EPICARDIAL MAPPING IN PATIENTS WITH NODOVENTRICULAR ACCESSORY PATHWAYS

Some patients with electrophysiologic features suggesting nodoventricular fibers have been shown to have right parietal atrioventricular (AV) accessory pathways with decremental conduction properties intraoperatively. The experience with 11 patients (7 women and 4 men, mean age +/- standard deviation 25 +/- 5 years) who had electrophysiologic features consistent with a nodoventricular pathway and who underwent operative correction was reviewed. At electrophysiologic study, all patients had absent or minimal preexcitation in sinus rhythm. During atrial pacing and extrastimulus testing, maximal preexcitation with left bundle branch block morphology developed and the AH and AV intervals progressively prolonged. Preexcited tachycardia was initiated in all patients (AV reentrant tachycardia in 10 patients and AV node reentrant tachycardia in 1 patient). At operation all patients had a right parietal accessory pathway demonstrated. Intraoperative mapping demonstrated the earliest site of ventricular activation during anterograde preexcitation to be at the midanterior right ventricle, consistent with insertion of these pathways into the right bundle branch system, in 7 patients. The ventricular insertion was at the AV groove in 4 patients, in keeping with the typical Wolff-Parkinson-White syndrome. Retrograde conduction over the pathway was not demonstrated in any patient. Two patients had evidence of a second accessory AV pathway in the left paraseptal region. Operative AV node ablation was electively performed in 2 patients without affecting preexcitation in either case. In 1 of these patients, accessory pathway conduction was temporarily abolished by ice mapping in the right anterolateral AV groove. In the remaining 9 patients the accessory pathway was permanently ablated in the right anterolateral AV groove. Three patients underwent operative dissection of the AV node as a concomitant procedure to prevent AV node reentrant tachycardia. All patients in this study with an electrophysiologic presentation suggesting a nodoventricular pathway were found to have a right AV pathway with decremental properties mimicking a nodoventricular pathway. Epicardial activation during anterograde preexcitation suggested ventricular insertion at the base of the heart as for typical AV pathways or insertion in the right bundle branch system.