Radiofrequency Current Application on Immature Porcine Atrial Myocardium: No Evidence of Areas of Slow Conduction After 12‐Month Follow‐Up

INTRODUCTION: Radiofrequency current (RFC) application is a widely used procedure for treatment of supraventricular arrhythmias. The purpose of this study was to investigate late electrophysiologic sequelae of RFC lesions at immature atrial myocardium in pigs, as they have not yet been systematically investigated in vitro. METHODS AND RESULTS: RFC application (temperature guided) was performed in seven piglets (mean age 6 weeks) by a steerable 6-French electrode catheter positioned at the lateral aspect of the tricuspid valve annulus. After 12 months, hearts were removed, and lesions with surrounding tissue were isolated. The viable tissue at the border of the specimen was paced with a cycle length of 500 and 600 msec. One hundred fifty impalements were performed on each specimen using capillary microelectrodes to record action potential characteristics from the lesion's surface and the surrounding tissue. In all seven specimens, no transmembrane action potentials from the fibrotic surface of each of the lesions could be recorded. The surrounding viable tissue was sharply demarcated electrically. No areas of slow conduction were detected. Action potential characteristics as mean maximum diastolic transmembrane potential, mean action potential duration at 90% repolarization, and upstroke velocity of phase 0 of the action potential were all normal. CONCLUSION: No evidence of areas of slow conduction 12 months after RFC application at immature atrial myocardium suggests that this technique is safe regarding occurrence of late atrial tachyarrhythmias after the procedure.