Decompensated heart failure after one year of successful therapy with mavacamten: a case report

Cardiac myosin inhibition is the first disease-specific therapeutic strategy for obstructive hypertrophic cardiomyopathy. Mavacamten, the first-in-class agent, has demonstrated an excellent safety profile and sustained efficacy in both clinical trials and real-world practice. However, its safe use requires careful monitoring and thorough patient education regarding potential drug–drug interactions.

We report a case of acute heart failure occurring after long-term clinical stability on mavacamten following concomitant fluconazole administration. It is reasonable to assume that the pharmacokinetic interaction resulted in excessive mavacamten exposure, leading to transient systolic dysfunction, severe functional mitral regurgitation, and adverse left ventricular remodelling.

This case report highlights the consequences of pharmacological interactions between mavacamten and a strong CYP2C19 inhibitor. Drug–drug interaction should always be considered and systematically excluded in a patient presenting with unexplained heart failure and left ventricular remodelling during mavacamten therapy.