Evaluation of left ventricular relaxation using the continuous-wave Doppler velocity profile of aortic regurgitation: noninvasive measurement of left ventricular negative dP/dt and time constant.

BACKGROUND

The maximal negative dP/dt [max (-)dP/dt] and time constant (T) are useful indices for evaluating left ventricular (LV) relaxation, but they require invasive procedures.

HYPOTHESIS

The purpose of this study was to obtain max (-)dP/dt and T using the continuous-wave Doppler aortic regurgitation velocity curve (AR-CW) noninvasively. Using the Bernoulli equation, the AR-CW allows accurate determination of the pressure gradients (PG) between the aorta and the left ventricle.

METHODS

In 10 patients with trivial to mild AR, the rising segment of the AR-CW reflecting LV pressure decrease was digitized with the cardiac image analysis system. Transpulmonary contrast-enhanced Doppler echocardiography was used in three patients to obtain intense velocity envelope. The PG curve and the firs derivative curve were reconstructed and the maximal point of the first derivative curve, which is consistent with max(-)dP/dt, was termed as maximal rate of pressure fall (maxRPF). As T (calculated according to the method of Weiss) can be obtained from T=Pm/max(-)dP/dt [Pm: LV pressure at the phase of max(-)dP/dt], we calculated T from Pm/maxRPF (Pm=dicrotic notch pressure-4Vm2) (Vm: AR velocity at the phase of maxRPF).

RESULTS

The Doppler-derived maxRPF and T (TD) approximated the catheter-derived max(-)dP/dt and T (y = 0.85x + 245, r = 0.97, p < 0.001, y = 0.79x + 4, r = 0.87, p < 0.001). In addition, dobutamine echocardiography was performed in nine patients showing increased maxRPF and decreased TD, indicating improvement of LV relaxation.

CONCLUSION

These Doppler-derived new indices are sufficiently useful to evaluate LV relaxation noninvasively.