Impact of Anterior Mitral Leaflet Length on the Efficacy of Intracardiac Echocardiography-Guided Endocardial Septal Ablation for HOCM

Background: Intracardiac echocardiography (ICE)-guided percutaneous endocardial septal ablation (PESA) is a promising alternative strategy for symptomatic hypertrophic obstructive cardiomyopathy (HOCM). However, the extent of left ventricular outflow tract gradient (LVOTG) reduction after PESA varies considerably among patients, and reliable echocardiographic predictors of procedural efficacy remain unclear. We aimed to identify echocardiographic predictors of procedural efficacy and to describe our ablation strategy. Methods: We retrospectively analyzed 30 consecutive symptomatic HOCM patients who underwent ICE-guided PESA. The primary endpoint was the absolute change in resting LVOTG from baseline to the 1-year follow-up; a key secondary endpoint was significant gradient reduction, defined as a ≥50% decrease in resting LVOTG. Associations between LVOTG reduction and baseline echocardiographic parameters, particularly anterior mitral leaflet length (AMLL) and interventricular septal thickness (IVST), were evaluated. Results: At 1 year, the mean resting LVOTG decreased from 86.03 ± 24.30 mmHg to 41.43 ± 18.49 mmHg (p < 0.001). For the key secondary endpoint (≥50% resting LVOTG reduction), AMLL was the only variable associated with the outcome in the prespecified multivariable logistic model (OR per 1 mm increase: 0.429; p = 0.006), with consistent findings in a Firth penalized logistic regression sensitivity analysis. ROC analysis identified an exploratory AMLL cutoff of approximately 29 mm (AUC 0.920; sensitivity 90%; specificity 80%). In the continuous-outcome analysis, each 1 mm increase in AMLL corresponded to approximately 4.3 mmHg less LVOTG reduction (β = −4.32; p < 0.001). Thinner IVST was not significantly associated with greater procedural efficacy (p = 0.052), suggesting a potential thickness-dependent limit that warrants further investigation. Conclusions: ICE-guided PESA effectively reduces LVOT obstruction in HOCM. Shorter AMLL predicted greater LVOT gradient reduction in this exploratory cohort, and a Youden-derived AMLL cutoff of approximately 29 mm may help identify patients who are more likely to achieve substantial gradient reduction.