Cardiogenic Shock in Hypertrophic Cardiomyopathy Treated With Mavacamten and Clarithromycin.

backgroundMavacamten use has potential for clinically significant ventricular systolic dysfunction, including with drug-drug interactions (DDI). CASE SUMMARY: A 66-year-old male with symptomatic obstructive hypertrophic cardiomyopathy was treated with mavacamten for 1.5 years. He received treatment for Helicobacter pylori infection with a combination therapy including clarithromycin. The patient developed cardiogenic shock (ejection fraction nadir of 21%) in the setting of new atrial fibrillation (AF) with rapid ventricular response and pulmonary infiltrates. A DDI between clarithromycin and mavacamten was felt to precipitate clinical decline. In this case, cardiogenic shock occurred in the setting of clarithromycin, AF, and possible infection. The CYP3A4 inhibitory effect of clarithromycin likely resulted in accumulation of mavacamten, a cardiac myosin inhibitor approved for treatment of symptomatic obstructive hypertrophic cardiomyopathy (metabolized by CYP2C19-CYP3A4). TAKE-HOME MESSAGES: This unique case highlights the potential for cardiogenic shock with mavacamten in the setting of AF, possible pneumonia, and suspected DDI. When using mavacamten, early recognition of systolic dysfunction and awareness of DDI is important.