Telemetry ECG monitoring during cardiac rehabilitation to detect myocardial ischemia

Abstract

Historically, telemetric ECG monitoring (TELE) has been thought to be incapable of detecting ST-segment changes during exercise. One hundred and nine patients underwent a diagnostic exercise test. A 12-lead ECG (12L) and TELE (modified Lead 11) were recorded simultaneously throughout the exercise test. A total of 1041 temporally correlated tracings were blinded, then interpreted by a cardiologist. ST depression was defined as >_ lmm horizontal or downsloping at .08 mm from the J point in 2 or more adjacent leads. One hundred and twenty-nine tracings (in 36 patients) were positive for ST depression on 12L. Corresponding changes (same time and lead group) were seen on TELE 61% (79/129) of the time. In normal 12L tracings, there were 29 ST abnormalities observed in TELE (e.g. false positive). When changes were observed on TELE, corresponding changes were observed on 12L 73% (79/108) of the time. TELE matched 12L in magnitude of ST depression within +/- 0.5 mm 54% of the time. In conclusion, TELE missed ST changes seen on 12L 39% of the time, and does not appear to be a sensitive marker of ischemia. However, when changes are seen on TELE, they indicate that ischemia may be present in a high percentage (73%) and should be taken seriously.