Cryosurgical ablation of fetal atrioventricular node: New model to treat fetal malignant tachyarrhythmias

Background Sustained tachyarrhythmia resulting in fetal hydrops is often refractory to medical therapy. Fetal atrioventricular node ablation associated with epicardial fetal pacing has the potential to be an effective procedure for this morbid association. Methods To assess the feasibility of therapeutic fetal heart block, we developed a technique of intrauterine cryosurgical ablation of fetal atrioventricular node without the need for cardiac bypass in 8 fetal lambs. Complete heart block was obtained by applying the cryoprobe over the coronary sinus. Fetal pacing was then performed to allow fetal survival. Results Complete heart block was achieved in 100% of the fetal lambs. Postoperative evaluations revealed persistent atrioventricular block. The hearts were studied at different postoperative times. Morphologic evaluation of the area containing the cryosurgical lesion revealed varied extension of necrosis of the atrioventricular node and hemorrhage, with involvement of the His bundle and proximal right bundle branch. Conclusions This procedure is technically feasible and offers an alternative approach to the treatment of drug-resistant, life-threatening fetal supraventricular tachyarrhythmias associated with hydrops fetalis.