USA). The tests of normality were carried out based on the histogram distribution and the Shapiro–Wilks test. For data with a normal distribution, continuous variables were expressed as the mean ± standard deviation. For data with a non-normal distribution, continuous variables were expressed as the median with interquartile range. For normally distributed data, comparison of means was done using the paired Student’s t-test. For non-normally distributed data, comparisons were done using the Mann–Whitney U-test. All echocardiographic variables were normally distributed, and the comparison of means was performed using the paired Student’s t-test. A P-value of <0.05 was considered statistically significant. RESULTS The baseline characteristics of all the patients are presented in Table 1. The overall mean age of patients at surgery was 48.6 ± 14.6 years, and the mean age in patients undergoing an SM alone was 47.5 ± 14.2 years, SM with MV repair was 48.7 ± 15.0 years, SM with MV replacement was 55.4 ± 15.0 years and MV replacement alone was 57.7 ± 14.3 years. Eleven (5.4%) patients previously underwent alcohol septal ablation for the management of LVOTO with recurrence of symptoms. Table 1: Baseline demographics Overall number of patients, n (%) 203 (100) Age at surgery (years), mean ± SD 48.6 ± 14.6 Male, n (%) 132 (65.0) History, n (%)  Atrial fibrillation 28 (13.8)  Previous PPM 14 (6.9)  Previous PPM for LVOTO 9 (4.4)  Previous ASA 11 (5.4)  Stroke 3 (1.5)  Peripheral vascular disease 1 (0.5)  Diabetes mellitus 9 (4.4)  Hypertension 58 (28.6) Overall number of patients, n (%) 203 (100) Age at surgery (years), mean ± SD 48.6 ± 14.6 Male, n (%) 132 (65.0) History, n (%)  Atrial fibrillation 28 (13.8)  Previous PPM 14 (6.9)  Previous PPM for LVOTO 9 (4.4)  Previous ASA 11 (5.4)  Stroke 3 (1.5)  Peripheral vascular disease 1 (0.5)  Diabetes mellitus 9 (4.4)  Hypertension 58 (28.6) ASA: alcohol septal ablation; LVOTO: left ventricular outflow tract obstruction; PPM: permanent pacemaker; SD: standard deviation. Table 1: Baseline demographics Overall number of patients, n (%) 203 (100) Age at surgery (years), mean ± SD 48.6 ± 14.6 Male, n (%) 132 (65.0) History, n (%)  Atrial fibrillation 28 (13.8)  Previous PPM 14 (6.9)  Previous PPM for LVOTO 9 (4.4)  Previous ASA 11 (5.4)  Stroke 3 (1.5)  Peripheral vascular disease 1 (0.5)  Diabetes mellitus 9 (4.4)  Hypertension 58 (28.6) Overall number of patients, n (%) 203 (100) Age at surgery (years), mean ± SD 48.6 ± 14.6 Male, n (%) 132 (65.0) History, n (%)  Atrial fibrillation 28 (13.8)  Previous PPM 14 (6.9)  Previous PPM for LVOTO 9 (4.4)  Previous ASA 11 (5.4)  Stroke 3 (1.5)  Peripheral vascular disease 1 (0.5)  Diabetes mellitus 9 (4.4)  Hypertension 58 (28.6) ASA: alcohol septal ablation; LVOTO: left ventricular outflow tract obstruction; PPM: permanent pacemaker; SD: standard deviation. Surgery The mean cardiopulmonary bypass time was 92.9 ± 47.8 min with a mean length of hospital stay of 10.5 ± 7.8 days. The mean weight of the septal tissue that was removed in 87 (42.3%) patients weighed 6.6 ± 4.3 g. The surgical procedures performed in patients are presented in Table 2. One hundred and fifty-nine (78.3%) patients had an SM alone. Twenty-five (12.3%) patients had an SM with MV repair, which included edge-to-edge (Alfieri) repair, valve plication, cleft repair, chordal repair and division of papillary muscle. Nine (4.4%) patients underwent an SM with MV replacement, 2 of which were bioprosthetic MV replacements; in 6 of these 9 patients, concomitant MV replacements were unplanned following unsuccessful repair, while the remainder were planned replacements. Four of these 6 patients had degenerative MV disease with residual moderate-to-severe MR following initial bypass and SM. The other 2 patients had an MV repair after SM with residual moderate-to-severe MR. None of these 6 patients had residual SAM following the initial SM. Ten (4.9%) patients had an MV replacement alone without an SM, one of which was a bioprosthetic MV replacement. Other concomitant procedures included coronary artery bypass grafting (n = 4), aortic valve replacement (n = 3), surgical maze with or without pulmonary vein radiofrequency ablation (n = 9), resection of subaortic membrane (n = 7), closure of a patent foramen ovale (n = 3) or an atrial septal defect (n = 1). Forty-six (22.7%) patients underwent closure of the left atrial appendage at the time of surgery. Thirteen (6.4%) patients of the 203 patients required reinstitution of cardiopulmonary bypass following the initial SM. This was required for an MV repair due to residual SAM/MR (n = 7), an MV replacement for residual MR following the initial repair (n = 2) and an MV replacement directly without an intermediate repair attempt (n = 4). Anatomical and echocardiographic indications for individual surgical approaches to the MV are presented in Table 3. Table 2: Surgical procedures Overall number of patients, n (%) 203 (100) Septal myectomy, n (%) 159 (78.3) Septal myectomy with MV repair, n (%) 25 (12.3)  Plication 4  Edge-to-edge Alfieri repair 11  Cleft repair 3  Division of papillary muscles 1  Chordal repair 6 Septal myectomy with MV replacement, n (%) 9 (4.4) MV replacement alone, n (%) 10 (4.9) Concomitant procedures (in 22 patients) 27  CABG, n (%) 4 (2.0)  Planned aortic valve replacement, n (%) 3 (1.5)  Maze, n (%) 9 (4.4)  Resection of the subaortic membrane, n (%) 7 (3.4)  Closure of a PFO, n (%) 3 (1.5)  Closure of an ASD, n (%) 1 (0.5) Overall number of patients, n (%) 203 (100) Septal myectomy, n (%) 159 (78.3) Septal myectomy with MV repair, n (%) 25 (12.3)  Plication 4  Edge-to-edge Alfieri repair 11  Cleft repair 3  Division of papillary muscles 1  Chordal repair 6 Septal myectomy with MV replacement, n (%) 9 (4.4) MV replacement alone, n (%) 10 (4.9) Concomitant procedures (in 22 patients) 27  CABG, n (%) 4 (2.0)  Planned aortic valve replacement, n (%) 3 (1.5)  Maze, n (%) 9 (4.4)  Resection of the subaortic membrane, n (%) 7 (3.4)  Closure of a PFO, n (%) 3 (1.5)  Closure of an ASD, n (%) 1 (0.5) ASD: atrial septal defect; CABG: coronary artery bypass grafting; MV: mitral valve; PFO: patent foramen ovale. Table 2: Surgical procedures Overall number of patients, n (%) 203 (100) Septal myectomy, n (%) 159 (78.3) Septal myectomy with MV repair, n (%) 25 (12.3)  Plication 4  Edge-to-edge Alfieri repair 11  Cleft repair 3  Division of papillary muscles 1  Chordal repair 6 Septal myectomy with MV replacement, n (%) 9 (4.4) MV replacement alone, n (%) 10 (4.9) Concomitant procedures (in 22 patients) 27  CABG, n (%) 4 (2.0)  Planned aortic valve replacement, n (%) 3 (1.5)  Maze, n (%) 9 (4.4)  Resection of the subaortic membrane, n (%) 7 (3.4)  Closure of a PFO, n (%) 3 (1.5)  Closure of an ASD, n (%) 1 (0.5) Overall number of patients, n (%) 203 (100) Septal myectomy, n (%) 159 (78.3) Septal myectomy with MV repair, n (%) 25 (12.3)  Plication 4  Edge-to-edge Alfieri repair 11  Cleft repair 3  Division of papillary muscles 1  Chordal repair 6 Septal myectomy with MV replacement, n (%) 9 (4.4) MV replacement alone, n (%) 10 (4.9) Concomitant procedures (in 22 patients) 27  CABG, n (%) 4 (2.0)  Planned aortic valve replacement, n (%) 3 (1.5)  Maze, n (%) 9 (4.4)  Resection of the subaortic membrane, n (%) 7 (3.4)  Closure of a PFO, n (%) 3 (1.5)  Closure of an ASD, n (%) 1 (0.5) ASD: atrial septal defect; CABG: coronary artery bypass grafting; MV: mitral valve; PFO: patent foramen ovale. Table 3: Anatomical and echocardiographic features in individual surgical mitral interventions Category of MV intervention ASH  <18 mm Angulation of the aorta Long AMVL Abnormal MV attachments Myxomatous MV Prolapse MR (Grade 3 or 4) SAM Papillary division (n = 1) 1 0 0 0 0 0 1 1 Cleft repair (n = 3) 0 0 1 0 0 0 3 3 Plication (n = 4) 1 1 3 0 0 1 4 4 Chord repair (n = 6) 1 0 0 3 2 1 4 5 Alfieri (n = 11) 4 3 5 2 1 2 9 10 SM and MV replacement (n = 9) 2 1 3 2 3 1 9 9 MV replacement alone (n = 10) 7 1 1 0 6 0 7 9 Category of MV intervention ASH  <18 mm Angulation of the aorta Long AMVL Abnormal MV attachments Myxomatous MV Prolapse MR (Grade 3 or 4) SAM Papillary division (n = 1) 1 0 0 0 0 0 1 1 Cleft repair (n = 3) 0 0 1 0 0 0 3 3 Plication (n = 4) 1 1 3 0 0 1 4 4 Chord repair (n = 6) 1 