Reproducibility and changes in vena caval blood flow by using 4D flow MRI in pulmonary emphysema and Chronic Obstructive Pulmonary Disease (COPD): The Multi-Ethnic Study of Atherosclerosis (MESA) COPD substudy

Background: Chronic obstructive pulmonary disease (COPD) is associated with hemodynamic changes in the pulmonary vasculature. However, cardiac effects are not fully understood and vary by phenotype of chronic lower respiratory disease. Purpose: To use four-dimensional (4D) flow MRI for comprehensive assessment of the right-sided cardiovascular system, assess its interrater and intraobserver reproducibility, and examine associations with venous return to the right heart in individuals with chronic COPD and emphysema. Materials and Methods: The Multi-Ethnic Study of Atherosclerosis COPD substudy prospectively recruited participants who smoked and who had COPD and nested control participants from population-based samples. Electrocardiography and respiratory gated 4D flow 1.5-T MRI was performed at three sites with full volumetric coverage of the thoracic vessels in 2014-2017 with postbronchodilator spirometry and inspiratory chest CT to quantify percent emphysema. Net flow, peak velocity, retrograde flow, and retrograde fraction were measured on 14 analysis planes. Interrater reproducibility was assessed by two independent observers, and the principle of conservation of mass was employed to evaluate the internal consistency of flow measures. Partial correlation coefficients were adjusted for age, sex, race/ethnicity, height, weight, and smoking status. Results: Among 70 participants (29 participants with COPD [mean age, 73.5 years 6 8.1 {standard deviation}; 20 men] and 41 control participants [mean age, 71.0 years 6 6.1; 22 men]), the interrater reproducibility of the 4D flow MRI measures was good to excellent (intraclass correlation coefficient range, 0.73-0.98), as was the internal consistency. There were no statistically significant differences in venous flow parameters according to COPD severity (P .05). Greater percent emphysema at CT was associated with greater regurgitant flow in the superior and inferior caval veins and tricuspid valve (adjusted r = 0.28-0.55; all P , .01), particularly in the superior vena cava. Conclusion: Four-dimensional flow MRI had good-to-excellent observer variability and flow consistency. Percent emphysema at CT was associated with statistically significant differences in retrograde flow, greatest in the superior vena cava.