The effect of heart rate on the slope and pressure half-time of the Doppler regurgitant velocity curve in aortic insufficiency.

The effect of the heart rate on the Doppler aortic regurgitant velocity curve was evaluated in 14 patients with aortic regurgitation. The heart rate was increased in two steps with either endocardial or transesophageal pacing in 12 patients and with atropine sulfate in 2 patients (increased from 66 +/- 7 to 82 +/- 4 beats per minute [step 1] to 100 beats per minute [step 2]) in all patients. The increased heart rate resulted in an increased regurgitant slope (from 3.3 +/- 1.2 to 4.5 +/- 1.7 m/s2 [step 1] to 5.8 +/- 1.9 m/s2 [step 2]; p < 0.01) and a shortened pressure half-time (PHT) (from 442 +/- 136 to 323 +/- 98 ms [step 1] to 254 +/- 69 ms [step 2]; p < 0.01). Such variations occurred in the presence of a prevalent hemodynamic improvement, noninvasively suggested by a decreased Doppler-derived left ventricular end-diastolic pressure (LVEDP) (from 23 +/- 10 to 14 +/- 10 mmHg at the highest heart rate; p < 0.05) and by an increased peak aortoventricular diastolic gradient (from 80 +/- 20 to 84 +/- 22 at the highest heart rate; p < 0.05). The PHT and slope correlated with diastolic time (r = 0.74 and -0.65, respectively; p < 0.001). The relative-PHT (PHT/diastolic time x 100) showed insignificant changes during the increase in heart rate and correlated better than the PTH with color Doppler assessment of regurgitation severity (r = -0.73; p = 0.003, and r = -0.53; p = 0.05, respectively). We concluded that the slope and PHT of the aortic regurgitant velocity curve were rate-dependent; the relative-PHT appeared to limit the influence of the heart rate on PHT.