0 0 3 2 1 4 5 Alfieri (n = 11) 4 3 5 2 1 2 9 10 SM and MV replacement (n = 9) 2 1 3 2 3 1 9 9 MV replacement alone (n = 10) 7 1 1 0 6 0 7 9 Numbers in each vertical column represent the number of patients with the listed specific feature. ASH: asymmetric septal hypertrophy; AMVL: anterior mitral valve leaflet; MR: mitral regurgitation; MV: mitral valve; SAM: systolic anterior motion; SM: septal myectomy. Table 3: Anatomical and echocardiographic features in individual surgical mitral interventions Category of MV intervention ASH  <18 mm Angulation of the aorta Long AMVL Abnormal MV attachments Myxomatous MV Prolapse MR (Grade 3 or 4) SAM Papillary division (n = 1) 1 0 0 0 0 0 1 1 Cleft repair (n = 3) 0 0 1 0 0 0 3 3 Plication (n = 4) 1 1 3 0 0 1 4 4 Chord repair (n = 6) 1 0 0 3 2 1 4 5 Alfieri (n = 11) 4 3 5 2 1 2 9 10 SM and MV replacement (n = 9) 2 1 3 2 3 1 9 9 MV replacement alone (n = 10) 7 1 1 0 6 0 7 9 Category of MV intervention ASH  <18 mm Angulation of the aorta Long AMVL Abnormal MV attachments Myxomatous MV Prolapse MR (Grade 3 or 4) SAM Papillary division (n = 1) 1 0 0 0 0 0 1 1 Cleft repair (n = 3) 0 0 1 0 0 0 3 3 Plication (n = 4) 1 1 3 0 0 1 4 4 Chord repair (n = 6) 1 0 0 3 2 1 4 5 Alfieri (n = 11) 4 3 5 2 1 2 9 10 SM and MV replacement (n = 9) 2 1 3 2 3 1 9 9 MV replacement alone (n = 10) 7 1 1 0 6 0 7 9 Numbers in each vertical column represent the number of patients with the listed specific feature. ASH: asymmetric septal hypertrophy; AMVL: anterior mitral valve leaflet; MR: mitral regurgitation; MV: mitral valve; SAM: systolic anterior motion; SM: septal myectomy. Early mortality Operative survival was 99.0% with 2 perioperative deaths within 30 days of surgery. One patient, a 67-year-old woman, sustained a ventricular septal defect identified on an intraoperative transoesophageal echocardiography following an SM with staple excision of the left atrial appendage. This was repaired immediately through a right ventriculotomy using bovine pericardial patches and continuous Prolene sutures to close the defect and the right ventricle. This patient developed progressive low cardiac output and died on Day 3. A second patient, a 30-year-old man, while undergoing an extended SM for severe concentric left ventricular hypertrophy and pulmonary vein isolation for the management of AF developed an aortic valve tear to the left coronary cusp which was repaired using two 8-0 Prolene sutures. This patient died on Day 3 from heart failure in the setting of aortic regurgitation, severe diastolic dysfunction and external pacemaker dysfunction. Survival at the 1-year follow-up was 98.5%, with 1 further death at 4 months due to heart failure postoperatively. There were no other deaths within the first year of surgery. Complications Fifty-six (27.6%) patients had documented postoperative AF, with 39 cases of new onset of postoperative AF. There were 2 perioperative transient ischaemic attacks (1.0%) with 4 perioperative strokes (2.0%). One stroke was assumed cardioembolic in nature in the setting of new-onset AF. The remaining cases had no documented AF. Thirteen (6.4%) patients had a permanent pacemaker device implanted for atrioventricular block. Five of these 13 patients had a planned prophylactic insertion of a permanent pacemaker for pre-existing high-grade atrioventricular block during the primary surgical admission. These patients were deemed to be at high risk for complete heart block with the additional inevitable left bundle branch block from SM. Eight further (3.9%) patients developed unexpected atrioventricular block requiring permanent pacemaker insertion. Ten (4.9%) patients had an implantable cardioverter device in the perioperative period, 3 of which were implanted to treat complete atrioventricular block in the setting of associated risk factors for sudden cardiac death. The remaining 7 patients had an implantable cardioverter device implanted based on the risk factors associated with sudden cardiac death. As described above, 3 (1.5%) patients suffered a ventricular septal defect requiring repair intraoperatively. One additional patient developed an acquired Gerbode defect postoperatively, which was successfully surgically repaired [15]. Two (1.0%) patients had an unplanned aortic valve repair due to a new valve tear intraoperatively. Two (1.0%) patients required further operative intervention during the initial surgical stay. Those patients who initially underwent SM with MV repair required reintervention with MV replacement on Day 4 and Day 14, respectively, due to severe MR. Clinical and echocardiogrpahic outcomes The mean NYHA class improved from 2.6 ± 0.5 preoperatively to 1.6 ± 0.6 postoperatively at the 1-year follow-up (P < 0.001). The majority of patients improved symptomatically, with 78.7% of the patients improving by at least one NYHA class postoperatively, with 19.5% of the patients remaining in the same NYHA functional class and a minority of patients (1.7%) in a higher NYHA function class at the 1-year follow-up. Echocardiographic variables are presented in Table 4. The mean interventricular septal wall thickness reduced from 19.1 ± 4.1 mm preoperatively to 13.9 ± 4.0 mm postoperatively (P < 0.001). Resting LVOT gradients reduced from 70.6 ± 40.3 mmHg preoperatively to 11 ± 10.5 mmHg after surgery at the 1-year follow-up (P < 0.001). One hundred and eighty-three (90.1%) patients had no evidence of resting or provoked LVOTO on the postoperative echocardiogram at the 1-year follow-up. Comparison of individual NYHA class and MR grade preoperatively and postoperatively are presented in Table 5. Table 4: Comparison of preoperative and postoperative echocardiographic variables using the paired t-test Preoperative (n = 203), mean ± SD Postoperative (n = 170), mean ± SD P-value IVS (mm) 19.1 ± 4.1 13.9 ± 4.0 <0.001 PWT (mm) 10.8 ± 2.8 10.1 ± 2.3 0.022 LAD (mm) 47.2 ± 7.7 45.8 ± 7.1 0.002 LAA (cm2) 30.6 ± 8.0 27.1 ± 7.0 0.003 LVEDd (mm) 46.0 ± 5.9 48.9 ± 6.3 <0.001 EF (%) 69.0 ± 6.8 62.1 ± 8.4 <0.001 Resting gradient (mmHg) 70.6 ± 40.3 11.0 ± 10.5 <0.001 Provoked gradient (mmHg) 91.1 ± 39.8 24.5 ± 32.0 <0.001 MR grade 2.4 ± 0.9 1.4 ± 0.7 Preoperative (n = 203), mean ± SD Postoperative (n = 170), mean ± SD P-value IVS (mm) 19.1 ± 4.1 13.9 ± 4.0 <0.001 PWT (mm) 10.8 ± 2.8 10.1 ± 2.3 0.022 LAD (mm) 47.2 ± 7.7 45.8 ± 7.1 0.002 LAA (cm2) 30.6 ± 8.0 27.1 ± 7.0 0.003 LVEDd (mm) 46.0 ± 5.9 48.9 ± 6.3 <0.001 EF (%) 69.0 ± 6.8 62.1 ± 8.4 <0.001 Resting gradient (mmHg) 70.6 ± 40.3 11.0 ± 10.5 <0.001 Provoked gradient (mmHg) 91.1 ± 39.8 24.5 ± 32.0 <0.001 MR grade 2.4 ± 0.9 1.4 ± 0.7 EF: ejection fraction; IVS: interventricular septal wall thickness; LAA: left atrial appendage; LAD: left atrial diameter; LVEDd: left ventricular end-diastolic diameter; MR: mitral regurgitation; PWT: posterior wall thickness; SD: standard deviation. Table 4: Comparison of preoperative and postoperative echocardiographic variables using the paired t-test Preoperative (n = 203), mean ± SD Postoperative (n = 170), mean ± SD P-value IVS (mm) 19.1 ± 4.1 13.9 ± 4.0 <0.001 PWT (mm) 10.8 ± 2.8 10.1 ± 2.3 0.022 LAD (mm) 47.2 ± 7.7 45.8 ± 7.1 0.002 LAA (cm2) 30.6 ± 8.0 27.1 ± 7.0 0.003 LVEDd (mm) 46.0 ± 5.9 48.9 ± 6.3 <0.001 EF (%) 69.0 ± 6.8 62.1 ± 8.4 <0.001 Resting gradient (mmHg) 70.6 ± 40.3 11.0 ± 10.5 <0.001 Provoked gradient (mmHg) 91.1 ± 39.8 24.5 ± 32.0 <0.001 MR grade 2.4 ± 0.9 1.4 ± 0.7 Preoperative (n = 203), mean ± SD Postoperative (n = 170), mean ± SD P-value IVS (mm) 19.1 ± 4.1 13.9 ± 4.0 <0.001 PWT (mm) 10.8 ± 2.8 10.1 ± 2.3 0.022 LAD (mm) 47.2 ± 7.7 45.8 ± 7.1 0.002 LAA (cm2) 30.6 ± 8.0 27.1 ± 7.0 0.003 LVEDd (mm) 46.0 ± 5.9 48.9 ± 6.3 <0.001 EF (%) 69.0 ± 6.8 62.1 ± 8.4 <0.001 Resting gradient (mmHg) 70.6 ± 40.3 11.0 ± 10.5 <0.001 Provoked gradient (mmHg) 91.1 ± 39.8 24.5 ± 32.0 <0.001 MR grade 2.4 ± 0.9 1.4 ± 0.7 EF: ejection fraction; IVS: interventricular septal wall thickness; LAA: left atrial appendage; LAD: left atrial diameter; LVEDd: left ventricular end-diastolic diameter; MR: mitral regurgitation; PWT: posterior wall thickness; SD: standard deviation. Table 5: Comparison of individual NYHA class and MR grade preoperatively and postoperatively overall and in those undergoing SM alone and those undergoing an MV intervention Overall (n = 203) SM