RV/LV Blood Pool T2 Ratio as a Predictive Biomarker in Pulmonary Hypertension: Prediction of Hospitalization in Combined Pre- and Postcapillary Patients

Background: Pulmonary hypertension (PH) is a progressive disease with high morbidity. Right heart catheterization (RHC) is the diagnostic gold standard, but its invasiveness limits longitudinal use. Cardiac magnetic resonance (CMR) with T2 mapping offers non-invasive tissue and functional assessment. Blood pool T2 values, which reflect oxygen saturation via the paramagnetic effects of deoxygenated hemoglobin (1,2), have not been evaluated in relation to invasive hemodynamics in PH. This study examined the clinical utility of the right ventricular-to-left ventricular (RV/LV) T2 ratio. We investigated the association between the RV/LV T2 ratio and invasive hemodynamic parameters, and its prognostic role in predicting outcomes.

Methods: This retrospective study included 31 PH patients classified by RHC as precapillary (n=13), postcapillary (n=6), or combined pre and postcapillary PH (CpcPH) (n=12). A control group of 21 healthy volunteers with T2 mapping was included. CMR with functional analysis and T2 mapping was performed on a 1.5T Siemens within one month of RHC. RV and LV blood pool T2 values were measured from mid-ventricular short-axis slices (see figure 1a and b). Correlations with mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance (PVR), and other indices were assessed. Multivariate regression identified independent predictors.

Results: The RV/LV T2 ratio was significantly lower in PH patients compared with controls (0.76 ± 0.07 vs. 0.90 ± 0.04, p< 0.0001 figure 1c). The ratio correlated positively with right ventricular ejection fraction (RVEF; R=0.63, p< 0.0001) and pulmonary arterial compliance (R=0.67, p< 0.0001), and negatively with mPAP (R=−0.67, p< 0.0001), PVR (R=−0.73, p< 0.0001) (figure 2), right atrial pressure (R=−0.65, p=0.007), and pulmonary arterial oxygen saturation (R=−0.73, p< 0.0001). regression analysis identified the RV/LV T2 ratio as an independent predictor of PVR (R²=0.71, p=0.033) and mPAP (R²=0.53, p=0.006).

During 3.4 ± 1.1 years of follow-up, adverse events occurred exclusively in the CpcPH subgroup, with 5 of 12 patients hospitalized for heart failure. In this group, pulmonary arterial wedge pressure, mPAP, PVR, RVEF, and left ventricular ejection fraction did not differ between hospitalized and non-hospitalized patients. However, the T2 RV/LV ratio was lower in patients who experienced hospitalization (0.71 vs. 0.75), showing a trend toward significance (ANOVA p=0.08; t-test p=0.04). ROC curve analysis identified an optimal T2 ratio cutoff of 0.73, with good discriminatory ability for hospitalization events (AUC = 0.85). Kaplan-Meier analysis using this cutoff showed significantly higher HF-hospitalization in patients with T2 ratios below 0.73 (log-rank p=0.016) (figure 3).

Conclusion: The RV/LV T2 ratio is a promising, non-invasive biomarker for PH assessment. Its strong correlation with invasive hemodynamics and prognostic value for hospitalization, particularly in CpcPH, supports its role in monitoring and risk stratification.

Figure 1: Assessment of blood pool T2 ratio in patients with A) pulmonary arterial hypertension (T2 ratio=0.9), and B) patient with CpcPH (T2 ratio= 0.68). C) T2 ratio was significantly lower in PH patients vs. healthy subjects (p < 0.0001).
Figure 2: Correlation plots showing the relationship of the RV/LV T2 ratio with A) pulmonary vascular resistance (PVR) and B) mean pulmonary arterial pressure (mPAP).
Figure 3: A) ROC analysis found a blood T2 ratio cutoff of 0.73 to provide an AUC of 0.85 to predict heart-failure hospitalization in the CpcPH group (N=12, 5 events). B) Kaplan Meier curve shows potential predictive utility of blood T2 ratio.