On line ST-segment analysis for detection of myocardial ischaemia during and after coronary revascularization

Purpose

A paucity of information exists to validate the accuracy and reliability of ECG monitoring in the operating room or ICU. The purpose of this study was to determine the accuracy, sensitivity, specificity, and predictive values of the Marquette ECG monitor for detection of perioperative myocardial ischaemia (PMI) as measured by ST segment changes in a high risk population.

Methods

Monitoring for PMI in 28 patients scheduled for aortocoronary bypass surgery was done with the Cardiodata PR® ambulatory continuous electrocardiography (ACECG) monitor lead V₅, and compared with lead V₅ of the Marquette® Series 7000 ECG/ Surgical operating room monitor, and ECG/Resp ICU monitor. The Marquette lead V₅ was evaluated using current criteria for the assessment of diagnostic tests including concordance, sensitivity, specificity, positive and negative predictive values, false positive and false negative rates and compared with the ACECG monitor which served as the reference or “gold standard.” Agreement beyond chance between the two methods was assessed using the Kappa statistic.

Results

Of the 53 observation data points, 27 were defined as ischaemic episodes by ACECG. Concordance between lead V₅ in each system was 83% (44/53 episodes). Discordance was 17% (9/53 episodes), predominantly in the postbypass interval (77%, 7/9; P = 0.0184). The incidences of false negatives and false positives for Marquette lead V₅ was 26% (7/27) and 7.7% ( 2/26), respectively. The sensitivity and specificity of the Marquette was 0.74 and 0.92. Positive predictive value was 0.91, negative predictive value was 0.77, and Kappa statistic was 66%.

Conclusion

Automated ST segment analysis with the Marquette® Series 7000 monitoring system demonstrates good diagnostic accuracy, moderate sensitivity, and high specificity. However, clinically significant false negative and false positive rates of ischaemia detection are associated with its use, especially in the postoperative period.