Pharmacological observations in patients with nodoventricular pathways.

Abstract

suMMARY 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.One of the rare types of re-entrant paroxysmal tachycardia reflects the occurrence of re-entrance via nodoventricular fibres. In these unusual tachycardias anterograde conduction is usually via a right sided inserting nodoventricular pathway, producing a tachycardia resembling ventricular tachycardia with a left bundle branch block pattern.Nodoventricular pathways might respond with an increase in refractoriness to drugs which depress the atrioventricular node or quinidine like agents, or both. There are few systemic data concerning the pharmacology of nodoventricular fibres and circus movement tachycardias using these fibres.We report the drug responses, the electrophysiology of nodoventricular fibres as related to anterograde dual atrioventricular nodal pathways, and observations on the nature of retrograde conduction during nodoventricular circus movement tachycardia in three patients with re-entrant paroxysmal tachycardia. Case I A 20 year old man with a five year history of paroxysmal tachycardia and no evidence of organic heart disease was studied. Electrocardiograms during sinus rhythm were normal (Fig. 1). During episodes of tachycardia the electrocardiogram showed wide QRS complexes (0.12 s) with left bundle branch block morphology, an axis of -20", and a heart rate of 230 beats/min. ELECTROPHYSIOLOGICAL STUDIESElectrophysiological studies showed normal conduction intervals during sinus rhythm (AH: 70 msec, HV: 47 msec, QRS: 90 msec). With incremental atrial pacing from heart rates of 100 to 160 beats/min the AH interval gradually increased from 75 to 105 msec and concomitantly the HV interval gradually decreased from 30 to 10 msec with the appearance of partial pre-excitation. At atrial paced rates of 170 to 200 beats/min the His bundle electrogram merged into the QRS complex, which had a left bundle branch block appearance similar to his spontaneous tachycardia (Fig. 2). The time from stimulus to the onset of the QRS co...

Radiofrequency Catheter Ablation of Atriofascicular Accessory Pathways Guided by Discrete Electrical Potentials Recorded at the Tricuspid Annulus

“…The ablation procedure was repeated in this location and was successful. A mean of seven pulses (range [1][2][3][4][5][6][7][8][9][10][11][12][13][14] were delivered to successfully eliminate AFAP conduction. Patients 1, 2, and 3 showed right bundle branch block morphology on surface ECG after the successful pulse.…”

“…As described by Klein et al,'' three mapping techniques have been proposed: stimulation-todelta wave mapping; premature atriai stimulation during tachycardia from a catheter on the atriai side ofthe tricuspid annulus; and recording of discrete electrical potentials. They treated four patients (3 with AFAP and 1 with AVAP) using the first and second proposed methods and eliminated AFAP conduction after a mean of 15 radiofrequency pulses (range [10][11][12][13][14][15][16][17][18][19]. Using the third pro-…”