alone (n = 159) MV intervention (n = 44) Preoperative Postoperative Preoperative Postoperative Preoperative Postoperative NYHA class (%)  1 2.0 47.4 2.6 45.7 0 53.8  2 36.7 48.6 37.3 50.0 34.1 43.6  3/4 61.3 4.0 60.1 4.3 65.9 2.6 MR grade (%)  0/1 14.2 52.9 17.3 51.2 2.4 59.5  2 42.4 43.0 44.7 44.4 34.1 37.8  3 31.9 4.1 29.3 4.4 41.5 2.7  4 11.5 0 8.7 0 22.0 0 Overall (n = 203) SM alone (n = 159) MV intervention (n = 44) Preoperative Postoperative Preoperative Postoperative Preoperative Postoperative NYHA class (%)  1 2.0 47.4 2.6 45.7 0 53.8  2 36.7 48.6 37.3 50.0 34.1 43.6  3/4 61.3 4.0 60.1 4.3 65.9 2.6 MR grade (%)  0/1 14.2 52.9 17.3 51.2 2.4 59.5  2 42.4 43.0 44.7 44.4 34.1 37.8  3 31.9 4.1 29.3 4.4 41.5 2.7  4 11.5 0 8.7 0 22.0 0 MR: mitral regurgitation; MV: mitral valve; NYHA: New York Heart Association; SM: septal myectomy. Table 5: Comparison of individual NYHA class and MR grade preoperatively and postoperatively overall and in those undergoing SM alone and those undergoing an MV intervention Overall (n = 203) SM alone (n = 159) MV intervention (n = 44) Preoperative Postoperative Preoperative Postoperative Preoperative Postoperative NYHA class (%)  1 2.0 47.4 2.6 45.7 0 53.8  2 36.7 48.6 37.3 50.0 34.1 43.6  3/4 61.3 4.0 60.1 4.3 65.9 2.6 MR grade (%)  0/1 14.2 52.9 17.3 51.2 2.4 59.5  2 42.4 43.0 44.7 44.4 34.1 37.8  3 31.9 4.1 29.3 4.4 41.5 2.7  4 11.5 0 8.7 0 22.0 0 Overall (n = 203) SM alone (n = 159) MV intervention (n = 44) Preoperative Postoperative Preoperative Postoperative Preoperative Postoperative NYHA class (%)  1 2.0 47.4 2.6 45.7 0 53.8  2 36.7 48.6 37.3 50.0 34.1 43.6  3/4 61.3 4.0 60.1 4.3 65.9 2.6 MR grade (%)  0/1 14.2 52.9 17.3 51.2 2.4 59.5  2 42.4 43.0 44.7 44.4 34.1 37.8  3 31.9 4.1 29.3 4.4 41.5 2.7  4 11.5 0 8.7 0 22.0 0 MR: mitral regurgitation; MV: mitral valve; NYHA: New York Heart Association; SM: septal myectomy. DISCUSSION According to the expert consensus, surgical management of LVOTO by SM is considered as the gold standard in the management of drug refractory symptomatic cases in HCM, with excellent outcomes in the majority of cases [2]. Multiple large surgical series have reported the outcomes of SM alone, which reflect partly the referral patterns to the large US centres [6, 8, 9]. The classical surgical approaches included the standard SM introduced by Morrow et al. [14] and MV replacement by Cooley et al. [16], both of which have shown to be successful in improving the symptoms and alleviating the LVOT gradients. In the majority of patients, SM is the only procedure required to treat LVOTO in HCM. Mitral abnormalities, however, do play an important role in the mechanism of LVOTO in individual patients such as those with limited hypertrophy, and we believe an individualized surgical approach is necessary for optimal surgical management [12]. The current series reflects experience of surgery for LVOTO in HCM in a national centre with referral of a wide phenotypic variation performing >70% of such UK practice over the period of the study. Preoperative and intraoperative imaging, including transthoracic echocardiography and transoesophageal echocardiography, are essential in the characterization of phenotypic abnormalities to allow for strategic surgical planning to address the causes of MR and SAM. Intrinsic MV abnormalities can pre-exist including annular, leaflet or chordal calcification or fibrosis, which may need to be addressed at the time of operation. Specific abnormalities of the MV apparatus, commonly seen in HCM patients, can contribute to the mechanism of LVOTO including both elongation of MV leaflets and abnormal mitral attachments [17]. Abnormal MV attachments, commonly seen with LVOTO, include anterior papillary muscle displacement, thickened bifid papillary muscles, direct insertion of the papillary muscle into the anterior MV leaflet or fibrotic chordal attachments. Complex cases with the involvement of both the mitral and the submitral apparatuses can be managed with a combination of SM and repair or replacement of the MV. The use of an extended SM can address this issue somewhat by extending the resection in a fan-like fashion moving distally in the septum. Ferrazzi et al. [18] reported good outcomes in patients undergoing a limited SM, with transaortic selective division of the fibrosed secondary chordae attached to the anterior MV leaflet body believed to be contributing to SAM. Elongation of the MV leaflets, particularly the anterior leaflet, result in SAM-related MR. In cases of limited septal hypertrophy, MV replacement has been performed as the primary surgery in the past; however, a range of newer surgical techniques for MV repair have evolved to address such cases in which adequate resection is technically challenging [19–21]. Controversy remains over individual techniques of MV repair in patients with LVOTO. The rate of concomitant MV intervention with SM varies from 8% in a recent large study of over 2000 patients from the Mayo Clinic operated on with SM for LVOTO to 25% in a paper from the Cleveland Clinic [6, 10]. Multiple surgical approaches have been advocated in the presence of elongated leaflets with post SM SAM and/or MR with good outcomes, including the edge-to-edge Alfieri repair, MV plication and anterior MV leaflet extension using a pericardial patch [19–21]. The edge-to-edge Alfieri MV repair was our preferred surgical approach to address the elongated anterior mitral leaflets with SAM-related MR with good resolution of LVOT gradients and improved symptoms. This was done using a transatrial rather than a transaortic approach, which allowed us to inspect the submitral apparatus extensively. The Alfieri technique has been used successfully in MR of various aetiologies [21]. There have been no early or late mortalities in this group of 11 patients in the current study, which documented good medium-term outcomes [22]. If an Alfieri repair is contemplated, assessment of the posterior MV leaflet length is important, as excess length can lead to bileaflet prolapse with SAM, making this type of repair less likely to be effective. The advantage of MV repair is that it obviates the need for MV replacement and its associated complications [23]. Late survival following SM with MV repair was superior to SM with MV replacement in the large Mayo clinical experience [10]. Contemporary data on MV replacement alone for relief of LVOTO in HCM in the literature are less robust than that for SM. Initial studies reported by Cooley et al. [16] showed good symptomatic relief and resolution of gradients. Further long-term studies by the same group showed good outcomes at 10 years [24]. Other early studies reported similar symptomatic and gradient reduction with MV replacement; however, higher mortality rates and complication rates were seen in these cohorts [25, 26]. More recent studies of MV replacement in patients with LVOTO have reported on SM with MV replacement rather than MV replacement alone [10, 27–29]. MV replacement alone can be a successful approach in cases unsuitable for repair or when used alone in those patients with thinner septae unsuitable for SM. In the early part of the series, there were few concomitant MV procedures performed. With an improved understanding of the mechanism of obstruction over time, more complex HCM phenotypes were operated on, particularly in older patients with concomitant cardiac disease with an increasing number of MV repairs and replacements. The decision to proceed with an MV replacement directly rather than a further bypass run to explore a potentially intermediate MV repair was carefully considered. In this study, it was noted that patients who required MV replacement were older and had more comorbidities than those who did not require an MV replacement. The preoperative phenotype and cardiac and non-cardiac comorbidities were factored into the surgical decision-making process, i.e. in consideration of the tolerance of a more extensive, longer operation. In selected older patients with atypical phenotypes and multiple comorbidities, in whom SM alone was deemed unlikely to be adequate and who were deemed to be unsuitable for multiple bypass runs, an upfront decision to perform MV replacement alone was made in this series. Figure 1 illustrates