AVNRT (atrioventricular nodal reentrant tachycardia) occurs in patients with dual AV nodal physiology. The fast pathway is anteriorly situated along septal portion of tricuspid annulus. Slow pathway is posteriorly situated close to the coronary sinus ostium.
Fast pathway ablation for AVNRT – Anterior approach
Fast pathway ablation for AVNRT is by the anterior approach and has a 90% success rate. But AV block occurs in about 7%. The recurrence rate for fast pathway ablation is about 9%. Fast pathway ablation is seldom being practised now.
Slow pathway ablationf or AVNRT – Posterior approach
Slow pathway ablation is done by the posterior approach by taking the ablation catheter away from the His bundle catheter towards the region of the coronary sinus catheter. Junctional beats occuring during the delivery of radiofrequency energy are a marker for successful ablation of slow pathway. The success rate of slow pathway ablation is 95-97%. AV block occurs in less than 0.5-1% cases of slow pathway ablation. The recurrence rate of slow pathway ablation is about 3%. Now adays the posterior approach preferred due to the higher efficacy, lower recurrence and AV block and higher chance of having of normal PR interval after ablation.