Right Ventricular to Left Ventricular (RV/LV) Blood Pool T2 Ratio Is Associated With Invasive Hemodynamics Across Pulmonary Hypertension Subgroups.

Pulmonary hypertension (PH) is defined by elevated mean pulmonary arterial pressure (mPAP). Pulmonary vascular resistance (PVR) and SvO2 (mixed venous oxygenation), measured by right heart catheterization (RHC), are key determinants of disease severity and prognosis. The right-to-left ventricular (RV/LV) blood-pool T2 ratio (T2RV/LV) by MRI has been proposed as a surrogate of RV-LV blood oxygenation differences and SvO2. Therefore, we analyzed 31 consecutive patients with PH (precapillary = 13, postcapillary = 6, combined = 12) compared to data from four patients with no PH and 21 healthy subjects. All subjects underwent 1.5 T MRI with cine for RV/LV and atrial volumes and T2 mapping. Blood T2RV/LV was measured on mid-ventricular short-axis images. Hemodynamic data (including mPAP, PVR, pulmonary arterial wedge pressure (PAWP) and oxygen saturations) were obtained from recent (within 1.5 months) RHC. We found that the T2RV/LV was significantly lower in PH patients than in healthy controls (0.76 ± 0.09 vs. 0.91 ± 0.05; p < 0.001) and correlated with pulmonary artery oxygen saturations (SvO2) (r = 0.77; p < 0.001). It also correlated with PVR (ρ = -0.74; p < 0.001), mPAP (r = -0.54; p < 0.001), RVEF (r = -0.61; p < 0.001). In multivariable analysis, T2RV/LV independently predicted mPAP (p < 0.001; R 2 = 0.64 with LA volume index and RVEF) and PVR (p < 0.001; R 2 = 0.63 with RVEF). Inter- and intra-observer variability for T2RV/LV was excellent (R = 0.96-0.97). In conclusion, blood T2RV/LV independently predicts invasive hemodynamic indices and is a non-invasive biomarker of SvO2, which might enable noninvasive risk stratification and treatment monitoring in PH.