a flow chart for consideration in the strategic planning of surgery in the management of non-classical LVOTO in HCM. These phenotypes include aortic angulation, limited hypertrophy or abnormally distributed hypertrophy along with abnormalities of the MV commonly including elongated leaflets, abnormal MV attachments or other intrinsic abnormalities of the MV. A stepwise approach is taken in the planning of individual cases, which is re-evaluated intraoperatively following the initial procedure and initial bypass run to evaluate whether further intervention is needed to the MV. The recent Mayo study of 174 patients surgically managed with SM and MV intervention revealed no difference in the intensive care unit length of stay, hospital length of stay or late mortality in those undergoing single or multiple cardiopulmonary bypass runs, indicating the safety of this approach in appropriate patients [10]. Figure 1: View largeDownload slide Flow chart depicting decision-making for surgical management. CPB: cardiopulmonary bypass; LVOTO: left ventricular outflow tract obstruction; MR: mitral regurgitation; MV: mitral valve; MWT: maximum wall thickness; TOE: transoesophageal echocardiography. Figure 1: View largeDownload slide Flow chart depicting decision-making for surgical management. CPB: cardiopulmonary bypass; LVOTO: left ventricular outflow tract obstruction; MR: mitral regurgitation; MV: mitral valve; MWT: maximum wall thickness; TOE: transoesophageal echocardiography. Hospital volume plays an important role in mortality outcomes of surgery for HCM. A recent national database study analysing 6386 SMs reported that surgery in lower volume centres was an independent predictor of mortality in the USA [30]. In high-volume centres, early surgical outcomes following SM have shown very low mortality rates with good resolution of symptoms [5, 6, 10, 30]. Mortality within this study was low and comparable to the current reported outcomes in high-volume centres for SM [8]. Additionally, 21.7% of patients included in this study had an MV surgery and 10.8% had a concomitant non-mitral surgery. This study reported good echocardiographic results with 83.7% of all patients at the 1-year follow-up, a rate that has not been achieved in many other studies of this size. Almost 80% of patients in this study showed an improvement in NYHA class postoperatively comparable to previous large studies [9, 11]. Over 90% of patients demonstrated a resolution of obstruction with an LVOT gradient of <30 mmHg on postoperative echocardiography at 1 year. This individualized approach to the management of LVOTO in variable phenotypes of HCM adopted by our institution has not compromised, at least, the 1-year surgical, clinical and echocardiographic outcomes. Limitations This study is a single-centre, retrospective consecutive experience, representing limitations inherent to this study design. We acknowledge that as a national referral centre with a large population of HCM patients attending for regular clinical review that this may introduce referral bias; however, we believe that a more variable set of phenotypes may be seen within such an environment, requiring a more individualized surgical approach. There were incomplete data on the exact distribution of hypertrophy from echocardiography in individual patients. CONCLUSIONS This study from a single-centre experience reports individualized surgical approaches to the management of LVOTO in HCM patients with low mortality rates and good clinical outcomes. The surgical strategy should be individualized depending on the underlying mechanism of obstruction with an appropriate evaluation of the MV. Conflict of interest: St Bartholomew's Hospital, London is a member of European Reference Network on Rare and Complex Diseases of the Heart (Guard-Heart) (http://guardheart.ern-net.eu). REFERENCES 1 Nishimura RA , Holmes DR. Hypertrophic obstructive cardiomyopathy . N Engl J Med 2004 ; 350 : 1320 – 7 . Google Scholar CrossRef Search ADS PubMed 2 Elliott PM , Anastasakis A , Borger MA , Borggrefe M , Cecchi F , Charron P et al. 2014 ESC Guidelines on diagnosis and management of hypertrophic cardiomyopathy: the Task Force for the Diagnosis and Management of Hypertrophic Cardiomyopathy of the European Society of Cardiology (ESC) . Eur Heart J 2014 ; 35 : 2733 – 9 . Google Scholar CrossRef Search ADS PubMed 3 Maron BJ. Hypertrophic cardiomyopathy: a systematic review . JAMA 2002 ; 287 : 1308 – 20 . 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A systematic review and meta-analysis of long-term outcomes after septal reduction therapy in patients with hypertrophic cardiomyopathy . JACC Heart Fail 2015 ; 3 : 896 – 905 . Google Scholar CrossRef Search ADS PubMed 8 Maron BJ , Dearani JA , Ommen SR , Maron MS , Schaff HV , Nishimura RA et al. Low operative mortality achieved with surgical septal myectomy: role of dedicated hypertrophic cardiomyopathy centers in the management of dynamic subaortic obstruction . J Am Coll Cardiol 2015 ; 66 : 1307 – 8 . Google Scholar CrossRef Search ADS PubMed 9 Ommen SR , Maron BJ , Olivotto I , Maron MS , Cecchi F , Betocchi S et al. Long-term effects of surgical septal myectomy on survival in patients with obstructive hypertrophic cardiomyopathy . J Am Coll Cardiol 2005 ; 46 : 470 – 6 . Google Scholar CrossRef Search ADS PubMed 10 Hong JH , Schaff HV , Nishimura RA , Abel MD , Dearani JA , Li Z et al. 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Individualized surgical strategies for left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

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Oxford University Press
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© The Author(s) 2017. 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/ezx458
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Abstract

Abstract OBJECTIVES Surgical strategies to treat drug refractory left ventricular outflow tract obstruction (LVOTO) in hypertrophic cardiomyopathy include septal myectomy (SM) and, less frequently, mitral valve (MV) repair or replacement. The primary aim of this study was to report the surgical technique and management outcomes in a consecutive group of patients with variable phenotypes of hypertrophic cardiomyopathy in a broad national specialist practice. METHODS A total of 203 consecutive patients, 132 men (mean age 48.6 ± 14.6 years) underwent surgery for the management of LVOTO. Surgical approaches included SM (n = 159), SM with MV repair (n = 25), SM with MV replacement (n = 9) and MV replacement alone (n = 10). Specific surgical approaches were performed based on the underlying mechanism of obstruction. Eleven (5.4%) patients had previous alcohol septal ablation for the management of LVOTO. Concomitant non-mitral cardiac procedures were carried out in 22 (10.8%) patients. RESULTS Operative survival rate was 99.0% with 2 deaths within 30 days. The mean bypass time was 92.9 ± 47.8 min, with a mean length of hospital stay of 10.5 ± 7.8 days. Surgical complications included 3 ventricular septal defects requiring repair (1.5%), 1 Gerbode defect surgically repaired, 2 aortic valve repairs (1.0%), 2 transient ischaemic attacks (1.0%) and 4 strokes (2.0%). Thirty-nine (19.2%) patients had perioperative new-onset atrial fibrillation and 8 (3.9%) patients had unexpected atrioventricular block requiring a permanent pacemaker. Mean resting left ventricular outflow tract gradient improved from 70.6 ± 40.3 mmHg preoperatively to 11.0 ± 10.5 mmHg at 1 year postoperatively (P < 0.001). Mean New York Heart Association class improved from 2.6 ± 0.5 preoperatively to 1.6 ± 0.6 at 1 year after the procedure. CONCLUSIONS In variable phenotypes of LVOTO in hypertrophic cardiomyopathy, an individualized surgical approach provided effective reductions in left ventricular outflow tract gradients and good symptomatic relief with acceptable mortality and morbidity. Septal myectomy, Mitral valve intervention, Left ventricular outflow tract obstruction, Hypertrophic cardiomyopathy INTRODUCTION Hypertrophic cardiomyopathy (HCM) is the commonest genetically inherited cardiac condition affecting 1 in 500 of the population. Complications include left ventricular outflow tract obstruction (LVOTO), atrial fibrillation (AF), ventricular arrhythmias, sudden cardiac death and heart failure [1–4]. Severe drug refractory symptoms can persist in up to one-third of cases. Expert consensus indicates surgical intervention to be the gold standard in the management of these patients [2]. Septal myectomy (SM) alone is the preferred surgical technique in the majority of patients with HCM, providing excellent outcomes [5–11]. The mechanism of LVOTO is often complex, with a variety of non-classical phenotypes seen in HCM. This includes limited septal hypertrophy, angulation of the aorta, elongation of the mitral leaflets and abnormalities of the submitral apparatus. Abnormal mitral attachments include thickened or anteriorly displaced papillary muscles, direct insertion of the papillary muscle into the anterior mitral valve (MV) leaflet or fibrotic chordal attachments [12]. These non-classical phenotypes may, in individual circumstances, dictate a different surgical approach. With an improved understanding of the mechanism of obstruction, an increasing number of MV repairs and replacements are being performed concomitantly with SM or alone. The primary aim of this study is to evaluate the early outcomes following individualized surgical strategies for the management of LVOTO in a wide spectrum of HCM patients. METHODS Study Between 2003 and 2015, 203 consecutive patients underwent surgical intervention for the management of LVOTO in HCM in a national specialized cardiomyopathy unit at the Heart Hospital, University College London Hospital. No patients were excluded. All patients were operated on by 1 of 2 surgeons (C.G.A.McG. and V.T.). Clinical assessment All patients were assessed in a clinic specializing in cardiomyopathy. Baseline demographic data including age, gender, medical and family history were documented, as was preoperative and postoperative New York Heart Association (NYHA) functional class. Variables from transthoracic echocardiography, including interventricular septal wall thickness, posterior wall thickness, left ventricular end-diastolic diameter, left atrial diameter, left ventricular ejection fraction, resting and provoked LVOT gradients and severity of mitral and aortic regurgitation, were collected. Drug refractory symptomatic LVOTO with an LVOT gradient >50 mmHg was the principal indication for surgery according to the international guidelines [2]. The conditions of all patients and the most suitable surgical approach that could be performed were discussed at a joint medical and surgical cardiac conference. Particular attention was paid to the MV on multimodality imaging preoperatively to decide whether an MV intervention might be required at the time of surgery. Surgical technique After median sternotomy and before cardiopulmonary bypass, direct simultaneous pressure measurements were performed with needles in the aorta and the left ventricle. Provocation was measured following a bolus of isoproterenol (5 μg) intravenously and repeated if an increase in the heart rate and/or reduction in the blood pressure was not attained. During the study period, the surgical technique of SM evolved from the classical Morrow myectomy to the Danielson modification of the classical Morrow myectomy [13, 14]. After the initial planned surgery and cessation of cardiopulmonary bypass, transoesophageal echocardiography was performed to assess the LVOT and the MV. Direct simultaneous pressure measurements were repeated with and without provocation as done pre-bypass. Indications to resume bypass and perform further surgery at this point were principally a significant residual gradient and/or persistent systolic anterior motion (SAM) related mitral regurgitation (MR). MV repairs included transatrial Alfieri edge-to-edge repair, transaortic mitral plication, cleft repair, division of papillary muscles or artificial chordal repair. Mitral annuloplasty was avoided in all patients. MV replacement was done at the time of SM using the standard techniques, and MV replacement was done alone without SM again using the standard techniques. Perioperative complications were defined as those occurring within the first 30 days following surgery. Follow-up All patients were followed up clinically at regular annual visits or more frequent intervals based on their clinical status. At the 1-year follow-up, postoperative echocardiographic data were available in 83.7% of patients. The remainder of the patients were followed up by their local cardiologist. Statistical analysis Variables were collected and assessed using the SPSS software, version 24 (IBM, Chicago, IL, USA). The tests of normality were carried out based on the histogram distribution and the Shapiro–Wilks test. For data with a normal distribution, continuous variables were expressed as the mean ± standard deviation. For data with a non-normal distribution, continuous variables were expressed as the median with interquartile range. For normally distributed data, comparison of means was done using the paired Student’s t-test. For non-normally distributed data, comparisons were done using the Mann–Whitney U-test. All echocardiographic variables were normally distributed, and the comparison of means was performed using the paired Student’s t-test. A P-value of <0.05 was considered statistically significant. RESULTS The baseline characteristics of all the patients are presented in Table 1. The overall mean age of patients at surgery was 48.6 ± 14.6 years, and the mean age in patients undergoing an SM alone was 47.5 ± 14.2 years, SM with MV repair was 48.7 ± 15.0 years, SM with MV replacement was 55.4 ± 15.0 years and MV replacement alone was 57.7 ± 14.3 years. Eleven (5.4%) patients previously underwent alcohol septal ablation for the management of LVOTO with recurrence of symptoms. Table 1: Baseline demographics Overall number of patients, n (%) 203 (100) Age at surgery (years), mean ± SD 48.6 ± 14.6 Male, n (%) 132 (65.0) History, n (%)  Atrial fibrillation 28 (13.8)  Previous PPM 14 (6.9)  Previous PPM for LVOTO 9 (4.4)  Previous ASA 11 (5.4)  Stroke 3 (1.5)  Peripheral vascular disease 1 (0.5)  Diabetes mellitus 9 (4.4)  Hypertension 58 (28.6) Overall number of patients, n (%) 203 (100) Age at surgery (years), mean ± SD 48.6 ± 14.6 Male, n (%) 132 (65.0) History, n (%)  Atrial fibrillation 28 (13.8)  Previous PPM 14 (6.9)  Previous PPM for LVOTO 9 (4.4)  Previous ASA 11 (5.4)  Stroke 3 (1.5)  Peripheral vascular disease 1 (0.5)  Diabetes mellitus 9 (4.4)  Hypertension 58 (28.6) ASA: alcohol septal ablation; LVOTO: left ventricular outflow tract obstruction; PPM: permanent pacemaker; SD: standard deviation. Table 1: Baseline demographics Overall number of patients, n (%) 203 (100) Age at surgery (years), mean ± SD 48.6 ± 14.6 Male, n (%) 132 (65.0) History, n (%)  Atrial fibrillation 28 (13.8)  Previous PPM 14 (6.9)  Previous PPM for LVOTO 9 (4.4)  Previous ASA 11 (5.4)  Stroke 3 (1.5)  Peripheral vascular disease 1 (0.5)  Diabetes mellitus 9 (4.4)  Hypertension 58 (28.6) Overall number of patients, n (%) 203 (100) Age at surgery (years), mean ± SD 48.6 ± 14.6 Male, n (%) 132 (65.0) History, n (%)  Atrial fibrillation 28 (13.8)  Previous PPM 14 (6.9)  Previous PPM for LVOTO 9 (4.4)  Previous ASA 11 (5.4)  Stroke 3 (1.5)  Peripheral vascular disease 1 (0.5)  Diabetes mellitus 9 (4.4)  Hypertension 58 (28.6) ASA: alcohol septal ablation; LVOTO: left ventricular outflow tract obstruction; PPM: permanent pacemaker; SD: standard deviation. Surgery The mean cardiopulmonary bypass time was 92.9 ± 47.8 min with a mean length of hospital stay of 10.5 ± 7.8 days. The mean weight of the septal tissue that was removed in 87 (42.3%) patients weighed 6.6 ± 4.3 g. The surgical procedures performed in patients are presented in Table 2. One hundred and fifty-nine (78.3%) patients had an SM alone. Twenty-five (12.3%) patients had an SM with MV repair, which included edge-to-edge (Alfieri) repair, valve plication, cleft repair, chordal repair and division of papillary muscle. Nine (4.4%) patients underwent an SM with MV replacement, 2 of which were bioprosthetic MV replacements; in 6 of these 9 patients, concomitant MV replacements were unplanned following unsuccessful repair, while the remainder were planned replacements. Four of these 6 patients had degenerative