Cardiomyocyte Responses to Thermal Excursions: Implications for Electrophysiological Cardiac Mapping

Cryotherapy is emerging as a treatment method to identify and ablate atrial and ventricular tachyarrhythmias. Cryotherapy utilizes reversible moderate ultra-hypothermic temperatures to transiently halt electrophysiological activity to identify target areas for ablation with minimal damage to the nonarrhythmogenic tissue. This represents a potential advantage over heat-based therapies. Subsequent application of subfreezing temperatures to the targeted cells results in cellular ablation and ultimately correction of the arrhythmia. An in vitro study was performed to characterize and investigate the efficacy of cryotherapy procedures in mammalian cardiac systems. Mammalian cardiomyocytes were isolated from neonatal rats and seeded in tissue culture plates. Samples experienced brief (15 sec to 60 sec) thermal excursions of temperatures ranging from 60°C to −20°C. Upon return to normal culture conditions (37°C), cellular metabolic activity and contractile response were monitored for 72 h and compared to control...