Mavacamten LVEF Drop Management — EECC MCQ

Correct answer: C — Mavacamten dose should be reduced or held — LVEF <50% on mavacamten indicates excessive myosin inhibition; the REMS programme requires LVEF monitoring every 12 weeks, with dose reduction if LVEF falls to 50-55% and drug interruption if LVEF drops below 50%

Mavacamten's mechanism (cardiac myosin inhibition) directly reduces contractility — this is therapeutic for LVOT obstruction but excessive inhibition can cause systolic impairment. The Risk Evaluation and Mitigation Strategy (REMS) programme mandates: (1) LVEF assessment before starting and every 12 weeks during treatment; (2) dose titration: start 5 mg → adjust based on LVOT gradient AND LVEF at each 12-week assessment; (3) dose REDUCTION if: LVEF 50-55% (reduce by one dose level); (4) drug INTERRUPTION if: LVEF <50% (hold mavacamten, recheck LVEF in 4 weeks — typically recovers once the drug washes out, half-life ~9 days); (5) contraindicated in combination with strong CYP2C19 inhibitors or strong CYP3A4 inhibitors (increase mavacamten levels). This patient's LVEF drop to 48% requires immediate drug interruption per the REMS protocol. Reassess LVEF in 4 weeks — if recovered, may restart at a lower dose.

Reference: ESC (2023): Cardiomyopathies; Mavacamten REMS