Early and Delayed Myocardial Infarction after Abdominal Aortic Surgery
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BACKGROUND: Although postoperative myocardial infarction (PMI) after vascular surgery has been described to be associated with prolonged ischemia, its exact pathophysiology remains unclear. METHODS: The authors used intense cardiac troponin I (cTnI) surveillance after abdominal aortic surgery in 1,136 consecutive patients to better evaluate the incidence and timing of PMI (cTnI > or = 1.5 ng/ml) or myocardial damage (abnormal cTnI < 1.5 ng/ml). RESULTS: Abnormal cTnI concentrations was noted in 163 patients (14%), of which 106 (9%) had myocardial damage and 57 (5%) had PMI. In 34 patients (3%), PMI was preceded by a prolonged (> 24 h) period of increased cTnI (delayed PMI), and in 21 patients (2%), the increase in cTnI lasted less than 24 h (early PMI). The mean times from end of surgery to PMI were 37 +/- 22 and 74 +/- 39 h in the early PMI and delayed PMI groups, respectively (P < 0.001). The mean time between the first abnormal cTnI and PMI in the delayed PMI group was 54 +/- 35 h, during which the cTnI profiles of the myocardial damage and delayed PMI groups were identical. In-hospital mortality rates were 24, 21, 7, and 3% for the early PMI, delayed PMI, myocardial damage, and normal groups, respectively. CONCLUSIONS: Intense postoperative cTnI surveillance revealed two types of PMI according to time of appearance and rate of increase in cTnI. The identification of early and delayed PMI may be suggestive of different pathophysiologic mechanisms. Abnormal but low postoperative cTnI is associated with increased mortality and may lead to delayed PMI.
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