ABSTRACT
To investigate the role of cardiac magnetic resonance imaging (CMRI) in evaluating pulmonary hemodynamics and right ventricular function in patients with chronic obstructive pulmonary disease (COPD) and pulmonary hypertension (PAH); and the relationship between CMRI parameters and pulmonary function parameters, blood gas analysis parameters and 6-minute walk test (6MWT) parameters in patients with COPD complicated with PAH. Methods Thirty-seven patients were diagnosed with COPD in the department of respiratory and critical care discipline of Ningxia Medical University General Hospital from October 2013 to October 2016, who underwent transthoracic echocardiography (TTE) to measure pulmonary arterial systolic pressure (PASP), and were divided into COPD group and COPD+PAH group according to whether there was PAH [PASP > 40 mmHg (1 mmHg = 0.133 kPa) was defined as PAH]. All patients completed pulmonary function tests [1 second forced expiratory volume to forced vital capacity ratio (FEV1/FVC), FEV1 predicted value (FEV1pred)], blood gas analysis [arterial blood oxygen partial pressure (PaO2), arterial blood carbon dioxide partial pressure (PaCO2)], CMRI examination [relative dilatation of the main pulmonary artery (mPAD), mean pulmonary artery pressure (mPAP), left ventricular ejection fraction (LVEF), right ventricular ejection fraction (RVEF), right ventricular end-diastolic myocardial mass (RVMED), right ventricular end-systolic myocardial mass (RVMES)], and 6MWD [6-minute walk distance (6MWD)] within 1 week. The obtained clinical parameters had been compared between the groups, and correlation was analyzed. Results Among the 37 patients with COPD, 16 patients were complicated with PAH. There were no significant differences in FEV1/FVC, FEV1pred, PaO2, PaCO2 and other baseline indicators between the two groups. In the COPD group, TTE obtained PASP of 2 patients were normal (PSAP < 40 mmHg), while CMRI measured mPAP were higher than the normal limit (> 25 mmHg). Compared with the COPD group, mPAD, RVEF and 6MWD were significantly decreased in the COPD+PAH group [mPAD: (25.64±5.01)% vs. (44.00±22.52)%, RVEF: 0.525±0.054 vs. 0.592±0.071, 6MWD (m): 319.3±116.5 vs. 408.2±38.0, all P < 0.01], mPAP, RVMED and RVMES were significantly increased [mPAP (mmHg): 28.89±3.16 vs. 20.18±2.43, RVMED (g): 57.19±15.46 vs. 40.71±15.44, RVMES (g): 45.99±11.16 vs. 33.71±13.39, all P < 0.01], and there was no significant differences in LVEF (0.663±0.082 vs. 0.699±0.075, P > 0.05). Correlation analysis showed that mPAD was positively correlated with FEV1/FVC and FEV1pred (r1 = 0.538, P1 = 0.021; r2 = 0.448, P2 = 0.049);RVMED was negatively correlated with PaO2 (r = -0.581, P = 0.015), and positively correlated with PaCO2 (r = 0.592, P = 0.014); 6MWD was positively correlated with RVEF (r = 0.485, P = 0.041), and had no correlation with LVEF (r = 0.271, P = 0.104). Conclusions Compared with COPD patients, changes in pulmonary hemodynamics and right ventricular function in COPD patients with PAH are related to the severity of airflow limitation. CMRI can early monitor pulmonary hemodynamics and right heart function changes in patients with COPD. Once PAH appears, pulmonary hemodynamics, right heart function and exercise tolerance have changed.