Cardiopulmonary exercise testing provides oxygen pulse as a continuous measure of stroke volume, which is superior to other stress-testing methods in which systolic function is measured at baseline and at peak stress. However, the optimal peak oxygen pulse criterion for distinguishing cardiac from noncardiac causes of exercise limitation is unknown. In comparing several peak oxygen pulse criteria against the clinical standard of cardiopulmonary exercise testing, we retrospectively studied 54 consecutive patients referred for cardiopulmonary exercise testing. These exercise tests included measurement of oxygen consumption, carbon dioxide production, breathing reserve, arterial blood gases at baseline and at peak stress, exercise electrocardiogram, heart rate, and blood pressure response. Results were blindly interpreted and patients were categorized as members either of our Cardiac Group (abnormal result secondary to cardiac causes of exercise limitation) or of our Noncardiac Group (normal or abnormal result secondary to any noncardiac cause of exercise limitation). The accuracy of the peak oxygen pulse criteria ranged from 50% for univariate criterion (≤15 mL/beat), to 61% for oxygen pulse curve pattern, to 63% for bivariate criterion (≤15 mL/beat for men, ≤10 mL/beat for women), to as high as 81% for a multivariate criterion. All multivariate criteria outperformed oxygen pulse curve pattern, univariate, and bivariate criteria. This is the first study to evaluate the optimal peak oxygen pulse criterion for differentiating cardiac from noncardiac causes of exercise limitation. Multivariate criteria (especially a criterion incorporating age, sex, height, and weight) should be used preferentially, as opposed to the commonly used univariate and bivariate criteria.

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Objectives: We sought to compare the effects of early versus delayed percutaneous coronary intervention (PCI) on the outcomes at 1 year in patients presenting with non-ST-segment elevation myocardial infarction (NSTEMI).Background: Prompt reperfusion in NSTEMI remains controversial. Randomized studies have shown conflicting results regarding the benefits of early intervention versus delayed intervention (defined as intervention performed within 24 hr vs. 24-72 hr of presentation, respectively). This study was conducted to determine the clinical outcomes post PCI in a large tertiary care center.Methods: A propensity-matched group of 1,640 NSTEMI patients [62.4% males (n = 1,023), median age 65 years] was studied for a composite of death, myocardial infarction (MI), stroke, and heart failure in 1 year as a primary endpoint after PCI. Patients were divided into an early intervention group (EIG) and delayed intervention group (DIG). Timing of PCI was determined by the treating interventional cardiologist.Results: The primary outcome was significantly lower in the EIG than DIG (20.4% vs. 24.9%, P = 0.029), which was mainly derived from mortality benefit in the EIG. There was no difference in occurrence of death, MI, stroke, or heart failure between the groups at 30 days.Conclusions: An earlier PCI in patients with NSTEMI is associated with a significant reduction in the composite outcome of death, MI, heart failure, or stroke at 1 year compared with delayed PCI. Based on this large cohort of patients from a real-world referral center, contemporary reperfusion practices in NSTEMI may need to be re-examined with a bias toward early intervention. K E Y W O R D SACS/NSTEMI, early intervention, delayed intervention, health care outcomes, Non-STsegment myocardial infarction, percutaneous coronary intervention, propensity-matched

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