Key result
In an intact rat model, severe hypothermia and rewarming did not induce ventricular arrhythmias, a resistance that was predicted by a steadily increasing QRS/QTc ratio.
Why the study?
Accidental hypothermia increases arrhythmia risk, and the QRS/QTc ratio was proposed to predict ventricular arrhythmias, but whether it reliably predicts the absence of arrhythmias in species tolerating hypothermia remained to be evaluated.
Does severe hypothermia and rewarming induce ventricular fibrillation and alter the QRS/QTc ratio in an intact rat model?
Does severe hypothermia and rewarming induce ventricular fibrillation and alter the QRS/QTc ratio in an intact rat model?
Absolute Event Rate: 0% vs 0%
Rats are resistant to hypothermia-induced ventricular fibrillation, and this resistance is predicted by a sustained increase in the QRS/QTc ratio, unlike the decrease seen in humans and rabbits.
Rat model shows arrhythmia resistance; cautions against human extrapolation and leaves open QRS/QTc translation.
Background Accidental hypothermia is associated with increased risk for arrhythmias, including ventricular fibrillation and cardiac arrest. Recently QRS/QTc was proposed as an ECG-marker, where decreasing QRS/QTc ratio could predict ventricular arrhythmias in such patients. If reliable it should also predict nonappearance of arrhythmias, observed in species like rat that regularly tolerate prolonged hypothermia, during sustained sinus rhythm. Methods A rat model designed for studying cardiovascular function during cooling, 4 h experimental hypothermia (15 °C core temperature) and subsequent rewarming was used, and ECG recorded throughout the experimental protocol. Results No ventricular arrhythmias occured and there was no sign of a hypothermia-induced reduction of QRS/QTc values during moderate hypothermia. The ratio steadily increased throughout the entire cooling period and remained above normothermic baseline until rewarmed. Conclusion Different from the high incidence of hypothermia-induced ventricular arrhythmias in accidental hypothermia patients, where QRS/QTc ratio is decreased in moderate hypothermia, hypothermia and rewarming of rats is not associated with increased risk for ventricular fibrillation. This resistance to lethal hypothermia-induced arrhythmias was predicted by the QRS/QTc ratio.
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Dietrichs et al. (2020) studied Hypothermia-induced arrhythmias (n=6). Experimental hypothermia and rewarming vs. Normothermic baseline (37°C) was evaluated on Occurrence of ventricular arrhythmias and changes in QRS/QTc ratio. In an intact rat model, severe hypothermia and rewarming did not induce ventricular arrhythmias, a resistance that was predicted by a steadily increasing QRS/QTc ratio.
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