• Arrhythmias
• Interventional Radiology
• Interventional Techniques & Devices

Claus Schmitt, MD, Medizinische Klinik IV, Städtisches Klinikum Karlsruhe, Karlsruhe, Germany, discussed practical strategies for radiofrequency (RF) catheter ablation of atrioventricular nodal reentry tachycardia (AVNRT), including slow and fast pathway ablation. Prof. Schmitt prefers a 3-catheter setting using the slow pathway. Using this technique, many interventionists start from a left anterior oblique (LAO) projection; in this position, a His bundle potential can be recorded simultaneously with the catheter in the His position.

To target the slow pathway, interventionists may use an anatomic approach, an electrogram-guided approach, or an integrated approach. Prof. Schmitt prefers the latter. A typical setup is a His bundle recording with a coronary sinus catheter and an ablation catheter. Isoproterenol is used if the patient can not be induced and to determine success of the ablation. Use of sedation may increase vagal tone and make it difficult to induce the arrhythmia. In noninducible patients, if there are no accessory pathways after tachycardia and there is documented supraventricular tachycardia (SVT) that is compatible with AVNRT, Prof. Schmitt recommends continuing with the ablation.

Slow pathway ablation typically is performed in sinus rhythm, starting from LAO or right anterior oblique projections using 20 to 30 watts for up to 60 seconds to reach >50°C. If there are many junctional beats (Figure 1) at the start of RF application, Prof. Schmitt paces the atrium to determine if the fast pathway is intact. It is best to stop at 60-second intervals if the fast pathway is compromised. Accelerated junctional rhythm occurs in almost 100% of effective sites but also in up to 65% of ineffective sites.

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Figure 1.

Start of Ablation: Junctional Beats.

Reproduced with permission from C. Schmitt, MD.

A successful ablation can be proved by noninducibility with or without isoproterenol. In a complete ablation of the slow pathway, there is no jump or echo beat. If the slow pathway is modified, it is acceptable to have a jump and up to 1 atrial echo beat. During RF ablation in atypical AVNRT, the slow pathway is mapped during tachycardia.

Some studies have reported that fast pathway ablation is an acceptable approach in patients with AVNRT and a prolonged PR interval [Reithmann C et al. J Cardiovasc Electrophysiol 2006]. There might be more than 1 slow pathway; however, and if care is taken, slow pathway ablation can be safe.

Prof Schmitt's laboratory reported a 98.8% acute success rate with a recurrence rate of 5.2% [Estner HL et al. Pacing Clin Electrophysiol 2005]. Complications, such as late AV block with RF lesion extension, have been reported in up to 0.4% of patients. The Cryoablation versus Radiofrequency Energy for the Ablation of Atrioventricular Nodal Reentrant Tachycardia study [CYRANO] [Deisenhofer I et al. Circulation 2010] reported that AVNRT recurrence is more frequent with cryoablation versus RF ablation (9.4% vs 4.4%; p=0.029).

• © 2012 MD Conference Express