Radiofrequency catheter ablation of Mahaim fibers at the tricuspid annulus.

Abstract

BACKGROUND The purpose of this study was to test the feasibility of radiofrequency catheter ablation of Mahaim fibers at the tricuspid annulus. METHODS AND RESULTS Four patients who fulfilled criteria for having Mahaim fibers and preexcited reciprocating tachycardia underwent radiofrequency catheter ablation. Three patients had atriofascicular connections, and one patient had an atrioventricular connection. The mean age was 27 years (age range, 11-48 years). All patients had highly symptomatic tachycardias, producing syncope in one patient and presyncope in the remaining three patients. Symptoms were present for a mean of 13 years (range, 4-23 years). All pathways conducted only anterogradely, and preexcitation resulted in a left bundle branch block QRS morphology. Adenosine caused block in the accessory pathway in the three patients in whom it was tested. The stimulus to delta interval increased by 75 msec (range, 35-90 msec) during rapid atrial pacing. The atrial insertion of the Mahaim fiber was in the right lateral atrium in one patient, right posterolateral atrium in two patients, and right posterior atrium in one patient. The ventricular insertion was in the distal right bundle branch in three patients and in the posterolateral right ventricle near the tricuspid annulus in the patient with an atrioventricular connection. Stimulus to delta wave mapping was used to help localize the atrial insertion of the atriofascicular connections. A mean of 15 radiofrequency pulses (range, 10-19 pulses) delivered to the tricuspid annulus in the posterior to lateral regions eliminated accessory pathway conduction in all patients. No complications occurred. Tachycardia did not recur during a mean follow-up of 8 months (range, 2-15 months). CONCLUSIONS Radiofrequency current applied to the tricuspid annulus can safely eliminate tachycardia in patients with Mahaim fibers.

Mahaim Accessory Pathways

“…[2][3][4][5][12][13][14][15][16][17] However, posteroseptal locations could also be found, 7,14 and true nodoventricular fibres have been identified (see Figure 5). 1,14,16 In addition, some of these pathways, so-called 'short'…”

Catheter ablation of atriofascicular Mahaim fibers guided by the activation potential

“…1 -Continuous programmed stimulation in high right atrium showing: (1A) with a stimulation cycle (S1-S1) of 460 ms, mild ventricular preexcitation occurs (*); (1B) continuing the tracing, progressive ventricular preexcitation is observed during the stimulation at progressively shorter cycles (S1-S1=390 ms) (**) with extension of the A-H and A-V intervals. pharmacological treatment, catheter ablation 5,6,[9][10][11][12]18 , and surgery 7,12 . The first experiences with catheter ablation used high-energy shocks in the atrioventricular node region.…”

“…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.…”

“…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.…”