Echocardiography as a Noninvasive Swan-Ganz Catheter

Abstract

Diwan and co-investigators report in this issue of Circulation that the interval between onset of mitral E and annular early diastolic velocity (Ea) by tissue Doppler, TE−Ea, can be used to estimate left ventricular (LV) filling pressure in patients with mitral valve disease.1 Garcia and colleagues were the first to report that the onset of Ea occurred 7.5±3.5 ms after peak mitral inflow velocity in 7 patients with restrictive cardiomyopathy, whereas Ea started 22±19 ms earlier than did E in the normal group.2 Subsequently, TE−Ea has been shown to correlate with the time constant of LV relaxation (τ) demonstrated by Hasegawa and associates in their elegant animal experiment.3 With worsening of heart failure by rapid pacing, Ea progressively decreased in velocity and delayed in onset. Mitral E occurred coincidently with the termination of the early diastolic left arterial (LA) and LV pressure gradient at baseline and all stages of heart failure. In contrast, with increasing heart failure, Ea was progressively delayed after LA to LV pressure crossover, and TE−Ea was related to τ. Rivas-Gotz, Nagueh, and their associates also demonstrated that TE−Ea was prolonged after constriction of the circumflex coronary artery in dogs.4 In patients with heart failure, LV myocardial relaxation and compliance are decreased. See p 3281 Although LV filling is initiated and enhanced by augmentable myocardial relaxation in healthy individuals, it is driven by high filling pressure in patients with heart failure because myocardial relaxation remains reduced, not being sensitive to preload. Myocardial relaxation also affects the isovolumic relaxation time (IVRT). As relaxation becomes abnormal, LV pressure falls more slowly and the opening of the mitral valve is delayed, resulting in a longer IVRT. IVRT, however, becomes shorter as LA pressure increases; hence, IVRT∝τ/LA pressure. Because TE−Ea∝τ, …