Digital assessment of the epicardial electrocardiogram: novel methodology for a core laboratory for clinical studies

The epicardial electrocardiogram (ECG) is a sensitive marker for cardiac ischemia and has been used as a measure of ischemia in clinical trials. We sought to examine the utility of a central ECG laboratory for determining ischemic-type ST-segment shifts from epicardial ECG recordings obtained from multiple clinical sites.

We speculated that an operator-assisted digital ECG core laboratory is feasible, reliable, and efficient, with the ability for rapid and accurate interpretation of the epicardial ECG.

The epicardial ECG was recorded via an angioplasty guidewire placed in a coronary artery of a patient undergoing angioplasty. Site investigators visually determined the time-to-onset of 0.1 and 0.3 mm ST-segment elevation, and the maximal ST-segment elevation during balloon inflation, and then compared the measurements with those made at an operator-assisted digital ECG core laboratory.

Agreement between the two methods occurred in 78% of the time-to-onset measurements, but in only 39% of the maximal ST-segment measurements. Overall, the visual measurements of the clinical investigators of time-to-onset differed from the digital core laboratory by 11.8 +/- 11.6 s for 0.1 mV, and 15.8 +/- 20.6 s for 0.3 mV. Recorded maximal ST-segment shifts differed by a mean of 0.47 +/- 0.69 mV.

The magnitude of inconsistency between the ECG core laboratory results using an operator-assisted digital method and the interpretations of clinical investigators using manual caliper-type analysis was surprisingly large. These results support the need for an ECG core laboratory in clinical trials where ECG ST-segment shifts are used as a response variable.