Wolff-Parkinson-White syndrome. Alterations in electrophysiologic characteristics of the bypass tract secondary to ischemia.

Accurate electrocardiographic diagnosis of myocardial ischemia or infarction is difficult in patients with the Wolff-Parkinson-White syndrome; however, myocardial ischemia may also have profound effects on the electrophysiologic characteristics of the bypass tract in these patients. Comparison of studies performed during and two months following an episode of significant myocardial ischemia demonstrated substantial prolongation of the refractoriness of the bypass tract during the period of ischemia. Bypass refractoriness was prolonged by 196 msec, yet atrioventricular nodal refractoriness was not significantly different from normal. These studies, therefore, suggest that, on occasion, the presence of acute myocardial ischemia may, in fact, obscure the electrocardiographic diagnosis of the Wolff-Parkinson-White syndrome.