Detection of myocardial infarction in the presence of Wolff-Parkinson-White syndrome by QRST isoarea map in dogs. The possibility of detecting myocardial infarction (MI) in the presence of Wolff-Parkinson-White (WPW) syndrome by means of body surface QRST isoarea maps was studied in eight dogs. Eighty-seven body surface ECGs were recorded simultaneously. Recordings were taken during right atrial (RA) and right atrial and right ventricular (RA + RV) sequential pacing, which simulated WPW syndrome, during control periods and at 1-hour intervals for up to 5 hours after occlusion of the left anterior descending coronary artery. In ECGs during the RA drive, diagnostic findings of MI such as abnormal Q waves were observed but became obscure during the RA + RV drive. On the contrary, the QRST values over the anterior chest during both drives were positive soon after coronary occlusion, decreased gradually as time passed, and became abnormally negative after 5 hours. The QRST isoarea maps during RA and RA + RV pacing showed quite similar patterns and were highly correlated with each other throughout this study (r greater than 0.95). These findings demonstrate that localized abnormalities resulting from MI are evident in QRST isoarea maps even in the presence of preexcitation and fusion. 