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Changes in ventricular fibrillation threshold during acute hypothermia. A model for future studies
E Mortensen1, R Berntsen, T Tveita
1Department of Medical Physiology, University of Tromsø, Norway.
Journal of Basic and Clinical Physiology and Pharmacology
|October 1, 1993
Summary
Hypothermia lowers the ventricular fibrillation threshold, increasing lethal arrhythmia risk. This study in dogs demonstrates that decreasing body temperature significantly reduces the electrical stimulation needed to induce ventricular fibrillation.
Area of Science:
- Cardiovascular Physiology
- Electrophysiology
- Hypothermia Research
Background:
- Hypothermia and rewarming increase the risk of lethal arrhythmias in humans.
- Understanding the electrophysiological changes during hypothermia is crucial for managing cardiac risks.
Purpose of the Study:
- To investigate the relationship between reduced body temperature and the ventricular fibrillation threshold.
- To explore the electrophysiological mechanisms underlying hypothermia-induced arrhythmias.
Main Methods:
- Studied 7 pentobarbital-anesthetized dogs, cooling and rewarming between 37°C and 25°C.
- Used programmable electrical stimulation to determine the ventricular fibrillation threshold.
- Measured electrocardiogram parameters (QRS duration, QTc) and monophasic action potentials.
Main Results:
- Ventricular fibrillation threshold decreased significantly with decreasing body temperature.
- At 37°C, 5 extrastimuli were needed for fibrillation; at 25°C, only 2 were required.
- QRS duration, action potential duration, and QTc increased, while conduction velocity decreased as temperature dropped.
Conclusions:
- Differential effects on cardiac conduction and action potential duration during hypothermia provide a basis for ventricular fibrillation induction.
- This canine model is valuable for studying mechanisms of hypothermia-related cardiac deaths.