MATCHING DICROTIC NOTCH AND MEAN PULMONARY-ARTERY PRESSURES - IMPLICATIONS FOR EFFECTIVE ARTERIAL ELASTANCE

It has been suggested that pulmonary artery pressure at the end of eje ction is close to mean pulmonary artery pressure, thus contributing to the optimization of external power from the right ventricle. We teste d the hypothesis that dicrotic notch and mean pulmonary artery pressur es could be of similar magnitude in 15 men (50 +/- 12 yr) referred to our laboratory for diagnostic right and left heart catheterization. Be at-to-beat relationships between dicrotic notch and mean pulmonary art ery pressures were studied 1) at rest over 10 consecutive beats and 2) in 5 patients during the Valsalva maneuver (178 beats studied). At re st, there was no difference between dicrotic notch and mean pulmonary artery pressures (21.8 +/- 12.0 vs. 21.9 +/- 11.1 mmHg. There was a st rong linear relationship between dicrotic notch and mean pressures 1) over the 10 consecutive beats studied in each patient (mean r = 0.93), 2) over the 150 resting beats (r = 0.99), and 3) during the Valsalva maneuver in each patient (r = 0.98-0.99) and in the overall beats (r = 0.99). The difference between dicrotic notch and mean pressures was - 0.1 +/- 1.7 mmHg at rest and -1.5 +/- 2.3 mmHg during the Valsalva man euver. Substitution of the mean pulmonary artery pressure by the dicro tic notch pressure in the standard formula of the pulmonary vascular r esistance (PVR) resulted in an equation relating linearly end-systolic pressure and stroke volume. The slope of this relation had the dimens ion of a volume elastance (in mmHg/ml), a simple estimate of volume el astance being obtained as 1.06(PVR/T), where T is duration of the card iac cycle. In conclusion, dicrotic notch pressure was of similar magni tude as mean pulmonary artery pressure. These results confirmed our pr imary hypothesis and indicated that human pulmonary artery can be trea ted as if it is an elastic chamber with a volume elastance of 1.06(PVR /T).