Oxygen Uptake Kinetics During and After Exercise are Useful Markers of Coronary Artery Disease in Patients With Exercise Electrocardiography Suggesting Myocardial Ischemia

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Background: The aim of the current study was to determine if the slowed exercise oxygen uptake (VO2) kinetics, which is developed by myocardial ischemia, would be accompanied by delayed recovery VO2 kinetics in patients with coronary artery disease (CAD). Methods and Results: Thirty-seven patients with significant ST depression during treadmill exercise underwent cardiopulmonary exercise testing with cycle ergometer. Measurements performed are the ratios of change in increase in oxygen (O2) uptake relative to increase in work rate (ΔVO2/ΔWR) across anaerobic threshold (AT) and 1 mm ST depression point (ST-dep), the time constants of VO2 during recovery (T1/2 VO2), stress radio-isotope scintigraphy and coronary angiography. Patients were divided into CAD positive (CAD+) and CAD negative (CAD-) groups, based on coronary angiography. In CAD+, ΔVO2/ΔWR decreased above AT and ST-dep, in contrast to CAD- patients. The T1/2 VO2 in CAD+ (103.1 ±13.0 s) was greater than that of CAD- (76.5 ±8.7 s) and showed negative correlations to the ratios of ΔVO2/ΔWR across AT and ST-dep. These parameters improved in the patients who underwent coronary bypass surgery. Conclusions: Exercise and recovery VO2 kinetics were slowed when myocardial ischemia was provoked by exercise. Measurement of exercise and recovery VO2 kinetics improve the accuracy of the exercise electrocardiogram diagnosis of CAD.
2009-09-20