Characterization of myocardial deformation in hypertrophic cardiomyopathy using speckle tracking: comparison with physiological hypertrophy

Abstract

Background: In young competitive athletes, the differential diagnosis between nonpathological changes in cardiac morphology associated with training (commonly referred to as athlete's heart) and certain cardiac diseases with potential for sudden death as Hypertrophic Cardiomyopathy (HCM), is an important & not uncommon clinical problem. Objective: This study was designed to characterize global & regional myocardial deformation using 2-dimensional strain & Strain Rate (SR) imaging in HCM & compare it to physiological hypertrophy in athletes. Methods: The study comprised 22 patients with HCM. 81% had asymmetric septal hypertrophy, 34 athletes with septal thickness >12 mm & 28 age matched healthy subjects as a control group. Apical four chamber view was displayed; speckle tracking was used to measure longitudinal peak systolic strain (ɛsys), peak systolic strain rate (SRsys), time to peak (ɛ) [TTP], post systolic strain (ɛPSS) and intra-ventricular systolic delay (intra-V delay). These parameters were quantified in basal, mid & apical segments of septal & lateral walls of the left ventricle. Results: Regional Myocardial deformation of LV segments was significantly reduced in comparison to corresponding segments in athletes & control (P<0.001). (ɛsys) and SRsys of the basal (-8.96±4.7%, -0.74±0.41 sec-1) and mid (-4.3±6.9%,-0.57±0.48 sec-1) segments were significantly lower than apical septal (-21.6±8.2%, -1.62±0.64 sec-1) & all lateral segments (-14.4±6.9%, -1.12±0.44 sec-1, -11.7±4.6%, -0.77±-0.42 sec-1, -16.7±7.3%, -0.8±0.34 sec-1 respectively, P<0.001) in HCM patients, while myocardial deformation was normal & almost homogenous in athletes. The later showed homogeneous systolic activation of the ventricular walls. Conversely, HCM group, showed significant increase of the intra-V systolic delay between segments which is more prominent in septal than lateral wall (P<0.001). While averaged ɛsys was negatively correlated to NYHA functional class and E/Em ratio (r= -0.5, r= -0.46 respectively, P<0.01), intraventricular delay showed direct relationship to LVM (r=0.63, P<0.01). A ɛsys cutoff value of basal and mid septum <-13%, <-12% differentiated between HCM and athletes with 91, 95% sensitivity and 91, 100% specificity respectively. Conclusion: The non uniform distribution & magnitude of LV hypertrophy in HCM, is associated with disorganized contraction & regional heterogeneity of myocardial systolic function. Deformation analysis using speckle tracking is a novel ultrasonic technique that helps to differentiate mechanical dysfunction in HCM from myocardial adaptations in physiologic hypertrophy.