Syncope (Fainting): Causes, Cardiac Risks, Tilt Table Testing, and Treatment

Assoc. Prof. Sezen Bağlan Uzunget, MD
Cardiologist

What Is Syncope?

Syncope is a sudden, brief loss of consciousness caused by a temporary reduction in blood flow to the brain.

It is typically associated with loss of postural tone, followed by spontaneous and complete recovery.

Syncope can occur at any age.

However, not every episode of loss of consciousness is syncope.

Epileptic seizures, hypoglycemia, metabolic disorders, and other neurological conditions may also cause altered or lost consciousness.

An important part of syncope evaluation is determining whether the episode is related to an underlying cardiac condition.

What Causes Syncope?

Syncope is generally classified into three main categories:

Reflex or neurally mediated syncope
Syncope due to orthostatic hypotension
Cardiac syncope

These conditions differ in their mechanisms, prognosis, and treatment.

1. Reflex Syncope (Vasovagal Syncope)

Reflex syncope is one of the most common causes of fainting.

An autonomic reflex causes a decrease in blood pressure, heart rate, or both.

The resulting temporary reduction in cerebral blood flow leads to loss of consciousness.

Common Triggers

Prolonged standing
Hot or crowded environments
Severe pain
Seeing blood
Blood draws or injections
Emotional distress
Dehydration

Symptoms Before Fainting

Patients may experience:

Dizziness
Blurred or darkening vision
Nausea
Cold sweating
Feeling hot
Pallor
Ringing in the ears
Weakness

These warning symptoms are not present in every patient.

Vasovagal syncope is generally benign, although recurrent episodes may cause injuries and reduce quality of life.

2. Orthostatic Hypotension

Orthostatic hypotension is an excessive fall in blood pressure after standing.

Classic orthostatic hypotension is defined by a reduction in systolic blood pressure of at least 20 mmHg or diastolic blood pressure of at least 10 mmHg within three minutes of standing.

Potential causes include:

Dehydration
Diuretics or certain antihypertensive medications
Autonomic dysfunction
Prolonged bed rest
Neurological disorders
Age-related changes in circulatory regulation

Symptoms often occur shortly after standing up.

3. Cardiac Syncope

Cardiac syncope results from heart rhythm disturbances or structural cardiovascular disease.

Some causes are potentially life-threatening.

Arrhythmia-Related Syncope

Possible causes include:

Advanced atrioventricular block
Severe bradycardia
Sinus node dysfunction
Ventricular tachycardia
Certain rapid supraventricular tachycardias
Inherited arrhythmia syndromes

Structural Cardiac Causes

These include:

Severe aortic stenosis
Hypertrophic cardiomyopathy
Certain forms of advanced heart failure
Pulmonary embolism
Pulmonary hypertension
Other serious cardiovascular disorders

Syncope occurring during exercise requires careful evaluation for a cardiac cause.

Which Episodes of Fainting Are Dangerous?

Warning features include:

Syncope during exertion
Syncope while lying down
Sudden fainting without warning symptoms
Palpitations immediately before fainting
Syncope associated with chest pain or breathlessness
Known structural heart disease
Family history of sudden cardiac death at a young age
Significant ECG abnormalities

These findings warrant prompt medical evaluation.

What Is the Difference Between Syncope and Epilepsy?

Syncope and epileptic seizures can sometimes appear similar.

Brief involuntary movements may occur during syncope, so the presence of jerking movements alone does not establish epilepsy.

Epileptic seizures may be associated with prolonged confusion after the event and other characteristic findings.

However, no single feature reliably distinguishes all cases.

The diagnosis is based on a detailed history, witness descriptions, examination, and additional testing when necessary.

How Is Syncope Evaluated?

1. Detailed Medical History

Important questions include:

Was the patient standing, sitting, or lying down?
Did the episode occur during exercise?
Were palpitations present beforehand?
Were there warning symptoms?
How long did unconsciousness last?
Was recovery immediate and complete?
Have similar episodes occurred before?

2. Physical Examination and Orthostatic Blood Pressure

Cardiovascular examination and blood pressure measurements during postural changes are important.

3. Electrocardiography (ECG)

A 12-lead ECG is a fundamental part of syncope assessment.

It helps identify rhythm disturbances, conduction abnormalities, and certain markers of arrhythmic risk.

4. Echocardiography

Echocardiography is used when structural heart disease is suspected.

It evaluates cardiac valves, myocardial structure, and ventricular function.

5. Ambulatory Rhythm Monitoring

Depending on the frequency of symptoms, monitoring may include:

24–48-hour Holter monitoring
Extended ambulatory ECG monitoring
External event recorders
Implantable loop recorders (ILRs)

Long-term monitoring can be particularly useful in patients with infrequent, unexplained syncope.

