Abstract 4358355: Impact of mavacamten on the rates of hospitalization and emergency room (ER) visits in patients with obstructive hypertrophic cardiomyopathy (HCM) in the United States

Background: Mavacamten has been shown to improve functional status and symptoms in patients with obstructive hypertrophic cardiomyopathy (HCM) in both clinical trials and real-world settings. However, data on its impact on healthcare resource utilization remain limited. Aims: To evaluate changes in hospitalization and emergency room (ER) visit rates following mavacamten treatment in patients with obstructive HCM. Methods: A self-controlled case series study was conducted using linked claims and electronic health record data from the Optum Market Clarity database. Adults with symptomatic obstructive HCM and ≥1 pharmacy claim for mavacamten (first claim was index) between April 28, 2022, and August 31, 2024, were included. Continuous enrollment was required for ≥1 month both before and after the index. The baseline period was ≤ 12 months pre-index, and follow-up continued until the earliest of mavacamten discontinuation, death, disenrollment, or end of database. Rate ratios (RRs) with 95% confidence intervals (CIs) and p-values were estimated for HCM-related, HCM symptom-related, cardiovascular (CV)-related, and all-cause hospitalizations and ER visits during follow-up vs. baseline using generalized estimating equations. Back pain-related outcomes, anticipated as non-associated with mavacamten, served as negative controls to evaluate unmeasured confounding. Results: A total of 554 patients (mean ± SD age 63.2 ± 12.8 years; 57.6% female) with a mean ± SD obstructive HCM duration of 4.3 ± 3.5 years were included ( Table ). Over a mean follow-up of 8.6 ± 6.6 months, hospitalization rates decreased by 86% for HCM-related, 55% for CV-related, and 37% for all-cause events compared to baseline ( Figure ). ER visit rates declined by 47% for HCM-related, 45% for HCM symptom-related, 36% for CV-related, and 25% for all-cause events. All reductions were statistically significant (p-value < 0.01). RRs for HCM symptom-related and back pain-related hospitalizations were not estimated due to insufficient event frequency. No statistically significant changes were observed for back pain-related ER visits (RR [95% CI] 1.7 [0.7, 3.7], p-value 0.27), suggesting a minimal risk of residual confounding. Conclusions: Mavacamten treatment was associated with significant reductions in the rates of HCM-related, HCM symptom-related, CV-related, and all-cause hospitalizations and ER visits in patients with obstructive HCM.