Potential ablation of accessory atrioventricular pathways: injection of alcohol into the atrioventricular groove

Successful ablation of a right concealed epicardial accessory pathway using ethanol infusion

INTRODUCTION

This study describes a rare case of concealed epicardial accessory pathway (AP) successfully ablated using ethanol infusion (EI) through a variant vessel connecting the right atrium (RA) and the right ventricle (RV) surface.

METHODS AND RESULTS

A 58-year-old male referred to our hospital for prior failed AP ablation. Cardiac-enhanced computerized tomography scan showed there was a variant vessel at the tip of right atrial appendage and a pulmonary artery (PA)-RA fistula at the roof of RA. The earliest activation was present at the site of the PA-RA fistula. A selective angiography showed that a small branch of the variant vessel covered the earliest excitation site of the AP. EI into this branch successfully repressed the AP without any recurrences within a follow-up period of 3 months.

CONCLUSION

Endocardial ablation is challenging for epicardial APs related to cardiac structural variations. If small vascular branches near the earliest activation site can be found, EI can successfully ablate these types of epicardial APs.

[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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Transcatheter subendocardial infusion. A novel technique for mapping and ablation of ventricular myocardium

BACKGROUND

Catheter ablation with radiofrequency energy is feasible in a limited subset of patients with ventricular tachycardia. The purpose of this study was to evaluate a technique for mapping and ablation of ventricular myocardium with the use of transcatheter subendocardial infusion.

METHODS AND RESULTS

A needle-tipped deflectable electrode catheter was used to deliver reagents to endocardial target sites. This was equipped with two central lumens to allow sequential administration of mapping and ablation injectants with minimal admixture. The mapping injectant consisted of a mixture of lidocaine, iohexal, and glycerin; the ablation injectant contained ethanol, iohexal, and glycerin. Infusion of the mapping injectant (1 cm3 over 3 or 5 seconds, n = 14) produced a stain on fluoroscopy and increased local capture threshold by 61%. No lesions resulted from mapping infusions. Infusion of the ethanol-containing injectant (n = 48) produced discrete lesions, with a mean volume ranging from 0.6 to 1.5 cm3. There was a direct relationship between infusion volume, infusion duration, and resultant lesion volume. Fibrosis in a region of healed myocardial infarction did not impair diffusion of the injectant or affect lesion dimensions. Microscopic analysis of chronic lesions showed a sharply demarcated border zone between fibrotic and normal myocardium.

CONCLUSIONS

Transcatheter subendocardial infusion can be used to reversibly impair local excitability and mark an injection site fluoroscopically. Subendocardial injection of ethanol can predictably ablate a large volume of ventricular myocardium. Additional study of this system in an arrhythmia model will help to define its potential for mapping and ablation of hypotensive ventricular tachycardia.