Ability of standard ECG parameters to detect the body surface isopotential abnormalities of pacing induced myocardial ischemia in the dog.

The ability of parameters derived from standard, scalar ECG leads to predict abnormal body surface isopotential distributions was tested in 25 dogs. Atrial pacing to rates of 170 beats per minute or greater, two weeks after implantation of an ameroid constrictor on the left circumflex coronary artery, resulted in abnormal isopotential patterns due to subendocardial ischemia. A total of 96 scalar ECG variables (potential and slope measurements at 20, 40, 60 and 80 msec into the ST-segment in each of 12 leads) were computed. Ability of each variable and potential-slope pairs to distinguish normal from ischemic map forms was tested using discriminant function analysis and simple classification procedures. Results demonstrated that accuracy of prediction was lead-dependent, and time-dependent, with different sensitivities, specificities and boundary values in different leads and at different instants during the ST-segment. These new concepts may have direct relevance to the selection of clinical exercise ECG diagnostic criteria.