Changes in the Cardiopulmonary Response to Exercise after Cardiac Transplantation in Patients Enrolled in an Early Rehabilitation Program

Abstract

OBJECTIVE: To evaluate the changes in the cardiopulmonary response to exercise in the first year after cardiac transplantation in patients enrolled in a rehabilitation program in the first three months post-transplantation.METHODS: A graded cycle exercise test with mixed expired gas analysis was performed on patients with end-stage cardiac failure before and serially after cardiac transplantation at one, three and 12 months.RESULTS: Before cardiac transplantation, seven patients were fit enough to be tested. They had a low peak oxygen uptake (VO_{2 max}) and a blunted heart rate and blood pressure response to exercise. They also displayed a restrictive pattern of ventilation during exercise. At three months following transplantation, patients (n=19) had a significantly higher VO_{2 max} (19.9±5.3 versus 9.8±1.4 mL/kg/min, P<0.05), higher peak systolic blood pressure (177±22 versus 94±18 mmHg, P<0.05), greater peak minute ventilation (70±23 versus 34±5 L/min, P<0.05) and lower slope of minute ventilation to carbon dioxide output (35.4±6.2 versus 45.1±6.7, P<0.05) than before transplantation. The VO_{2 max} measured at 12 months post-transplant was similar to the three month value and was on average equal to 59% of the predicted value.CONCLUSIONS: These results indicate that there is a rapid and marked improvement in exercise capacity in patients following cardiac transplantation. These changes are associated with significant respiratory and cardiovascular adaptations. However, despite the marked improvement in exercise capacity, the VO_{2 max} of cardiac transplant recipients enrolled in an early rehabilitation program did not return to normal at 12 months after surgery.