6. Exercise Testing

Exercise testing may be considered when syncope occurs during or immediately after physical exertion.

7. Tilt Table Testing

Tilt table testing is used to investigate reflex syncope and selected orthostatic intolerance disorders.

What Is a Tilt Table Test?

A tilt table test evaluates heart rate and blood pressure responses when a patient is moved from a horizontal to an upright position under controlled conditions.

The aim is to reproduce symptoms and identify abnormal cardiovascular reflexes.

How Is the Test Performed?

The patient lies on a specially designed table.
Heart rhythm and blood pressure are monitored.
The table is tilted to approximately 60–70 degrees.
Symptoms and circulatory responses are observed.
Pharmacological provocation may be used according to the testing protocol.

Dizziness, nausea, sweating, or syncope may occur during testing.

How Are Tilt Table Test Results Interpreted?

Different response patterns may be observed.

Vasodepressor Response

A fall in blood pressure is the dominant finding.

Cardioinhibitory Response

Marked slowing of the heart rate or transient asystole is the dominant feature.

Mixed Response

Both blood pressure reduction and heart rate slowing occur.

Results must be interpreted in the context of the patient's spontaneous episodes.

A positive tilt test does not prove that every spontaneous episode has the same mechanism, and a negative test does not completely exclude reflex syncope.

Is POTS the Same as Syncope?

No.

Postural orthostatic tachycardia syndrome (POTS) is characterized by excessive heart rate increase after standing, accompanied by orthostatic symptoms.

In adults, a sustained heart rate increase of at least 30 beats per minute within 10 minutes of standing, without significant orthostatic hypotension, is an important diagnostic feature when accompanied by the appropriate clinical history.

Symptoms may include:

Palpitations
Dizziness
Fatigue
Exercise intolerance
Difficulty concentrating

Patients with POTS may faint, but fainting is not required for the diagnosis.

How Is Vasovagal Syncope Treated?

Treatment aims to reduce recurrence, prevent injuries, and improve quality of life.

1. Avoiding Triggers

Patients should recognize and avoid triggers such as prolonged standing, heat exposure, and dehydration when possible.

2. Hydration

Increasing fluid intake may help selected patients.

Additional salt intake may be considered in some cases, but it may be inappropriate for patients with hypertension, heart failure, or kidney disease.

3. Physical Counterpressure Maneuvers

Patients who recognize warning symptoms may benefit from:

Leg crossing with muscle tensing
Handgrip exercises
Arm and leg muscle contraction

These maneuvers may help maintain blood pressure.

4. Medication

Medication may be considered in selected patients with frequent, troublesome reflex syncope.

Treatment depends on age, blood pressure, and the underlying mechanism.

5. Pacemaker Therapy

Pacemaker implantation is not routinely indicated for vasovagal syncope.

It may be appropriate for selected patients with recurrent severe episodes and documented significant spontaneous bradycardia or asystole.

A slow heart rate during tilt testing alone does not automatically justify pacemaker implantation.

How Is Cardiac Syncope Treated?

Treatment depends on the underlying cardiac disorder.

Examples include:

Pacemaker implantation for selected severe bradyarrhythmias or conduction disorders
Implantable cardioverter-defibrillator (ICD) therapy for certain dangerous ventricular arrhythmias
Catheter ablation for appropriate arrhythmias
Valve intervention for severe valvular disease
Disease-specific treatment for structural heart conditions

What Should You Do When Someone Faints?

If warning symptoms occur, the person should sit or lie down promptly.

Elevating the legs may help in certain situations.

When assisting someone who has fainted:

Check breathing.
Place the person in a safe position.
Do not give food or drinks while consciousness is impaired.
Seek emergency help if consciousness does not return promptly.
If the person is not breathing normally, contact emergency services and begin basic life support.

When Is Emergency Assessment Necessary?

Emergency assessment is particularly important when fainting:

Occurs during exercise
Is associated with chest pain
Follows significant palpitations
Occurs with shortness of breath
Causes serious injury
Involves prolonged unconsciousness
Occurs in a patient with known significant heart disease

Does Recurrent Syncope Always Mean Serious Heart Disease?

No.

Many recurrent fainting episodes are caused by reflex mechanisms.

However, repeated episodes may cause injuries and significantly affect daily life.

Identifying the mechanism is essential for appropriate treatment.

This content is provided for general educational purposes. The evaluation and management of syncope should be individualized according to medical history, physical examination, ECG findings, and additional investigations when indicated.