Hospital Procedural Volume and Clinical Outcomes Following Septal Reduction Therapy in Obstructive Hypertrophic Cardiomyopathy

BACKGROUND: Prior national data showed a substantial in-hospital mortality in septal myectomy (SM) with an inverse volume– outcomes relationship. This study sought to assess the contemporary outcomes of septal reduction therapy and volume– outcome relationship in obstructive hypertrophic cardiomyopathy. METHODS AND RESULTS: All septal reduction therapy admissions between 2010 to 2019 in the United States were analyzed using the National Readmission Databases. Hospitals were stratified into tertiles of low-, medium-, and high-volume based on annualized procedural volume of alcohol septal ablation and SM. Of 19 007 patients with obstructive hypertrophic cardiomyopathy who underwent septal reduction therapy, 12 065 (63%) had SM. Two-thirds of hospitals performed ≤5 SM or alcohol septal ablation annually. In all SM encounters, 482 patients (4.0%) died in-hospital post-SM. In-hospital mortality was <1% in 1505 (88.4%) hospitals, 1% to 10% in 30 (1.8%) hospitals, and ≥10% in 167 (9.8%) hospitals. There were 63 (3.7%) hospitals (averaging 2.2 SM cases/year) with 100% in-hospital mortality. Post-SM (in low-, medium-, and high-volume centers, respectively), in-hospital mortality (5.7% versus 3.9% versus 2.4%, P=0.003; adjusted odds ratio [aOR], 2.86 [95% CI, 1.70– 4.80], P=0.001), adverse in-hospital events (21.30% versus 18.0% versus 12.6%, P=0.001; aOR, 1.88 [95% CI, 1.45–2.43], P=0.001), and 30-day readmission (17.1% versus 12.9% versus 9.7%, P=0.001; adjusted hazard ratio, 1.53 [95% CI, 1.27–1.96], P=0.001) were significantly higher in low-versus high-volume hospitals. For alcohol septal ablation, the incidence of in-hospital death and all other outcomes did not differ by hospital volume. CONCLUSIONS: In-hospital SM mortality was 4% with an inverse volume-mortality relationship. Mortality post-alcohol septal ablation was similar across all volume tertiles. Morbidity associated with SM was substantial across all volume tertiles.