Estimated Ventricular Size, Asthma Severity, and Exacerbations

Abstract

BACKGROUND: Relative enlargement of the pulmonary artery (PA) on chest CT imaging is associated with respiratory exacerbations in patients with COPD or cystic fibrosis. We sought to determine whether similar findings were present in patients with asthma and whether these findings were explained by differences in ventricular size. METHODS:We measured the PA and aorta diameters in 233 individuals from the Severe Asthma Research Program III cohort. We also estimated right, left, and total epicardial cardiac ventricular volume indices (eERVVI, eELVVI, and eETVVI, respectively). Associations between the cardiac and PA measures (PA-to-aorta [PA/A] ratio, eERVVI-to-eELVVI [eRV/eLV] ratio, eERVVI, eELVVI, eETVVI) and clinical measures of asthma severity were assessed by Pearson correlation, and associations with asthma severity and exacerbation rate were evaluated by multivariable linear and zero-inflated negative binomial regression.RESULTS: Asthma severity was associated with smaller ventricular volumes. For example, those with severe asthma had 36.1 mL/m 2 smaller eETVVI than healthy control subjects (P ¼ .003) and 14.1 mL/m 2 smaller eETVVI than those with mild/moderate disease (P ¼ .011). Smaller ventricular volumes were also associated with a higher rate of asthma exacerbations, both retrospectively and prospectively. For example, those with an eETVVI less than the median had a 57% higher rate of exacerbations during follow-up than those with eETVVI greater than the median (P ¼ .020). Neither PA/A nor eRV/eLV was associated with asthma severity or exacerbations. CONCLUSIONS:In patients with asthma, smaller cardiac ventricular size may be associated with more severe disease and a higher rate of asthma exacerbations.

Estimated Ventricular Size

“…In an autopsy study by Saetta et al 9 of patients who died of asthma attacks, the peripheral pulmonary arteries adjacent to occluded and inflamed bronchioles exhibited evidence of inflammation, although none of the patients had narrowed lumens of the peripheral pulmonary arteries compared with the control group, evidence of the morphologic changes of chronic hypoxia or cor pulmonale. The authors of the current study 6 concluded that the pulmonary hypertension in COPD is likely due to parenchymal destruction and regional hypoxia, both of which are more pronounced in COPD than in asthma. This finding is supported by previous research showing that, among other risk factors, use of supplemental oxygen and a larger percentage of emphysema on CT imaging is associated with a PA/A ratio > 1 in COPD.…”

“…Perhaps more importantly, in multivariate analysis, the investigators discovered that patients with smaller ventricular volumes had increased rates of asthma exacerbations, both in the year prior to enrollment and during follow-up. These results 6 are perhaps not altogether surprising. The SARP investigators have previously reported CT imaging evidence of decreased size of the peripheral pulmonary vasculature (pruning) in patients with asthma and that this finding was correlated with a 150% increase in the odds of an asthma exacerbation.…”

“…As for the correlation between decreased ventricular volumes and asthma exacerbations, decreased heart size has been previously noted on chest radiographs in obstructive lung disease. 1,6 Traditionally, this has been believed to be due in part to hyperinflation as well as a visual effect caused by the lowering of the diaphragm, leading to rotation of the cardiac apex. In the current study by Ash et al, 6 the association of decreased ventricular volumes and asthma exacerbations was observed after correcting for LAA, lung volume, and percent predicted FEV 1 among other risk factors.…”

“…1,6 Traditionally, this has been believed to be due in part to hyperinflation as well as a visual effect caused by the lowering of the diaphragm, leading to rotation of the cardiac apex. In the current study by Ash et al, 6 the association of decreased ventricular volumes and asthma exacerbations was observed after correcting for LAA, lung volume, and percent predicted FEV 1 among other risk factors. Lung volumes and LAA both had a statistically significant correlation with ventricular volumes in this study; however, the correlations were overall weak and likely do not explain a significant amount of the change in ventricular volumes in patients with asthma.…”

“…3 In other obstructive lung diseases such as cystic fibrosis and COPD, this ratio has also been associated with increased odds of both past and future exacerbations. 4,5 In this issue of CHEST, Ash et al 6 used CT measurements of the PA/A ratio and an automated method for estimating the epicardial right ventricular (eRV) and left ventricular (eLV) volumes and their ratio (eRV/eLV) as potential predictors of asthma severity. This study used volumetric, noncontrast, non-ECG-gated chest CT scans from 233 patients with both severe and nonsevere asthma from the third phase of the Severe Asthma Research Program (SARP) as well as a smaller group of healthy control subjects.…”