Diabetic patients with non-ST-segment elevation acute coronary syndromes (ACS) appear to benefit from early invasive treatment, a benefit that has not been observed in nondiabetic patients.

“In terms of absolute benefit, the number of nonfatal MIs (myocardial infarctions) prevented with an invasive strategy over 1 year per 1,000 diabetic patients was 37 compared with only one nonfatal MI prevented per 1,000 patients without diabetes mellitus,” wrote Michelle O’Donoghue, MD, MPH, from Brigham and Women’s Hospital in Boston, and colleagues.

“During 12 months of follow-up, the triple composite endpoint of incidence of death, MI, or rehospitalization with ACS was 30.5% in diabetic patients versus 20.3% in nondiabetic patients (P<0.001),” they reported in the Journal of the American College of Cardiology.

In their meta-analysis, O’Donoghue and colleagues reviewed nine randomized clinical trials conducted between 1994 and 2012; cardiovascular outcomes were provided for each trial and stratified by diabetes status, resulting in a cohort of 9,904 patients. Of this group, 1,789 (18.1%) presented with diabetes at baseline. They found the diabetic patients had more extensive coronary artery disease on angiography, including a higher prevalence of three-vessel or left main coronary artery disease (48% versus 31%, P<0.001). The researchers noted that the frequency of revascularization was similar between groups (67.8% versus 66%, P=0.31). However, diabetic patients were more likely to have undergone coronary artery bypass graft surgery (31.9% versus 25.9%, P<0.001). In addition, when compared with nondiabetics, the patients with diabetes had higher rates of MI, rehospitalization, and death:   Death: 9.3% versus 3.2% (P<0.001) Nonfatal MI: 11.3% versus 7.1% (P<0.001) Rehospitalization with ACS: 18.1% versus 13% (P<0.001) The researchers found that the invasive strategy was associated with a comparable relative reduction in death, MI, or rehospitalization with ACS among the diabetic patients (relative risk 0.87, 95% CI 0.73 to 1.03) versus the nondiabetic group (RR 0.86, 95% CI 0.70 to 1.06). However, they found a trend toward a greater relative reduction in nonfatal MI in diabetic patients managed with an invasive strategy (RR 0.71, 95% CI 0.55 to 0.92) compared with nondiabetics (RR 0.98, 95% CI 0.74 to 1.29). Also, the absolute reduction in nonfatal MI risk with an invasive strategy was greater in diabetic than nondiabetic patients (absolute RR 3.7% versus 0.1%). “An invasive strategy significantly reduced the risk of rehospitalization with ACS by 25% in patients with and without diabetes mellitus,” the authors wrote. “By contrast, an invasive strategy did not reduce the RR of death in either diabetic or nondiabetic patients.” The researchers also analyzed the creatine kinase–myocardial band or troponin biomarkers among the diabetic and nondiabetic patients and found the diabetics had a comparable reduction in death or MI with an invasive strategy, regardless of whether they also had elevated biomarkers. In contrast, elevated biomarkers did identify nondiabetics with a greater benefit from an invasive strategy (RR 0.68, 95% CI 0.55 to 0.84). “The findings of this collaborative meta-analysis suggest that a diagnosis of diabetes mellitus helps to identify an important subset of individuals at increased risk of adverse outcomes who may benefit more from an invasive strategy after non–ST-segment elevation ACS,” the authors stated. The authors noted the standard limitations of meta-analysis including heterogeneity among trials and publication bias. There may also have been diabetes status misclassification. In addition, tests for interactions between subgroups were conservative and may have missed a true interaction when one existed and patient-level data were not available, so individual-level covariates could not be explored.