Cardiac complications, including cardiac death, nonfatal myocardial infarction (MI), heart failure, or ventricular tachycardia, pose a significant risk to patients undergoing major noncardiac surgery. Of these, perioperative MI is the most common major cardiovascular complication. Issues related to perioperative MI in patients undergoing noncardiac surgery will be reviewed in this topic. Perioperative MI after coronary artery bypass graft surgery is discussed separately. (See "Early cardiac complications of coronary artery bypass graft surgery", section on 'Perioperative MI'.)
Patients at increased risk for major cardiac complications, such as MI, can be identified using validated risk indices. The initial preoperative evaluation, the surgery-specific risk, the major indices used for risk stratification, the role of noninvasive testing, the management of cardiac risk in an attempt to reduce morbidity and mortality associated with noncardiac surgery, and issues related to the perioperative evaluation and management of heart failure in patients undergoing noncardiac surgery are discussed separately. (See "Estimation of cardiac risk prior to noncardiac surgery" and "Management of cardiac risk for noncardiac surgery" and "Perioperative heart failure in noncardiac surgery".)
The pathophysiology of perioperative myocardial infarction (MI) is highly debated. Although supply-demand mismatch (eg, hypertension, hypotension, or tachycardia) has long been thought to explain many perioperative MIs, the evidence to support this explanation is extremely weak. However, plaque rupture may play a central role in many cases. In one angiographic study, nearly 50 percent of patients with perioperative acute coronary syndrome had evidence of plaque rupture .
Postoperatively, the incidence of troponin elevations is between 10 and 45 percent, depending on the sensitivity of the cardiac troponin (cTn) assay used and the population studied (most of the studies have been in moderate- to high-risk patients). The etiology of these elevations has not been definitively studied but most appear to be related to the presence of significant coronary artery disease and an episode of supply-demand imbalance. In most studies, a definitive diagnosis of myocardial infarction (MI) with the universal definition has been diagnosed far less often (1 to 5 percent), perhaps because of the absence of symptoms and the high frequency of nonspecific electrocardiographic (ECG) findings. It is likely that with more data, these percentages will rise. However, the incidence of perioperative MI in patients undergoing noncardiac surgery varies with the definition of MI used, patient risk (including the type of surgery), monitoring strategy (eg, systematic biomarker monitoring after surgery), and the population studied . (See "Criteria for the diagnosis of acute myocardial infarction", section on 'Third Universal Definition of MI'.)
With regard to the definition, the incidence of MI is directly related to the sensitivity of the biomarker used. Thus, it is likely that as the sensitivity of cTn assays improve, and the recommended cut-off values that define MI fall, the frequency of identifying perioperative MI will increase. Although it is thought that most elevations of cTn after noncardiac surgery are due to acute MI, all elevations of cTn should not be assumed to be due to acute MI. Cardiac injury may help to explain some of the heretofore unexplained morbidity associated with noncardiac surgery.