Oxygen uptake attenuation at ventilatory threshold in men with coronary artery disease

Purpose: Maximal oxygen uptake (VO2) and ventilatory threshold (VT) are widely used to assess cardiorespiratory fitness in healthy people, as well as in patients with various clinical conditions. The aim of this study was to determine whether an attenuation of VO2 occurs above the VT in patients with stable coronary artery disease. Methods: A total of 33 male patients participating in an outpatient cardiac rehabilitation/secondary prevention program underwent maximal incremental cycle ergometry at increasing pedaling cadences up to the limit of tolerance. Ventilatory gas-exchange variables were measured breath by breath while work rate was recorded continuously. Ventilatory threshold was determined by a dual linear regression model (V-slope analysis). Result: Four patients were excluded from the analysis because they were unable to pedal at the increasing cadences required by the protocol. The remaining 29 patients successfully completed the test without complications or evidence of significant ST segment depression. The slope of the VO2/work rate relationship above the VT decreased significantly (- 44.6%on average) in 23 of the 26 patients in which VT was able to be determined. VO2 at the start of VO2 attenuation (VO2att) and at VT were highly correlated and in strong agreement (1637 ± 451 mL/min vs 1650 ± 473 mL/min, r 2=0.96, P <.01). Conclusions: VO2att does occur and coincides with the VT in the majority of patients tested with stable coronary artery disease.