Clinical, scintigraphic, and angiographic predictors of oxygen pulse abnormality in patients undergoing cardiopulmonary exercise testing

Background The oxygen (O2) pulse curve obtained at cardiopulmonary exercise testing provides information on cardiorespiratory fitness and the presence of cardiovascular disease. O2 pulse abnormalities have been attributed to myocardial ischemia, among other conditions, but the predictors of abnormal O2 pulse curves are not completely known. Hypothesis Perfusion abnormalities detected by myocardial perfusion scintigraphy (MPS) may be associated with abnormal O2 pulse curves. Methods Forty patients with normal left ventricular function underwent cardiopulmonary exercise testing with radiotracer injection at peak exercise, followed by MPS. The O2 pulse curves were classified as (A) normal; (B) probably normal (normal slope with lower peak value); (C) probably abnormal (flat, with low peak value); or (D) definitely abnormal (descending slope), and analyzed as A/B vs C/D. Coronary artery disease (CAD) was defined as >50% stenosis. MPS perfusion scores were calculated (summed rest score [SRS], indicating myocardial fibrosis; summed difference score, indicating ischemia). Results Comparing patients with A/B vs C/D curves, the latter were more frequently female and had higher SRS. The prevalence of ischemic MPS, of any CAD, or multivessel CAD was not significantly different among patients with A/B or C/D curve patterns. On logistic regression, female sex, body mass index, and the SRS were significantly associated with C/D curves. Conclusions Female sex, increasing body mass index, and myocardial fibrosis were significant predictors of abnormal O2 pulse curves. Myocardial ischemia and the presence and extent of CAD were not associated with the abnormal patterns of the O2 pulse curve.