Novel Noninvasive Assessment of Pulmonary Arterial Stiffness Using Velocity Transfer Function

Background Pulmonary artery (PA) stiffness is associated with increased pulmonary vascular resistance (PVR). PA stiffness is accurately described by invasive PA impedance because it considers pulsatile blood flow through elastic PAs. We hypothesized that PA stiffness and impedance could be evaluated noninvasively by PA velocity transfer function (VTF), calculated as a ratio of the frequency spectra of output/input mean velocity profiles in PAs. Methods and Results In 20 participants (55±19 years, 14 women) undergoing clinically indicated right‐sided heart catheterization, comprehensive phase‐contrast and cine‐cardiac magnetic resonance imaging was performed to calculate PA VTF, along with right ventricular mass and function. PA impedance was measured as a ratio of frequency spectra of invasive PA pressure and echocardiographically derived PA flow waveforms. Mean PA pressure was 29.5±13.6 mm Hg, and PVR was 3.5±2.8 Wood units. A mixed‐effects model showed VTF was significantly associated with PA impedance ...