CATHETER ABLATION OF ATRIOVENTRICULAR NOD AL REENTRANT TACHYCARDIA

Electrophysiological data of atrioventricular nodal reentrant tachycar dia recensed over the last 40 years in the animal and in man has not r esolved the question as to the exact site of the reentry circuit: an e xclusively intranodal pathway or a pathway involving part of the atriu m? The remarkable efficacy of modern radical therapy of this arrhythmi a with preservation of atrioventricular conduction reinforces the conc ept of reentry involving not only the atrioventricular node but also t he juxta nodal atrium and the superior and inferior atrionodal connect ions. Radical treatment was initially surgical and then by catheter ab lation. The technique of specific ablation of the rapid anterior pathw ay was the first to be described. Its limitation is the relatively hig h risk (about 10%) of complete atrioventricular block. Very quickly, r adiofrequency ablation of the slow posterior pathway became the method of reference. Most patients do not have retrograde conduction in the slow pathway. The pathway is located in sinus rhythm by recording its specific potentials: either the rapid potential described by Jackman e t al or the fragmented potential described by Haissaguerre and Warin. The former is recorded from the posterior septal position anterior to the orifice of the coronary sinus; the second is recorded at the same level but slightly above in the mid septal position. Ablation of the s low pathway can be performed on these purely anatomical criteria. Usin g these approaches, an immediate success rate of over 90% may be obtai ned. The recurrence rate is 0 to 5%; that of complete atrioventricular block ranges from 0 to 4%. Therefore, ablation of the slow pathway ha s considerably reduced the risk of complete atrioventricular block wit hout having completely suppressed it. This fact should always be taken into consideration when the indication of ablation of an atrioventric ular reentrant tachycardia is envisaged, usually for a functional prob lem.