4D flow MRI offers insight into COPD, emphysema

Four-dimensional (4D) flow MRI can provide valuable diagnostic insight in patients with chronic obstructive pulmonary disease (COPD) and emphysema, according to a July 24 study published in Radiology.

Among 70 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) COPD substudy, the technique provided comprehensive assessment of right heart blood flow and “good to excellent” reproducibility, reported co-author Ozair Rahman, with Feinberg School of Medicine at Northwestern University in Chicago, and colleagues.

“Our multicenter study found that 4D flow MRI provided a promising way of measuring blood flow in the superior and inferior caval veins and right heart, which may provide further insight into physiologic and pathologic blood flow patterns in individuals with COPD and emphysema,” Rahman and colleagues wrote.

4D MRI records blood flow in multiple phases and directions, and can provide advanced information such as wall-shear stress and kinetic energy loss. While it has been studies in many areas, including congenital heart disease, aortic aneurysm and valvular heart disease, it is less studied in COPD and emphysema.

Rahman et al. looked at 29 patients with COPD who smoked and 41 controls who had electrocardiography and respiratory gated 4D flow MRI performed at one of three sites between 2014 and 2017. Participants also had postbronchodilator spirometry and inspiratory chest CT to quantify percent emphysema.

The researchers found that flow metrics had high reproducibility (interclass correlation coefficient range of 0.73-0.98) on 14 planes, which were comparable to conventional cardiac MRI measurements. Blood flow was not greatly altered in COPD patients, but emphysema was associated with higher right heart regurgitant flow in the superior and inferior caval veins and tricuspid valve, most notably in the superior vena cava—potentially related to higher pulmonary vascular resistance.

“These findings suggest that, whereas pulmonary vascular dysfunction and damage occurs in COPD and particularly in emphysema with likely higher pulmonary vascular resistance, pulmonary vascular damage may not be the sole cause of reduced cardiac output in emphysema,” Rahman et al. wrote. “Upstream causes may also play a role.”