In typical atrial flutter, circular activation around the tricuspid ring is possible because the terminal crest prevents short-circuiting on the posterior wall, and the myocardium between the inferior vena cava (IVC) and the lower rim of the tricuspid ring is the obligatory pathway to close the circuit in the low right atrium (RA) (Figure 1). This IVC-tricuspid ring isthmus (cavotricuspid isthmus) has become the preferred target for ablation because it is the narrowest point of the circuit, it is easily accessible, and it is located far from the AV junction.
