Background: Little is known about the role of abnormal lung function in heart size and heart dysfunction in patients with COPD. We studied the relationship of lung function with heart size and heart dysfunction and associated consequences for 6-min walk distance (6MWD) in patients with COPD of different severitites.
Methods: In 138 patients with COPD (Global Initiative for Obstructive Lung Disease [GOLD] I-IV), we measured the size of all cardiac chambers, left ventricular diastolic dysfunction (relaxation and filling), and global right ventricular dysfunction (Tei-index) by echocardiography. We also measured lung function (spirometry, body plethysmography, and diffusion capacity) and 6MWD.
Results: The size of all cardiac chambers decreased with increasing GOLD stage. Overall, moderate relationships existed between variables of lung function and cardiac chamber sizes. Static hyperinflation (inspiratory-to-total lung capacity ratio [IC/TLC], functional residual capacity, and residual volume) showed stronger associations with cardiac chamber sizes than airway obstruction or diffusion capacity. IC/TLC correlated best with cardiac chamber sizes and was an independent predictor of cardiac chamber sizes after adjustment for body surface area. Patients with an IC/TLC < or = 0.25 had a significantly impaired left ventricular diastolic filling pattern and a significantly impaired Tei-index compared with patients with an IC/TLC > 0.25. An impaired left ventricular diastolic filling pattern was independently associated with a reduced 6MWD.
Conclusions: An increasing rate of COPD severity is associated with a decreasing heart size. Hyperinflation could play an important role regarding heart size and heart dysfunction in patients with COPD.