Correlative Anatomy and Electrophysiology for the Interventional Electrophysiologist:

The cavotricuspid isthmus (CVTI) is the well-established location of atrial tissue critical for the maintenance of typical atrial flutter. The CVTI begins at the electrically inert tricuspid valve and includes the atrial myocardium up to the inferior vena cava (IVC). In this article, we discuss relevant CVTI and right atrial anatomy of interest to the electrophysiologist. Critical questions that are considered include why ablation is sometimes difficult across the CVTI and how best to deal with anatomic variation including sub-Eustachian pouches or large pectinate muscles encroaching onto the isthmus. Important electroanatomic features of the right atrium (RA) including sites for naturally occurring conduction block and the anatomy of the "lower loop" are reviewed. Following this discussion on the impact of the underlying anatomy for right atrial flutter ablation, an approach to dealing with difficulty when mapping or ablating this common arrhythmia is presented.