Paroxysmal tachycardia with atrioventricular dissociation in a patient with a variant of pre-excitation syndrome

Wide QRS supraventricular tachycardia due to coexisting Mahaim and Kent pathways

In two patients with Wolff-Parkinson-White syndrome, we observed the unusual coexistence of functional Mahaim and accessory atrioventricular pathways. In the first patient, three types of reciprocating tachycardia were demonstrable: (1) anterograde conduction over the atrioventricular (AV) node with right bundle branch block (RBBB) and retrograde conduction via a right-sided atrioventricular accessory pathway; (2) anterograde conduction through the AV node with RBBB and retrograde conduction via two (right-sided and septal) anomalous pathways; and (3) anterograde conduction through nodoventricular fibers and retrograde conduction over a right-sided accessory pathway. In the second patient the reentry circuit was comprised of AV node fasciculoventricular fiber in an anterograde direction and a right-sided accessory pathway in a retrograde direction. We believe this to be the first report of triple accessory pathways, consisting of two atrioventricular and one nodoventricular connection, demonstrated by intracardiac electrophysiologic study.

Surface electrocardiographic clues suggesting presence of a nodofascicular Mahaim fiber

Standard electrocardiograms from 87 consecutive patients with tachycardia of left bundle branch block configuration were analyzed retrospectively for features that might be characteristic of tachycardia utilizing a nodofascicular Mahaim fiber. The study group consisted of 13 patients with nodofascicular tachycardia, 34 with supraventricular tachycardia and aberrant conduction over the His-Purkinje system, 22 with ventricular tachycardia and 18 with antidromic tachycardia utilizing a right-sided accessory atrioventricular pathway. Six variables present during tachycardia of left bundle branch block configuration were predictive of a nodofascicular fiber: cycle length between 220 and 450 ms, QRS axis of 0 to -75 degrees, QRS duration 0.15 second or less, R wave in lead I, rS wave in precordial lead V1 and a precordial transition from a negative to a positive QRS complex after lead V4. All six criteria were present in 16 of the 87 patients. No patient with ventricular tachycardia satisfied these criteria, whereas 3 of 34 with supraventricular tachycardia, 1 of 18 with antidromic tachycardia and 12 of 13 with tachycardia using a nodofascicular fiber did. It is concluded that analysis of the surface electrocardiogram during tachycardia may suggest the presence of a nodofascicular fiber.

Pharmacological observations in patients with nodoventricular pathways

Three patients with accessory nodoventricular pathways and re-entry tachycardia are reported. In all three patients the accessory nodoventricular pathway formed the anterograde limb of the re-entry circuit while the His-Purkinje-atrioventricular node axis formed the retrograde limb of the tachycardia in two of the patients and a concealed accessory pathway formed the retrograde limb in the remaining patient. All three patients also manifested dual anterograde atrioventricular nodal pathways with conduction through the accessory nodoventricular pathways being associated with the atrioventricular nodal fast pathway. Type I antiarrhythmic drugs, especially disopyramide and quinidine, were effective for the treatment of the re-entry tachycardia because of their depressive action on the nodoventricular pathway. Beta blockers were also effective because of their action on the atrioventricular nodal portion of the re-entry circuit in one patient and most probably due to atypical (atrioventricular nodal like) properties of a retrogradely conducting accessory pathway in a second patient.

Quintuple pathways participating in three distinct types of atrioventricular reciprocating tachycardia in a patient with Wolff-Parkinson-White syndrome

