CONGRESS ABSTRACT

Case Report: A 46-year-old male with hypertrophic obstructive cardiomyopathy (HOCM) due to a MYH7 mutation was diagnosed at age 30 through familial screening. Despite treatment with bisoprolol and disopyramide at maximum tolerated doses, the patient experienced persistent dyspnea with mild exertion. Investigations revealed characteristic ECG findings: pseudonecrosis Q waves in V1-V2, ST-segment elevation in the same leads, fragmented QRS complexes, and signs of left ventricular (LV) hypertrophy and overload. An echocardiogram in April 2024 showed normal ejection fraction, a septal maximum wall thickness (MWT) of 19 mm, LV outflow tract (LVOT) obstruction (gradient of 35 mmHg, increasing to 52 mmHg with Valsalva), elevated filling pressures (E/e′ = 13), and left atrial (LA) enlargement (LAVi = 50 ml/m²). CPET and stress echocardiography confirmed an increased LVOT gradient (75 mmHg), worsening diastolic function, reduced exercise capacity (VO2 = 15.1 ml/min/kg, 67% predicted), and reduced ventilatory efficiency (VE/VCO2s = 32.3). In April 2024, the patient initiated therapy with Mavacamten (cardiac myosin inhibitor), up to 10 mg/day, and discontinued disopyramide within a month. Subjective improvement was reported within 20 days, including resolution of dyspnea. Follow-up evaluations demonstrated progressive normalization of ECG findings within two months, including reduced QRS fragmentation and near-complete resolution of repolarization abnormalities. After 30 weeks of Mavacamten therapy, echocardiography  revealed reduced septal wall thickness (MWT = 15 mm), resolution of LVOT obstruction, improved diastolic function (E/e′ = 9), and decreased LA volume (LAVi = 37 ml/m²). CPET showed no LVOT gradient, improved exercise capacity (VO2 = 21 ml/min/kg, 91% predicted), and enhanced ventilatory efficiency (VE/VCO2s = 27.5). Discussion:This case illustrates the efficacy of Mavacamten in treating HOCM, demonstrating its impact on both structural remodeling (e.g., reduced wall thickness and atrial size) and functional improvement (e.g., resolution of obstruction, enhanced exercise capacity). Mavacamten’s therapeutic potential extends to delaying or avoiding surgical interventions, including myectomy, by addressing underlying pathophysiology. Conclusion:Mavacamten is a promising treatment for HOCM, offering substantial benefits in structural, functional, and symptomatic domains, as demonstrated by this patient’s remarkable clinical and echocardiographic recovery.