TIME-COURSE OF LUNG-FUNCTION AND EXERCISE PERFORMANCE AFTER HEART-TRANSPLANTATION

To study the time course of exercise performance and the diffusion cap acity after heart transplantation, we submitted two groups of patients to graded symptom-limited supine exercise. Patients in group 1 (n = 1 1) 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 s tudy. Respiratory and cardiovascular parameters were evaluated noninva sively 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 co mpared 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 ac hieved (13.0 +/- 4.6 versus 17.5 +/- 6.3 L/min, not significant). Inte restingly, significant differences were also observed for diffusion ca pacity 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 associate d with a time-dependent change in the diffusion characteristics of the alveolocapillary membrane.