MR Imaging-derived Regional Pulmonary Parenchymal Perfusion and Cardiac Function for Monitoring Patients with Chronic Thromboembolic Pulmonary Hypertension before and after Pulmonary Endarterectomy

Purpose: To evaluate surgical success after pulmonary endarterectomy (PEA) by means of cardiopulmonary magnetic resonance (MR) imaging. Materials and Methods: In this institutional review board-approved study, 20 patients with chronic thromboembolic pulmonary hypertension were examined at 1.5 T with a dynamic contrast material-enhanced three-dimensional fast low-angle shot sequence before and 12 days after PEA (25th-75th percentile range, 11-16 days). Lung segments were evaluated visually before PEA for parenchymal hypoperfused segments. Pulmonary blood flow (PBF), first-pass bolus kinetic parameters, and biventricular mass and function were determined. Mean pulmonary artery pressure (mPAP) and 6-minute walking distance were measured before and after PEA. The Shapiro-Wilk test, paired two-sided Wilcoxon rank sum test, Spearman rho correlation, and multiple linear regression analysis were performed. Results: Two weeks after PEA, regional PBF increased 66% in the total lung from 32.7 to 54.2 mL/min/100 mL (P = .0002). However, after adjustment for cardiac output, this change was not evident anymore (increase of 7% from 7.03 to 7.54 mL/min/100 mL/L/min, P = .1). Only in the lower lobes, a significant increase in PBF after cardiac output adjustment remained: a 16% increase in the right lower lobe from 7.53 to 8.71 mL/min/100 mL (P = .01) and a 14% increase in the left lower lobe from 7.42 to 8.47 mL/min/100 mL/L/min (P < .05). Right ventricular mass and function also improved. mPAP decreased from 46 to 24 mm Hg (P < .0001). Six-minute walking distance increased from 390 to 467 m (P = .02) 5 months after PEA. Percentage change of mPAP and PBF in the lower lobe tended to be significant predictors of percentage change in 6-minute walking distance (beta = -1.79 [P = .054] and beta = 0.45 [P = .076], respectively) in multiple linear regression analysis. Conclusion: Improvement of PBF after PEA was observed predominantly in the lower lungs, and the magnitude of improvement of PBF in the lower lobes correlated with the improvement in exercise capacity, reflecting surgical success.