Characteristics and Outcomes of Mavacamten Use in 2440 Patients With Obstructive Hypertrophic Cardiomyopathy

BACKGROUND: Our objective was to assess real-world outcomes and health care use associated with commercial mavacamten use in patients with obstructive hypertrophic cardiomyopathy. METHODS: We used the Symphony Dataverse to study patients receiving mavacamten between May 25, 2022 and June 30, 2024. Safety outcomes were prespecified. RESULTS: We included 2440 patients and 18 494 mavacamten dispenses (63% women, median age 66 years [interquartile range {IQR}, 55-73]). Patients were followed for a median of 3037.0 days (IQR, 2808-3221) before mavacamten initiation and for 240 days (IQR, 117-407) on mavacamten. Atrial fibrillation or flutter (AF/AFL) at baseline were present in 536 (22%) of patients, whereas new-onset AF/AFL requiring therapy occurred in 125 patients (5%) and new heart failure (HF) in 100 patients (4%). During follow-up, 154 patients (6%) received new dispenses of loop diuretics, 102 (4%) oral anticoagulants, 78 (3%) amiodarone, 17 (0.7%) sotalol, and 6 (0.2%) dofetilide. There was a total of 306 patients (13%) with 428 acute care episodes (most common claims were HF (n=80, 26%), AF (n=74, 24%), and AFL (n=16, 5%)). Predictors of outcomes (new HF, new AF/AFL, ventricular tachycardia, or transient ischemic attack/stroke claim) were age at mavacamten start, obesity, transient ischemic attack/stroke history, and residence in the Western versus Southern United States. CONCLUSIONS: Over an 8-month median follow-up on mavacamten in patients with obstructive hypertrophic cardiomyopathy, new AF/AFL and HF occurred in 5% and 4%, respectively. Further work is needed to better understand the expected incidence of AF/AFL, HF, and other long-term outcomes of mavacamten treatment in obstructive hypertrophic cardiomyopathy.