In a hypothermic patient, which arrhythmia is most likely to occur?

• A. Sinus tachycardia
• B. Atrial flutter
• C. Junctional rhythm
• D. Ventricular fibrillation

Answer: (D)

In hypothermia, the heart’s electrical system becomes unstable as core temperature drops. Cold slows SA node firing and conduction, lengthens refractoriness, and makes ventricular tissue more irritable. While mild hypothermia often shows a slow, regular rhythm (bradycardia), severe hypothermia carries a high risk of chaotic, ineffective ventricular activity—ventricular fibrillation. This life-threatening rhythm can occur as temps fall or during rewarming, leading to sudden cardiac arrest if not treated promptly. Atrial flutter or junctional rhythms aren’t the classic dangerous progression in this scenario, and sinus tachycardia is unlikely because hypothermia depresses heart rate. So the most likely dangerous arrhythmia in a hypothermic patient is ventricular fibrillation.