Accessory atrioventricular node with properties of a typical accessory pathway: Anatomic-electrophysiologic correlation

We report an accessory AV node producing ventricular preexcitation and comp rising the retrograde limb of AV reentrant tachycardia (AVRT), A 66-year-ol d man presented with an anteroseptal myocardial infarction and thereafter d eveloped recurrent, drug-refractory AVRT requiring multiple cardioversions. Electrophysiologic findings were typical for a concealed anteroseptal acce ssory pathway 0.5 cm anterior to the His bundle. The patient died of intrac table heart failure after endocardial resection for a left ventricular aneu rysm and coronary bypass grafting. Pathologic examination revealed a para-H isian accessory AV node connecting the right atrium to ventricular myocardi um immediately anterior to the His bundle at a depth of 4 mm from the endoc ardium. No typical AV accessory pathway was found. This is the first report of an accessory AV node that participated in AVRT. It was deeper than typi cal radiofrequency catheter ablation lesions.