Abstract 18354: Cardiac Magnetic Resonance Allows Noninvasive and Accurate Monitoring of Serial Changes in Pulmonary Vascular Resistance and the Acute Vasodilator Response in Chronic Pulmonary Hypertension

Abstract

Background: Monitoring pulmonary vascular resistance (PVR) during the follow-up of patients with pulmonary hypertension (PH) and the acute vasodilator response require invasive right heart catheterization. A noninvasive method would be valuable. Hypothesis: Cardiac magnetic resonance (CMR) allows noninvasive monitoring of PVR and the acute vasodilator response. Methods: Two experimental models of chronic PH were developed in pigs. A precapillary PH model was induced by repeated pulmonary embolization with microspheres (n=8). A postcapillary PH model was generated with surgical banding of the main pulmonary vein (n=10). At baseline and every month, animals were evaluated by CMR (pulmonary artery mean flow velocity [PAvel] from phase-contrast images) with simultaneous invasive quantification of PVR using a CMR-compatible Swan-Ganz catheter (N=60 pairs of measurements). Generalized estimating equations analysis was used to correlate repeated measurements of PVR and PAvel. Additionally, correlation between acute changes in PAvel and PVR induced by pulmonary embolization (n=10) or vasodilator administration (n=10) inside the magnet was assessed using Spearman correlation. Results: Both models generated chronic PH (mPAP=30.8±4.8 and 54.5±12.8, pre and postcapillary respectively) with typical changes on pathology. CMR-model based on PAvel strongly correlated with serial measurements of PVR in both precapillary (r=0.86, p<0.01) and postcapillary (r=0.97, p<0.01, examples in figure A) models. Additionally, acute changes in PAvel were strongly correlated with the increase in PVR induced by acute embolization (r=-0.98, p<0.001, figure B) or the fall in PVR produced by vasodilator testing (r=-0.89, p<0.001, figure C). Conclusions: CMR allows noninvasive and accurate monitoring of acute and chronic changes in PVR and the acute vasodilator response in a broad spectrum of PH. This may be very valuable for the evaluation and follow-up of patients with PH.