J. Clementy

Characteristics of the Ventricular Insertion Sites of Accessory Pathways With Anterograde Decremental Conduction Properties

BACKGROUNDnAccessory pathways (APs) with anterograde decremental conduction properties referred to as Mahaim fibers have recently been recognized as originating from the right lateral atrium. Little information is available about their distal insertion. The purpose of this study was to determine the different kinds of APs involved and the characteristics of their distal insertion site.nnnMETHODS AND RESULTSnTwenty-one patients (mean age, 28 +/- 13 years) with reciprocating tachycardia or atrial fibrillation were studied. Right-sided atrial and/or ventricular endocardial mapping during tachycardia identified different types of APs. (1) Seventeen patients had long APs originating from the right lateral atrium and coursing several centimeters to the right ventricle. In 10 patients, the AP terminated in or close to the right bundle-branch system (atriofascicular AP) and in 7, the AP terminated in the anterior right ventricle (atrioventricular AP). Patients with atriofascicular APs had narrower QRS complexes (133 +/- 10 versus 165 +/- 26 milliseconds, P = .02) and narrower initial r wave in leads V2 through V4 during maximal preexcitation than patients with atrioventricular APs. In addition, they had earlier His-bundle and right bundle-branch retrograde activation, ie, shorter V-His (16 +/- 5 versus 37 +/- 9 milliseconds, P < .01) and V-right bundle intervals (3 +/- 5 versus 25 +/- 6 milliseconds, P < .01). In 6 patients, minimal preexcitation not readily apparent was present in sinus rhythm despite the appearance of a narrow QRS complex. A wide distal insertion site of 0.5 to 2 cm in diameter consistent with arborization of the AP was found in 10 patients. The distal application of radiofrequency current produced a change in the preexcitation pattern in 4 patients and ablated the AP in 2 patients. In the other patients, radiofrequency current was applied more proximally and successfully ablated the AP bundle (n = 9) or AP proximal insertion (n = 6). No recurrence was observed during a follow-up period of 12 +/- 10 months. (2) Four patients had short paratricuspid atrioventricular APs; in one, the decremental conduction property was acquired as demonstrated by two electrophysiological studies performed 7 years apart. Radiofrequency ablation was successfully accomplished in all 4 patients at the tricuspid annulus.nnnCONCLUSIONSnDifferent types of APs account for tachycardias previously called Mahaim fibers. Long and short atrioventricular APs are observed in 81% and 19%, respectively. Long APs often have a distal arborization and may have either a fascicular or ventricular insertion. Radiofrequency current is more efficient when applied to the AP bundle or AP proximal insertion rather than to the distal insertion in patients with long APs.

Electrocardiographic characteristics and catheter ablation of parahissian accessory pathways.

BackgroundAccessory pathways may be located in close proximity to the His bundle, resulting in a high risk of heart block during attempted surgical or electrical interruption of these pathways. This study reports the prevalence, ECG characteristics, and results of catheter ablation of parahissian accessory pathways. They were defined on the basis of both the presence of a high amplitude (>0.1 mV) of His bundle potential at the ablation site and an exclusion of anteroseptal or midseptal location of the accessory pathway. Methods and ResultsEight patients with a parahissian accessory pathway were identified among 582 consecutive patients who underwent radiofrequency ablation of an acces-sory pathway. They were six males and two females with a mean age of 21±9 years. During maximal preexcitation, the ECG showed a positive delta wave in leads I, II, and aVF in all patients: six had a negative delta wave in leads V1 and V2 instead of the positivity usually observed in anteroseptal accessory pathways. This pattern had a sensitivity of 75%, a specificity of 96%, a positive predictive value of 86%, and a negative predictive value of 93% for a parahissian location in comparison with a group of 28 patients with anteroseptal accessory pathways. At the successful ablation site, the mean amplitude of the His bundle potential was 0.2±0.1 (0.12 to 0.4 mV). All accessory pathways were successfully ablated without causing heart block using 5 to 20 W of radiofrequency energy. ConclusionsParahissian accessory pathways have a preexcitation pattern that is distinctive from that of anteroseptal accessory pathways. Catheter ablation of these pathways is feasible using low energy with preservation of normal atrio-ventricular conduction.

Ablation par radiofréquence de la fibrillation auriculaire

Resume La possibilite de guerir les patients souffrant de fibrillation paroxystique au moyen d’un traitement par radiofrequence est un bouleversement dans la prise en charge de cette arythmie. La deconnexion des veines pulmonaires est efficace et sure, passe l’effet d’apprentissage de l’operateur. Cette isolation des veines pulmonaires est l’etape initiale et indispensable permettant l’elimination des fibrillations auriculaires chez 70xa0% des patients. La modification du substrat fibrillatoire grâce aux lesions lineaires augmente le taux de succes a 75xa0% dans les fibrillations chroniques et 82xa0% dans les fibrillations paroxystiques. L’ablation de la fibrillation auriculaire doit etre vue comme un acte chirurgical a cœur ferme isolant des structures et sectionnant des tissus que les progres techniques (nouveaux catheters de radiofrequence) a venir faciliteront probablement. Des etudes comparatives avec le traitement medical evaluent leur efficacite, securite et couts respectifs et pourraient entrainer une augmentation considerable des patients pouvant beneficier de ces gestes curatifs.