AUTOMATED ELECTROCARDIOGRAPH ST SEGMENT TRENDING MONITORS - ACCURACY IN DETECTING MYOCARDIAL-ISCHEMIA

Continuous automated ST segment trending devices (ST trending monitors ) are included in most new operating room electrocardiography (ECG) mo nitors to facilitate ischemia detection, but their efficacy is not wel l validated. Therefore, we compared their accuracy with that of Holter ECG recorders in detecting ST segment changes (both analyzed offline) in 94 patients undergoing coronary artery bypass graft surgery. Holte r ECG tapes were analyzed using standard criteria for determining ECG ischemic episodes, which were compared with those measured by the ST t rending monitors. Overall, 42 ischemic episodes were detected by using the Holter monitor in 30 patients. Of the 42 episodes, 38 (90%) were also detected by the ST trending monitors. Sixteen episodes of ST segm ent deviation were detected by the ST trending monitors, but not by th e Holter. The sensitivity of the three ST trending monitors in detecti ng ischemia was 75%, 78%, and 60% for the Marquette (Milwaukee, WI), H ewlett Packard (Andover, MA), and Datex (Helsinki, Finland) monitors, respectively, with a specificity of 89%, 71%, and 69% relative to the Holter. Compared with the HP and Datex monitors, the Marquette monitor has the best agreement with the Holter (K 0.64). Conditions in which ST trending monitors may be inaccurate were identified and included th e appearance of small R-wave amplitude, drifting base-line, and during periods of conduction abnormalities and pacing. We conclude that ST t rending monitors have only moderate sensitivity and specificity (<75% overall) in accurately detecting ECG ST segment changes compared with Holter ECG recordings. Therefore, sole reliance on ST trending monitor s for the detection of myocardial ischemia may be insufficient. Implic ations: Using Holter recordings as the reference standard for detectio n of intraoperative ischemia, ST trending monitors were found to have overall sensitivity and specificity of 74% and 73%, respectively. Seve ral conditions contribute to the inaccuracy of ST trend monitoring, an d additional modification of their performance is necessary to achieve better agreement with the Holter analysis.