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Perioperative myocardial ischemia: importance of the preoperative ischemic pattern
A A Knight1, M Hollenberg, M J London
1Department of Anesthesia, University of California, San Francisco 94121.
Insights
Preoperative myocardial ischemia occurred in 42% of patients before coronary-artery bypass grafting (CABG) surgery. Postoperative ischemia incidence rose to 40%, with longer episodes, highlighting the need to consider preoperative patterns in CABG patients.
Area of Science:
- Cardiology
- Cardiac Surgery
- Clinical Monitoring
Background:
- Previous studies on myocardial ischemia during coronary-artery bypass grafting (CABG) have overlooked preoperative ischemic patterns.
- Understanding these patterns is crucial for predicting intra- and postoperative ischemia and infarction.
Purpose of the Study:
- To compare the frequency and severity of ischemic episodes before, during, and after CABG surgery.
- To investigate the relationship between preoperative ischemia and perioperative events.
Main Methods:
- Continuous electrocardiography (ECG) monitoring (Holter) for 50 male patients with severe coronary artery disease undergoing elective CABG.
- Monitoring included 2 preoperative days, intraoperative period, and 2 postoperative days (totaling 4,363 hours).
- Ischemic episodes defined as ST-segment depression ≥0.1 mV or elevation ≥0.2 mV.
Main Results:
- 42% of patients experienced preoperative ECG ischemic episodes, with 87% being clinically silent.
- Intraoperative ischemia occurred in 18% of patients, while postoperative incidence increased to 40%.
- Ischemic episode frequency per hour was similar across all periods; however, postoperative episodes were significantly longer (41 min vs. 16-18.5 min).
Conclusions:
- A significant portion of patients exhibit preoperative myocardial ischemia before CABG, often asymptomatic.
- Postoperative ischemia is common and prolonged, suggesting a link to preoperative conditions.
- The study underscores the importance of assessing preoperative ischemic patterns for better patient management during and after CABG.
Abstract:
Previous studies investigating the incidence of myocardial ischemia in patients undergoing coronary-artery bypass grafting (CABG) surgery have not considered the potential significance of the preoperative ischemic pattern in the development of intra- and postoperative myocardial ischemia and infarction. Accordingly, the authors compared the frequency and severity of pre-, intra-, and postoperative ischemic episodes (ST-segment depression greater than or equal to 0.1 mV or elevation greater than or equal to 0.2 mV) in 50 men with severe coronary artery disease scheduled for elective CABG. All subjects were monitored by continuous electrocardiography (ECG) (Holter monitor) for 2 preoperative days, intraoperatively, and 2 postoperative days (total monitoring time = 4,363 h). Routine anti-anginal medications were continued until the morning of surgery, and the anesthetic management of the patient was not controlled. During the preoperative period, 42% of the patients had ECG ischemic episodes, 87% of which were clinically silent. Only 18% developed intraoperative ischemia. Postoperatively, the incidence increased to 40%. The number of ischemic episodes/hour (epis/h) of monitoring among the three monitoring periods was similar (0.09 +/- 0.12 epis/h preoperatively, 0.11 +/- 0.20 epis/h intraoperatively, and 0.05 +/- 0.08 epis/h postoperatively; P = NS). The median duration of ischemic episodes was similar pre- and intraoperatively (16 vs. 18.5 min, P = NS), but greater postoperatively (41 min, P less than 0.05). Seventy-six per cent of the perioperative ECG ischemia occurred without acute change (+/- 20% of control) in blood pressure or heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)