Characteristics and predictors of unsatisfactory outcome of alcohol septal ablation in patients with hypertrophic obstructive cardiomyopathy

Background: Alcohol septal ablation (ASA) effectively reduces the left ventricular outflow tract gradient (LVOTG) in hypertrophic obstructive cardiomyopathy (HOCM). We aimed to identify characteristics and predictors of unsatisfactory outcome after ASA.

Methods: All consecutive ASAs between 1997 and 2023 at our institution were retrospectively considered for analysis. Patients with atypical HOCM, previous septal reduction therapy (SRT) or missing follow-up (FU) were excluded. Patients with unsatisfactory outcome (PUO) were defined as still meeting the guideline criteria for SRT (NYHA ≥III or NYHA ≥II with exertional syncope and resting/exercise-induced LVOTG ≥50mmHg). PUO and patients with good outcome (PGO) were compared. Results are expressed in % or median and interquartile range (IQR). Logistic regression analysis was performed to identify pre-procedural predictors of poor hemodynamic outcome.

Results: Of the 1003 patients eligible for analysis, 65 were PUO (6.5%). PUO were younger (48.0 years [40.5-61.8] vs. 57.0 years [IQR 47.0-67.0] in PGO; p=0.0030), had lower body-mass-index (26.4kg/m² [23.8-29.2] vs. 27.7kg/m² [25.2-23.1] in PGO; p=0.0160), and more often reported syncope at baseline (35.4% vs. 22.2% in PGO; p=0.0214). Resting LVOTG at baseline was higher in PUO (53.0mmHg [24.5-82.0]) than in PGO (40.0mmHg [22.0-75.0]; p=0.0292; Table 1). There were no differences in sex, family history of sudden cardiac death, NYHA-class, medication, and interventricular septum diameter (IVSD) at baseline (all p>0.05; Table 1).

Using multiple logistic regression controlling for confounders, age (OR 1.023; CI: 1.005-1.042; p=0.0129), syncope at baseline (OR 1.890; CI: 1.049-3.324; p=0.0296), and BMI (OR 1.072; CI: 1.007-1.145; p=0.0355) were found to independently influence poor hemodynamic response to ASA. Sex, baseline IVSD and LVOTG were not found to influence poor hemodynamic outcome (p>0.05).

There were no differences regarding the size of the balloon used to cover the septal branch (1.5mm in both groups), number of embolized branches (1 in both groups), volume of ethanol (PUO: 1.4ml [1.0-2.0]; PGO: 1.5ml [1.2-2.0]), or creatine kinase release (PUO: 879.0U/l [375.0-1187.0]; PGO: 842.0U/l [501.5 - 1234]) (all p>0.05).

At 6-months-FU, PUO had higher IVSD (18.0mm [13.5-22.0] vs. 16.0mm [12.0-19.0] in PGO; p=0.008), higher resting LVOTG (31.0mmHg [20.0-55.5] vs. 14.0mmHg [10.0-22.0] in PGO; p<0.0001) and higher exercise-induced LVOTG (105.0mmHg [84.5-143.0] vs. 35.0mmHg [22.0-64.0] in PGO; p<0.0001).

Conclusion: The proportion of patients with unsatisfactory outcome after ASA is low indicating high efficacy of ASA in a general HOCM population. Only syncope, age, and BMI were found predicting poor hemodynamic outcome.

Table 1: Baseline characteristics.