Real-World Experience of Mavacamten for Patients With Obstructive Hypertrophic Cardiomyopathy in South Korea: A Prospective Multi-Center Observational Study

Background and Objectives: Mavacamten has shown promise in obstructive hypertrophic cardiomyopathy (oHCM); however, real-world evidence is limited in Asians. We aimed to provide the first multicenter, real-world analysis of mavacamten use in Korea. Methods: This prospective observational study included symptomatic oHCM patients treatedat 7 tertiary hospitals in Korea. Changes in key parameters, including left ventricular outflow tract (LVOT) gradients, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and New York Heart Association functional class (NYHA Fc), were serially assessed. Adverse events, including death, arrhythmia, and heart failure hospitalizations were documented. Results: Forty-six patients were followed for a median of 147 days (interquartile range 56-205). There was one sudden cardiac death and one non-cardiac death. Resting and Valsalva LVOT gradients significantly decreased from 58.4±46.4 mmHg and 92.6±46.8 mmHg to 17.5±21.3 mmHg and 25.7±27.1 mmHg, respectively (both p<0.001). NT-proBNP levels also decreased significantly, strongly correlating with LVOT gradient reductions. Among the 44 survivors, 25 (58.1%) had at least one NYHA Fc improvement. Moreover, left atrial volume and maximal left ventricular (LV) wall thickness significantly decreased. However, mean reduction in LV ejection fraction (LVEF) was −3.4% with one patient experiencing LVEF <50%. We observed 2 newly-detected atrial fibrillations and 2 ischemic strokes. Conclusions: This first real-world experience of mavacamten in Korean patients with oHCM demonstrates its efficacy and safety, aligning with previous pivotal trials. With the implementation of national insurance coverage, mavacamten will be more accessible to broader oHCM population, offering a non-invasive and effective therapeutic option aside from invasive septal reduction therapies.