Small differences among body surface and epicardial QRST integral maps recorded during normal activation and experimentally simulated left bundle branch block or preexcitation in canine hearts.
QRST integral maps were constructed from 87-lead body surface electrocardiograms (ECGs) and from 45-lead epicardial electrograms during artificial pacing, which simulated left bundle branch block (LBBB) and Wolff-Parkinson-White syndrome in 12 dogs. Although the ECGs and electrograms differed in configuration for each conduction model, the body surface and the epicardial QRST integral maps showed only small differences. Correlation coefficients (r) and root mean square differences (rms) were calculated to assess quantitatively the similarities in the QRST integral maps among the different conduction models. Mean r values between the normal conduction and the left bundle branch block models were 0.95 in the body surface maps and 0.89 in the epicardial maps. Mean r values between the normal conduction and the Wolff-Parkinson-White ECG models were 0.97 in the body surface maps and 0.91 in the epicardial maps, and rms values were small enough. The small differences were also verified by the difference maps and by paired t tests. QRST integral maps on the epicardium and on the body surface were largely independent of altered activation sequences in both the left bundle branch block and the Wolff-Parkinson-White ECG models.