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Hospital were studied. Patients with unstable angina or MI within the preceding three months were excluded. Perioperative clinical data were recorded prospectively. The preoperative 12-lead electrocardiogram (ECG) was analyzed based on the Sokolow-Lyon criteria for left ventricular hypertrophy (LVH) as previously described (16). Monitoring included continuous intra-arterial blood pressure and pulse oximetry measurement during surgery and for at least another day. Seven patients had regional (epidural or continuous spinal) anesthesia; 65 had combined general and epidural anesthesia, and 113 patients had general anesthesia only. After completion of surgery, patients were treated in the recovery room or intensive care unit at least until the morning after surgery. All preoperative medications were resumed postoperatively as soon as the patients were able to take fluids by mouth. All cardiac signs and symptoms during the hospitalization were recorded, and a 12-lead ECG was obtained before hospital discharge. Continuous 12-lead ECG recording Before induction of anesthesia, patients were connected to a continuous 12-lead ECG monitor (Solar 7000, Marquette Electronics, Milwaukee, Wisconsin) wired through a network to a Cardiac Review Station (ST-Guard). Each minute the ST-Guard stored all 12-lead ECG complexes, measured the ST-segment deviation in all leads compared with the baseline ECG and displayed the ST trends. The ST segment was measured 60 ms after the J point, and an episode of ST deviation was defined as ST depression or elevation of ≥0.2 mV in one lead or ≥0.1 mV in two contiguous leads that lasted >10 min. Each episode of ST-segment deviation was automatically detected and marked by the ST-Guard. Monitoring was continued for 72 h, except in carotid endarterectomy patients who usually ambulated after 48 h. Treating physicians were blinded to the ST-Guard data. However, if ischemia was clinically suspected based on other monitors or clinical signs, physicians were allowed to examine the changes on ST-Guard and treat those patients accordingly. Treatment to reverse ischemia included: improving oxygenation, intravenous beta-adrenergic blocking agents (esmolol/labetalol), nitroglycerine and correction of anemia by blood transfusion, as clinically indicated. The 12-lead ST-segment trends were reviewed by the study investigators, and artifacts were deleted. Periods marked by the ST-Guard as ST-segment deviations were inspected visually for accuracy, and those reflecting artifacts or pure up-sloping ST-segment depression were not considered as ischemia. Each patient’s longest and cumulative ischemia duration was recorded. Mean heart rate during the 30 min before, at the onset of and at maximum ST deviation was recorded from the ST-Guard. Cardiac markers Cardiac troponin-I and CK-MB were measured in all patients immediately after surgery daily for the first three postoperative days and later if clinically indicated. Cardiac troponin-I was measured using a Stratus II analyzer (Dade International, Deerfield, Illinois) by mass immunoassay with two monoclonal specific antibodies. Serum total CK and its MB isoenzyme activity were measured by a Kodak Ektachem multiple-point rate assay (Johnson & Johnson Co., New Brunswick, New Jersey). Cardiac events\ Cardiac death was defined as death secondary to MI, arrhythmia or congestive heart failure. Myocardial infarction was defined as an increase in cTn-I >3.1 ng/ml (12,17)accompanied by at least one of the following: typical ischemic symptoms, ECG changes indicative of ischemia (ST-segment depression or elevation) or new pathological Q waves. Cardiac troponin-I >3.1 ng/ml is also above the 99th percentile of a reference population in our lab. This
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