Relation of Etiology of Heart Failure (Ischemic Versus Nonischemic) Before Transplantation to Delayed Pulmonary Oxygen Uptake Kinetics After Heart Transplantation

The effect that pretransplantation heart failure cause has on pulmonary oxygen uptake (V̇O2p) kinetics and peak aerobic power (V̇O2peak) in heart transplant recipients (HTRs) has not been studied. We examined V̇O2p kinetics and V̇O2peak in HTRs with previous ischemic heart failure (I-HTRs; n = 16, mean age 64 ± 6 years) or nonischemic heart failure (NI-HTRs; n = 13, mean age 50 ± 12 years). HTRs performed an incremental exercise (V̇O2peak) test and a constant work rate submaximal exercise (V̇O2p kinetics) test. A monoexponential model was used to determine the phase II V̇O2p time constant (τ). Phase II V̇O2p τ was slower in I-HTRs (49 ± 10 seconds) than in NI-HTRs (34 ± 10 seconds) (p <0.001). No significant difference was found between I-HTRs and NI-HTRs for V̇O2peak (19.0 ± 6.4 vs 23.0 ± 8.2 ml · kg−1 · min−1, respectively), change in heart rate from rest to steady-state exercise (11 ± 8 vs 9 ± 9 beats · min−1, respectively), or peak exercise heart rate (140 ± 22 vs 144 ± 22 beats · min−1, respectively). In conclusion, the prolonged phase II V̇O2p τ in I-HTRs compared with NI-HTRs suggests that the magnitude of alteration in V̇O2p kinetics after heart transplantation may be dependent on previous heart failure cause.