MV disease with residual moderate-to-severe MR following initial bypass and SM. The other 2 patients had an MV repair after SM with residual moderate-to-severe MR. None of these 6 patients had residual SAM following the initial SM. Ten (4.9%) patients had an MV replacement alone without an SM, one of which was a bioprosthetic MV replacement. Other concomitant procedures included coronary artery bypass grafting (n = 4), aortic valve replacement (n = 3), surgical maze with or without pulmonary vein radiofrequency ablation (n = 9), resection of subaortic membrane (n = 7), closure of a patent foramen ovale (n = 3) or an atrial septal defect (n = 1). Forty-six (22.7%) patients underwent closure of the left atrial appendage at the time of surgery. Thirteen (6.4%) patients of the 203 patients required reinstitution of cardiopulmonary bypass following the initial SM. This was required for an MV repair due to residual SAM/MR (n = 7), an MV replacement for residual MR following the initial repair (n = 2) and an MV replacement directly without an intermediate repair attempt (n = 4). Anatomical and echocardiographic indications for individual surgical approaches to the MV are presented in Table 3. Table 2: Surgical procedures Overall number of patients, n (%) 203 (100) Septal myectomy, n (%) 159 (78.3) Septal myectomy with MV repair, n (%) 25 (12.3)  Plication 4  Edge-to-edge Alfieri repair 11  Cleft repair 3  Division of papillary muscles 1  Chordal repair 6 Septal myectomy with MV replacement, n (%) 9 (4.4) MV replacement alone, n (%) 10 (4.9) Concomitant procedures (in 22 patients) 27  CABG, n (%) 4 (2.0)  Planned aortic valve replacement, n (%) 3 (1.5)  Maze, n (%) 9 (4.4)  Resection of the subaortic membrane, n (%) 7 (3.4)  Closure of a PFO, n (%) 3 (1.5)  Closure of an ASD, n (%) 1 (0.5) Overall number of patients, n (%) 203 (100) Septal myectomy, n (%) 159 (78.3) Septal myectomy with MV repair, n (%) 25 (12.3)  Plication 4  Edge-to-edge Alfieri repair 11  Cleft repair 3  Division of papillary muscles 1  Chordal repair 6 Septal myectomy with MV replacement, n (%) 9 (4.4) MV replacement alone, n (%) 10 (4.9) Concomitant procedures (in 22 patients) 27  CABG, n (%) 4 (2.0)  Planned aortic valve replacement, n (%) 3 (1.5)  Maze, n (%) 9 (4.4)  Resection of the subaortic membrane, n (%) 7 (3.4)  Closure of a PFO, n (%) 3 (1.5)  Closure of an ASD, n (%) 1 (0.5) ASD: atrial septal defect; CABG: coronary artery bypass grafting; MV: mitral valve; PFO: patent foramen ovale. Table 2: Surgical procedures Overall number of patients, n (%) 203 (100) Septal myectomy, n (%) 159 (78.3) Septal myectomy with MV repair, n (%) 25 (12.3)  Plication 4  Edge-to-edge Alfieri repair 11  Cleft repair 3  Division of papillary muscles 1  Chordal repair 6 Septal myectomy with MV replacement, n (%) 9 (4.4) MV replacement alone, n (%) 10 (4.9) Concomitant procedures (in 22 patients) 27  CABG, n (%) 4 (2.0)  Planned aortic valve replacement, n (%) 3 (1.5)  Maze, n (%) 9 (4.4)  Resection of the subaortic membrane, n (%) 7 (3.4)  Closure of a PFO, n (%) 3 (1.5)  Closure of an ASD, n (%) 1 (0.5) Overall number of patients, n (%) 203 (100) Septal myectomy, n (%) 159 (78.3) Septal myectomy with MV repair, n (%) 25 (12.3)  Plication 4  Edge-to-edge Alfieri repair 11  Cleft repair 3  Division of papillary muscles 1  Chordal repair 6 Septal myectomy with MV replacement, n (%) 9 (4.4) MV replacement alone, n (%) 10 (4.9) Concomitant procedures (in 22 patients) 27  CABG, n (%) 4 (2.0)  Planned aortic valve replacement, n (%) 3 (1.5)  Maze, n (%) 9 (4.4)  Resection of the subaortic membrane, n (%) 7 (3.4)  Closure of a PFO, n (%) 3 (1.5)  Closure of an ASD, n (%) 1 (0.5) ASD: atrial septal defect; CABG: coronary artery bypass grafting; MV: mitral valve; PFO: patent foramen ovale. Table 3: Anatomical and echocardiographic features in individual surgical mitral interventions Category of MV intervention ASH  <18 mm Angulation of the aorta Long AMVL Abnormal MV attachments Myxomatous MV Prolapse MR (Grade 3 or 4) SAM Papillary division (n = 1) 1 0 0 0 0 0 1 1 Cleft repair (n = 3) 0 0 1 0 0 0 3 3 Plication (n = 4) 1 1 3 0 0 1 4 4 Chord repair (n = 6) 1 0 0 3 2 1 4 5 Alfieri (n = 11) 4 3 5 2 1 2 9 10 SM and MV replacement (n = 9) 2 1 3 2 3 1 9 9 MV replacement alone (n = 10) 7 1 1 0 6 0 7 9 Category of MV intervention ASH  <18 mm Angulation of the aorta Long AMVL Abnormal MV attachments Myxomatous MV Prolapse MR (Grade 3 or 4) SAM Papillary division (n = 1) 1 0 0 0 0 0 1 1 Cleft repair (n = 3) 0 0 1 0 0 0 3 3 Plication (n = 4) 1 1 3 0 0 1 4 4 Chord repair (n = 6) 1 0 0 3 2 1 4 5 Alfieri (n = 11) 4 3 5 2 1 2 9 10 SM and MV replacement (n = 9) 2 1 3 2 3 1 9 9 MV replacement alone (n = 10) 7 1 1 0 6 0 7 9 Numbers in each vertical column represent the number of patients with the listed specific feature. ASH: asymmetric septal hypertrophy; AMVL: anterior mitral valve leaflet; MR: mitral regurgitation; MV: mitral valve; SAM: systolic anterior motion; SM: septal myectomy. Table 3: Anatomical and echocardiographic features in individual surgical mitral interventions Category of MV intervention ASH  <18 mm Angulation of the aorta Long AMVL Abnormal MV attachments Myxomatous MV Prolapse MR (Grade 3 or 4) SAM Papillary division (n = 1) 1 0 0 0 0 0 1 1 Cleft repair (n = 3) 0 0 1 0 0 0 3 3 Plication (n = 4) 1 1 3 0 0 1 4 4 Chord repair (n = 6) 1 0 0 3 2 1 4 5 Alfieri (n = 11) 4 3 5 2 1 2 9 10 SM and MV replacement (n = 9) 2 1 3 2 3 1 9 9 MV replacement alone (n = 10) 7 1 1 0 6 0 7 9 Category of MV intervention ASH  <18 mm Angulation of the aorta Long AMVL Abnormal MV attachments Myxomatous MV Prolapse MR (Grade 3 or 4) SAM Papillary division (n = 1) 1 0 0 0 0 0 1 1 Cleft repair (n = 3) 0 0 1 0 0 0 3 3 Plication (n = 4) 1 1 3 0 0 1 4 4 Chord repair (n = 6) 1 0 0 3 2 1 4 5 Alfieri (n = 11) 4 3 5 2 1 2 9 10 SM and MV replacement (n = 9) 2 1 3 2 3 1 9 9 MV replacement alone (n = 10) 7 1 1 0 6 0 7 9 Numbers in each vertical column represent the number of patients with the listed specific feature. ASH: asymmetric septal hypertrophy; AMVL: anterior mitral valve leaflet; MR: mitral regurgitation; MV: mitral valve; SAM: systolic anterior motion; SM: septal myectomy. Early mortality Operative survival was 99.0% with 2 perioperative deaths within 30 days of surgery. One patient, a 67-year-old woman, sustained a ventricular septal defect identified on an intraoperative transoesophageal echocardiography following an SM with staple excision of the left atrial appendage. This was repaired immediately through a right ventriculotomy using bovine pericardial patches and continuous Prolene sutures to close the defect and the right ventricle. This patient developed progressive low cardiac output and died on Day 3. A second patient, a 30-year-old man, while undergoing an extended SM for severe concentric left ventricular hypertrophy and pulmonary vein isolation for the management of AF developed an aortic valve tear to the left coronary cusp which was repaired using two 8-0 Prolene sutures. This patient died on Day 3 from heart failure in the setting of aortic regurgitation, severe diastolic dysfunction and external pacemaker dysfunction. Survival at the 1-year follow-up was 98.5%, with 1 further death at 4 months due to heart failure postoperatively. There were no other deaths within the first year of surgery. Complications Fifty-six (27.6%) patients had documented postoperative AF, with 39 cases of new onset of postoperative AF. There were 2 perioperative transient ischaemic attacks (1.0%) with 4 perioperative strokes (2.0%). One stroke was assumed cardioembolic in nature in the setting of new-onset AF. The remaining cases had no documented AF. Thirteen (6.4%) patients had a permanent pacemaker device implanted for atrioventricular block. Five of these 13 patients had a planned prophylactic insertion of a permanent pacemaker for pre-existing high-grade atrioventricular block during the primary surgical admission. These patients were deemed to be at high risk for complete heart block with the additional inevitable left bundle branch block from SM. Eight further (3.9%) patients developed unexpected atrioventricular block requiring permanent pacemaker insertion. Ten (4.9%) patients had an implantable cardioverter device in the perioperative