[Comparative study of cardiac alternans of action potential duration in hypothermia in rabbits and ground squirrels].
Cardiac alternans is a promising predictor of sudden death, yet its role in the mechanism of hypothermic arrhythmia induction is unclear. We aimed to investigate the effect of hypothermia on spatial-temporal characteristics of repolarization pattern in the Langendorff-perfused hearts of summer active (SA, n = 6) and winter hibernating (WH, n = 7) ground squirrels Spermophilus undulatus and rabbits (n = 5), who were immobilized with the excitation-contraction uncoupler BDM (10 mM) and optically mapped using the voltage sensitive dye di-4-ANNEPS and CCD camera (128 x 128 pixels; 500 frames/sec). Action potential duration (APD) restitution was quantified over the posterior epicardial heart surface and estimated using Nolasco-Dahlen criterion. In rabbit hearts, hypothermia resulted in arrhythmogenic overshoots of APD alternans as well as increase of APD restitution curve steepness. In contrast, significant APD alternans were observed in SA hearts at 27 degrees C, and at 17 degrees C in WH hearts. Moreover, slope of APD restitution curve in ground squirrels hearts did not reached arrhythmogenic threshold (43 +/- 9 degrees and 39 +/- 5 degrees for SA and WH respectively). Our results demonstrate different resistance of hibernating and non-hibernating mammals against induction of arrhythmogenic cardiac alternans which is closely associated with adaptive changes in intracellular Ca2+ cycling during hibernation.
Egorov
Iu V
IuV
Glukhov
A V
AV
Artiukhov
V S
VS
Efimov
I R
IR
Rozenshtraukh
L V
LV
D000200:Action Potentials / Q000502:physiology*; D000222:Adaptation, Physiological; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism / Q000503:physiopathology*; D002118:Calcium / Q000378:metabolism; D022062:Electrophysiologic Techniques, Cardiac; D006329:Heart Conduction System / Q000378:metabolism / Q000502:physiology / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006605:Hibernation / Q000502:physiology*; D007035:Hypothermia / Q000503:physiopathology*; D011817:Rabbits; D012589:Sciuridae; D013045:Species Specificity
D002118:Calcium