| Abstrakt: |
The heart of hibernating mammals is known to demonstrate the nature\'s model of resistance to rhythm disturbances, including ventricular arrhythmias, during hypothermia. However, electrophysiological mechanism of this phenomenon is not completely understood. Using optical mapping technique with voltage-sensitive dye di-4-ANEPPS, we investigated the spatiotemporal characteristics of ventricular activation in Langendorff-perfused hearts of winter hibernating ground squirrels Spermophyllus undulatus and rabbits at temperatures from +37 degrees C to +3 degrees C. In rabbit hearts, reduction of temperature from 37 to 17 degrees C resulted in significant decrease of conduction velocity and increase of conduction anisotropy. Excitation failure was observed in the rabbit heart at 12+/-1 degree C. In contrast, ground squirrels exhibited significantly faster conduction velocity compared with rabbits at all temperatures and insensibility of conduction anisotropy to cooling down to 3C which can protect the hibernator heart against arrhythmias during hypothermia. |
