Changes in mitral regurgitation after alcohol septal ablation in hypertrophic obstructive cardiomyopathy: a retrospective cohort study

BackgroundThe primary mechanism of mitral regurgitation (MR) in hypertrophic obstructive cardiomyopathy (HOCM) is systolic anterior motion (SAM) of the mitral leaflets due to septal hypertrophy narrowing the left ventricular outflow tract (LVOT), influencing leaflet movement and closure. Among patients undergoing percutaneous alcohol septal ablation (ASA) to reduce the interventricular septum, the impact on MR and the underlying mechanism of MR reduction remains less studied. Therefore, we aimed to determine the prevalence of MR before and changes in MR severity after ASA, and analyze echocardiographic (ECHO) parameters associated with MR changes. MethodsAll patients who underwent ASA at Karolinska University Hospital in Stockholm, Sweden, 2009-2021, were included in this retrospective cohort study, with follow-up until mid 2025. ECHO parameters were collected before ASA, at 1-year follow-up and at the latest follow-up registered. Linear and logistic regression models were used to assess the association between ECHO parameters and the direction of change in MR at follow-up. Results154 patients were included with mean follow-up time 4.0{+/-}3.9 years. 13.6% (n=21) had at least moderate MR at baseline, of which 90.1% (n=19) decreased and 9.9% (n=2) had persistent moderate MR at the last follow-up. The patients with decreased (n=19, 12.3%) or persistent grade of MR (n=71, 46.1%) showed significant reduction of median basal septal wall thickness and LVOT peak pressure gradients (decreased MR: 20.0mm to 14.0mm, p<0.001, 137.5mmHg to 4.8mmHg, p<0.001, persistent MR: 19.0mm to 16.0mm, p<0.001, 95.0mmHg to 25.0mmHg) between the baseline and the last follow-up ECHO. In contrast, no significant differences were seen in the patients with increased MR grade (n=7, 4.5%, 21.0mm to 18.0mm, p=0.251, 57.0mmHg to 51.0mmHg, p=0.336). ConclusionIn most patients with at least moderate MR prior to ASA, MR decreased at follow-up, as a supposed effect of septal reduction, and reduced SAM.