Association of Noninvasively Measured Left Ventricular Mechanics With In Vitro Muscle Contractile Performance: A Prospective Study in Hypertrophic Cardiomyopathy Patients

BACKGROUND Hypertrophic cardiomyopathy (HCM) is a primary myopathic process in which regional left ventricular dysfunction may exist without overt global left ventricular dysfunction. In obstructive HCM patients who underwent surgical myectomy (SM), we sought to determine if there is a significant association between echocardiographic longitudinal strain, histopathology, and in vitro myocardial performance (resting tension and developed tension) of the surgical specimen. METHODS AND RESULTS HCM patients (n=122, 54±14 years, 54% men) undergoing SM were prospectively recruited. Longitudinal systolic strain and diastolic strain rates were measured at that basal septum (partially removed at SM) by using velocity vector imaging on preoperative echocardiography. Semiquantitative histopathologic grading of myocyte disarray and fibrosis and in vitro measurements of resting tension and developed tension were made in septal tissue obtained at SM. Mean basal septal systolic strain and diastolic strain rate were -8.3±5% and 0.62±0.4/s, while mild or greater degree of myocyte disarray and interstitial fibrosis were present in 85% and 87%, respectively. Mean resting tension and developed tension were 2.8±1 and 1.4±0.8 g/mm(2). On regression analysis, basal septal systolic strain, diastolic strain rate, disarray, and fibrosis were associated with developed tension (β=0.19, 0.20, -0.33, and -0.40, respectively, all P<0.01) and resting tension (β=0.21, 0.22, -0.25, and -0.28, respectively, all P<0.01). CONCLUSION In obstructive HCM patients who underwent SM, left ventricular mechanics (echocardiographic longitudinal systolic strain and diastolic strain rates), assessed at the basal septum (myocardium removed during myectomy) and histopathologic findings characteristic for HCM (disarray and fibrosis) were significantly associated with in vitro myocardial resting and developed contractile performance.