Diagnostic Performance of Magnetic Resonance Imaging in Chronic Thromboembolic Pulmonary Hypertension: A Systematic Review

BACKGROUND: Chronic thromboembolic pulmonary hypertension (CTEPH) requires accurate identification of thromboembolic and perfusion defects for diagnosis and operability assessment. Magnetic resonance imaging (MRI) provides radiation-free evaluation of vascular morphology, perfusion distribution and cardiopulmonary function. However, its diagnostic performance in CTEPH has not been comprehensively synthesised. PURPOSE: This review aimed to evaluate the diagnostic accuracy of MRI techniques for detecting chronic thromboembolic material and perfusion defects in CTEPH. METHODS: A systematic review was conducted according to PRISMA guidelines and was prospectively registered with PROSPERO (CRD420251134001). PubMed, Medline, Embase and Google Scholar were searched from January 2000 to October 2025 for studies assessing MRI-based detection of CTEPH using accepted reference standards, including computed tomography pulmonary angiography (CTPA), digital subtraction angiography (DSA), ventilation-perfusion (V/Q) scintigraphy or multidisciplinary consensus. Eligible studies evaluated MRI perfusion, contrast-enhanced MR angiography (ce-MRA), non-contrast MRA or advanced MRI techniques in adults with suspected or confirmed CTEPH. Data extraction was performed in duplicate, and the risk of bias was assessed using QUADAS-2. Due to heterogeneity among the included studies, the Synthesis Without Meta-analysis (SWiM) framework was used to guide data synthesis. RESULTS: Nine studies involving 563 participants met the inclusion criteria. Across eight MRI perfusion studies, the median sensitivity was 97% and the median specificity was 92.5%. Standard MRI perfusion demonstrated similar performance (median sensitivity 97%, specificity 92%). Three ce-MRA studies yielded a median sensitivity of 87.7% and specificity of 98.1%. Non-contrast MRA showed lower standalone diagnostic accuracy (sensitivity 45%, specificity 76%) but improved markedly when combined with ce-MRA. Risk of bias was moderate to high across studies, driven primarily by non-consecutive patient selection, variable reference standards and heterogeneity in MRI protocols. CONCLUSION: MRI demonstrates encouraging diagnostic performance for detecting perfusion defects and chronic thromboembolic material in CTEPH, with MRI perfusion offering high sensitivity and ce-MRA showing high specificity. Non-contrast MRA adds value for proximal vessel assessment when used alongside ce-MRA. However, methodological limitations and study heterogeneity constrain the certainty of existing evidence. Larger, standardised prospective studies are needed to define the precise role of MRI within contemporary CTEPH diagnostic pathways.