Hypertrophic cardiomyopathy is the most common heart disease in cats and results from cardiac sarcomeric protein mutations with subsequent left ventricular wall thickening.1 Potential complications include congestive heart failure, arterial thromboembolism, arrhythmias, and sudden death. Therapies with proven efficacy for delaying progression or providing survival benefits in subclinical patients are lacking.
This randomized, controlled crossover study* evaluated a single dose of aficamten (2 mg/kg PO), a novel small molecule myosin inhibitor designed to target the interaction of actin and myosin, in 5 purpose-bred Maine coon cats with A31P MYBPC3 mutation and a diagnosis of subclinical hypertrophic obstructive cardiomyopathy. Aficamten significantly reduced left ventricular fractional shortening secondary to increased left ventricular systolic internal dimension, preserved left ventricular diastolic internal dimension, and reduced isovolumic relaxation time, suggesting improvement in diastolic function. Additional studies to determine the optimal dosage and long-term treatment effects are warranted.