Characteristic myocardial strain identified in hypertrophic cardiomyopathy subjects with preserved left ventricular ejection fraction using a novel multi-layer transthoracic echocardiography technique

Abstract

Purpose: In order to evaluate compensatory mechanisms in hypertrophic-cardiomyopathy (HCM) subjects with preserved left-ventricular (LV) ejection-fraction (EF), we measured myocardial percentage endocardial strain dependency, as represented by 2D LV global longitudinal (GLS) and circumferential-strain (GCS), using a novel, multi-layer, speckle-tracking transthoracic-echocardiography (TTE) technique.

Methods: A total of 60 subjects (40 HCM with preserved LV EF (30 male; 62 ± 15 years, all LV EF>50%)) and 20 controls (10 male; 59 ± 10 years) underwent TTE (Vivid-E9). Quantitative strain-measurements of: endocardial, all and epicardial layers were performed at each-site. We defined percentage endocardial strain dependency as the ratio of endocardial strain to epicardial strain.

Results: Absolute GLS values at all views in all, endocardial and epicardial myocardial layers were significantly smaller in HCM subjects than in controls (all P<0.001). There were no significant differences between both-groups in absolute GCS values in the endocardial layers, at the mitral valve and papillary muscle levels. Percentage endocardial GCS dependency at all levels were greater in HCM subjects than in controls (all P<0.01). In HCM subjects, percentage endocardial GCS dependency at the mitral valve and papillary muscle levels revealed significant, moderate, negative correlations with LV end-diastolic and systolic dimensions (correlation coefficients -0.505, -0.451 (mitral valve level) and -0.533, -0.591 (papillary muscle level), respectively).

Conclusions: In HCM subjects with preserved LV EF, 2D LV GLS was lower than in controls, but endocardial GCS was maintained in compensation for reduction in endocardial GLS; thus percentage endocardial GCS dependency may increase, and the larger the LV size, the smaller this compensatory effect.

Keywords: Hypertrophic cardiomyopathy; Myocardial strain; Novel multi-layer technique; Preserved left ventricular ejection fraction; Speckle tracking transthoracic echocardiography technique.