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both longest ischemia and cumulative ischemia duration (r = 0.83, p < 0.0001 and r = 0.78, p < 0.0001, respectively) (Fig. 1). In contrast, maximal CK-MB correlated poorly with longest or cumulative ischemia duration (r = 0.25 and r = 0.19, respectively). Scatter plots of highest levels of troponin-I obtained during the first three postoperative days versus the longest ischemia duration recorded on the continuous 12-lead ST-trend monitor. Linesrepresent the linear regression and the 95% confidence limits. r = Pearson’s correlation coefficient. Cardiac troponin-I >3.5 ng/ml was associated with the maximal area under the longest ischemia duration ROC (Fig. 2)and close to maximal area (0.923) under the CK-MB ROC. Similarly, longest ischemia duration of >120 min was associated with maximal area under the cTn-I ROC .Receiver-operator characteristic (ROC) curves of (A). Longest ischemia duration obtained at different cutoff levels of troponin-I representing myocardial infarction. (B)Highest cardiac troponin-I ROC curves obtained at different cutoff values of longest ischemia duration signifying myocardial infarction. AUC = area under the curve. Patients who sustained MI had more than fivefold longer episodes of ischemia, and the cumulative ischemia duration was more than sevenfold longer, compared with patients with ischemia but not MI . Of 13 patients with longest ischemia episodes of >100 min, only two had cTn-I levels below 3.1 ng/ml and in only one of the patients with cTn-I >3.1 ng/ml was the longest ischemia <100 min. Ten (83%) of the patients with infarction had elevated CK-MB as well. All ischemic events culminating in PMI were preceded by an increase in heart rate. In the 38 patients with ischemia, heart rate during the 30 min before ischemia was 84 ± 12 beats/min (range: 60 to 108). It increased to 106 ± 18 beats/min (range: 71 to 160, p < 0.0001) at the onset of ischemia and to 116 ± 18 beats/min (range: 82 to 162, p < 0.0001) at the time of maximal ST-segment deviation. Among patients with ischemia, there was no difference in heart rate during ischemia between patients with and without MI . Blood pressure at onset of ischemia in patients with MI was within their preoperative range, except for one patient who was mildly hypotensive (90/60 mm Hg). Five (45%) patients with MI had hemoglobin concentration <10 gr/dl, and, in all but one patient, the hemoglobin concentration was lower during ischemia than it was before surgery (Δ hemoglobin = 2.9 ± 1.5 gr/dl). There was no difference, however, between patients with and without MI in either the postoperative hemoglobin concentration (11.3 ± 1.5 gr/dl and 11.3 ± 1.4 gr/dl, respectively) or its decrement from the preoperative value (Δ hemoglobin = 1.9 ± 1.3 gr/dl and 1.6 ± 1.6 gr/dl, respectively, p = NS). Preoperative predictors of MI depicts the preoperative predictors of perioperative MI. By multivariate logistic regression analysis, diabetes mellitus and LVH were the only independent predictors of PMI (odds ratio = 4.1, 95% confidence interval [CI] = 1.2 to 14.4, p = 0.027; odds ratio = 3.77, 95% CI = 1.1 to 12.7, p = 0.032, respectively). Timing of myocardial ischemia and infarction Twenty-six (68%) of all the longest ischemic events started during the period between 50 min before and 60 min after the end of surgery, during emergence from anesthesia. In eight (67%) of the patients with PMI, the longest ischemic episodes started within the same time period (Fig. 3), and their cTn-I reached >3.1 ng/ml within less than 18 h. In the other four patients with PMI, the rise in cTn-I >3.1 ng/ml occurred in the second and third postoperative days. The time of onset of longest ischemia relative to the end of surgery (T = 0). Striped barsrepresent the onset time of longest ischemic events of all patients who had ischemia but no myocardial infarction; black barsrepresent the onset time of
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