Facebook
Twitter
LinkedIn
Email
 |
Checking for direct PDF access through Ovid | |
Excerpt
Departments of Anaesthesiology and Critical Care Medicine, Cardiology, and Vascular Surgery, Hadassah University Hospital, Jerusalem, Israel
Anesthesiology, 96: 264–270, 2002
Usually perioperative myocardial ischemia is monitored using five ECG leads, with only one precordial lead placed at V5. This convention was reassessed by analyzing data obtained from continuous on-line 12-lead ECG monitoring in 185 consecutive patients undergoing vascular surgery.
Patients were monitored by continuous 12-lead ST-trend analysis during and for 48 to 72 hr after surgery. Cardiac troponin I was measured in the first 3 postoperative days. Cardiac outcome was prospectively recorded. Ischemia was defined as ST deviation, relative to the reference preanesthesia ECG, of 0.2 mV or more in one lead or 0.1 mV or more in two contiguous leads, lasting >10 min.
During 11,132 patient-hours of monitoring, 38 patients had 66 ischemic episodes with all but one denoted by ST-segment depression. The duration of all patients’ longest ischemic event was 96 ± 127 min. Twelve patients had a myocardial infarction defined as cardiac troponin I of 3.1 ng/mL or more. All of them were non-Q type and were detected either during or within 18 hr from a prolonged, transient ST-segment depression. Of the 38 patients with ischemia, lead V3 (86.8%) most frequently demonstrated ischemia, followed by V4 (78.9%) and V5 (75%). Combining two precordial leads increased the sensitivity for detecting ischemia (97.4% for V3 plus V5 and 92.1% for either V4 plus V5 or V3 plus V4) and infarction (100% for V4 plus V5 or V3 plus V5 and 83.3% for V3 plus V4). On average, baseline preanesthesia ST was above isoelectric in V1 through V3 and below isoelectric in V5 through V6. Lead V4 was closest to the isoelectric level on the baseline ECG, rendering it most suitable for ischemia monitoring.
There was strong positive correlation among the chest leads and between the chest and the inferior and lateral leads in ST-segment depression during ischemia. Negative correlation in ST deviation occurred between the inferior and lateral leads, probably reflecting reciprocal ST changes.
As a single lead, V4 is more sensitive and appropriate than V5 for detecting prolonged postoperative ischemia and infarction. More than one precordial lead is necessary to approach a sensitivity >95% in detecting postoperative ischemia and infarction. If only one precordial lead is available, the ECG lead with the most isoelectric ST level of leads V3, V4, and V5 on the preoperative ECG is recommended for monitoring of ischemia.
