Our analysis suggests that for the treatment of NSTE-ACS, CABG and PCI are similar with respect to long-term mortality and myocardial infarction rates. The analysis further suggests that CABG is associated with decreased rates of long-term MACE and re-revascularization.
This is the first meta-analysis to address this important topic; our results are relevant as a substantial number of patients worldwide present with NSTE-ACS every year; in Germany over a period of 10 years 2.77 million cases of NSTE-ACS were recorded. In the United States there are more than 1 million hospitalizations per year due to acute coronary syndrome , with the proportion of patients with non-ST-elevation myocardial infarction being over 50% of all infarctions and increasing over time . In other studies the annual incidence of NSTE-ACS has been reported with 88 per 100 000 inhabitants .
Previous studies have suggested that an invasive strategy might be superior to a conservative one[3, 14], but have not summarized a recommendation for a specific invasive therapy (PCI or CABG). Currently, only 4-10% of the patients with NSTE-ACS receive CABG and 30-40% of them PCI [1, 15].
Our findings support the current guidelines, where no clear recommendation for PCI or CABG is given and a suggestion that the criteria applied for patients with stable coronary artery disease should be applied to stabilized patients with NSTE-ACS is made . Both American and European guidelines recommend a heart-team approach to revascularization decisions in NSTE-ACS [4, 16] and that, factors such as extent and complexity of the coronary artery disease, as well as other factors should be considered.
It has been proposed that the survival benefit of PCI or CABG may be primarily due to an infarct-preventing mechanism rather than to revascularization per se [17, 18]. This theory might provide a mechanistical explanation of our results, showing no mortality difference in 2 invasive treatments treating the same acute events. This line of argumentation finds supports in a meta-analysis we performed demonstrating an association of a survival advantage of CABG over PCI only in cases when there was also a difference in the rate of myocardial infarction .
STUDY STRENGTH AND LIMITATIONS
This is the first meta-analysis to address this important topic. Moreover, we analyzed 5 different outcomes and performed different subgroup analyses and a meta-regression of 14 different pre-operative factors. However, this work has the intrinsic limitations of observational series, including the risk of methodological heterogeneity of the included studies, residual confounders and ecological fallacy of meta-regression. In addition, treatment allocation bias is likely present in all observational series comparing two interventions with different operative risk and invasiveness.