Changes in ventricular fibrillation threshold during acute hypothermia. A model for future studies. 1993

E Mortensen, and R Berntsen, and T Tveita, and D A Lathrop, and H Refsum
Department of Medical Physiology, University of Tromsø, Norway.

Hypothermia and rewarming are associated with an increased incidence of lethal arrhythmias in man. The relationship between reduction in body temperature and ventricular fibrillation threshold was studied in 7 pentobarbital anaesthetized dogs using programmable electrical stimulation while cooling and rewarming between 37 degrees C and 25 degrees C in steps of 3 degrees C. Fibrillation threshold was defined as the number of extrastimuli required to evoke ventricular fibrillation. QRS-durations and corrected QT-intervals (QTc) were measured from surface electrocardiograms. Monophasic action potential durations were recorded from the base and apex of the heart. Fibrillation threshold decreased with decreasing temperatures; e.g., at 37 degrees C ventricular fibrillation was not inducible after 5 extrastimuli, while at 25 degrees C only 2 extrastimuli were required. From 37 degrees C to 25 degrees C QRS-width, monophasic action potential durations and QTc increased while conduction velocity decreased. The differential effects on conduction and monophasic action potential duration provide a basis for induction of ventricular fibrillation during acute hypothermia. This model of hypothermia-induced ventricular fibrillation should prove useful for future studies aimed at understanding the mechanisms responsible for hypothermia-related deaths.

UI MeSH Term Description Entries
D007035 Hypothermia Lower than normal body temperature, especially in warm-blooded animals. Hypothermia, Accidental,Accidental Hypothermia,Accidental Hypothermias,Hypothermias,Hypothermias, Accidental
D008297 Male Males
D004195 Disease Models, Animal Naturally-occurring or experimentally-induced animal diseases with pathological processes analogous to human diseases. Animal Disease Model,Animal Disease Models,Disease Model, Animal
D004285 Dogs The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065) Canis familiaris,Dog
D004558 Electric Stimulation Use of electric potential or currents to elicit biological responses. Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D005260 Female Females
D000200 Action Potentials Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli. Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D014693 Ventricular Fibrillation A potentially lethal cardiac arrhythmia that is characterized by uncoordinated extremely rapid firing of electrical impulses (400-600/min) in HEART VENTRICLES. Such asynchronous ventricular quivering or fibrillation prevents any effective cardiac output and results in unconsciousness (SYNCOPE). It is one of the major electrocardiographic patterns seen with CARDIAC ARREST. Fibrillation, Ventricular,Fibrillations, Ventricular,Ventricular Fibrillations

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