New Electrophysiologic Features and Catheter Ablation of Atrioventricular and Atriofascicular Accessory Pathways:

Abstract

The identification of Mahaim spiked potentials may be the optimal method to permit their successful ablation. Detailed electrophysiologic assessment is indispensable for successful ablation of tachycardias associated with Mahaim fibers because tachycardias unassociated with Mahaim fibers can occur despite complete elimination of the Mahaim fiber.

Catheter ablation of atriofascicular Mahaim fibers guided by the activation potential

“…Ablation was successful in all patients, with a mean of 15 radiofrequency applications. The elevated number of applications reported in this and other series 13 suggests that the technique, although effective, may be imprecise in locating the exact atrial insertion of the fiber. On the other hand, the release of extrastimuli in tachycardia has been considered more technically difficult and time-consuming, and no consistent results have been reported in the medical literature so far 9,14 .…”

“…With the evolution of electrophysiology, more satisfactory results were obtained, aiming at the ablation of the atrial insertion of these fibers [9][10][11][12][13] . Because its distal insertion is not located adjacent to the tricuspid ring, as with the accessory atrioventricular pathways (Wolff-ParkinsonWhite syndrome), mapping the earliest ventricular activation in regard to QRS is useless in these cases.…”

“…In addition, because these fibers do not have retrograde conduction, mapping the ventriculoatrial conduction is not possible. Therefore, the following special techniques for mapping these fibers were reported: 1) mapping atrial extrastimuli along the tricuspid ring to identify the shortest spike-Delta interval (pace-mapping); 2) release of extrastimuli along the tricuspid ring during antidromic tachycardia searching for the point of the greatest "advancement" (preexcitation) of the subsequent QRS; and 3) mapping the fiber activation potential in sinus rhythm [9][10][11][12][13][14] . Klein et al 9 reported on 4 patients who underwent ablation with pace-mapping in the atrium.…”

“…The criteria for the diagnosis of Mahaim fiber were as follows: absence of ventricular preexcitation in sinus rhythm or discrete preexcitation with left bundle-branch block morphology; presence of progressive ventricular preexcitation during continuous atrial stimulation associated with an increase in the A-V interval and a reduction in the H-V interval; induction of antidromic atrioventricular tachycardia with left bundle-branch block morphology, this morphology being similar to that of maximum preexcitation 9,10,[11][12][13][14][15][16] . Bardy et al 17 described typical Mahaim tachycardia as follows: 1) left bundle-branch block morphology; 2) QRS axis superior to or between 0º and 75º; 3) presence of R wave in D1; 4) presence of rS in V1; and 5) QRS transition in V4 or after V4.…”

“…Recently, most of these pathways have been classified as atriofascicular fibers that connect the right atrium to distal portions of the right branch of the His bundle with decremental properties 7,8 . Because they have different anatomical and electrophysiological characteristics, the following special ablation techniques have been considered: 1) atrial stimulation (pace-mapping) along the tricuspid ring, looking for the shortest "spike-Delta" interval 9 ; 2) mapping with extrastimuli during antidromic tachycardia, searching for the point of greatest "preexcitation" of the subsequent QRS; and 3) mapping of the activation potential of the fiber in sinus rhythm [10][11][12][13] . The latter has been considered more precise than the others; however, due to the rarity of this type of fibers, little experience has been reported in the medical literature.…”