Dual accessory nodoventricular pathways: role in paroxysmal wide QRS reciprocating tachycardia.

Clinical electrophysiological study in an otherwise healthy 21-year-old male with paroxysmal wide QRS tachycardia (cycle length 300 ms, heart rate 200/min) suggested the presence of two nodoventricular (NV) bypass connections. The first NV connection pre-excited the base of the interventricular septum (NVs), as evidenced by a short HV interval during sinus rhythm (15-20 ms), with local ventricular activation occurring earlier at the septal base than at either the right ventricular apex or the base of the left ventricle. The second NV connection appeared to connect the AV junction with the right ventricle (NVRV). Intracardiac recordings from a portion of the right-bundle branch of the interventricular conduction system demonstrated right ventricular pre-excitation by NVRV during both atrial pacing and reciprocating tachycardia. The latter finding supported participation of NVRV in the tachycardia. Further, following exclusion of atrial participation in the arrhythmia, premature depolarization of the right ventricle and interventricular septum appeared to advance the tachycardia without altering the timing of His bundle depolarization, implicating NVS in the retrograde limb of a re-entry circuit. Consequently, this study demonstrated the presence of two NV connections and provided further support to the concept that NV accessory bypass connections may comprise portions of a re-entry pathway during reciprocating tachycardia in man.