What is the difference between pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension on phase-resolved functional lung MRI? A cross-sectional observational study.

Abstract

To assess whether phase-resolved functional lung MRI (PREFUL-MRI) can differentiate pulmonary arterial hypertension (PAH) from chronic thromboembolic pulmonary hypertension (CTEPH) and to compare PREFUL-derived perfusion and ventilation characteristics between the two entities. In this single-center study (January 2024-March 2025), patients with pulmonary hypertension (PH) who underwent PREFUL-MRI, ventilation/perfusion single-photon emission CT/CT (V/Q SPECT/CT), and right-heart catheterization within 1 week were retrospectively enrolled. PREFUL-MRI was acquired with a free-breathing fast spoiled gradient echo sequence to generate perfusion and ventilation maps. PREFUL maps and V/Q SPECT/CT were assessed by four blinded readers. Quantitative PREFUL parameters were compared between PAH and CTEPH, and correlations with hemodynamics were analyzed. Fifty-three PH patients were included (PAH 26, CTEPH 27). All manifested multiple perfusion defects on PREFUL maps. Visual assessment with PREFUL yielded 70% sensitivity and 38% specificity for CTEPH, lower than V/Q SPECT/CT (sensitivity 95%, specificity 95%). CTEPH had higher perfusion defect percentage and lower mean perfusion than PAH (median QDP_exclusive 51.9% vs. 24.4%, p < 0.001; QDP_total 58.4% vs. 30.85%, p < 0.001; mean perfusion 2.8% vs. 3.9%, p = 0.003). QDP_exclusive represents areas with perfusion defects but without ventilation defects, whereas QDP_total indicates the overall perfusion defect percentage. Across the cohort, QDP_exclusive correlated positively with pulmonary vascular resistance (PVR) (ρ = 0.313, p = 0.031). PREFUL-MRI did not reliably distinguish PAH from CTEPH on visual assessment, although CTEPH exhibited a larger perfusion defect burden. It may be more suitable for functional evaluation of PH rather than for initial differential diagnosis. QuestionCan phase-resolved functional lung MRI (PREFUL-MRI) noninvasively distinguish pulmonary arterial hypertension (PAH) from chronic thromboembolic pulmonary hypertension (CTEPH), and reflect their hemodynamic severity? FindingsPREFUL-MRI showed limited visual discrimination compared to V/Q SPECT/CT; CTEPH exhibited more severe perfusion defects; perfusion defect percentage correlated with pulmonary vascular resistance. Clinical relevancePREFUL-MRI provides radiation- and contrast-free perfusion metrics reflecting hemodynamic burden in pulmonary hypertension. Though suboptimal for initial discrimination in disease subtypes, it supports functional evaluation once the diagnosis is established.