Effects of mitral valve surgery on static lung function and exercise performance.

Lung function at rest was assessed in 50 patients before and six months after mitral valve surgery. There were small increases in spirometric volumes (FEV1 and vital capacity) with decreases in total lung capacity and residual volume, but no change in carbon monoxide transfer factor or transfer coefficient (KCO). Progressive exercise tests performed before and after operation in 19 of the patients confirmed an improved exercise capacity after surgery. The patients with the greatest symptomatic improvement in breathlessness were also those who achieved the greatest increase in maximum work load and the greatest decrease in ventilation for a given oxygen consumption. Depression of the ST segment of the electrocardiogram and frequent ventricular ectopic beats on exercise remained common after surgery and may have been due to digoxin treatment.