Right ventricular systolic time intervals: comparison of echocardiographic and Doppler-derived values

Although the clinical utility of right ventricular (RV) systolic time intervals (STI) has been well documented, their use is at times limited by an inability to obtain adequate M-mode echocardiographic images of the pulmonary valve. Therefore the relationship between the pulmonary artery Doppler flow tracing and the timing of pulmonary valve opening and closure was investigated to determine if the more readily available Doppler recording could be utilized for determining RV STIs. We compared RV preejection period (PEP), ejection time (VET), and PEP/VET ratio derived from the pulsed Doppler frequency-time curve recorded in the main pulmonary artery with measurements from a simultaneously recorded M-mode pulmonary valve echocardiogram (Echo). The nadir of the late systolic flow reversal, rather than the point at which the frequency spectrum crosses the zero baseline, correlated best with the point of pulmonary valve closure. By the use of this method for determining end-systole, all three Doppler-derived measurements were highly correlated with the values from the pulmonary valve echocardiogram: PEPEcho = 1.01 PEPDoppler - 3.1 (r = 0.990, S.E.E. PEPEcho = 2.7 msec); VETEcho = 0.98 VETDoppler + 10.2 (r = 0.998, S.E.E. VETEcho = 3.3 msec); (PEP/VET)Echo = 0.95 (PEP/VET)Doppler + 0.007 (r = 0.980, S.E.E. (PEP/VET)Echo = 0.012 msec). The Doppler velocity-time curve provides accurate measurement of RV STIs that can be recorded with relative ease compared with the pulmonary valve echocardiogram. This expanded availability of RV STIs permits an improved ability to investigate the hemodynamic determinants of these indices and their relation to the status of the pulmonary vasculature and right ventricular performance.