Objective: To determine if the ST-segment monitoring software of a bedside electrocardiograph (ECG) monitor would detect postoperative myocardial ischemia (POMI) as reliably as the clinical gold standard 12-lead ECG, and to compare the characteristics of ischemia thus detected with prior studies performed using Holter monitoring.
Design: Prospective study.
Setting: University hospital.
Participants: One hundred patients who had undergone coronary artery bypass grafting (CABG).
Interventions: Continuous ST-segment trends in leads II and V5 were recorded using Hewlett-Packard Merlin monitors postbypass until discharge from the postsurgical unit, and printouts were analyzed for episodes of ischemia. Simultaneous 12-lead ECGs and monitor strips were recorded during ischemic episodes in 24 patients and were independently analyzed by two blinded cardiologists quantitatively for ST-segment values and qualitatively for an overall ischemia rating.
Measurements and main results: The ST-segment values directly measured by the cardiologists on the simultaneous 12-lead ECGs and those recorded by the monitor during ischemic episodes were found to be clinically comparable (bias, 0.1 mm for both leads; precision, 0.5 mm lead II, 0.9 mm lead V5). The sensitivity of the monitor compared with 12-lead ECGs for the detection of POMI was 73%. Ninety-eight episodes of significant ST deviation were identified in 39 patients. The characteristics of the ischemia detected in this study were similar to those reported in other studies performed using continuous Holter-type monitoring.
Conclusion: Bedside monitoring of the ST segment in leads II and V5 using Hewlett-Packard Merlin monitors after CABG surgery is as accurate for the measurement of ST deviation in those leads as the clinical gold standard of a 12-lead ECG read by an experienced cardiologist. However, the 12-lead ECG will detect POMI more reliably than an automated two-lead bedside ST-segment analyzer because it allows evaluation of more leads and of ST-segment and T-wave morphology. Bedside ST-segment monitoring in this study confirmed the high incidence of ischemia after CABG surgery shown previously using Holter monitoring.