Prognostic Impact of Coronary Collaterals in Acute Coronary Syndrome: A Meta-Analysis (PICC-ACS)

Background: The coronary collateral circulation (CCC) is an alternative source of blood supply in coronary artery disease (CAD). A recent meta-analysis found that among patients with stable CAD, the presence of CCC has a relevant protective effect in terms of mortality. Among patients with acute coronary syndrome (ACS), surrogate end-points such as infarct size, systolic function, ventricular dilatation and post-infarct aneurysm formation have positive results in relation to the presence of CCC. The prognostic value of the presence of CCC at the time of ACS is still undefined with regard to hard outcomes, specifically, reduction of mortality. Objective: To determine whether the presence of CCC demonstrated by coronary angiography during an ACS is associated with a reduction in mortality Methodology: We conducted a systematic search of studies using MEDLINE, EMBASE, ScienceDirect, Scopus, and the Cochrane Central Register of Controlled Trials databases in all languages and examined the reference lists of the studies. The inclusion criteria for studies were (1) observational or randomized controlled trials; (2) population included adults ≥19 years old with ACS; (3) reported data on mortality in association with the presence or absence of CCC on angiography; and (4) if observational study, should have controlled for confounders by using logistic regression analysis. Studies identified were assessed for quality using either the Newcastle-Ottawa Quality Assessment Scale for observational studies or the Cochrane Tool for Assessing Risk of Bias for randomized trials. The outcome of interest was reduction in all-cause mortality, assessed using Mantel-Haenszel analysis of random effects to compute for relative risk, carried out using Review Manager (RevMan) 5.3. Results: Pooled analysis from 12 identified trials showed that among patients with ACS who underwent coronary angiography, the presence of CCC showed a trend towards benefit in terms of mortality but no statistical difference from no CCC (RR 0.69, 95% CI 0.44–1.08, p<0.0001, I2=73%). In the secondary analysis, patients with ACS and CCC treated with PCI had a significant reduction in mortality compared to those without CCC (RR 0.48, 95% CI 0.35–0.65, p<0.00001, I2=0%). Conclusion: The presence of CCC during ACS showed a trend towards mortality reduction. Further, among patients treated with PCI, those with CCC had an incremental significant reduction in mortality compared to those without CCC.