ASSESSMENT OF PULMONARY VASCULAR IMPEDANCE IN PATIENTS WITH SEVERE PULMONARY ARTERIAL HYPERTENSION

Abstract

Introduction:​​ Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary artery (PA) pressure and resistance due to pulmonary vascular remodeling. Patients with PAH have progressive pulmonary vascular remodeling with the development of plexiform-like legions, but the functional effect of this vascular remodeling on the pulsatile pulmonary hemodynamics has not been studied. Pulmonary vascular impedance (PVZ) represents the relationship between pulsatile pressure and flow in the pulmonary artery and provides a comprehensive view of pulmonary arterial function. We hypothesized that decreased pulmonary vascular compliance and increased pulmonary vascular resistance would significantly alter the pulsatile pulmonary hemodynamics and PVZ in patients with severe PAH. Methods: ​​Patients with pulmonary hypertension (mPAP ≥ 25 mmHg) and control patients (mPAP < 25 mmHg) with both an echocardiogram including right ventricular outflow tract (RVOT) images and a right heart catheterization (RHC) were identified from the University of Arizona PH registry. The PH patients were divided into those with PVR < 3 mmHg*min/L, mildPAH (3 ≤ PVR < 4.6 mmHg*min/L), moderate PAH (4.6 ≤ PVR < 7.5 mmHg*min/L) and severe PAH (PVR ≥ 7.5 mmHg*min/L). Right ventricular outflow tract (RVOT) Doppler flow velocity profiles were first traced using a custom MATLAB program. Flow velocity profiles were multiplied by the average PA diameter (ratio of cardiac output and mean RVOT flow velocity) to determine PA flow profiles. Pulmonary vascular impedance (PVZ) was calculated in the frequency domain using RHC measured PA pressure and PA flow profiles. Characteristic Impedance (Z​C​) was calculated as the mean of Z​2-4​. Data is presented as median [interquartile range].