Cardiovascular magnetic resonance pulmonary artery peak flow velocity as a marker of pulmonary vascular resistance in fibrotic interstitial lung disease

Abstract Background. Pulmonary hypertension (PH) is a common and severe complication of interstitial lung disease (ILD), yet early diagnosis remains challenging. Cardiovascular magnetic resonance (CMR) offers non-invasive assessment of pulmonary vascular hemodynamics, but evidence in PH associated with ILD is limited. This study aimed to evaluate the relationship between CMR-derived parameters and invasive hemodynamics in patients with fibrotic ILD. Methods. In this prospective observational study, 41 patients with fibrotic ILD underwent pulmonary function testing, cardiopulmonary exercise testing, transthoracic echocardiography, and CMR. Twenty patients additionally underwent RHC. CMR-derived measurements included ventricular function parameters, heart chamber and great vessel dimensions, and pulmonary artery flow hemodynamic metrics. Associations between CMR parameters, invasive hemodynamics, exercise capacity and symptom burden were assessed using correlation, regression, and receiver operating characteristic (ROC) analyses. Results. Among 20 patients who underwent RHC, PH was confirmed in all cases, including 15 with isolated precapillary PH and 5 with combined PH. Pulmonary vascular resistance (PVR) of over 5 Wood units defined severe PH in 6 patients who met the criteria. Pulmonary artery peak flow velocity (PA-Vmax) measured on CMR was significantly higher in the non-severe PH group (81.15 ± 19.27 cm/s vs. 52.33 ± 5.13 cm/s, p < 0.001) and demonstrated promising discriminatory performance for identifying severe PH (AUC 0.923, 95% CI 0.778-1.000, p = 0.004), with a threshold of < 62.5 cm/s yielding 100% sensitivity and 92.3% specificity. An inverse-transformed PA-Vmax model demonstrated a strong association with invasive PVR (R 2 = 0.651, F = 31.65, p < 0.001). Higher PA-Vmax correlated with greater exercise capacity, including higher anaerobic threshold (r = 0.419, p = 0.015) and maximal workload (r = 0.329, p = 0.050). Lower CMR-derived TAPSE was independently associated with greater dyspnea severity (β=-0.426, p = 0.025), while CMR-TAPSE/RHC-mPAP ratio demonstrated an even stronger association with symptom burden (r s =-0.570, p = 0.021). Conclusions. In patients with fibrotic ILD, CMR-derived PA-Vmax was significantly associated with PVR measured by RHC and demonstrated promising discrimination for severe PH in this exploratory cohort. CMR measurements of right ventricular adaptation were associated with functional capacity and dyspnea severity. These findings support further evaluation of CMR as a promising non-invasive modality for pulmonary vascular assessment in fibrotic ILD patients undergoing evaluation for suspected PH.