Time course of lung function and exercise performance after heart transplantation.

To study the time course of exercise performance and the diffusion capacity after heart transplantation, we submitted two groups of patients to graded symptom-limited supine exercise. Patients in group 1 (n = 11) underwent operation 12.9 +/- 7.0 months before the study; those in group 2 (n = 10) underwent operation 53.9 +/- 14.8 months before the study. Respiratory and cardiovascular parameters were evaluated noninvasively at rest, at individual peak exercise, and 10 minutes later with a commercially available Sensormedics MMC 4400 metabolic measurement chart. Short-term survivors exhibited a lower maximum work capacity compared with that of long-term survivors (63.6 +/- 25.9 versus 100 +/- 50 W, p < 0.05), with a concomitant lower terminal heart rate (123 +/- 19 versus 137 +/- 17 beats/min, p < 0.05) that accounts for the lower cardiac output in this group, but statistical significance was not achieved (13.0 +/- 4.6 versus 17.5 +/- 6.3 L/min, not significant). Interestingly, significant differences were also observed for diffusion capacity before exercise (11.9 +/- 4.8 versus 19.3 +/- 7.3 ml/min/mm Hg, p < 0.05). The improvement of the diffusion capacity may be associated with a time-dependent change in the diffusion characteristics of the alveolocapillary membrane.