What should you know about valsalva syncope?

Bearing down during a bowel movement, lifting, coughing, urinating, or other exertion can raise pressure inside the chest. This can temporarily reduce blood returning to the heart, lower blood pressure, and limit brain blood flow. Warning symptoms may include light-headedness, blurred vision, nausea, sweating, or ringing in the ears before a blackout. Fainting after straining can have this mechanism, but other causes such as dehydration, low blood sugar, anaemia, or a heart rhythm problem also need consideration.

If warning symptoms start, stop the activity, lie flat, and raise your legs if possible. Loosen tight clothing and avoid standing until you feel fully recovered. Arrange a medical assessment after an unexplained blackout, particularly if it is a first episode, happened during exertion, or caused an injury. Keep a record of the trigger, posture, symptoms beforehand, recovery, medicines, and fluid intake.

Call emergency services for fainting with chest pain, severe breathlessness, palpitations, prolonged confusion, seizure-like movements, serious injury, or failure to wake promptly. Urgent assessment is also needed when fainting occurs during exercise, while sitting or lying down, or repeatedly without a clear trigger. Do not drive until a clinician has advised you about safety.

Does the trigger and warning pattern fit reflex fainting? Should I have an electrocardiogram or blood tests? Could a medicine, dehydration, or another condition be contributing? What activities should I avoid until review?