Abstract 4725: Left Ventricular Myocardium Shows Base-to-Apex Deformation Gradient during Isovolumic Relaxation Period in Healthy Subjects
Introduction: Deformation of LV myocardium during isovolumetric relaxation period (IVR) is not well described.
Methods: We performed echocardiography (Vivid 7, GE Medical) in 90 healthy subjects at rest (mean age 38 ±13 years, 34 males). Standard long and short LV axis views were acquired with high frame rate (65–100 fps) and used for strain rate (Sr) measurement by speckle tracking (EchoPac PC) in three directions: longitudinal (SrL), circumferential (SrC) and radial (SrR). Segmental Sr curves were the average Sr in each LV levels, i.e. base (B), mid (M) and apex (A) and normalized by R-R interval duration (Panel A and B). We then calculated Sr gradients during IVR as maximal instantaneous difference between apex-to-base or mid-to-base LV Sr (Sr(A-B) or Sr(M-B), Panel C). Pulsed wave Doppler flow profiles were used to determine cardiac intervals.
Results: SrL(A-B), SrC(A-B) and SrR(A-B) were 0.53 ±0.43, 0.67 ±0.46, −1.89± 1.52 s-1. SrL(M-B), SrC(M-B) and SrR(M-B) were 0.37±0.15, 0.5±0.34 and −2.14±1.4 s-1. Both types of gradient were identified for all strains (p<0.001 vs. zero), and were also different from each other (p<0.001, Sr(A-B) vs. Sr (M-B) for similar strain). The gradients were driven by faster relaxation in apical and mid LV segment and brief shortening in basal segment (see Figure⇓ inset).
Conclusions: Differential deformation of LV exists during IVR. This deformation difference in the base to apex direction may facilitate changes in LV geometry that result in rapid intra-cavitary pressure reduction.