Early invasive versus conservative strategies for unstable angina & non-ST-elevation myocardial infarction in the stent era.

BACKGROUND: In patients with unstable angina and non-ST-elevation myocardial infarction (UA/NSTEMI) two strategies are possible: a routine invasive strategy where all patients undergo coronary angiography shortly after admission and, if indicated, coronary revascularization; or a conservative strategy where medical therapy alone is used initially with selection of patients for angiography based on clinical symptoms or investigational evidence of persistent myocardial ischemia.

OBJECTIVES: To determine the benefits of an invasive compared to a conservative strategy for treating UA/NSTEMI in the stent era.

SEARCH STRATEGY: The Cochrane Central Register of Controlled Trials (Issue 3 2005), MEDLINE and EMBASE were searched from 1996 to September 2005 with no language restrictions.

SELECTION CRITERIA: Included studies were prospective trials comparing invasive with conservative strategies in UA/NSTEMI.

DATA COLLECTION AND ANALYSIS: We identified 5 studies (7818 participants). Using intention-to-treat analysis with random effects models, summary estimates of relative risk (95% confidence interval [CI]) were determined for primary end-points of all-cause death, fatal and non-fatal myocardial infarction; all-cause death or non-fatal myocardial infarction; and refractory angina. Further analysis of included studies was undertaken based on whether glycoprotein IIb/IIIa receptor antagonists were used routinely. Heterogeneity was assessed using chi-square and variance (I(2)) methods.

MAIN RESULTS: In the all-study analysis, mortality during initial hospitalization showed a trend to hazard with an invasive strategy; relative risk 1.59 (95% CI 0.96 to 2.64). Mortality and myocardial infarction assessed at 2-5 years in two trials were significantly decreased by an invasive strategy with relative risk of 0.75 (95% CI 0.62 to 0.92) and 0.75 (95% CI 0.61 to 0.91) respectively. The composite end-point of death or non-fatal myocardial infarction was significantly decreased by an invasive strategy at several time points after initial hospitalization. The incidence of early (<4 months) and intermediate (6-12 months) refractory angina were both significantly decreased by an invasive strategy; relative risk 0.47 (95% CI 0.32 to 0.68) and 0.67 (95% CI 0.55 to 0.83) respectively, as were early and intermediate rehospitalization rates with relative risk 0.60 (95% CI 0.41 to 0.88) and 0.67 (95% CI 0.61 to 0.74) respectively. The invasive strategy was associated with a two-fold increase in the relative risk of peri-procedural myocardial infarction (as variably defined) and a 1.7-fold increase in the relative risk of bleeding.

AUTHORS' CONCLUSIONS: An early invasive strategy is preferable to a conservative strategy in the treatment of UA/NSTEMI.