Abstract
Introduction
Left ventricular (LV) relaxation time constant, Tau (τ), is one of the best indexes to evaluate left ventricular diastolic function and is usually assessed invasively. Tau is the time constant of the exponential regression Pt =(P0-P∞)e-t/τ+P∞ that expresses left ventricular isovolumic pressure decay, where Pt is LV pressure (LVP) at time t, P0 is LVP at dP/dtmin and P∞ is the asymptotic pressure, to which relaxation would lead if completed without LV filling. Several noninvasive methods were developed to calculate Tau, however, they are time-consuming and complicated. Recently, a simple method regional left ventricular pressure–strain loops and myocardial work was introduced and validated. We hypothesize that left ventricular relaxation time constant can be derived and calculated from the LV pressure–strain loops.
Objective
To calculate noninvasively Tau using LV pressure–strain loops and compare it to invasive Tau assessment.
Methods
The study includes patients with preserved LV systolic function without significant valvular disease that were scheduled to elective coronary catheterization. During catheterization, a fluid-filled catheter was placed in the LV to measure pressure. Echocardiography was performed simultaneously with LV pressure recording. Three standard apical views were acquired and subsequently 2D strain analysis was performed using commercially available GE software and LV pressure–strain loops were calculated. Doppler signal was used for timing of valvular events. Tau was calculated by the equation τ =P/(-dP/dt) that is a derivative of the ventricular pressure decline P = P0e-t/τ+PB with respect to time. The pressure between peak negative dP/dt and the lowest LV pressure shortly after mitral valve opening was used for this calculation. The study was approved by the institutional ethics committee.
Results
Forty patients, (mean age 65.1 ± 10.9 years, 27 male, BSA1.93 ± 0.18 m2) were included in the study. Heart rate and the mean blood pressure at the time of catheterization were 69.9 ± 11.8 min-1 and 85.2 ± 18.8 mmHg, respectively. The mean LV end diastolic diameter was 44 ± 4 mm, the LV mass was 86.7 ± 25.2 g/m2, LVEF 58.4 ± 6.6% and GLS 21.0 ± 3.2%. Tau, calculated noninvasively using derivative method was significantly lower than invasively derived measurement (40.1 ± 13.4 vs 49.8 ± 7.7 msec, p = 0.002). However, a significant positive correlation was observed between the two methods (r =0.67, p <0.001, Figure).
Conclusions
This preliminary study demonstrates that Tau estimated by a noninvasive method using LV pressure–strain loops has a good correlation with Tau measured invasively. Therefore, Tau can be estimated noninvasively using novel left ventricular pressure–strain loop method.
Abstract P1510 Figure.
Calculation of Left Ventricular Relaxation Time Constant-Tau in Patients With Aortic Regurgitation by Continuous-Wave Doppler
