Decreases in Left Atrial Strain With Mavacamten Therapy and Associations With Atrial Fibrillation.

Abstract

In obstructive hypertrophic cardiomyopathy, the cardiac myosin inhibitor mavacamten improves left ventricular outflow tract obstruction and functional capacity. Symptoms and exertional capacity in obstructive hypertrophic cardiomyopathy are also influenced by left atrial function, commonly assessed by left atrial strain (LAS). Current data regarding effects of cardiac myosin inhibitors on LAS are mixed. To assess changes in LAS in patients on mavacamten and correlate strain patterns to atrial fibrillation (AF) development. Serial echocardiograms were obtained following mavacamten initiation. We remeasured 2-dimensional and Doppler-derived measurements and obtained strain measurements. We examined temporal changes in LAS and related parameters, including those determining atrial preload and afterload, along with ventricular changes affecting atrial function. We included 434 echocardiograms from 65 patients. After 24 weeks of therapy, left ventricular outflow tract gradient, global longitudinal strain, and left ventricular ejection fraction all decreased. Left atrial volume index (p <0.001), mitral regurgitation severity (p = 0.01), and E/e' velocities (p = 0.01) also decreased. All 3 components of LAS worsened (p <0.001). Seven patients with baseline AF had recurrences, and 4 others had new-onset AF. LAS predicted AF as a time-dependent variable. Decreases in LAS seen with mavacamten may be downstream effects of alterations to other hemodynamic parameters, a decline in atrial function, or a combination thereof. LAS reductions may therefore represent harmful effects on the left atrium or neutral byproducts of other changes, although the association between LAS and AF is notable and may highlight prognostic implications of strain measurements in this population.