Pulmonary blood velocity patterns in an animal model of pulmonary hypertension

Relationships between pulmonary artery blood velocity patterns and elevated pulmonary artery pressure and resistance were studied in an animal model of chronic pulmonary hypertension. Monocrotaline pyrrole was injected into the right atria of 1-3-day-old lambs. The animals were subjected to an acute terminal study 4-6 weeks postinjection. Using an intraluminal 20-MHz pulsed Doppler probe, pulmonary blood velocity was measured at 2-mm intervals across the posterior-anterior axis, from which 2-D instantaneous velocity profiles were reconstructed and the characteristics of the waveforms examined. Preliminary computations indicate that the significant increase in pulmonary blood-flow reversal observed near the posterior wall in normal lambs with acute pulmonary hypertension created by hypoxia is not always present in animals with chronic pulmonary hypertension. However, the triangular shape of the waveform associated with pulmonary hypertension is apparent in all studies, and the maximum value of the ratio of reverse flow to forward flow calculated by sampling site correlated significantly with both pulmonary artery pressure and pulmonary vascular resistance.<>