Abstract 707: Nonuniformity of Left Ventricular Apical-to-Basal Diastolic Lengthening in Patients with Hypertrophic Nonobstructive Cardiomyopathy
Quantification of left ventricular (LV) apex-to-base dispersion has been feasible with two-dimensional echocardiographic tissue tracking system (2DTT, Hitachi EUB7500), which based on pattern matching algorithm. Although impairment of LV relaxation was characterized in patients with hypertrophic cardiomyopathy (HCM), the behavior of LV apical and basal diastolic lengthening and its relation to LV filling are unknown. We obtained basal and apical LV short-axis views in 22 patients with non-obstructive HCM and 25 healthy volunteers (N). Eight equiangular points on endo-myocardium at end-diastole were placed in each view, and the shortening ratios of four directions were calculated and averaged by 2DTT. Then, the time-LV shortening and lengthening curves were obtained. The time intervals from the aortic valve closure to the point of the first 40% of peak lengthening (T40) were measured in each view. Isovolumic relaxation time (IRT) was measured by pulsed Doppler LV in- and out-flow recordings. Although both apical and basal T40 were similar in N (145.8±38.4 vs. 134.3±34.2msec0.5, ns.), the apical T40 in HCM was longer compared to base (118.7±51.1 vs. 168.8±52.5msec0.5, p<0.0001). The time difference of T40 between apex and base was related to LV IRT (r=0.59, p<0.0001). Nonuniformity of apical-to-basal left ventricular lengthening during early diastole was present in HCM. This apex-to-base dispersion, especially apical delay in timing of LV lengthening may have a physiologic importance for impairment of LV relaxation in HCM.