period, 3 of which were implanted to treat complete atrioventricular block in the setting of associated risk factors for sudden cardiac death. The remaining 7 patients had an implantable cardioverter device implanted based on the risk factors associated with sudden cardiac death. As described above, 3 (1.5%) patients suffered a ventricular septal defect requiring repair intraoperatively. One additional patient developed an acquired Gerbode defect postoperatively, which was successfully surgically repaired [15]. Two (1.0%) patients had an unplanned aortic valve repair due to a new valve tear intraoperatively. Two (1.0%) patients required further operative intervention during the initial surgical stay. Those patients who initially underwent SM with MV repair required reintervention with MV replacement on Day 4 and Day 14, respectively, due to severe MR. Clinical and echocardiogrpahic outcomes The mean NYHA class improved from 2.6 ± 0.5 preoperatively to 1.6 ± 0.6 postoperatively at the 1-year follow-up (P < 0.001). The majority of patients improved symptomatically, with 78.7% of the patients improving by at least one NYHA class postoperatively, with 19.5% of the patients remaining in the same NYHA functional class and a minority of patients (1.7%) in a higher NYHA function class at the 1-year follow-up. Echocardiographic variables are presented in Table 4. The mean interventricular septal wall thickness reduced from 19.1 ± 4.1 mm preoperatively to 13.9 ± 4.0 mm postoperatively (P < 0.001). Resting LVOT gradients reduced from 70.6 ± 40.3 mmHg preoperatively to 11 ± 10.5 mmHg after surgery at the 1-year follow-up (P < 0.001). One hundred and eighty-three (90.1%) patients had no evidence of resting or provoked LVOTO on the postoperative echocardiogram at the 1-year follow-up. Comparison of individual NYHA class and MR grade preoperatively and postoperatively are presented in Table 5. Table 4: Comparison of preoperative and postoperative echocardiographic variables using the paired t-test Preoperative (n = 203), mean ± SD Postoperative (n = 170), mean ± SD P-value IVS (mm) 19.1 ± 4.1 13.9 ± 4.0 <0.001 PWT (mm) 10.8 ± 2.8 10.1 ± 2.3 0.022 LAD (mm) 47.2 ± 7.7 45.8 ± 7.1 0.002 LAA (cm2) 30.6 ± 8.0 27.1 ± 7.0 0.003 LVEDd (mm) 46.0 ± 5.9 48.9 ± 6.3 <0.001 EF (%) 69.0 ± 6.8 62.1 ± 8.4 <0.001 Resting gradient (mmHg) 70.6 ± 40.3 11.0 ± 10.5 <0.001 Provoked gradient (mmHg) 91.1 ± 39.8 24.5 ± 32.0 <0.001 MR grade 2.4 ± 0.9 1.4 ± 0.7 Preoperative (n = 203), mean ± SD Postoperative (n = 170), mean ± SD P-value IVS (mm) 19.1 ± 4.1 13.9 ± 4.0 <0.001 PWT (mm) 10.8 ± 2.8 10.1 ± 2.3 0.022 LAD (mm) 47.2 ± 7.7 45.8 ± 7.1 0.002 LAA (cm2) 30.6 ± 8.0 27.1 ± 7.0 0.003 LVEDd (mm) 46.0 ± 5.9 48.9 ± 6.3 <0.001 EF (%) 69.0 ± 6.8 62.1 ± 8.4 <0.001 Resting gradient (mmHg) 70.6 ± 40.3 11.0 ± 10.5 <0.001 Provoked gradient (mmHg) 91.1 ± 39.8 24.5 ± 32.0 <0.001 MR grade 2.4 ± 0.9 1.4 ± 0.7 EF: ejection fraction; IVS: interventricular septal wall thickness; LAA: left atrial appendage; LAD: left atrial diameter; LVEDd: left ventricular end-diastolic diameter; MR: mitral regurgitation; PWT: posterior wall thickness; SD: standard deviation. Table 4: Comparison of preoperative and postoperative echocardiographic variables using the paired t-test Preoperative (n = 203), mean ± SD Postoperative (n = 170), mean ± SD P-value IVS (mm) 19.1 ± 4.1 13.9 ± 4.0 <0.001 PWT (mm) 10.8 ± 2.8 10.1 ± 2.3 0.022 LAD (mm) 47.2 ± 7.7 45.8 ± 7.1 0.002 LAA (cm2) 30.6 ± 8.0 27.1 ± 7.0 0.003 LVEDd (mm) 46.0 ± 5.9 48.9 ± 6.3 <0.001 EF (%) 69.0 ± 6.8 62.1 ± 8.4 <0.001 Resting gradient (mmHg) 70.6 ± 40.3 11.0 ± 10.5 <0.001 Provoked gradient (mmHg) 91.1 ± 39.8 24.5 ± 32.0 <0.001 MR grade 2.4 ± 0.9 1.4 ± 0.7 Preoperative (n = 203), mean ± SD Postoperative (n = 170), mean ± SD P-value IVS (mm) 19.1 ± 4.1 13.9 ± 4.0 <0.001 PWT (mm) 10.8 ± 2.8 10.1 ± 2.3 0.022 LAD (mm) 47.2 ± 7.7 45.8 ± 7.1 0.002 LAA (cm2) 30.6 ± 8.0 27.1 ± 7.0 0.003 LVEDd (mm) 46.0 ± 5.9 48.9 ± 6.3 <0.001 EF (%) 69.0 ± 6.8 62.1 ± 8.4 <0.001 Resting gradient (mmHg) 70.6 ± 40.3 11.0 ± 10.5 <0.001 Provoked gradient (mmHg) 91.1 ± 39.8 24.5 ± 32.0 <0.001 MR grade 2.4 ± 0.9 1.4 ± 0.7 EF: ejection fraction; IVS: interventricular septal wall thickness; LAA: left atrial appendage; LAD: left atrial diameter; LVEDd: left ventricular end-diastolic diameter; MR: mitral regurgitation; PWT: posterior wall thickness; SD: standard deviation. Table 5: Comparison of individual NYHA class and MR grade preoperatively and postoperatively overall and in those undergoing SM alone and those undergoing an MV intervention Overall (n = 203) SM alone (n = 159) MV intervention (n = 44) Preoperative Postoperative Preoperative Postoperative Preoperative Postoperative NYHA class (%)  1 2.0 47.4 2.6 45.7 0 53.8  2 36.7 48.6 37.3 50.0 34.1 43.6  3/4 61.3 4.0 60.1 4.3 65.9 2.6 MR grade (%)  0/1 14.2 52.9 17.3 51.2 2.4 59.5  2 42.4 43.0 44.7 44.4 34.1 37.8  3 31.9 4.1 29.3 4.4 41.5 2.7  4 11.5 0 8.7 0 22.0 0 Overall (n = 203) SM alone (n = 159) MV intervention (n = 44) Preoperative Postoperative Preoperative Postoperative Preoperative Postoperative NYHA class (%)  1 2.0 47.4 2.6 45.7 0 53.8  2 36.7 48.6 37.3 50.0 34.1 43.6  3/4 61.3 4.0 60.1 4.3 65.9 2.6 MR grade (%)  0/1 14.2 52.9 17.3 51.2 2.4 59.5  2 42.4 43.0 44.7 44.4 34.1 37.8  3 31.9 4.1 29.3 4.4 41.5 2.7  4 11.5 0 8.7 0 22.0 0 MR: mitral regurgitation; MV: mitral valve; NYHA: New York Heart Association; SM: septal myectomy. Table 5: Comparison of individual NYHA class and MR grade preoperatively and postoperatively overall and in those undergoing SM alone and those undergoing an MV intervention Overall (n = 203) SM alone (n = 159) MV intervention (n = 44) Preoperative Postoperative Preoperative Postoperative Preoperative Postoperative NYHA class (%)  1 2.0 47.4 2.6 45.7 0 53.8  2 36.7 48.6 37.3 50.0 34.1 43.6  3/4 61.3 4.0 60.1 4.3 65.9 2.6 MR grade (%)  0/1 14.2 52.9 17.3 51.2 2.4 59.5  2 42.4 43.0 44.7 44.4 34.1 37.8  3 31.9 4.1 29.3 4.4 41.5 2.7  4 11.5 0 8.7 0 22.0 0 Overall (n = 203) SM alone (n = 159) MV intervention (n = 44) Preoperative Postoperative Preoperative Postoperative Preoperative Postoperative NYHA class (%)  1 2.0 47.4 2.6 45.7 0 53.8  2 36.7 48.6 37.3 50.0 34.1 43.6  3/4 61.3 4.0 60.1 4.3 65.9 2.6 MR grade (%)  0/1 14.2 52.9 17.3 51.2 2.4 59.5  2 42.4 43.0 44.7 44.4 34.1 37.8  3 31.9 4.1 29.3 4.4 41.5 2.7  4 11.5 0 8.7 0 22.0 0 MR: mitral regurgitation; MV: mitral valve; NYHA: New York Heart Association; SM: septal myectomy. DISCUSSION According to the expert consensus, surgical management of LVOTO by SM is considered as the gold standard in the management of drug refractory symptomatic cases in HCM, with excellent outcomes in the majority of cases [2]. Multiple large surgical series have reported the outcomes of SM alone, which reflect partly the referral patterns to the large US centres [6, 8, 9]. The classical surgical approaches included the standard SM introduced by Morrow et al. [14] and MV replacement by Cooley et al. [16], both of which have shown to be successful in improving the symptoms and alleviating the LVOT gradients. In the majority of patients, SM is the only procedure required to treat LVOTO in HCM. Mitral abnormalities, however, do play an important role in the mechanism of LVOTO in individual patients such as those with limited hypertrophy, and we believe an individualized surgical approach is necessary for optimal surgical management [12]. The current series reflects experience of surgery for LVOTO in HCM in a national centre with referral of a wide phenotypic variation performing >70% of such UK practice over the period of the study. Preoperative and intraoperative imaging, including transthoracic echocardiography and transoesophageal echocardiography, are essential in the characterization of phenotypic abnormalities to allow for strategic surgical planning to address the causes of MR and SAM. Intrinsic MV abnormalities can pre-exist including annular, leaflet or chordal calcification or fibrosis, which may need to be addressed at the time of operation. Specific abnormalities of the MV apparatus, commonly seen in HCM patients, can contribute to the mechanism of LVOTO including both elongation of MV leaflets and abnormal mitral attachments [17]. Abnormal MV attachments, commonly seen with