Background Numerous studies have demonstrated diverse abnormalities in subcellular structures of pressure-overloaded hypertrophied and failing heart. Long-term administration of etomoxir, a carnitine palmitoyltransferase-1 inhibitor, partially normalized the proportion of myosin isozyme V₁ and number of active Ca²⁺ pumps in hypertrophied rat myocardium.

Methods and Results To test the hypothesis that long-term etomoxir treatment improves the performance of hypertrophied ventricle, sham-operated rats and rats with ascending aorta constriction were treated with racemic etomoxir (15 mg/kg per day) for 12 weeks. Left ventricular geometry, dynamics of isovolumic contractions, as well as myosin isozymes as marker of etomoxir-induced phenotype changes were assessed. Etomoxir stimulated (P<.05) slight hypertrophic growth in right and left ventricles of sham-operated rats as well as in right ventricles but not in overloaded left ventricles of rats with aortic constriction. In all treated rats, etomoxir increased (P<.05) maximal developed pressure, left ventricular pressure-volume area, and ±dP/dt_max. Enhanced values (P<.05) of derived indexes of myocardial performance (normalized stress-length area, maximal rate of wall stress rise, and decline) indicated that myocardial changes were responsible for the improved performance. The etomoxir treatment increased selectively (P<.05) the proportion of myosin V₁ in pressure-overloaded left ventricles.

Conclusions The long-term treatment with etomoxir improved functional capacity of pressure-overloaded left ventricle, which can be attributed to an enhanced myocardial performance. Chronic carnitine palmitoyltransferase-1 inhibition may thus represent a candidate approach for developing novel agents that are useful in the prevention of undesirable consequences of pressure overload–induced cardiac hypertrophy.