A Study to Evaluate Mavacamten Impact on Myocardial Structure in Participants With Symptomatic Obstructive Hypertrophic Cardiomyopathy

Inclusion Criteria * Diagnosed with obstructive hypertrophic cardiomyopathy (oHCM), in accordance with current American College of Cardiology Foundation/American Heart Association and European Society of Cardiology guidelines as below:. * Left ventricular outflow tract (LVOT) peak gradient ≥ 30 mmHg and ≥ 50 mmHg after Valsalva or after exercise. * Left ventricular ejection fraction (LVEF) ≥ 55% at rest. * New York Heart Association (NYHA) functional class II or III symptoms. Exclusion Criteria * A known infiltrative or storage disorder causing cardiac hypertrophy that mimics oHCM. * Documented obstructive coronary artery disease or history of myocardial infarction. * A history of resuscitated sudden cardiac arrest or life-threatening ventricular arrhythmia within 6 months prior to screening. * An implantable cardioverter defibrillator (ICD) or pacemaker, or another contraindication for cardiac magnetic resonance imaging (CMR). * Other protocol-defined inclusion/exclusion criteria apply.