[Transcatheter subendocardial infusion: a novel technique for ablation of atrial arrhythmias]

Ablation of typical atrial flutter using radiofrequency energy is limitted by difficulties in creating a continuous line of block across the istmus between the tricuspid anulus and the inferior vena cava. Recent studies from our laboratory have shown that a novel infusion ablation technique can create large endocardial lesions in a safe and predictable fashion. The purpose of our study was to assess the feasibility of transcatheter subendocardial infusion of a mixture of 95% enthanol, iodinated contrast and glycerin to create atrial lesions resulting in complete ablation of the critical isthmus mediating typical atrial flutter.

Seven closed-chest dogs (weight 24+/-1 kg) were studied during general anesthesia with isoflurane. Two transcatheter subendocardial infusions of 0.5 cc of ethanol, contrast medium and glycerin were made over an injection time of 5 s into the posterior right atrial isthmus in each dog. Staining of the target site was monitored on fluoroscopy. Sinus rate, AH interval and AV block cycle length were determined before and after infusion ablation. Arterial blood pressure and right atrial pressure were continuously recorded. Six infusion ablations were also performed in the lateral wall of the right atrium. Lesion dimensions were measured pathologically, thereafter.

A total of 14 infusions was made in the isthmus of the right atrium. The mean lesion volume was 0.21+/-0.18 cc. The lesions were 6+/-3 mm in width, the length was 12+/-5 mm and the average deepness was 6+/-4 mm. An ablation of the entire isthmus was, achieved in five dogs. Disturbances in AV conduction were not observed after ablation in any dog. The isthmus lesions were not proarrhythmic during programmed stimulation. 4/6 infusion ablations in the lateral atrial wall caused a penetration of contrast media of the pericardial sac. Hemodynamic deterioration was not seen after any ablation attempt.

Direct subendocardial insusions can be used to create large ablation lesions in the posterior right atrium. The lesion size is predictable and can be directly visualized on fluoroscopy. Infusion ablations into the right atrial isthmus do not cause damage to the AV node or to the right coronary artery. Transcatheter infusions in the posterior right atrium seem to be promising for ablation of the entire isthmus mediating typical atrial flutter. Additional studies of this technique in an arrhythmia model seem warranted.