Extent of ischemia modifies revascularization benefit in stable CAD
MedWire News: The relative benefits of early revascularization for stable coronary artery disease (CAD) as opposed to medical therapy may depend on the extent of myocardial ischemia, new research suggests.
In a large series of patients undergoing stress-rest myocardial perfusion scintigraphy, those with significant ischemia and without extensive scar tissue tended to benefit from early revascularization, whereas those with minimal ischemia benefited more from medical therapy.
"These findings provide support for current guidelines concerning the use of ischemia testing in stable patients prior to revascularization and strengthen those guidelines that recommend a medical approach among patients with overt evidence of CAD but minimal ischemia," write Daniel Berman (Ceders-Sinai Heart Institute, Los Angeles, USA).
Berman's team studied 13,555 consecutive patients with known or suspected CAD who underwent adenosine or exercise stress myocardial perfusion scintigraphy (MPS) over a 6-year period.
The patients' mean age was 66 years, 61% were male, and 35% had a history of CAD. In all, 1226 underwent revascularization within 90 days of MPS while the remainder were treated medically. The mean duration of follow-up was 8.7 years, during which time 3893 patients died from any cause.
The authors used semi-quantitative methods to classify MPS images for each patient according to the percent of myocardium with ischemic (%I) or fixed (%F) defects.
After adjusting for baseline differences and propensity scores, they found that the extent of ischemia significantly modulated the survival benefit associated with early revascularization in patients without prior myocardial infarction.
Specifically, in patients with little or no ischemia, early revascularization was associated with around a 50% greater risk for death than medical therapy. By contrast, in patients with extensive ischemia (>20% myocardium), the risk for all-cause death was around 30% lower with early revascularization as opposed to medical therapy.
Further analysis revealed that, after excluding patients with scars extending to >10% of the myocardium, the extent of ischemia identified a survival benefit in all patients.
Writing in the European Heart Journal, the authors suggest that the presence of extensive scar tissue may increase the procedural risk of revascularization, "potentially obviating any downstream benefit that may accrue."
They call for their findings to be validated in a prospective study, and conclude: "In the interim, our results imply that both the absence of significant ischemia and the presence of extensive MI identify patients who are unlikely to benefit from referral for revascularization."
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By Joanna Lyford