Diagnosis of Acute MyocardialInfarction after Coronary Artery Bypass Graft (CABG) Surgery: ASystematic Review

Abstract

Myocardial infarction after coronary artery bypass grafting is a serious complication and one of the most common causes of perioperative morbidity and mortality. The primary aims of treatments in patients with ischemic heart disease are to alleviate anginal symptoms and to prevent complications, such as acute myocardial infarction, congestive heart failure and death. Coronary artery bypass grafting is often a very effective method of relieving angina and it has also been shown to improve survival. The development of new surgical techniques and the concomitant progress in anesthesia and intensive care have made CABG a fairly save procedure. Myocardial infarction following coronary artery bypass grafting is termed type V MI. The detection and quantification of postsurgical myocyte necrosis is complex as cardiac-specific biomarkers such as troponin and CK-MB may not be able to differentiate ischemic injury from the non-ischemic injury caused by cardiac manipulation, suture insertion or placement on cardiopulmonary bypass. Consequently, biomarker release may be determined by the complexity of surgery and not ischemic injury alone. Diagnosis will be established according to creatine kinase values more than five times the 99th percentile of the normal reference range during the first 72 hours following CABG, (or Troponin or CKMB more than ten time increase) when associated with the appearance of new pathological Q-waves or new LBBB, or angiographically documented new graft or native coronary artery occlusion, or imaging evidence of new loss of viable myocardium, should be considered as diagnostic of a CABG related MI. We conducted a systematic search in MEDLLINE (PubMed), EMBASE,Google Scholar and the Cochrane Libraryincluding all studies which focused on the diagnostic methods for AMI after CABG surgery. A total of 23 of the 1372 studies identified in the systematic search were included. The maximum peak level of the Tn was seen after 72 hoursafter CABG surgery. Various levels have been recommended for considering a diagnosis of POMI.We noticed that the sensitivity is variable and ranging between 44% and 100%. We conclude that Troponin I and T can both be used to indicate myocardial damage, with the level correlating well with the level of injury. However until issues such as a ‘gold standard’ for peri-operative MI are addressed, one single cut-off point cannot be recommended for either test.