Competition for Intrathoracic Space Reduces Lung Capacity in Patients With Chronic Heart Failure: Results
The relationship between NYHA class and absolute lung volume and percentage of TTCV that is taken up by the lung is shown in Figure 3, top, A, and bottom, B, respectively. These data suggest a clear relationship between increasing NYHA class and elevated cardiac volume and reduction in lung volume. Figure 4 demonstrates the close correlation (r = — 0.81, p < 0.001) between elevated cardiac size and reduction in lung volume within the entire population separated by groups. In this study, we found the following in patients with heart failure compared to control participants: (1) marked increases in cardiac size reaching twice that of healthy age- and gender-matched control participants; (2) a clear relationship between the severity of heart failure and increase in cardiac size; (3) and a negative correlation between the percentage of TTC occupied by lung and the percentage of TTC occupied by the heart. add comment
These findings demonstrate that a progressive increase in cardiac volume in chronic heart failure plays a significant role in the loss of lung volume and function that has been associated with this patient population. A number of studies have examined pulmonary function before and after cardiac transplantation. Although there are a number of physiologic changes that may account for the improvements in lung function after transplantation (eg, reduced pulmonary hypertension and congestion), alteration of cardiac size in relation to other organs occupying the thoracic cavity (ie, the lungs) is a likely mechanism through which improvement in pulmonary function occur. For instance, Ravenscraft et al demonstrated that correction of severe congestive heart failure by cardiac transplantation results in normalization of FVC, FEV1, and total lung capacity (TLC). Similarly, Hosenpud and colleagues demonstrated that spirometrically assessed pulmonary function (ie, FVC and FEV1) in pretransplant heart failure patients were significantly improved 15 months after cardiac replacement; these authors suggest that the restrictive but not obstructive pulmonary limitations are at least in part directly related to the increased intrathoracic space occupied by the heart. Only one study has attempted to examine the influence of cardiac size on lung function specifically in relation to the size of the thoracic cavity. Agostoni and colleagues demonstrated that heart failure patients with cardiomegaly defined by increased cardiothoracic index (the ratio between the maximal linear width measurement of the heart and thoracic cavity on the posteroanterior view of the chest radiograph) have significantly reduced FEV1 and vital capacity.
Figure 3. Top, A: Absolute lung volume measurement separated by groups. Bottom, B: Percentage of TTCV taken up by the lungs separated by groups. *p < 0.05 vs control group; tp < 0.05 vs group A. See Figure 2 legend for expansion of abbreviation.
Figure 4. Correlation between the percentage of TTCV taken up by the heart and lungs for the study population divided by groups. O, control; ■, group A; □, group B.