Abstract 13735: Utility of Peak Oxygen Pulse in Differentiating Cardiac Causes From Other Etiologies in Patients Presenting With Dyspnea
Introduction: Cardiopulmonary exercise testing (CPX) is the only stress test modality that provides information on the cardiovascular system’s ability to meet metabolic demands in terms of oxygen consumption (VO2) and carbon dioxide production (VCO2). In addition, CPX provides oxygen (O2) pulse as a continuous measure of stroke volume, which is its superiority to other stress modalities in which systolic function is measured at peak stress and rest. However, operating test characteristics and optimal cutoff of O2 pulse for distinguishing cardiac from noncardiac causes of exercise limitation are unknown.
Hypothesis: We tested several cutoff points against the clinical standard to define the optimal O2 pulse cutoff point.
Methods: We studied 54 consecutive patients referred for CPX. Comprehensive CPX included VO2, VCO2, breathing reserve, etc. and arterial blood gasses at rest and peak stress as well as exercise ECG, heart rate and blood pressure response. CPX was blindly interpreted and patients categorized as cardiac normal: normal results or abnormal results secondary to any noncardiac cause of exercise limitation; or as cardiac abnormal: abnormal results secondary to cardiac causes of exercise limitation. Seven O2 pulse reference cutoff points included nongender-based (<15 ml/beat), gender-based (<15 ml/beat for males and <10 ml/beat for females) and <80% of O2 pulse based on five different definitions of predicted VO2 max (Table).
Results: O2 pulse based on definitions by Wasserman had the highest accuracy, specificity and positive predictive value, with a fair agreement demonstrated by kappa statistic (Table).
Conclusions: This is the first study to evaluate the optimal O2 pulse value at peak stress for discrimination of cardiac and noncardiac causes. Nongender-based or gender-based cutoffs underperformed, and definitions incorporating age, sex, height and weight like Wasserman’s should be used preferentially as they have greater accuracy.
- © 2013 by American Heart Association, Inc.