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The purpose of this study was to determine if the electrophysiologic properties and the anatomic location of manifest accessory pathways affect the local electrogram intervals recorded at sites of successful radiofrequency ablation. Accessory pathways in 149 consecutive patients were categorized according to their anatomic location on the basis of the site of successful ablation. Three anatomic groups comprised 90 left free wall, 28 right free wall, and 31 posteroseptal pathways. The accessory pathways were also categorized according to their electrophysiologic properties on the basis of a hierarchical classification of the accessory pathway block cycle length. Four electrophysiologic groups (A, B, C, and D) comprised 54, 51, 28, and 16 accessory pathways, with mean accessory pathway block cycle lengths of 254 +/- 9, 288 +/- 10, 347 +/- 19, and 458 +/- 56 msec, respectively. The local atrial to ventricular (A-V) and atrial to accessory (A-K) pathway electrogram intervals recorded in sinus rhythm at the successful ablation site were significantly affected by the electrophysiologic group and were longest in group D compared with groups A, B, and C (A-V interval F(3,145) = 13.6, p < 0.001; A-K interval F(3,88) = 12.6, p < 0.001). The local A-V interval was also affected by the anatomic group and was longer in posteroseptal compared with free wall accessory pathways (F(2,146) = 15.0, p < 0.001). In contrast, the timing of the local ventricular activation to the delta wave onset (delta-V) was not significantly affected by the electrophysiologic group or the anatomic location of the accessory pathway. Thus the local A-V interval at the successful ablation site may vary because it is affected by the electrophysiologic properties and location of the accessory pathway, whereas the delta-V interval remains unaffected. These effects should be taken into account when selecting ablation sites in patients with manifest accessory pathways.

Previous descriptions of the four anatomic regions of dissection in Wolff-Parkinson-White syndrome have been largely qualitative. In this study quantitative data describing this anatomy are presented, together with statistical analysis of selected anatomic relationships. Fourteen human hearts were dissected. The borders of the posteroseptal dissection along the mitral anulus, tricuspid anulus, and epicardium were measured. A positive correlation between the mitral and tricuspid annular dimensions was found (r = 0.55; p = 0.04); however, the length of epicardial dissection was more variable. The dimensions of the anteroseptal space and the position of the right coronary artery within this space were measured. These measurements emphasize the proximity of the aortic sinuses of Valsalva to the right atrial endocardium near the posteromedial extent of the dissection. The dimensions of the right and left free walls and the position of the coronary arteries within these spaces were measured. A positive correlation was found between the width of the atrioventricular groove and the length of the dissection necessary to separate the atrioventricular groove fat from the ventricular surface (r = 0.89; p = 0.0001, right free wall; r = 0.87; p = 0.0001, left free wall). The quantitative data presented in this article are intended to enhance the surgeon's appreciation of the anatomy relevant to the treatment of Wolff-Parkinson-White syndrome. The knowledge gained from this quantitative analysis may improve accuracy in the electrophysiologic localization and surgical disruption of accessory atrioventricular connections.

A new method for vital staining of the conduction system during heart operations, the iodine gas method, was used in 12 patients. The right bundle branch stained well in all cases, and could be confirmed by the naked eye. The conduction system was not damaged by the staining procedure. The iodine gas used in this method had no adverse effects on thyroid function (thyroxine, triiodothyronine, thyroxine binding globulin, protein bound iodine) or liver function (serum glutamate oxaloacetate transaminase, serum glutamate pyruvate transaminase, lactic dehydrogenase). This method, therefore, was found to be valuable and without complication for preventing conduction disturbances during cardiac operations.

There is a widely recognized relationship between the atrioventricular conduction bundle and the margins of the ventricular septal defects according to whether the defect is perimembranous or muscular. We have shown that this relationship may in turn be markedly influenced by the precise topography of the trabecula septomarginalis. Fifteen hearts, each with a ventricular septal defect, were studied by serial sectioning. Four hearts had an isolated ventricular septal defect in the setting of normal chamber connections and relations. One heart had a truncus arteriosus, seven hearts had Fallot's tetralogy, and three hearts exhibited complete transposition. In those hearts with outlet defects in which a bar of muscle separated the rim of the defect from the position of the conduction bundle, deficiency of the posterior limb of the trabecula septomarginalis permitted the right-sided margin of the conduction axis to "surface" in directly subendocardial position. Moreover, in some of these outlet defects, the conduction axis in the region of the branching bundle was exposed directly upon the crest of the muscular septum. The position of the medial papillary muscle complex was the best landmark to this potential danger area. In some of the examples of Fallot's tetralogy, we observed a firm muscle bar overlying the posteroinferior margin of the defect, which nonetheless was perimembranous. This protected the nonbranching component of the conduction axis in the anticipated danger area. Paradoxically, a deficiency in the trabecula septomarginatis then permitted the branching bundle to sit directly astride the septum along the inferior rim of the defect. We noted particularly marked variability of the atrioventricular conduction axis among the hearts with tetralogy. Our results suggest that close inspection during the operation may reveal whether or not a well-developed trabecula septomarginalis is present and permit conclusions to be drawn concerning the precise position of the atrioventricular conduction axis.

The development of the procedure for interruption of a Kent bundle for the correction of the tachyarrhythmias associated with the Wolff-Parkinson-White syndrome has been hampered by the lack of anatomic descriptions of the pathways. Only 21 descriptions are given in enough detail for guidance to the surgeon. Our experience with our first 100 patients operated upon for serious dysrhythmias associated with Kent bundles has supplemented this information. In our first 40 patients the Kent was divided in 22 of 39, one having elective and four having forced interruption of the His bundle, with success in 28. In the next 60 the Kent was divided in 52 of 59 attempts, one had elective and three had forced His bundle interruption, and the success rate was 56 of 60 patients. This increased success occurred because we learned the following: (1) The anomalous pathways are best approached through the atrium and can be for out in the fat, even subepicardial in the coronary sulcus or adjacent to the anulus. (2) Interruption should be started with an incision made just above the anulus fibrosus. (3) Posterior septal pathways can be adjacent to the His bundle or in the septum from this point posteriorly to the crux. (4) Anterior septal pathways can be divided and the His bundle protected. The details for the approach to the right and left free wall, posterior septal, and anterior septal pathways will be given. The approach to all pathways is now safe enough to allow the surgeon to offer this operation to patients with life-threatening tachyarrhythmias as well as the ones with rhythm disturbances that are either burdensome or impossible to treat medically.