Comparison of Cardiopulmonary Exercise Test Derived Ventilation-, Metabolic- and Cardiac-Thresholds in Patients with Coronary Artery Disease

Background: Identification of ventilation-, metabolic- and cardiac thresholds during maximal cardiopulmonary exercise tests (CPET) in Coronary Artery Disease (CAD) is crucial to prescribe safe and effective exercise training.
Purpose: To compare 10 methods for threshold-identification with the respiratory compensation point (RCP) on lactate accumulation. Oxygen consumption (VO₂) heart rate (HR) and workload (W) at RCP were compared to VO₂, HR and W determined by heart rate turning point (HRTP), Wasserman V-slope (V-slope), ventilation thresholds (VT1-VT2), respiratory quotient (RQ1), fixed lactate thresholds at 2 and 4mmol/L, first and second lactate turning points (LTP1-LTP2) determined by R-project multiple linear regression or by Keul.
To examine whether these methods relate differently in endurance profiled (EP) versus resistance profiled (RP) patients.
Results: 42 patients with CAD (58.1 ± 9.2 years) had a maximal CPET.
VO₂, HR and W at 4mmol/L fixed, at LTP2 by linear regression or as by Keul were not different from the same parameters at RCP in the total population. HR at HRTP was significantly lower while VO₂ and W were the same as at RCP.
VO₂, HR and W at V-slope, at 2mmol/L fixed and at RQ1 were equal but significantly lower than at RCP. When comparing EP with RP, the most striking finding was that VO₂, HR and W at RCP were the same at 4mmol/L and LTPT2 in the RP but preceded RCP in the EP.
Conclusions: V-slope, 2mmol/L threshold and RQ1 precede the occurrence of RCP. VT1 and LTPT1 occur significantly earlier than V-slope.
Lactate thresholds based on 4mmol/l, LTP2 and Keul are comparable with the RCP. HR based on HRTP is lower than HR at RCP thus generates a lower training HR.
In CAD patients with an EP, LTPT2 precedes the RCP. In patients with a RP, LTPT2 is the same as RCP.