Syncope
Also known as: Fainting, Passing out, Blackout
Syncope is the medical term for fainting: a brief loss of consciousness caused by a temporary drop in blood flow to the brain, followed by full recovery. The most common type, vasovagal syncope, is triggered by things like standing for a long time, heat, pain, the sight of blood, or emotional distress, and is usually harmless. Fainting can also be caused by a drop in blood pressure on standing (orthostatic hypotension), often related to dehydration or medication. Less commonly, and more seriously, syncope results from a heart rhythm or structural heart problem. Because the harmless and dangerous types can look similar, any first faint, and any faint with warning features, deserves medical assessment.
At a Glance
- Common symptoms
- Sudden, brief loss of consciousness with collapse, Warning signs beforehand: lightheadedness, nausea, sweating, warmth, tunnel vision, or ringing in the ears, Pale or gray skin
- Main treatments
- For vasovagal syncope: education about triggers and warning signs, and often no further treatment, Reviewing and adjusting medications that lower blood pressure, Treating the underlying cause: a pacemaker for slow rhythms, ablation or other treatment for fast rhythms, or surgery for structural heart problems
- Category
- Cardiovascular · Very common; a large share of people faint at least once in their lifetime
- See a doctor if
- Any first episode of fainting, so a cause can be identified
Symptoms
Causes
- Vasovagal reflex: a sudden drop in heart rate and blood pressure triggered by pain, emotion, or prolonged standing
- Situational triggers such as coughing, urinating, or straining
- Orthostatic hypotension from dehydration, blood loss, or medications such as blood pressure drugs
- Heart rhythm problems (very slow or very fast rhythms)
- Structural heart disease such as aortic stenosis or hypertrophic cardiomyopathy
- Autonomic disorders including POTS and neuropathy
Risk Factors
- Previous episodes of fainting
- Older age, particularly with multiple medications
- Heart disease or a family history of sudden cardiac death
- Dehydration, heat exposure, or prolonged standing
- Diabetes, Parkinson's disease, or other causes of autonomic dysfunction
Diagnosis
- Detailed account of the event, including triggers, warning symptoms, and witness descriptions
- Physical examination with lying and standing blood pressure
- 12-lead ECG for everyone who faints
- Blood tests for anemia, blood sugar, and electrolytes
- Heart monitoring, echocardiogram, tilt-table testing, or electrophysiology studies when a cardiac or unclear cause is suspected
Treatment
- For vasovagal syncope: education about triggers and warning signs, and often no further treatment
- Reviewing and adjusting medications that lower blood pressure
- Treating the underlying cause: a pacemaker for slow rhythms, ablation or other treatment for fast rhythms, or surgery for structural heart problems
- Medications such as midodrine or fludrocortisone for recurrent orthostatic or vasovagal syncope in selected cases
- Supportive: adequate fluids and salt (if your doctor agrees), avoiding dehydration and heat
- Supportive: physical counter-pressure maneuvers (crossing the legs, clenching the fists, tensing the muscles) at the first warning sign
- Supportive: lying down and raising the legs when you feel faint rather than trying to push through
Prevention
- Stay hydrated, especially in hot weather or when unwell
- Stand up slowly and avoid long periods of standing still
- Learn your personal triggers and warning signs and act on them early
- Have blood tests or injections lying down if needles trigger you
- Review medications regularly, particularly in older age
When to See a Doctor
- Any first episode of fainting, so a cause can be identified
- Fainting during exercise, while lying down, or with chest pain or palpitations (seek urgent care)
- No warning before the faint, or injury resulting from it
- A family history of sudden cardiac death or known heart disease
- Repeated episodes, or confusion lasting more than a few minutes afterward
Frequently Asked Questions
Related Conditions
Related Reading
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