First Successful Cardiac Myosin Inhibitor Use for Donor-Derived HCM After Heart Transplant

BACKGROUND: Donor-derived hypertrophic cardiomyopathy (HCM) is an exceptionally rare posttransplant complication, traditionally diagnosed years after transplant. CASE SUMMARY: A 55-year-old woman received a heart from a 30-year-old man donor who suffered sudden cardiac death. On postoperative day 1, she developed severe dynamic left ventricular outflow tract obstruction (peak gradient, 110 mm Hg). Despite calcium channel blocker therapy and later beta-blockade, she remained in NYHA functional class III with persistent gradients. Cardiac magnetic resonance imaging 5 months posttransplant confirmed donor-derived HCM. Mavacamten (Camzyos; Bristol Myers Squibb) was initiated at 11 months, inducing gradient reduction to 11 mm Hg at rest and 25 mm Hg post-Valsalva, without adverse interactions with tacrolimus. At 50 months posttransplant, she demonstrated sustained intracavitary gradient reduction and functional recovery. DISCUSSION: This is the first report of early donor-derived HCM treated with mavacamten within 1 year of transplant. Targeted myosin inhibitor therapy appears promising, and CYP3A4-mediated pharmacokinetic interactions may be lower than previously believed. TAKE-HOME MESSAGES: Mavacamten may be safe and effective for donor-derived HCM in the early posttransplant period. Utilization of carefully selected donors with HCM or left ventricular hypertrophy could increase the donor pool.