Does early coronary artery bypass surgery improve survival in non-ST acute myocardial infarction?

Abstract

A best evidence topic was written according to a structured protocol. Lack of evidence exists regarding the optimal timing for coronary artery bypass graft (CABG) surgery after non-ST myocardial infarction (NSTEMI). While some authors address the importance of the timing of surgery alone, others take into account the extent of myocardial damage. The question addressed was whether early or late CABG surgery improves hospital mortality and cardiovascular events after NSTEMI in stable patients. Using a designated search strategy, 459 articles were found, of which seven represented the best available evidence. All of these studies were level 3 (retrospective cohort studies). Studies could be divided into those which assessed CABG outcome based on preoperative cardiac troponin I (cTnI) level as a measure of the extent of myocardial damage and those which considered only the timing after myocardial infarction. Outcome measures included short-term survival, hospital mortality, length of hospital stay and major adverse cardiovascular events (MACEs). The biggest retrospective study analysing postoperative outcomes based on the timing of surgery after NSTEMI concluded that operative mortality is higher when surgery is performed within 6 h of the event. After 6 h, mortality is similar at any timepoint after 6h of NSTEMI. While other smaller studies agree that there are fewer postoperative complications when surgery is performed after 48 h of the event, no consensus is found regarding mortality between early (less than 48 h) and late CABG surgery. Taking into account preoperative cTnI values, CABG has a higher incidence of MACEs and hospital mortality in patients with cTnI >0.15 ng/ml. When surgery is performed within 24 h of symptoms, preoperative cTnI >0.72 ng/ml is associated with worse outcomes. In view of the methodological limitations and level of evidence of the studies included, it appears that surgery may be safely performed in NSTEMI patients at any time after the first 6 h of the event in patients with cTnI <0.15 ng/ml, whereas in those patients with higher values of cTnI, waiting for cTnI to reduce before considering surgery seems to be a wise option in order to decrease the incidence of MACEs and hospital mortality.