Flow velocity patterns in the pulmonary artery and pulmonary hypertension

Abstract

Pulmonary hypertension impacts negatively on right ventricular function; however, understanding pulmonary vasculature can be difficult. Data from invasive monitoring or traditional echocardiography may not represent the full extent of pulmonary arterial disease. An important element missing from invasive monitoring is the ability to take into account the effects of pulsatile flow; therefore, mean pressures and mean flows are employed in the calculation of pulmonary vascular resistance. Traditional echocardiography yields right ventricular systolic pressures but only in the presence of tricuspid regurgitation. In these Perioperative Cardiovascular Rounds, we show the utility of interpreting pulmonary artery (PA) pulsed-wave Doppler (PWD) and colour-flow Doppler in the assessment of the pulmonary vasculature, and we describe the physiology behind their genesis. We show these concepts in a case vignette involving a patient in a low cardiac output state after a complex re-do sternotomy. Additionally, we describe four distinct patterns of PA PWD tracings and illustrate the ability of PA PWD analysis to assess the pulmonary vasculature in both a qualitative and semi-quantitative way. In the critical care setting, it is vital to understand alterations in the pulmonary circulation, and analysis of PA PWD can provide additional information to complement data from other sources.