A clinicopathologic study of the accessory bypass tracts in six cases of Wolff-Parkinson-White syndrome.

A clinical and histologic correlation study was conducted to examine the accessory bypass tracts in 6 cases of Wolff-Parkinson-White syndrome. (1) Types A, B (Rosenbaum) and C (Ueda) were found in 2 cases each. From the polarity of the delta waves, the site of the bypass tract was assumed to be in the left posterior and left lateral free wall in type A, the right lateral and right posterior paraseptal regions in type B and in the right posterior paraseptal and right anterior paraseptal areas in type C. (2) In 6 cases 19 bypass tracts were found, consisting of 18 Kent bundles and 1 Mahaim fiber, from a total of 146,400 serial sections. The site of the bypass tract was the left lateral and left posterior walls in 2 type A cases, and the right lateral and right posterior walls in 2 type B cases, with good correspondence to our assumption. In both type C cases it was biventricular, composed of left posterior paraseptal and right lateral regions with an additional Mahaim fiber in 1 case. (3) A total of 46 cases of WPW syndrome were collected from the literature and the present paper; they consisted of 16 cases of type A, 20 of type B, 4 of type A + B and 6 of type C. Seventy % of type A cases showed a bypass tract in the left heart, and 64% of type B in the right heart. In 6 cases of type C, the bypass tract was found in various sites and in various combinations, requiring further investigation.