Myocardial ischemia and infarction

Postoperative ischemia can be detected by ECG, echocardiography, or biochemical tests and the incidence depends on the method used, as there is no agreed gold standard. Echocardiography may be more sensitive than ECG, but it is more expensive and requires greater expertise so that it is not yet considered for routine use. Moreover, detection of ischemia by monitoring regional wall motion abnormalities is controversial since not all such abnormalities are of ischemic origin.

Ischemia is most common in the first 2 days, with a peak incidence 2 h after completion of anastamoses. There is no clear relationship of ischemic episodes to hemodynamic indices. Although tachycardia may be more frequent in patients with postoperative ischemia, approximately half of detected episodes are unrelated to hemodynamic changes.

The etiology of postoperative myocardial ischemia is multifactorial and the relative contributions of global changes in hemodynamics, incomplete revascularization, graft thrombosis or spasm, embolus, kinking, and native coronary artery spasm remain to be defined. The relationship between perioperative ischemia and perioperative infarction is also unclear.

Infarction may be silent or accompanied by hemodynamic changes. More specific markers of myocardial injury, such as the troponin complex proteins troponin I and T, may provide more sensitive diagnosis in the future. Ischemia is treated by reducing myocardial oxygen demand and maximizing supply. The consequences and mangement of infarction will depend on its location and size.

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