Wagner_Marriot's Practical Electrocardiography, 12e

F I G U R E 7 . 1 0 . Bundle of Kent general locations. 1, LA-LV free wall; 2, posterior septal; 3, RA-RV free wall, a combination of Milstein and colleagues’ right anteroseptal and right lateral locations. (Modified from Tonkin AM, Wagner GS, Gallagher JJ, et al. Initial forces of ventricular depolarization in the Wolff-Parkinson-White syndrome. Analysis based upon localization of the accessory pathway by epicardial mapping. Circulation. 1975;52:1030–1036, with permission.)

Although accessory pathways may be found anywhere in the connective tissue between the atria and ventricles, nearly all are found in three general locations, as follows:

1. Left laterally, between the left-atrial and left-ventricular free walls (50%). 2. Posteriorly, between the atrial and ventricular septa (30%). 3. Right laterally or anteriorly, between the right-atrial and right-ventricular free walls (20%). The three general locations are illustrated as a schematic view (from above) of a cross- section of the heart at the junction between the atria and the ventricles in Figure 7.10. The ventricular outflow aortic and pulmonary valves are located anteriorly, and the ventricular inflow mitral (bicuspid) and tricuspid valves are located posteriorly. Tonkin and associates 9 presented a simple method for localizing accessory pathways to one of the foregoing areas on the basis of the direction of the delta wave (Table 7.2). They considered a point 20 milliseconds after the onset of the delta wave in the QRS complex as their reference.

Tab l e 7 . 2 .

Consideration of Delta Wave at QRS Onset 0.02 s

Direction of Preexcitation

Location of Pathway

Incidence Correct

Rightward

LA-LV free wall Posterior septal RA-RV free wall

10 of 10

Leftward and superior Leftward and inferior

9 of 10

6 of 7

LA, left atrial; LV, left ventricular; RA, right atrial; RV, right ventricular.

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CHAPTER 7: Ventricular Preexcitation