Characterization of Pulmonary Artery Blood Velocity Patterns in Lambs

Optimal management of patients with congenital heart disease often depends on the ability to assess pulmonary vascular impairment and monitor pulmonary hemodynamics. Need for improved techniques has prompted investigations of relationships between abnormal pulmonary circulations and pulmonary artery blood velocity patterns that can be observed noninvasively with pulsed Doppler ultrasound. Features commonly associated with pulmonary hypertension in humans (observed in the main pulmonary artery) are increased flow reversal [1,2], decreased rise time (time from onset of systole to peak velocity)[3–6] and a velocity waveform with a triangular or skewed shape, [7] as illustrated in Figure 1. Unfortunately, none of the techniques derived for estimating pulmonary pressure and flow solely from features of pulmonary velocity waveforms has been proven sufficiently reliable to be widely adopted in clinical practice. Failure has been attributed to individual variability and changing flow patterns in various parts of the pulmonary trunk [8,9]. Though studies examining the effects of acutely altered pulmonary hemodynamics on velocity patterns in animals have been reported, [10–12] surprisingly little work has been reported using animal models with chronically altered hemodynamics. Thus the goal of this report is to describe progress made in our laboratory in examining the velocity patterns in animal models of chronically elevated pulmonary blood pressure and flow, which are more analogous to the patient population of interest.