Intraoperative myocardial infarction in non-cardiac surgery: is a universal definition feasible?

Diagnostic criteria for the redefinition of acute myocardial infarction (AMI) have been recently published. In this new classification, intraoperative (IPEMI) or post-operative (POMI) AMI, in the setting of non-cardiac surgery, were not included. It is well known that this category of AMI occurs under particular circumstances while the diagnostic criteria have not been fully elucidated. Patients with pre-operative cardiac risk undergoing intermediate or high surgical risk operations are more prone to IPEMI and POMI. Meanwhile, stent thrombosis in patients with coronary artery disease undergoing noncardiac surgery could pose a specific risk factor, because the time for complete endothelization varies among subjects. This risk increases in case of pre-operative anticoagulation therapy alteration for fear of bleeding. Mortality from IPEMI and POMI varies between 40 and 70%, especially because these are frequently underdiagnosed. On top, patients during the perioperative period cannot easily complain of angina. During surgery, it is not necessary to have haemodynamic instability, for an AMI to occur. Subtle ST-segment changes in electrocardiogram are not always appreciated, unless there is a computerized monitor analysis. The majority of perioperative AMIs are non-Q wave and electrocardiographic changes are therefore non-specific. Transoesophageal echocardiogram, although not routinely used, could reveal segmental wall motion abnormalities, in patients with ‘unusual intraoperative cardiac behaviour’. Laboratory values of CPK and CPKMB are not reliable, because of co-existing muscle damage. Troponins need to be measured frequently in the immediate post-operative period. However, the 99th percentile of the upper reference limit, above which troponin levels become diagnostic of IPEMI and POMI, is still unknown. Apart from high mortality, increased surgical morbidity (sepsis, wound infection, pneumonia, and deep vein thrombosis) is common, when IPEMI–POMI occur. In 50% of patients who die of perioperative AMI, neither intracoronary thrombi nor atherosclerotic plaque rupture are found in autopsy. On the basis of the above, the majority of IPEMI and POMI should be classified as type 2, while there would be a few that could belong to anywhere between 3 and 4b, according to the new reclassification, but still a certain percentage remains unclassified. In conclusion, non-cardiac surgery IPEMI– POMI consists of a particular category with high morbidity and mortality, and not fully clarified diagnostic criteria. They deserve to be included in the universal redefinition of AMI as a separate type-category.