Diastolic mitral annular velocityduring the development of heart failure

Abstract

ObjectivesWe sought to investigate the mechanism of reduced diastolic mitral annular velocity with diastolic dysfunction, despite elevated left atrial (LA) pressure. BackgroundThe peak rate of left ventricular (LV) early diastolic filling (E) and velocity of the mitral annulus due to long-axis lengthening (EM) are reduced in mild diastolic dysfunction. With more severe dysfunction, E increases in response to increased LA pressures. In contrast, EMdecreases, despite increased LA pressure. MethodsWe studied eight dogs instrumented to measure LA pressure, LV pressure, and internal dimensions during the progressive development of heart failure (HF) produced by rapid pacing. ResultsEarly diastolic filling decreased after four days of pacing from 114 ± 32 to 88 ± 22 ml/s (p < 0.05), but with more severe HF, it progressively increased to 155 ± 32 ml/s (p < 0.05). In contrast, EMprogressively decreased from 44 ± 12 mm/s during the control period to 24 ± 8 mm/s after four weeks (p < 0.05). Although EMwas related to the time constant of LV relaxation (tau) (R2= 0.85), E was not. The latter occurred coincident with termination of the early diastolic LA to LV pressure gradient during all conditions. In contrast, with increasing HF, EMwas progressively delayed after LA to LV pressure crossover by 37 ± 12 ms (p < 0.05). The time from E to EMwas related to tau (R2= 0.97). ConclusionsWith slowed relaxation during the development of HF, EMis reduced and delayed so that it occurs after early, rapid filling. Thus, with slowed relaxation, EMdoes not respond to the early diastolic LA to LV pressure gradient, because it occurs when LV pressure is greater than or equal to LA pressure.