Non-invasive methods for estimating mPAP in COPD using cardiovascular magnetic resonance imaging

Abstract

Purpose: Pulmonary hypertension (PH) is associated with a poor outcome in chronic obstructive pulmonary disease (COPD) and is diagnosed invasively. We aimed to assess the diagnostic accuracy and prognostic value of non-invasive cardiovascular magnetic resonance (CMR) models.

Methods: Patients with COPD and suspected PH, who underwent CMR and right heart catheter (RHC) were identified. Three candidate models were assessed: 1, CMR-RV model, based on right ventricular (RV) mass and interventricular septal angle; 2, CMR PA/RV includes RV mass, septal angle and pulmonary artery (PA) measurements; 3, the Alpha index, based on RV ejection fraction and PA size.

Results: Of 102 COPD patients, 87 had PH. The CMR-PA/RV model had the strongest diagnostic accuracy (sensitivity 92%, specificity 80%, positive predictive value 96% and negative predictive value 63%, AUC 0.93, p<0.0001). Splitting RHC-mPAP, CMR-RV and CMR-PA/RV models by 35mmHg gave a significant difference in survival, with log-rank chi-squared 5.03, 5.47 and 7.10. RV mass and PA relative area change were the independent predictors of mortality at multivariate Cox regression (p=0.002 and 0.030).

Conclusion: CMR provides diagnostic and prognostic information in PH-COPD. The CMR-PA/RV model is useful for diagnosis, the RV mass index and PA relative area change are useful to assess prognosis.

Key points: • Pulmonary hypertension is a marker of poor outcome in COPD. • MRI can predict invasively measured mean pulmonary artery pressure. • Cardiac MRI allows for estimation of survival in COPD. • Cardiac MRI may be useful for follow up or future trials. • MRI is potentially useful to assess pulmonary hypertension in patients with COPD.

Keywords: Cardiac; Chronic Obstructive Pulmonary Disease; Cor Pulmonale; Magnetic Resonance Imaging; Pulmonary Hypertension.

Fig. 1

Diagram showing the methodology of calculation of the cardiac MRI metrics. Pulmonary artery relative area change (a) taken from cine images taken at the level of the pulmonary trunk, perpendicular to the main pulmonary artery; septal angle (b) taken as the angle made between the insertion points of the RV to the mid septum on the end-systolic image from the short axis stack; and (c) ventricular mass index taken by segmentation of the muscle mass of the left and right ventricle on the stack of images taken in the short axis plane

Fig. 2

Patient selection

Fig. 3

Scatter plots showing correlations of each MRI model with right heart catheter measured mPAP

Fig. 4

Bland-Altman plots showing accuracy of models against RHC-mPAP

Fig. 5

ROC curve for the diagnosis of pulmonary hypertension

Fig. 6

Kaplan-Meier survival tables, all dichotomised by 35