Tricuspid Isthmus Imaged by CARTOsound, Patients With Typical Atrial Flutter

The investigators propose a third hypothesis based on the anatomic observations made in pathological studies. The investigators hypothesize that the anatomic architecture determines the functional properties of the TV-IVC isthmus. As a result, • Muscular bundles are preferential routes of conduction through the TV-IVC isthmus. The isthmus acts like a series of discreet conduction routes rather than as a sheet of tissue. The muscular bundles form selective targets for ablation and therefore the entire anatomic line need not be ablated. This has direct implications for ablation of the isthmus.