NONINVASIVE ASSESSMENT OF LEFT-VENTRICULAR RELAXATION USING CONTINUOUS-WAVE DOPPLER AORTIC REGURGITANT VELOCITY CURVE - ITS COMPARATIVE VALUE TO THE MITRAL REGURGITATION METHOD

Background The most established parameters of left ventricular (LV) re laxation are peak negative value of the first derivative of LV pressur e (-dP/dt(max)) and the time constant of isovolumic LV pressure fall. The instantaneous pressure gradient between the aorta and the LV durin g diastole can be calculated from the continuous-wave Doppler aortic r egurgitant velocity spectrum. Because the fluctuation of aortic pressu re during LV isovolumic relaxation is negligibly minor and because LV minimal pressure is negligibly low, LV pressure during the isovolumic relaxation period may be derived from the continuous-wave Doppler aort ic regurgitant velocity spectrum. This study was designed to clarify w hether analysis of continuous-wave Doppler aortic regurgitation record ing provides accurate measures of LV relaxation over a wide range of L V function and to determine comparative values of aortic and mitral re gurgitation methods in the assessment of LV relaxation. Methods and Re sults In eight mongrel dogs with acute ischemic LV dysfunction, the co ntinuous-wave Doppler aortic regurgitant velocity spectrum was recorde d simultaneously with high-fidelity LV and aortic pressures, while the continuous-wave Doppler mitral regurgitant velocity spectrum was reco rded simultaneously with high-fidelity left atrial and LV pressures. T he aortic regurgitant velocity spectrum was provided for the determina tion of Doppler-derived mean rate of LV pressure fall in 20 ms after t he onset of aortic regurgitation (Delta P/Delta t-AR) and the time int erval from the onset of aortic regurgitation to the point at (1-1/e)(1 /2) of the maximal aortic regurgitant velocity as an estimate of the t ime constant. The mitral regurgitant velocity spectrum was provided fo r Doppler-derived mean rate of LV pressure fall in 20 ms after the poi nt of -dP/dt(max) (Delta P/Delta t-MR) and the time interval from the point of -dP/dt(max) to the point with mitral regurgitant velocity of (1/e)(1/2) of the mitral regurgitant velocity at the point of -dP/dt(m ax) as an estimate of the time constant. Delta P/Delta t-AR and Delta P/Delta t-MR correlated well with catheter-derived -dP/dt(max) (r=.92, r=.98, P<.01, respectively). The time constant derived from aortic an d mitral regurgitant velocity spectra (tau-AR and tau-MR) also correla ted well with catheter-derived time constant (r=.84, r=.76, P<.01, res pectively). However, a mean difference of the catheter-derived time co nstant minus tau-MR was larger than tau-AR (29+/-30 versus 4+/-17 ms, P<.01, presented as mean+/-2 SD). Conclusions LV relaxation can be ass essed from the continuous-wave Doppler aortic regurgitant velocity spe ctrum. The aortic regurgitation method provides an even more accurate estimate of the time constant compared with the mitral regurgitation m ethod, particularly in the presence of LV dysfunction.