| Electrophysiological base of atrioventricular nodal reentrant tachycardia is dual AV nodal pathway, most(85% ) of typical atrioventricular nodal reentrant tachycardia( AVNRT) show dual AV nodal pathway . Radiofrenquency(RF) catheter ablation of the slow pathway allows the elimination of atrioventricular nodal reentrant tachycardia( AVNRT) with a low rale of complications. However, the successful treatment of AVNRT is not always associated with elimination of slow pathway conduction. There are many electrophysiological changes after the ablation of the slow pathway. This study examined the different electrophysiological changes of patients with versus those without persistent dual AV nodal physiology after successful ablation of AVNRT, the purpose is to find the mechanism of tachycardia elimination.MethodsThe study group consisted of 70 of 93 consecutive patients undergoing slow pathway modification in our laboratory between January 2002 and December 2003. AV node conduction curves were analyzed following successful ablation in 70 patients with typical AVNRT. There are 28 men and 42 women (age 49.44 16. 51years) . twenty patients (28% ) had complete elimination(groupl ) where-as fifty patients (72% ) had persistence (group2)of dual AV mode physiology. Next to measure the FP - ERP SP - ERP WB - CL SP - AH FP - AH com-paring the front to the after ablation.ResultsProgrammed atrial or ventricular stimulation induced typical (slow -fast) AVNRT( mean cycle length 347 61.32ms) in all patients. As required by the inclusion criteria , all the patients had successful AVnode modification at the end of the study,the mean ablation time is 348.57 283.73s,the mean frenquency is 8,39 7.48,the mean energy is 19784.33 18972.48.A significant increase in AV node Wenckebach cycle length ( WB - CL) and a decrease in the fast pathway ERPand an increase in the maximum fast pathway(FP)AH internal were observed in the groupl(complete ablation).In the group 2( persistence AY node physiology) , a significant increase in AV node Wenckebach cycle length ( WB - CL) and a decrease in the fast pathway ERP also were observed, but the maximum fast pathway ( FP) AH internal and slow pathway ERP(SP - ERP) have no changes,as well as the maximum slow pathway (sp) AH internal. At the same time the change in the maximum SP - AH following ablation showed a significant inverse relation to the maximum SP - AH at the baseline in group2. Patients with a long maximum slow pathway AH internal at the baseline showed a decrease, whereas patients with a short maximum slow pathway AH internal at the baseline showed a significant increase following ablation.DiscussionPersistent dual AV node physiology is a common finding after successful AV modification,up to 65% of the successfully treated patients have some evidence of persistent dual physiology in previous reports. The most consistent finding in patients with complete elimination of slow pathway conduction was a significant inciease in the AV node Wenckebach cycle lenghth and a decrease in the fast pathway ERP,the change most likely due to elimination of an electrotonic inter-action between the two pathways. In the patients with the persistent AV node physiology after ablation,There are different changes in AV node physiology ..How is the tachycardia rendered noninducible when dual physiology persists? the reason (1) the radiofrequency energy application eliminating tachycardia most likely destroys critical areas of the reentrant circuit. (2) the maximum SP - AH internal change the increase in the maximum slow pathway conduction time after ablation that was observed in patients with short slow pathway conduction times at baseline could be the result of nonspecific damage to the node especially when more anterior ablation are required. (3 ) ablation location previous studies have shown that slow pathway with long AH internals can be ablated posterior (at or below the CS os) , whereas slow pathways with short AH internals required ablation closer to the compact AV...
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