What is a common arrhythmic risk in cold-water submersion?

• A. Atrial fibrillation due to dehydration
• B. Ventricular fibrillation or other ventricular arrhythmias due to hypothermia
• C. Sinus tachycardia from heat exposure
• D. Ventricular tachycardia unrelated to cold

Answer: (B)

Cold-water submersion creates hypothermia, which destabilizes the heart’s electrical system. As core temperature falls, conduction slows and repolarization becomes uneven, increasing the likelihood of dangerous ventricular rhythms. Ventricular fibrillation is the classic and most feared arrhythmia in this setting because the cold-induced electrical instability can trigger chaotic, uncoordinated ventricular activity that stops effective pumping. While the body’s diving reflex can cause an initial slow heartbeat, the progression to severe hypothermia makes ventricular fibrillation or other ventricular arrhythmias the common risk. Other options don’t fit the cold-induced mechanism: dehydration–related atrial fibrillation and heat-induced sinus tachycardia aren’t the typical hazards in cold-water submersion, and ventricular tachycardia “unrelated to cold” ignores the temperature-driven substrate promoting these rhythms.