Microfidelity (MIFI) Ablation Technology Versus Standard Ablation Catheter for Atrioventricular Nodal Ablation A Comparative Pilot Study of Time to Success

Introduction In some elderly patients with atrial fibrillation (AF), especially in combination with heart failure, a rate control strategy may be preferred. When pharmacological therapy is ineffective or not tolerated, it is reasonable to perform atrioventricular (AV) node ablation with ventricular pacing as a class IIA indication per current guidelines.

Usually, the procedure is simple and straightforward and complete heart block can be achieved without any difficulty. However, this "simple" procedure can sometimes prove to be a most difficult case. The most common reason for failure to achieve complete heart block is the inability to localize the compact AV node using the His signal with standard intracardiac electrograms. As these patients come to the laboratory in AF, the His signal may be obscured by AF waves. In some patients with a deeper intramyocardial location of the His bundle and compact AV node it becomes necessary to produce deeper ablation lesions using an irrigated catheter to achieve block.

In patients with AF, the target of ablation for the "ablate and pace" approach is the compact AV node, located at the apex of the triangle of Koch. Ideally, ablation is performed at the most proximal penetrating part of the His bundle in order to maintain a proximal automatic junctional rhythm and avoid pacemaker dependence.

Para Hisian pacing is most commonly used to reveal the presence of a septal accessory pathway.

The His bundle is a deep insulated structure and it is difficult to capture it at usual energy outputs. Using a high- output pacing (usually 20 mA at 2 msec) it is possible to directly capture the deeply situated His bundle, which is confirmed by a narrower QRS complex on the paced electrograms. Thus, high-output pacing can be utilized to map the His bundle area in difficult situations.