Termination of Spiral-wave Reentry by Regional Cooling in 2-dimensional Rabbit Ventricular Myocardium

Abstract

Spiral-wave reentry is a principal mechanism of life-threatening ventricular tachyarrhythmias. We investigated the effects of regional cooling (RC) on the dynamics of spiral-waves. Methods and Results: Optical action potential signals were recorded from 2-dimensional ventricular myocardium (1 mm thick) of Langendorff-perfused rabbit hearts. Ventricular tachycardias (VTs, >2 min) were induced by burst stimulation. RC (by 5-7ºC) was applied to the left ventricular free wall using a transparent cooling device (diameter, 10 mm). RC caused a marked prolongation of action potential (by 25±4%) and a slight reduction of conduction velocity (by 16±5%) in the affected region under constant pacing (2.5Hz, n=10). Spiral-wave dynamics during VTs were transformed by RC from stationary to chaotic meandering types. During RC, the rotors moved irregularly around the cooled region, and often collided with the anatomical boundary (atrioventricular groove) resulting in spontaneous termination. The incidence of termination of VTs within 15 s was increased from 2/18 (11%) without RC to 14/18 (78%) with RC. Conclusion: RC facilitates spontaneous termination of spiral-wave reentry through the unpinning of rotors. [J Physiol Sci. 2006;56 Suppl:S129]