2.5 Statistical analysis
Statistical analysis was performed with the SPSS statistical package version 22.0 (SPSS Inc., Chicago, IL, USA). Categorical data were expressed as frequency distributions and single percentages and were compared between groups using Fisher’s exact test if the expected frequency was < 5 or the chi-square test. Normally distributed continuous variables were expressed as the mean ± standard deviation and were compared between groups using an independent-samples t -test; non-normally distributed continuous variables were expressed as median and interquartile range (IQR) and were compared between groups with the Wilcoxon rank sum test. A two-sided p -value less than 0.05 was considered statistically significant.
3. Results
3.1. Study population
A total of 208 adult patients who met the inclusion criteria were reviewed. Forty patients were excluded due to concomitant valvular heart disease requiring surgery (27 patients), concomitant Maze procedure (3 patients), concomitant enlargement of right ventricular outflow tract (2 patients), and undergoing septal myectomy via transseptal approach through right atrium (8 patients), which left 168 eligible patients for data analysis. There were 83 male patients and 85 female patients with a mean age of 56.8 ± 12.3 years. The baseline characteristics are listed in Table 1. Despite the fact that 39.9% of the population had a history of hypertension, it was not deemed severe enough to be the primary cause of ventricular hypertrophy. Nine (5.4%) patients underwent previous alcohol septal ablation. Atrial fibrillation and right bundle branch block were recorded in 14 (8.3%) patients and 4 (2.4%) patients, respectively. All patients manifested severe limiting symptoms, such as dyspnea, angina-like chest pain and syncope, with New York Heart Association (NYHA) functional class III and IV in 86.3% of the population.
TTE examination revealed a mean maximum LVOT gradient of 94.4 ± 22.6 mmHg with a mean interventricular septal thickness of 18.3 ± 3.1mm. Systolic anterior motion (SAM) was observed in all patients, of whom 97 (57.7%) were diagnosed with moderate or more MR. Importantly, midventricular obstruction was recorded in 7 (4.2%) patients. Mitral subvalvular anomalies were identified in 45 (26.8%) patients, including false cords (11 patients), fibrotic and retracted secondary chordae (29 patients), and PM abnormalities (13 patients).
All patients underwent transaortic septal myectomy with a mean aortic cross-clamping time of 36.0 ± 8.1 minutes (median, 35.0 min). 45 (26.8%) patients received mitral subvalvular procedures in addition to myectomy, including false cords cutting (11 patients), fibrotic and retracted secondary chordae cutting (29 patients), and M release and/or resection (13 patients).
3.2 Intraoperative results
The immediate repeat procedure was recorded in 9 (5.4%) patients. Of them, 5 patients were identified as residual LVOT obstruction or moderate or more MR due to inadequate initial septal myectomy, and underwent a “more” extended myectomy in terms of depth and length and/or leftward direction from the left ventricular free wall toward the MV according to TEE findings (4 patients) and received transaortic mitral valve repair using the “edge-to-edge” technique (one patient); another 2 patients underwent repair of a left ventricular free wall rupture due to free wall rupture; and the remaining 2 patients underwent repairs of septal defect and aortic right valve due to iatrogenic perforation, respectively.
TEE examination showed that the maximum LVOT gradients following myectomy fell to 10.8 ± 6.3 mmHg with the interventricular septal thickness of 13.8 ± 2.1 mm, both of which were significantly lower than the preoperative values (p<0.001). No residual obstruction was recorded. SAM was observed in 16 (9.5%) patients, of whom one was identified as moderate MR. No instances of more than moderate MR were observed.