Cardiovascular responses of heart transplant recipients to graded exercise testing.
A group of orthotopic heart transplant (OHT, n = 28) and heart surgery (n = 19) patients, with similar ejection fractions and left ventricular end-diastolic pressures, were exercised to symptom-limited maximum to describe differences in cardiovascular and gas exchange responses. Testing was performed at a mean of 3 and 6 mo after surgery, respectively (P less than 0.05). OHT patients have a greater resting systolic and diastolic blood pressure (P less than 0.01) and a significantly greater (P less than 0.01) heart rate (HR) at rest in the supine and standing positions and during minutes 2 through 7 of supine recovery. Peak treadmill time was significantly less (P less than 0.01) in OHT patients. No significant differences were found for systolic blood pressure (SBP) during recovery, peak HR, ventilation, relative O2 uptake (VO2), body weight, ventilatory equivalents for O2 and CO2, O2 pulse, and HR-SBP product (peak HR x peak SBP). Peak pulse pressure, heart rate reserve, total VO2, and absolute VO2 at ventilatory threshold were significantly lower (P less than 0.01) in the OHT patients. We concluded that 1) complete cardiac decentralization is evident, 2) the significantly reduced VO2 at ventilatory threshold should be considered when activities of daily living are prescribed, and 3) SBP response is more appropriate than HR for assessing recovery of the decentralized heart after maximal exercise.