RELATIONSHIP OF LACTATE AND VENTILATORY THRESHOLDS IN CARDIAC TRANSPLANT PATIENTS

The ventilatory threshold (VT) has been suggested as a method for determining exercise training intensity in cardiac transplant patients (CTPs), Since the VT has not been validated against the more accepted marker of the anaerobic threshold, the lactate threshold (LT), in CTPs, the purpose of this investigation was to compare the VT to the LT within, as well as between, CTPs and normal subjects (NLs). Ten male orthotopic CTPs and 10 age, size, and gender matched NLs were exercised to symptom-limited maximal levels following incremental treadmill protocols. The VT was determined using the V-slope method, and the LT was identified using the log-log transformation method. The NLs had significantly higher absolute levels of VO2 at both the VT (1298.6 +/- 78.5 vs 919.0 +/- 57.2 ml . min-1) and LT (1561.1 +/- 144.2 vs 921.6 +/- 47.6 ml . min-1) compared with the CTPs. However, there was no significant difference in the relative VO2 (% peak) between CTPs and NLs at the VT (57.2 +/- 3.0 vs 49.0 +/- 3.5%) or LT (58.2 +/- 3.3 vs 58.5 +/- 4.9%), respectively. Within groups there was no significant difference between the VT and LT for either CTPs (919.0 +/- 57.2 vs 921.6 +/- 47.6 ml . min-1) or NLs (1298.6 +/- 78.5 vs 1561.1 +/- 144.2 ml . min-1). From the results of this investigation it appears that the VT may be used as an indicator of LT in CTPs and is within a range acceptable for clinical application. Thus, VT can be used to prescribe exercise training intensities that will either elict or not elict significant elevations in blood lactate in CTPs.