Björn Wieslander

Background Late diagnosis of pulmonary hypertension (PH) causes poor outcomes. Echocardiography lacks accuracy for PH. Definitive diagnosis requires invasive right heart catheterization, while magnetic resonance imaging (MRI) provides gold standard characterization of prognostic cardiovascular variables. A novel contrast- and radiation-free MRI 4D-flow technique can accurately diagnose PH by estimating mean pulmonary arterial pressure. Objective To achieve the overall goal of a safe, non-invasive, contrast-free accurate <2-minute automated MRI- based method of determining mPAP, the following specific hypotheses will be tested: 1. The coefficient of determination (R2) between MRI-determined pulmonary artery vortex duration in images acquired using a phase-contrast sequence with compressed sensing, and simultaneously measured invasive mPAP is between 0.8 and 0.95 in patients with suspected PH without atrial fibrillation. 2. Reduction of mPAP following clinically motivated pharmacological pulmonary vasodilation is reflected in MRI-determined mPAP. 3. The addition of arrhythmia rejection to the MRI pulse sequence results in a similar correlation with invasive mPAP as for patients without arrhythmia. 4. The minimum scan duration that allows sufficient signal-to-noise ratio for accurate mPAP-estimation can be identified through comparison of retrospective reconstruction of MRI 4D-flow images with varying amounts of data. 5. An interpretation algorithm can be identified to determine the duration of vortical blood flow on MRI 4D-flow images and thereby estimate mPAP automatically. Workplan One-hundred patients with suspected PH will undergo clinically motivated interventional MRI at Karolinska University Hospital during 2023-2024. Gold standard interventional measurements will be compared to non-invasive MRI-based estimates of mean pulmonary artery pressure (mPAP). Significance The combination of availability of interventional MRI, the experience of the applicant, international collaborations, and sufficient volume of patients with PH provides a unique opportunity to optimize and validate this MRI-method in the short term (2023-2025). This would allow the medium term (2026-) acquisition of standardized data necessary for further validation and improved automation of image interpretation. The results could improve the diagnosis and care of patients with PH, as well as facilitate research the role of PH in left heart failure and lung disease.