LVOTO, include anterior papillary muscle displacement, thickened bifid papillary muscles, direct insertion of the papillary muscle into the anterior MV leaflet or fibrotic chordal attachments. Complex cases with the involvement of both the mitral and the submitral apparatuses can be managed with a combination of SM and repair or replacement of the MV. The use of an extended SM can address this issue somewhat by extending the resection in a fan-like fashion moving distally in the septum. Ferrazzi et al. [18] reported good outcomes in patients undergoing a limited SM, with transaortic selective division of the fibrosed secondary chordae attached to the anterior MV leaflet body believed to be contributing to SAM. Elongation of the MV leaflets, particularly the anterior leaflet, result in SAM-related MR. In cases of limited septal hypertrophy, MV replacement has been performed as the primary surgery in the past; however, a range of newer surgical techniques for MV repair have evolved to address such cases in which adequate resection is technically challenging [19–21]. Controversy remains over individual techniques of MV repair in patients with LVOTO. The rate of concomitant MV intervention with SM varies from 8% in a recent large study of over 2000 patients from the Mayo Clinic operated on with SM for LVOTO to 25% in a paper from the Cleveland Clinic [6, 10]. Multiple surgical approaches have been advocated in the presence of elongated leaflets with post SM SAM and/or MR with good outcomes, including the edge-to-edge Alfieri repair, MV plication and anterior MV leaflet extension using a pericardial patch [19–21]. The edge-to-edge Alfieri MV repair was our preferred surgical approach to address the elongated anterior mitral leaflets with SAM-related MR with good resolution of LVOT gradients and improved symptoms. This was done using a transatrial rather than a transaortic approach, which allowed us to inspect the submitral apparatus extensively. The Alfieri technique has been used successfully in MR of various aetiologies [21]. There have been no early or late mortalities in this group of 11 patients in the current study, which documented good medium-term outcomes [22]. If an Alfieri repair is contemplated, assessment of the posterior MV leaflet length is important, as excess length can lead to bileaflet prolapse with SAM, making this type of repair less likely to be effective. The advantage of MV repair is that it obviates the need for MV replacement and its associated complications [23]. Late survival following SM with MV repair was superior to SM with MV replacement in the large Mayo clinical experience [10]. Contemporary data on MV replacement alone for relief of LVOTO in HCM in the literature are less robust than that for SM. Initial studies reported by Cooley et al. [16] showed good symptomatic relief and resolution of gradients. Further long-term studies by the same group showed good outcomes at 10 years [24]. Other early studies reported similar symptomatic and gradient reduction with MV replacement; however, higher mortality rates and complication rates were seen in these cohorts [25, 26]. More recent studies of MV replacement in patients with LVOTO have reported on SM with MV replacement rather than MV replacement alone [10, 27–29]. MV replacement alone can be a successful approach in cases unsuitable for repair or when used alone in those patients with thinner septae unsuitable for SM. In the early part of the series, there were few concomitant MV procedures performed. With an improved understanding of the mechanism of obstruction over time, more complex HCM phenotypes were operated on, particularly in older patients with concomitant cardiac disease with an increasing number of MV repairs and replacements. The decision to proceed with an MV replacement directly rather than a further bypass run to explore a potentially intermediate MV repair was carefully considered. In this study, it was noted that patients who required MV replacement were older and had more comorbidities than those who did not require an MV replacement. The preoperative phenotype and cardiac and non-cardiac comorbidities were factored into the surgical decision-making process, i.e. in consideration of the tolerance of a more extensive, longer operation. In selected older patients with atypical phenotypes and multiple comorbidities, in whom SM alone was deemed unlikely to be adequate and who were deemed to be unsuitable for multiple bypass runs, an upfront decision to perform MV replacement alone was made in this series. Figure 1 illustrates a flow chart for consideration in the strategic planning of surgery in the management of non-classical LVOTO in HCM. These phenotypes include aortic angulation, limited hypertrophy or abnormally distributed hypertrophy along with abnormalities of the MV commonly including elongated leaflets, abnormal MV attachments or other intrinsic abnormalities of the MV. A stepwise approach is taken in the planning of individual cases, which is re-evaluated intraoperatively following the initial procedure and initial bypass run to evaluate whether further intervention is needed to the MV. The recent Mayo study of 174 patients surgically managed with SM and MV intervention revealed no difference in the intensive care unit length of stay, hospital length of stay or late mortality in those undergoing single or multiple cardiopulmonary bypass runs, indicating the safety of this approach in appropriate patients [10]. Figure 1: View largeDownload slide Flow chart depicting decision-making for surgical management. CPB: cardiopulmonary bypass; LVOTO: left ventricular outflow tract obstruction; MR: mitral regurgitation; MV: mitral valve; MWT: maximum wall thickness; TOE: transoesophageal echocardiography. Figure 1: View largeDownload slide Flow chart depicting decision-making for surgical management. CPB: cardiopulmonary bypass; LVOTO: left ventricular outflow tract obstruction; MR: mitral regurgitation; MV: mitral valve; MWT: maximum wall thickness; TOE: transoesophageal echocardiography. Hospital volume plays an important role in mortality outcomes of surgery for HCM. A recent national database study analysing 6386 SMs reported that surgery in lower volume centres was an independent predictor of mortality in the USA [30]. In high-volume centres, early surgical outcomes following SM have shown very low mortality rates with good resolution of symptoms [5, 6, 10, 30]. Mortality within this study was low and comparable to the current reported outcomes in high-volume centres for SM [8]. Additionally, 21.7% of patients included in this study had an MV surgery and 10.8% had a concomitant non-mitral surgery. This study reported good echocardiographic results with 83.7% of all patients at the 1-year follow-up, a rate that has not been achieved in many other studies of this size. Almost 80% of patients in this study showed an improvement in NYHA class postoperatively comparable to previous large studies [9, 11]. Over 90% of patients demonstrated a resolution of obstruction with an LVOT gradient of <30 mmHg on postoperative echocardiography at 1 year. This individualized approach to the management of LVOTO in variable phenotypes of HCM adopted by our institution has not compromised, at least, the 1-year surgical, clinical and echocardiographic outcomes. Limitations This study is a single-centre, retrospective consecutive experience, representing limitations inherent to this study design. We acknowledge that as a national referral centre with a large population of HCM patients attending for regular clinical review that this may introduce referral bias; however, we believe that a more variable set of phenotypes may be seen within such an environment, requiring a more individualized surgical approach. There were incomplete data on the exact distribution of hypertrophy from echocardiography in individual patients. CONCLUSIONS This study from a single-centre experience reports individualized surgical approaches to the management of LVOTO in HCM patients with low mortality rates and good clinical outcomes. 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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: Dec 26, 2017

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