Radiofrequency current application on immature porcine atrial myocardium: No evidence of areas of slow conduction after 12-month follow-up

Electrophysiologic Sequelae 12 Months After Radiofrequency Current Applicat ion. Introduction: Radiofrequency current (RFC) application is a widely use d procedure for treatment of supraventricular arrhythmias, The purpose of t his study was to investigate late electrophysiologic sequelae of RFC lesion s at immature atrial myocardium in pigs, as they have not yet been systemat ically 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 isola ted. 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 o n each specimen using capillary microelectrodes to record action potential characteristics from the lesion's surface and the surrounding tissue. In al l seven specimens, no transmembrane action potentials from the fibrotic sur face of each of the lesions could be recorded, The surrounding viable tissu e was sharply demarcated electrically, No areas of slow conduction were det ected, Action potential characteristics as mean maximum diastolic transmemb rane potential, mean action potential duration at 90% repolarization, and u pstroke velocity of phase 0 of the action potential were all normal. Conclusion: No evidence of areas of slow conduction 12 months after RFC app lication at immature atrial myocardium suggests that this technique is safe regarding occurrence of late atrial tachyarrhythmias after the procedure.