Cold water and heart palpitations: what to know

Sudden cold can activate the body's stress response, narrowing surface blood vessels and changing breathing. The resulting surge of alertness may make the heartbeat feel pounding, fluttering or skipped. Anxiety, dehydration, low blood sugar, anaemia and an overactive thyroid can also cause palpitations. An irregular rhythm such as atrial fibrillation is another possibility, while heart failure is more often associated with breathlessness, swelling or reduced exercise tolerance.

The sensation does not identify one cause. Record whether it starts on entering cold water, how long it lasts, whether the rhythm feels regular, and what other symptoms occur.

Leave the cold water, warm up gradually, sit or lie safely, and breathe slowly without forcing deep breaths. Drink fluids if you may be dehydrated. Avoid repeating the exposure until the pattern has been assessed, and do not drive if you feel faint. Arrange a GP review for recurrent episodes, symptoms lasting beyond the exposure, or a known heart or thyroid condition; an examination and heart-rhythm check may be needed.

Call emergency services for palpitations with chest pain or pressure, severe breathlessness, fainting, new confusion, blue-grey lips, or a sustained very fast or clearly irregular heartbeat. Seek prompt medical advice for episodes that recur, occur during exercise, wake you from sleep, or come with dizziness. Do not dismiss symptoms simply because cold water was the trigger.

Could this be a cold-triggered stress response or an abnormal rhythm? Do I need an ECG or other checks? Should I change my activity, fluid intake or exposure to cold water while this is being assessed?