Reduced shear stress and associated aortic deformation in the thoracic aorta of patients with chronic obstructive pulmonary disease

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Abstract

Objective:

Central aortic stiffness and chronic obstructive pulmonary disease (COPD) are associated with increased incidence of devastating aortopathies. However, the exact mechanism leading to elevated aortic stiffness in patients with COPD is unknown. The purpose of this study was to quantify flow and shear hemodynamic indices, known markers of vascular remodeling, in the thoracic aorta of patients with mild to moderate COPD (n = 16) and to compare these results with an age-matched control group (n = 10).

Methods:

Four-dimensional flow magnetic resonance imaging has been applied to measure hemodynamic wall shear stress (WSS) at four specific planes along the ascending aorta, aortic arch, and proximal descending aorta for all subjects. Peak systolic WSS and time-averaged WSS, which respectively reflect magnitude and temporal shear variability, were calculated at standardized planes. Aortic deformation was measured by means of relative area change (RAC) at the midlevel of the ascending and descending aorta.

Results:

Compared with controls, patients with COPD had significantly reduced RAC in the mid ascending aorta (9% vs 18%; P < .0001) and descending aorta (15% vs 19%; P = .0206). Peak systolic WSS in COPD patients was significantly reduced in all considered planes, with the most dramatic difference occurring in the descending aorta (0.46 vs 0.86 N/m2; P < .0001). Peak systolic WSS and time-averaged WSS were both significantly correlated with aortic RAC at each evaluated plane.

Conclusions:

Reduced flow shear metrics assessed at specific aortic regions correlated with RAC, a marker of aortic stiffness. Reduced hemodynamic WSS may then contribute to central aortic stiffening and perpetuate the risk for development of severe aortopathy.

Clinical Relevance:

Central aortic stiffness and chronic obstructive pulmonary disease are associated with increased incidence of devastating aortopathies including aneurysmal degeneration, aortic dissections, development of atherosclerosis, and overall increased cardiovascular morbidity and mortality. The exact mechanism leading to elevated aortic stiffness in patients with chronic obstructive pulmonary disease is yet to be determined. Hemodynamic forces can actively modulate endothelial cell alignment, extracellular matrix composition, vascular tone, and inflammation present in the wall of the aorta. In this study, we observed reduced flow shear assessed at specific aortic regions correlated with relative area strain, a marker of aortic stiffness.

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