Diffusing capacity decreases after heart transplantation.

We evaluated the following spirometric values: forced vital capacity (FVC), first second expiratory volume (FEV1), FEV1/FVC, the lung volumes, total lung capacity (TLC), residual volume (RV), and single breath diffusing capacity for CO in 22 patients, before and after heart transplant. We found abnormal pulmonary function in 21 patients before heart transplantation. Despite postoperative increases in lung volumes in 10 patients, abnormal pulmonary function persisted in 20 patients after heart transplant. Mean values for lung volumes and flow rates did not change but diffusion for CO decreased significantly after heart transplantation. Diffusion failed to correlate with ejection fraction, pulmonary arterial pressure, pulmonary capillary wedge pressure (PCWP), and pulmonary vascular resistance; however, in a subset of patients with improved postoperative lung volumes, preoperative diffusion for CO correlated with preoperative PCWP. We conclude that pulmonary function abnormalities are common among heart transplant recipients. Diffusion abnormalities are not linearly related to indices of cardiac function measured before transplantation and diffusion abnormalities appear to be multifactorial in cause. The posttransplant decrease in diffusion appears to result from the combined effects of decreased postoperative lung volumes in some patients and relief of heart failure induced pulmonary vascular engorgement in others. Improvement in lung volumes and flow rates may occur but cannot be expected after heart transplantation, and diffusion decreases after heart transplantation. The fact that pulmonary function and lung volumes do not improve following heart transplantation implies to underlying lung disease or permanent lung alterations result from chronic heart failure.