Pulmonary artery stiffness in chronic obstructive pulmonary disease (copd) and emphysema: The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study

Purpose: Chronic obstructive pulmonary disease (COPD) and particularly emphysema are characterized by stiffness of the aorta, due in part to accelerated elastin degradation in the lungs and aorta. Stiffness of the pulmonary arteries (PAs) may also be increased in COPD and emphysema, but data are lacking. We assessed PA stiffness using MRI in patients with COPD and related these measurements to COPD severity and percent emphysema. Materials and Methods: The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study recruited 290 participants, age 50–79 years with 10 or more packyears and free of clinical cardiovascular disease. COPD severity were defined on postbronchodilator spirometry by ATS/ERS criteria. Percent emphysema was defined as the percentage of regions of the lung < -950 Hounsfield units on full-lung computed tomography (CT). PA stain was defined by the percent change in cross-sectional PA area between systole and diastole on MRI. Blood flow across the tricuspid and mitral valves was assessed by phase-contrast MRI for determination of the ventricular diastolic dysfunction (E/A ratio). Results: PA strain was reduced in COPD compared with controls (P = 0.002) and was inversely correlated with COPD severity (P = 0.004). PA strain was inversely associated to percent emphysema (P = 0.01). PA strain was also markedly correlated with right ventricular diastolic dysfunction measured by E/A ratios in the fully adjusted mix models (P = 0.02). Conclusion: PA strain is reduced in COPD, related in part to percent emphysema on CT scan, which may have implications for pulmonary small vessel flow and right ventricular function. Level of Evidence: 2 Technical Efficacy: Stage

Pulmonary hyperinflation due to gas trapping and pulmonary artery size: The MESA COPD Study.

BackgroundPulmonary hypertension is associated with increased morbidity and mortality in chronic obstructive pulmonary disease (COPD). Since pulmonary artery (PA) size increases in pulmonary hypertension, we measured PA cross-sectional area using magnetic resonance imaging (MRI) to test the hypothesis that pulmonary hyperinflation due to gas trapping is associated with PA cross-sectional area in COPD.MethodsThe MESA COPD Study recruited participants with COPD and controls from two population-based cohort studies ages 50-79 years with 10 or more pack-years and free of clinical cardiovascular disease. Body plethysmography was performed according to standard criteria. Cardiac MRI was performed at functional residual capacity to measure the cross-sectional area of the main PA. Percent emphysema was defined as the percentage of lung voxels less than -950 Hounsfield units as assessed via x-ray computed tomography. Analyses were adjusted for age, gender, height, weight, race-ethnicity, the forced expiratory volume in one second, smoking status, pack-years, lung function, oxygen saturation, blood pressure, left ventricular ejection fraction and percent emphysema.ResultsAmong 106 participants, mean residual volume was 1.98±0.71 L and the mean PA cross-sectional area was 7.23±1.72 cm2. A one standard deviation increase in residual volume was independently associated with an increase in main PA cross-sectional area of 0.55 cm2 (95% CI 0.18 to 0.92; p = 0.003). In contrast, there was no evidence for an association with percent emphysema or total lung capacity.ConclusionIncreased residual volume was associated with a larger PA in COPD, suggesting that gas trapping may contribute to pulmonary hypertension in COPD

Relationship between residual volume and pulmonary artery cross-sectional area^*.

<p>Relationship between residual volume and pulmonary artery cross-sectional area^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0176812#t002fn001" target="_blank">*</a>}.</p

Mean difference in systolic main pulmonary artery cross-sectional area by residual volume.

<p>Original model was adjusted for age, gender, race or ethnic group, height, weight, cohort, cohort, percent emphysema_{-950 HU}, forced expired volume in the first second and oxygen saturation, smoking status, pack-years of smoking history, systolic blood pressure, diastolic blood pressure and left ventricular ejection fraction.</p

Baseline characteristics of MESA COPD Study participants with plethysmograph and MRI measures^*.

<p>Stratified by quartiles percent predicted residual volume.</p

Relationship between percent emphysema and pulmonary artery cross-sectional area^*.

<p>Relationship between percent emphysema and pulmonary artery cross-sectional area^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0176812#t003fn001" target="_blank">*</a>}.</p