Electrophysiologic studies were performed in a patient with recurrent supraventricular tachyarrhythmias. Sinus and paced atrial beats had QRS complexes characteristic of atrioventricular (A-V) conduction through a manifest left lateral accessory pathway (Wolff-Parkinson-White syndrome, type A). Three distinct types of A-V reciprocating tachycardia and three different modes of retrograde atrial activation were demonstrated. Type 1 tachycardia involved the slow A-V nodal pathway and a second (left lateral or left paraseptal) accessory A-V pathway capable of retrograde conduction only. Type 2 tachycardia was of the slow-fast A-V nodal pathway type. Type 3 tachycardia involved in heretofore undescribed circuit in that retrograde conduction occurred through an accessory A-V pathway with long retrograde conduction times and anterograde conduction through both the manifest left lateral accessory A-V pathway and fast A-V nodal pathway. Premature ventricular beats delivered late in the cycle of this tachycardia advanced (but did not change) the retrograde atrial activity without affecting the timing of the corresponding anterograde H deflection. In summary, this patient had five (three accessory and two intranodal) pathways participating in three different types of A-V reciprocating tachycardia; the recurrence of these were prevented with oral amiodarone therapy.

Termination of ventricular tachycardia by carotid sinus massage

Intracardiac electrophysiologic studies were performed in two patients who had recurrent sustained ventricular tachycardia. In both, the tachycardia was repeatedly terminated by carotid massage. In one patient, intracardiac electrophysiologic studies revealed ventricular tachycardia with 2:1 retrograde ventriculoatrial (VA) block. Carotid massage resulted in alternate Wenckebach retrograde VA conduction terminated by ventricular echo beats. When ventricular echo beats occurred at a coupling interval of 340 - 400 msec, the tachycardia was terminated. Similarly, induced atrial depolarizations (during ventricular tachycardia) produced ventricular capture and terminated the tachycardia when the resultant ventricular coupling interval was 330 - 395 msec. In the second patient, progressively premature atrial or ventricular depolarizations did not terminate the tachycardia. carotid massage had no consistent effect on retrograde VA conduction during ventricular tachycardia, but usually resulted in gradual increases in the tachycardia cycle length (50 - 100 msec) before abrupt termination of the tachycardia. This is the first report documenting termination of ventricular tachycardia by carotid massage alone (i.e., without prior drug intervention); hence, tachycardia termination by simple carotid sinus massage does not prove a supraventricular origin. The mechanism of tachycardia termination was due to ventricular echo beats from retrograde atrioventricular nodal reentry in one patient and to direct vagal effects on either the ventricular muscle or the ventricular specialized conduction system in the other.

His-ventricular dissociation in a patient with reciprocating tachycardia and a nodoventricular bypass tract

A patient with recurrent bouts of atrial fibrillation and wide-complex regular tachycardia underwent electrophysiologic studies. Premature atrial stimulation or atrial pacing during sinus rhythm resulted in gradual lengthening of the PR and AH intervals, narrowing of the HV interval and progressive preexcitation with a left bundle branch block and left-axis contour. Induction of tachycardia was dependent on critical delay in the atrioventricular interval and was associated with attainment of a maximal preexcitation pattern. During tachycardia, the ventriculoatrial interval was constant, whereas the interval from His bundle deflection to the ventricular complex was variable. We postulate that the tachycardia circuit involved reciprocation within the atrioventricular node and that a nodoventricular bypass tract was present in close anatomic or functional association with the slow atrioventricular nodal pathway. Our data suggest that both the nodoventricular bypass tract and the His-Purkinje system may be passive "bystanders" rather than essential components of the tachycardia circuit. In addition, although HV dissociation usually implies ventricular tachycardia, this case demonstrates that HV dissociation during wide-complex regular tachyarrhythmia is not diagnostic of ventricular tachycardia.

Role of Mahaim fibers in cardiac arrhythmias in man

Twelve patients with evidence of Mahaim fibers are reported, six with nodoventricular (NV) fibers and six with fasciculoventricular (FV) fibers. All patients with NV fibers had left bundle branch block morphology, and a sustained reentrant tachycardia with this morphology was proved in each case. In three of the six, ventriculoatrial dissociation occurred during tachycardia. We postulate that the mechanism of this tachycardia is a macroreentry circuit using the NV fiber for the antegrade limb and the His-Purkinje system with a portion of the atrioventricular node for the retrograde limb. ECGs of patients with FV fibers were varied, suggesting a functional relation to the right or left side of the septum. No direct relationship of FV fibers to observed arrhythmias could be found.