Routine icu monitoring fails to detect postoperative myocardial ischemia

Introduction: Paücnts at nsk for postoperative myocardial ischemia are routinely followed in an ICU with continuous 2-lead ECG monitors (with or without ST segment analysis). ICU admission is felt to provide improved surveillance for myocardial ischemia, but adds significantly to the cost of hospitalizanon. Moreover, the sensitivity and specificity of this system has never been compared to continuous 12-lead ECG monitoring (gold standard). Methods: After IRB approval and informed consent, 35 patients scheduled for vascular reconstruction were studied. All pattens were monitored postoperatively with both continuous 2-lead (leads II and modified V5) and 12-lead ECG. The 12-lead ECG was transmitted through an ethemet and interpreted in real time every two minutes by a centralized ST segment microprocessor (ST Guard, Marquette Electronics). Events were defined as ischemia in two adjacent leads (ST segment elevation or depression 2 1mm) continuously for fourteen minutes or longer. This was compared to detection of ischemia based on "routine" ICU monitoring (clinical exam, combined with visual detection of ST segments and/or routine monitoring of ST alarm limits) All patients were questioned for angina or SOB during the study period. Reralb: Data from 35 patients woe analyzed. The mean age was 73. Eleven of the patients had aortic reconstruction and 24 had lower extremity revascularizauon. Patients were monitored for a mean of 33.1 hours. Fifteen patients (43%) exhibited ischemia by continuous 12-lead, with no angina or SOB. 12- lead ECG + 12-lead ECG - Routine1 1 Routine - 14 19 The sensitivity of routine monitoring, compared to continuous 12-lead monitoring, is 6% (C.I. 0.4-34)'and the specificity is 95% (C.I. 78-100). Condufion: Postoperative myocardial ischémie events are asymptomatic and routine clinical and 2-lead ECG monitoring is insensitive for adequate surveillance. Further research is needed to determine whether real-time 12-lead ECG analysis could be performed on the ward with greater sensitivity and specificity and, at a reduced cost.