Which finding can help confirm the diagnosis of perioperative myocardial infarction?

New Q waves on the postoperative ECG are considered a definitive finding that can help confirm the diagnosis of perioperative myocardial infarction. The development of Q waves indicates the presence of myocardial necrosis and is a key indicator of an infarct. Specifically, when Q waves appear in certain leads of the ECG, it suggests that there has been a significant loss of myocardial tissue in the area supplied by the affected coronary artery.

While troponin I elevation can indicate myocardial injury, it is not specific to myocardial infarction nor does it confirm an infarct on its own, as elevated levels can occur in various situations of cardiac stress or injury. Similarly, widespread ST depression may reflect myocardial ischemia but does not provide the conclusive evidence of necrosis associated with myocardial infarction. ST elevation signifies acute injury in specific patterns but doesn't universally confirm an infarct as it can occur in conditions other than an infarction, including pericarditis or coronary vasospasm.

Therefore, the emergence of new Q waves post-surgery is a specific and relevant finding that closely aligns with the diagnosis of perioperative myocardial infarction, making it the best option among the provided choices.