From January 2001 to December 2024, 47 patients were referred for surgical therapy of HOCM and symptomatic LVOTO. Isolated septal myectomy was performed in 18 patients (=group 1), while concomitant MV surgery was done in 29 patients (=group 2). Alcohol septal ablation was performed as first therapy in 8 patients, which was successful in 4 patients, but required surgical treatment in 4 other patients for recurrent/residual LVOTO. These patients were included in group 1.

The decision for surgical treatment of HOCM was based on the diagnosis of a symptomatic and hemodynamically significant LVOTO, resulting in an obstructive peak gradient > 50 mm Hg at rest, and/or an increasing peak gradient at exercise or during Valsalva maneuver >70 mm Hg. Surgery consisted basically of a transaortic septal myectomy, by preference extending unto the base of the anterior papillary muscle, performed at the nadir of the right coronary sinus over a width of approximately 1 cm.

A concomitant MV procedure was proposed when a combination of following features was observed: (1) significant SAM-related MR ≥ grade 2, (2) presence of obvious morphological MV anomalies like accessory chordal attachments, leaflet prolapse or pronounced calcific degeneration of MV components, (3) measurement of a narrow aorto-mitral angle <110° at echocardiography. The basic intention of MV repair was to displace the coaptation zone of MV at systole away from the LVOT, by patch augmentation of the anterior leaflet to widen the subaortic LVOT, reduction of the posterior leaflet height by segmental resection or neochords, and eventually displacing of the anterior papillary head posteriorly. Through the disinserted anterior MV leaflet, secondary chordae were routinely transected. Sometimes, an oversized annuloplasty device was added for remodeling of the MV annulus to enhance the posterior displacement of the coaptation. Patch augmentation of AML was done with decellularized equine pericardial tissue (Matrix Patch, Autotissue Berlin GmbH, Berlin, Germany) or glutaraldehyde-fixed equine pericardial patch (Supple Peri-Guard, Baxter Healthcare, Australia). In case of severe calcific degeneration, MV replacement was preferred.

Intra-operative transesophageal echocardiography was done for assessment of the LVOT and MV function at baseline conditions. The surgical result was judged to be acceptable if the LVOT gradient was less than 10 mm Hg and MR ≤grade 1 under anesthesia, and stable hemodynamic condition without use of inotropic drug agents.

Pre-, intra- and post-operative data were extracted from electronic medical files. Data on previous history specifically related to HOCM as ICD or pacemaker implantation were recorded. Assessment of functional clinical status was based on NYHA classification. Clinical follow-up included survival, functional status and need for reoperation related to the index procedure or cardiac disease. The follow-up closing date was set at 31 May 2025.

Echocardiographic assessment was performed preoperatively, at discharge, and then yearly at the time of each clinical visit during follow-up. For patients followed by out-of-hospital cardiologists, the electronic echocardiographic report was consulted. Essential elements of the echocardiography were the mean and peak LVOT gradient at rest and during Valsalva, and MV function including MR severity by semi-quantitative grading of the regurgitant jet, as well as the transmitral forward gradient. LV dimensions were measured at end-diastole and systole on the long-axis 2-chamber view. LV hypertrophy was quantified by measuring the interventricular septal and posterior wall thickness, followed by calculation the LV mass indexed to the patient’s body surface area. LV function relied on calculation of LVEF by the Simpson’s method. During the preoperative echocardiography, additional attention was paid to measure the length of anterior and posterior leaflets, the aorto-mitral valve angle, as well as the degree of pulmonary hypertension based on the regurgitant TV signal. All echocardiographic measurements were done according to the updated JASE guidelines .

Statistical analysis was performed using SPSS Statistics 28 (IBM SPSS Statistics for Windows, Version 29.0). Data distribution is verified for normality by the Shapiro–Wilk test. Categorical variables are expressed by number and percentage. Continuous variables are noted as mean and standard deviation or as median and interquartile range, depending on the distribution normality of the data. Categorical variables were compared between the study groups by Chi-square or Fisher’s exact test. Comparison of continuous data was done by the unpaired t-test or Mann-Whitney U-test.

Within- and between-group comparison of echocardiographic data based on a continuous variable, before surgery, at discharge and at last follow-up was done by Anova-analysis for repeated measures based on the Wilk’s Lamda test. Post-hoc Bonferroni correction is done for multiple comparisons. As MV regurgitation grade was registered as an ordinal variable, the longitudinal analysis of MV function between the 2 groups over the 3 time intervals was performed with the generalized estimating equation method for an ordinal logistic model, using MV function as dependent variable and type of procedure as fixed independent variable. The effect size was expressed as hazard ratio (HR) and 95% confidence interval (CI). Survival analysis was performed by the Kaplan–Meier estimation method, and the differential effect of the study groups on survival was defined by the hazard ratio(HR) and 95% confidence interval (CI) through Cox-regression analysis. All tests were performed 2-tailed and considered as statistically significant for p < 0.05.

The study population of HOCM patients comprised 18 patients treated by septal myectomy only, and 29 patients treated by septal myectomy with concomitant MV repair or replacement. The median patient age was 54.3 years (IQR: 43.3–63.2), and was comparable for both groups. Approximately 2/3 of the patients were male. The majority of patients were highly symptomatic in NYHA Class II or III, despite medical therapy with B-blockers. Dyspnea was more frequent in group 2 (group 1: n = 12 (66.7%) versus group 2: n = 28 (90.3%), p = 0.042). Thirteen patients (27.6%) had already a previous cardiac procedure, that is, alcohol septal ablation (n = 4), of whom 3 underwent MV surgery associated to septal myectomy, coronary artery revascularization by CABG or PCI (n = 3), and implantation of ICD or pacemaker (n = 6). In 8 patients (17.0%) a predisposing genetic mutation was documented. All patient characteristics are depicted in Table 1 .

Out of the 31 patients of group 2, MV repair was performed in 26, of whom one required intraoperative MV replacement because of persistent SAM. MV repair consisted of augmentation of the anterior leaflet with an equine pericardial patch in 20 patients. Additional secondary chordae were cut in 15 patients. In 2 patients prolapse of the posterior MV leaflet was corrected by lowering the PML by neochordae. The edge-to-edge stitch repair was done in 2 patients. At the time of repair, an annuloplasty device was used in only 8 patients with a median ring size of 36 (IQR: 34–38). Seven patients were treated with MV replacement at the index operation for severe degenerative MV disease (n = 5), failed MV repair (n = 1) and endocarditis (n = 1) respectively. Replacement was done with a mechanical (n = 5) or biological valve prosthesis (n = 2).

The aortic clamping time (group 1: 39.5 ± 18.0 minutes– group 2: 77.5 ± 47.5 minutes, p = 0.011) and cardiopulmonary bypass time (group 1: 67.1 ± 24.7 min– group 2: 113.9 ± 66.2 minutes, p = 0.031) were significantly shorter in group 1 compared to group 2. Procedures associated to septal myectomy with/without MV surgery were coronary artery bypass grafting (n = 3) and atrial fibrillation ablation therapy (n = 2).