Vasovagal Syncope: Symptoms, Causes & Treatment

Vasovagal syncope is a temporary loss of consciousness resulting from a sudden drop in blood flow to the brain. It is by far the most common cause of fainting, occurring due to an overreaction of the autonomic nervous system (via the vagus nerve) that slows the heart rate and widens the blood vessels, so blood pressure suddenly drops and blood reaching the brain decreases.

An attack is often triggered by known triggers such as standing for long periods, especially in hot or crowded places, severe pain, seeing blood or needles, stress and fear, dehydration, or straining during urination or coughing. Distinctively, the attack is often preceded by warning signs for seconds: dizziness, pallor, cold sweating, nausea, blurred vision, or ringing, which gives a chance for prevention if the person lies down or sits immediately.

In the vast majority of cases, vasovagal syncope is benign and not dangerous, and the person recovers within seconds to minutes without aftereffects. Nevertheless, it is important to evaluate any fainting medically to ensure there is no serious cardiac or neurological cause, especially if it occurs during exertion or without warning or comes with palpitations or chest pain. Management relies mainly on education and avoiding triggers, increasing water and salt intake (under medical supervision), and learning maneuvers that raise blood pressure when feeling early signs, along with treating any accompanying cause.

• Warning signs before fainting: dizziness, pallor, cold sweating, nausea, blurred vision.
• Brief loss of consciousness (seconds to a minute) with a fall.
• Quick recovery after lying down, sometimes with mild fatigue.

• An overreaction of the autonomic nervous system that slows the heart and widens vessels.
• Triggers: prolonged standing, heat, pain, seeing blood/needles, stress, dehydration.
• Straining during urination, coughing, or swallowing.

• Clinical assessment, history, and a description of the attack and its triggers.
• Electrocardiogram to rule out cardiac causes.
• A tilt-table test and additional tests in selected cases.

Education and avoiding triggers

• Recognizing early signs and lying down or sitting immediately and raising the legs.
• Avoiding prolonged standing, heat, dehydration, and known triggers.

Supportive measures

• Increasing water and salt intake under medical supervision, and counter-pressure maneuvers (tensing limb muscles).
• Medications in frequent severe cases as determined by the doctor.

This content is educational and does not replace medical advice.

• Injuries from falling during fainting.
• Anxiety and avoiding activities for fear of attacks.
• An atypical faint may hide a cardiac cause needing evaluation.

• Drinking enough water and avoiding dehydration.
• Avoiding prolonged standing and heat, and rising slowly.
• Lying down immediately when feeling early signs.