The clinical significance of reversed flow in the main pulmonary artery detected by doppler color flow imaging.

Abstract

BACKGROUND: Using Doppler color flow imaging, abnormal flow patterns were reported to occur with pulmonary artery (PA) dilation. We have frequently observed red signals in the main PA, suggesting reversed flow (RF) in patients without overt pulmonary hypertension. The clinical implication of these signals has not been extensively studied. PATIENTS AND METHODS: We studied 191 of 412 patients referred for echocardiography (99 men and 92 women; mean +/- SD age, 62 +/- 13 years), in whom the main PA diameter had been adequately measured. If a red signal was observed by color flow imaging, a pulsed Doppler echocardiogram of the red signal was recorded simultaneously. The presence of the red signal was correlated with the PA diameter and the PA systolic pressure determined using the modified Bernoulli equation. In 54 patients who also underwent cardiac catheterization studies, the red signal was correlated with PA and pulmonary capillary wedge (PCW) pressures, and with pulmonary vascular resistance. RESULTS: Red signals adjacent to the medial PA border were detected in parallel with systolic blue signals in 127 patients (66%). Pulsed Doppler recordings revealed that they were caused by RF occurring immediately after the forward systolic signal and persisted in diastole. The PA diameter (28 +/- 4.8 mm) and the estimated PA systolic pressure (34 +/- 16 mm Hg) of patients with the RF signal were significantly greater (p < 0.001 and p < 0.05, respectively) than those of patients without the signal (22 +/- 2.5 mm and 28 +/- 6.0 mm Hg, respectively). Among patients who had hemodynamic studies, PA and PCW pressures were significantly higher (p < 0.05) in the 41 patients with the RF signal (22 +/- 12 mm Hg vs 15 +/- 2.6 mm Hg and 11 +/- 5.5 mm Hg vs 8 +/- 3.1 mm Hg, respectively). CONCLUSION: : RF signals in the main PA occur mostly as a result of PA dilation, which may be caused by primary pulmonary hypertension or chronic elevation of left atrial pressure in left-sided cardiac abnormalities.