Epicardial connections across the cavotricuspid isthmus

The cavotricuspid isthmus (CTI), is a critical connection for many right atrial (RA) macro-reentrant flutters and is a safe and effective ablation target. Bidirectional block across the CTI is the accepted endpoint of the procedure and may be difficult to achieve because of the presence of sub-Eustachian pouches, presence of a prominent Eustachian ridge, or enlarged pectinate muscles, among other challenges.1 Block can be confirmed with several approaches, such as differential pacing maneuvers or electroanatomic mapping.