The Relationship Between Vortical Flow and Pressure Gradient Reversal in Pulmonary Hypertension-A 4D Analysis of...

Diagnosing pulmonary hypertension (PH) requires invasive right heart catheterization (RHC). However, mean pulmonary artery pressure (mPAP) can be non-invasively estimated using 4D analysis of cardiovascular magnetic resonance (CMR) flow imaging to assess the duration of pathological vortex flow (T_vortex) in the main pulmonary artery (MPA). Early systolic pressure reversal has been hypothesized to drive vortex formation but has yet to be quantified in-vivo. The virtual work-energy relative pressure (vWERP) method enables accurate temporal characterization of intravascular pressure gradients from 4D analysis of CMR flow images. We aimed to characterize the relationship between T_vortex and early systolic pressure reversal in the MPA using 4D analysis of CMR flow images from patients with a range of RHC-determined mPAP. A total of 36 patients who underwent a clinically indicated RHC for any reason were recruited for a research-motivated CMR-exam. Intravascular MPA pressure gradients were estimated from a stack of multidirectional 2D-flow slices covering the pulmonary artery using vWERP. Correlations between continuous variables were assessed using linear regression analysis. There were significant but weak correlations between time to systolic pressure reversal (T_rev) and T_vortex (R ²: 0.17; p = 0.012), pulmonary vascular resistance (PVR) (R ²: 0.29; p = 0.001), and mPAP (R ²: 0.27; p = 0.001), respectively. Multivariable analysis showed no independent correlation between T_vortex and T_rev once either PVR or mPAP were added as predictor variables. Our results suggest that early systolic pressure reversal is associated with, but is unlikely to be the sole cause of, observed vortical flow in the MPA.