Key result
In a rat model of hypothermia and rewarming, no ventricular arrhythmias occurred (0%), and this resistance to lethal arrhythmias was predicted by an increased QRS/QTc ratio.
Why the study?
Decreasing QRS/QTc is proposed to predict hypothermia-induced ventricular arrhythmias, but whether it also reliably predicts the nonappearance of arrhythmias in species like rats that tolerate prolonged hypothermia was unknown.
In a rat model, an increased QRS/QTc ratio during hypothermia predicted resistance to ventricular fibrillation, contrasting with the decreased ratio and high arrhythmia risk seen in human accidental hypothermia.
Rat hypothermia model links QRS/QTc rise to arrhythmia resistance; leaves open translation to humans where ratio falls with high VF risk.
Accidental hypothermia is associated with increased risk for arrhythmias. QRS/QTc is proposed as an ECG-marker, where decreasing values predict hypothermia-induced ventricular arrhythmias. If reliable it should also predict nonappearance of arrhythmias, observed in species like rat that regularly tolerate prolonged hypothermia. A rat model designed for studying cardiovascular function during cooling, hypothermia and subsequent rewarming was chosen due to species-dependent resistance to ventricular arrhythmias. ECG was recorded throughout the protocol. No ventricular arrhythmias occurred during experiments. QRS/QTc increased throughout the cooling period and remained above normothermic baseline until rewarmed. 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 QRS/QTc.
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Dietrichs et al. (2021) studied Hypothermia-induced ventricular arrhythmias. Hypothermia and rewarming vs. Normothermic baseline was evaluated on Ventricular arrhythmias. In a rat model of hypothermia and rewarming, no ventricular arrhythmias occurred (0%), and this resistance to lethal arrhythmias was predicted by an increased QRS/QTc ratio.
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