This is an investigator-initiated two-center study. The goal of this study is to investigate the feasibility, safety and efficacy outcomes of a seamless transition from mavacamten to aficamten in patients with obstructive hypertrophic cardiomyopathy (oHCM).

Inclusion Criteria:

• Documented history of oHCM with documented resting and/or Valsalva LVOT obstruction ≥ 50 mmHg who are currently receiving mavacamten commercially.
• Echo-derived LVEF ≥55% on mavacamten at the time of enrollment.
• Patient willing to consent for the study and undergo the study procedures.

Exclusion Criteria:

• Severe aortic stenosis or sub-aortic obstruction
• Known infiltrative or storage disorder causing cardiac hypertrophy that mimics HCM (eg, Noonan syndrome, Fabry disease, amyloidosis).
• History of LVEF <30%.
• Paroxysmal atrial fibrillation (AF) with documented episode within 3 months.
• Atrial fibrillation (paroxysmal or permanent) not on systemic anticoagulation.
• Documented history of current obstructive coronary artery disease (> 70% stenosis in one or more epicardial coronary arteries) or documented history of myocardial infarction.