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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aim of our study was to measure conduction velocity and pattern of excitation during hypothermia in hearts of ground squirrels Citellus undulatus, known to be most resilient hibernators. We imaged electrical conduction in intact isolated hearts of summer active and winter hibernating ground squirrels at temperatures varying from +37 degrees C to +3 degrees C. Electrical activity was mapped using CCD camera (500 frames/sec) and voltage-sensitive dye di-4-ANEPPS during normal sinus rhythm and ventricular pacing. No spontaneous tachyarrhythmia was observed in all hearts at any temperature. Hearts were able to maintain spontaneous sinus rhythm and normal pattern of epicardial excitation throughout the whole range of studied temperatures. Despite responsiveness to pacing in all hearts ventricular conduction velocity was significantly reduced (about 10-fold) at low temperatures +3 degrees C. Our data provides the first direct demonstration that isolated heart of the summer active and winter hibernating ground squirrel Citellus undulatus is able to maintain normal excitation pattern in a range of temperatures from +37 degrees C to +3 degrees C.
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PMID:[Pattern of excitation in isolated heart of hibernator ground squirrel Citellus undulatus]. 1594 Jan 84

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.
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PMID:[Comparative study of cardiac alternans of action potential duration in hypothermia in rabbits and ground squirrels]. 1956 29