Anatomical structure of the isthmus between the inferior vena cava and tricuspid annulus investigated with a three-dimensional electroanatomical mapping system.

We studied the anatomical structure of the isthmus between the inferior vena cava and tricuspid annulus in humans with a three-dimensional electroanatomical mapping system (CARTO, Biosense, Haifa, Israel). Fifteen patients with atrial flutter were studied. Thirteen patients had underlying heart disease. We investigated the anatomical structure of the isthmus with cross sections made from the three-dimensional right atrial map. The cross sections of the isthmus showed a concave shape in 7 patients (47%: group A), convex shape in 2 (13%: group B), and complex shape in 6 (40%: group C). The distance between the IVC and TA was 34+/-17 mm (group A), 25+/-2 mm (group B), 34+/-16 mm (group C), and 32+/-15 mm (Total), respectively. The distance between the top and bottom was 6+/-5 mm (group A), 3 mm (group B), 6+/-3 mm (group C), and 6+/-4 mm (total), respectively. Seven of 15 patients exhibited an uneven surface of more than 5 mm in depth and 4 of 15 patients had one of more than 10 mm. The anatomical structure of the isthmus varies. To carry out precise catheter ablation, these variations should be taken into consideration to ensure an effective procedure.