RV/LV blood pool T2 ratio as a predictive biomarker in pulmonary hypertension: a cardiac MRI-based study

Abstract Introduction Pulmonary hypertension (PH) is a complex condition with high morbidity and mortality rates, currently necessitating invasive testing for diagnosis and risk stratification. Cardiac MRI is often performed in PH, and includes T2 mapping, which is an important tool for myocardial tissue characterization. However, it is known that blood pool T2 values reflect blood oxygen saturation levels (1) via the paramagnetic effects of deoxygenated hemoglobin, which have recently been investigated in patients with chronic thromboembolic PH (2). However, there is a lack of information regarding comparisons among PH subgroups and RHC data. This study evaluates the clinical utility of the right ventricular-to-left ventricular (RV/LV) T2 ratio in PH patients. Purpose To determine the relationship between the ratio (RV T2 /LV T2) and key hemodynamic parameters in PH subgroups. Methods This IRB-approved retrospective study included 31 PH patients classified into precapillary (n=13), postcapillary (n=6), and combined pre- and postcapillary (n=12) PH groups based on right heart catheterization (RHC). Average age was 64.41± 12.34 and 62.5%were male. Cardiac MRI, including conventional T2 mapping (3) and functional analysis, was performed within one month of RHC. Mid-ventricular short-axis images were analyzed to measure RV and LV blood pool T2values (Figure 1a, see inset) using Segment. Twenty-one (n=21) healthy volunteers with identical T2 mapping served as controls. Circular regions of interest at least 1.5 cm² in size, were carefully placed in artifact-free areas of the blood pool, avoiding the papillary muscles and myocardium. Statistical analyses assessed correlations, group differences, and predictive models for mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR). Results The RV/LV T2 ratio was significantly lower in PH patients (0.76 ± 0.07) compared to controls (0.90 ± 0.04, p<0.0001). Significant correlations were observed between the RV/LV T2 ratio and RVEF (R²=0.40, p<0.0001), mPAP (R²=0.45, p<0.0001), and PVR (R²=0.54, p<0.0001), pulmonary arterial saturation (R²=0.54, p=<.0001), right atrial pressure (R²=0.19, p=0.007), pulmonary arterial compliance (R²=0.46, p<.0001) (Figure 1). Multivariate analyses (including right ventricular ejection fraction (RVEF), right ventricular end diastolic volume index, RV/LV T2 ratio, vertical/horizontal length of LV in diastole and systole) revealed the RV/LV T2 ratio as an independent predictor of PVR (R²=0.71) and mPAP (R²=0.53) (table 1 and 2). Conclusion The RV/LV T2 ratio could be a promising, non-invasive and reproducible biomarker for monitoring PH patients. Its strong correlation with key hemodynamic parameters underscores its potential utility in regular assessment and risk stratification.