SERIAL ASSESSMENT OF EXERCISE CAPACITY AFTER HEART-TRANSPLANTATION

Background: Exercise capacity after heart transplantation is abnormal. This reduced exercise performance may in part be due to treatment wit h high-dose immunosuppressive therapy, deconditioning, graft rejection , or cardiac denervation. Methods: To investigate whether exercise cap acity significantly improves over time as immunosuppression is lessene d or whether reinnervation occurs, we measured peak exercise oxygen co nsumption in 60 patients 0.5 to 60 months after transplantation (age: 52 +/- 11 years; left ventricular ejection fraction: 56% +/- 10%) and in 14 healthy subjects (age: 44 +/- 8 years; p = Not significant). Res ting hemodynamic measurements, left ventricular ejection fraction, and immunosuppressive therapy were recorded at the time of each of the pa tients' 116 exercise tests. Exercise test results were stratified into groups according to time after transplantation. Results: Exercise cap acity significantly improved after transplantation (pretransplantation peak exercise oxygen consumption: 9.9 +/- 4.3; posttransplantation: 1 6.6 +/- 4.0 ml/kg/min; p < 0.001). Patient groups after transplantatio n were without significance differences with regard to age, gender, le ft ventricular ejection fraction, resting hemodynamic measurements, an tihypertensive regimen, and number of rejection episodes. For those pa tients exercising at 2 months compared with the patients exercising at 12 months, a significant increase was observed in peak exercise oxyge n consumption (14.0 +/- 3.8 ml/kg/min at 2 +/- 2 months to 16.2 +/- 3. 8 ml/kg/min at 12 +/- 2 months) and maximum heart rate (124 +/- 24 to 137 +/- 24 beats/min). No significant changes were found in peak exerc ise oxygen consumption or maximum heart rate after the first year afte r transplantation. Patients' exercise capacities as measured by peak e xercise oxygen consumption remained abnormal (N1 peak exercise oxygen consumption: 35 +/- 11 ml/kg/min) despite significant reductions in st eroid, azathioprine, and cyclosporine therapy. Peak exercise oxygen co nsumption was significantly correlated with maximal heart rate (r = 0. 42) (p < 0.0001) but not with maximal blood pressure response, change in heart rate, left ventricular ejection fraction, or resting cardiac index (all p = Not significant). Conclusions: Exercise capacity is mar kedly improved after heart transplantation although it remains impaire d compared with healthy individuals. Patients achieve their maximal ex ercise capacity by 1 year after transplantation. Subsequently, exercis e capacity does not improve despite significant reductions in immunosu ppressive agents. The lack of alteration in the heart rate response to exercise over time suggests that no significant functional reinnervat ion occurs.