Effects of heart rate and pulmonary artery pressure on Doppler pulmonary artery acceleration time in experimental acute pulmonary hypertension.

Chronic pulmonary hypertension in humans is characterized by shortening of the pulmonary artery acceleration time as measured by Doppler echocardiography, such that the higher the pulmonary artery pressure, the shorter the pulmonary acceleration time. Increases in heart rate are also known to produce decreases in the pulmonary artery acceleration time. To explore the relationship between mean pulmonary artery pressure, heart rate, and Doppler pulmonary artery acceleration time, experimental acute pulmonary hypertension was created in nine Duroc swine, either by infusion of Sephadex beads with embolization of the pulmonary arterial circulation or by partially occluding the main pulmonary artery 8 to 10 cm distal to the pulmonic valve. Pulmonary artery Doppler flow velocity recordings and invasive pressure measurements were made at baseline and at paced atrial rates ranging from 60 to 160 beats per minute, in 20-beat increments. The results in this acute animal model reveal that increases in heart rate produced significant decreases in Doppler pulmonary artery acceleration time at mean pressures below 25 mm Hg. However, with mean pulmonary artery pressures greater than 25 mm Hg, both heart rate and increases in pulmonary artery pressure had no significant effect on acceleration time.