Abstract 1874: Circumferential and Radial Left Ventricular Mechanics in Elderly Canines with Hypertensive Heart Disease
Introduction: Cross-sectional studies in patient with hypertensive heart disease (HHD) and heart failure with normal ejection fraction (HFnlEF) suggested impairment of longitudinal myocardial mechanics as assessed by tissue Doppler imaging. It has been suggested that enhanced circumferential, and/or radial LV mechanics or LV remodeling compensates for depression in longitudinal function and thus, preserves EF in HHD or HFnlEF.
Hypothesis: We hypothesized that if longitudinal performance is depressed, whether due to increased afterload or to intrinsic myocardial dysfunction, circumferential and radial LV mechanics would also be effected. To test this hypothesis, we used an aged canine model of hypertension.
Methods: Elderly dogs (n=22) underwent bilateral renal wrapping to induce hypertension. 2D echocardiography (mid-short axis views) was performed before and 8 weeks after renal wrapping; peak radial (PR) and peak circumferential (PC) regional strains were measured by speckle tracking averaging data from 6 segments. Ejection fraction (EF), LV mass index (LVMI), systolic blood pressure (SBP), and circumferential wall stress (CWS) were assessed as well.
Results: See table⇓. PR correlated with PC (r=0.65), EF (r=0.67), LWMI (r=0.71) and CWS (r=0.58) (p<0.005 for all). PC correlated also with EF (r=0.60), LWMI (r=0.49) and CWS (r=0.48) (p<0.01 for all). The relationship between EF and CWS (r2=0.64, p<0.001) was modified by the addition of either PC (r2=0.74, p for PC =0.005) or PR strain(r2=0.69, p for PR =0.04).
Conclusions: These data show that development of hypertension with LV hypertrophy does not enhance but impairs circumferential and radial LV mechanics as assessed with strain imaging, and that like EF, circumferential and radial strain are related to afterload (wall stress). However, both confer additional information regarding contractility. Conclusions regarding myocardial function based on strain imaging must account for its load dependence.