Correlating Pulmonary Hemodynamics With HP ¹²⁹Xe Dissolved-Phase MRSI in a Controlled Porcine Intervention Study

Pulmonary hypertension is related to a 1-year mortality ranging from < 5% to > 20% in low- and high-risk groups. Right heart catheterization is the diagnostic gold standard, associated with a 1.1% rate of severe adverse events, posing the need for a non-invasive diagnostic tool. This study aims to delineate the effects of controlled changes on pulmonary hemodynamics by quantifying corresponding changes in hyperpolarized ¹²⁹Xe MRSI dissolved-phase parameters, including RBC oscillations.

Seven Danish Landrace pigs underwent hyperpolarized ¹²⁹Xe dissolved-phase 3D MRSI with interleaved MRS under baseline conditions and three vasoactive interventions, monitored with invasive catheters or phase-contrast MRI. Results were evaluated using one-way ANOVA or mixed-effects analysis followed by Dunnett's multiple comparisons test.

Hypoxia increased mPAP (p = 0.038), reduced RBC:M (-31%, p = 0.007) and RBC:G (-34%, p = 0.009), while increasing RBC chemical shift (0.57%, p = 0.020). Adenosine and dobutamine increased RBC:M (22%, p = 0.003) and RBC:G (30%, p = 0.009), while decreasing RBC chemical shift (-0.38%, p = 0.11). Linear regression revealed an inverse correlation between mPAP and RBC oscillation amplitude (R² = 0.158, p = 0.04), RBC:M (R² = 0.25, p = 0.05), and RBC:G (R² = 0.22, p = 0.01).

This study demonstrates that dissolved-phase hyperpolarized ¹²⁹Xe MRSI parameters are sensitive to hemodynamic changes, exhibiting consistent inverse relationships with invasively measured mPAP. By leveraging concurrent invasive reference measurements, these findings provide physiological validation that dissolved-phase ¹²⁹Xe metrics reflect pulmonary vascular pressure, supporting their further development as a non-invasive adjunct to right heart catheterization.