Abstract 14806: Comparison of Afterload Dependency Between Left Ventricular Myocardial Strain and Strain Rate in Healthy Subjects

Abstract

Background: Left ventricular (LV) myocardial strain and strain rate (SR) both depend upon afterload. However, the difference in the afterload dependency between these 2 indices has not been investigated. Methods: Echocardiography was performed in 41 healthy volunteers before and during handgrip exercise. The handgrip exercise was performed at 50% of the maximum grasping power for 4 minutes. Meridional wall stress (MWS) was calculated from end-systolic LV dimension and wall thickness as well as systolic blood pressure. By using speckle tracking echocardiography, longitudinal peak strain (LS) and systolic peak SR (LSR) were measured and averaged in 3 apical views. These parameters were indicated in the absolute values. Results: During handgrip exercise, systolic blood pressure increased from 98±11 to 116±15 mmHg and MWS increased from 660±130 to 975±174 dyn•mm -2 (%change: 49±18%). In response to this increase in MWS, LS decreased by 8.4±4.8% (from 17.2±1.7 to 15.7±1.4%). In comparison, LSR decreased by 6.4±5.5% (from 0.80±0.09 to 0.75±0.08 s -1 ), which was significantly smaller than the decrease in LS (p<0.05). There were significant linear correlations between MWS and LS (r=-0.53, p<0.01) or LSR (r=-0.28, p<0.05) among all points before and during handgrip exercise and the absolute value of correlation coefficient for LS (0.53) tended to be greater than that for LSR (0.28). The dispersions of LS and LSR, expressed as the root mean square error in the standardized regression analysis, were similar (0.86 SD and 0.98 SD, respectively). Therefore, the difference in the correlation coefficients was considered to be a reflection of the difference in the afterload dependency between LS and LSR, but not the dispersion of the measurements. Conclusions: Myocardial strain more strongly depends on afterload than myocardial strain rate in healthy subjects.