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Ischemia Testing Before Coronary Artery Bypass Grafting: What's the Value Added?

Summary and Comment |
June 19, 2013

Ischemia Testing Before Coronary Artery Bypass Grafting: What's the Value Added?

  1. Howard C. Herrmann, MD

In a substudy of the STICH trial, stress-induced ischemia predicted neither mortality nor increased benefit from CABG in patients with LV systolic dysfunction.

  1. Howard C. Herrmann, MD

In the STICH trial, coronary artery bypass grafting (CABG) was not superior to medical therapy alone in patients with coronary artery disease (CAD) and left ventricular (LV) dysfunction, whether or not myocardial viability was identified (JW Cardiol Apr 4 2011). In this analysis, investigators examined the effects of inducible ischemia in a subset of 399 STICH patients (33% of those enrolled) who underwent stress testing with radionuclide studies, dobutamine echocardiology, or both.

Kaplan-Meier Estimates of All-Cause Mortality Rates
Study patients are divided according to the presence or absence of ischemia on stress testing, regardless of treatment allocation.

Reprinted with permission from Panza JA et al. J Am Coll Cardiol 2013; 61:1860.
Kaplan-Meier Estimates of All-Cause Mortality Rates

Study patients are divided according to the presence or absence of ischemia on stress testing, regardless of treatment allocation.

Reprinted with permission from Panza JA et al. J Am Coll Cardiol 2013; 61:1860.

In this cohort (mean LV ejection fraction, 26%), the rate of demonstrable myocardial ischemia was 64% and did not differ between the two test types. The extent of ischemia was ≥10% in 50% of the patients and was ≥20% in 19%. Outcomes, including all-cause mortality, cardiovascular mortality, and hospitalization, did not differ significantly between patients with and those without inducible ischemia (see figure), regardless of whether they received CABG or medical therapy alone.

Comment

Most clinicians believe that ischemia on stress testing is evidence in favor of revascularization. However, data supporting this view is mostly derived from studies in patients with normal or slightly reduced left ventricular ejection fractions. In these patients with severe LV dysfunction, inducible ischemia did not identify a subgroup that benefited more from coronary artery bypass grafting than from optimal medical therapy. The analysis has important limitations: It is observational and underpowered for clinical endpoints, and stress testing occurred at physicians' discretion. For these reasons, this study cannot be considered definitive, but it emphasizes the challenges of managing severe CAD with LV dysfunction and the importance of individualizing treatment decisions in this patient population.

  • Disclosures for Howard C. Herrmann, MD at time of publication Consultant / Advisory board Gerson Lehrman Group; Siemens; St. Jude Medical Speaker's bureau American College of Cardiology Foundation; Cardiovascular Institute; Cardiovascular Research Foundation; Christiana Medical Center; Coastal Cardiovascular Society; Crozer-Chester Hospital; Mayo Clinic; New York Cardiology Society Equity Micro-Interventional Devices, Inc. Grant / research support Abbott Vascular; Edwards Lifesciences; Gore; Medtronic; St. Jude Medical Editorial boards Catheterization and Cardiovascular Interventions; Circulation-Cardiovascular Interventions; Journal of Interventional Cardiology; Journal of Invasive Cardiology

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