What is Venous Syncope?

Syncope is defined as a brief loss of consciousness with an inability to maintain postural tone that is followed by a rapid and complete recovery.

Syncope is common and about one-third of the population experiences a syncopal episode in their life. Syncope may be an alarming sign in some people who have a serious underlying medical condition. In a younger age group, more than 75% of cases are not associated with an underlying medical problem.

What are the symptoms?

Syncope is often preceded by symptoms of ‘faintness’ including:
  • Lightheadedness or dizziness
  • Blurring of vision
  • Heaviness in the lower limbs and swaying
  • Loss of consciousness
  • Drowsiness
  • Pale skin
  • Sweating
  • Nausea

What are the causes?

A number of causes can lead to syncope. To remain conscious, oxygen-rich blood must supply the brain without delay. A delay of blood to the brain for even 3-5 seconds can result in syncope.

Consciousness is regained after falling or lying down because blood returns to the brain once gravity is removed. A number of medical conditions can cause syncope.

The most common causes include:

A. Vasovagal Syncope

This is the most common type of syncope. This is triggered by a number of conditions including physical or emotional stress, fear (i.e. sight of blood), dehydration, bleeding, pain, anemia, fever, or fasting.

These conditions or ‘triggers’ stimulate a nerve to slow the heart rate and dilate the blood vessels, which causes blood to pool in the legs, resulting in low blood pressure (hypotension). This leads to a decrease or delay in blood flow to the brain resulting in syncope.

Symptoms include nausea, sweating, stomach pain, hyperventilation, weakness, and confusion.


B. Cardiac Syncope:

Cardiac syncope can be due to arrhythmia or obstruction to cardiac outflow.

  • Alteration of the heart rate and rhythm can produce cardiac syncope. The heart rate and rhythm are controlled by the natural pacemaker of the heart known as the Sinoatrial Node.

This regulates the electrical activity of the heart which follows through a conduction pathway.

Syncope can occur due to problems at several places in this pathway.

When this is altered the condition is termed as arrhythmia.

Arrhythmias are produced by:

– Bradycardia: this means the heart rate is slower than normal. A slow heart rate does not allow enough blood flow to reach the brain.

– Heart Block: The transmission of impulses from the sinoatrial node are blocked. This interrupts the heart rate, making it slow and delaying blood flow to the brain.

– Ventricular Tachycardia: this refers to a fast heart rate. The ventricles in the heart send out their own rapid electrical impulses, over taking the normal rhythm produced from the sinoatrial node. This causes an inadequate amount of blood flow to the brain.

– Supraventricular Tachycardia: this also includes a fast heart beat, although the generation of rapid electrical impulses originates above the ventricles.


  • Obstruction to cardiac outflow may also result in a sudden loss of consciousness. The most common causes of obstruction are due to hypertrophic cardiomyopathy (exertional syncope) and aortic stenosis.

– Hypertrophic Cardiomyopathy: is a thickening of the left ventricular muscle wall. This can lead to inadequate blood flowreaching the brain.

– Aortic Stenosis: is the thickening of the aortic valve in the heart leads to inadequate blood flow leaving the heart and can also lead to hypertrophic cardiomyopathy.

Other obstructive causes include mitral stenosis, pulmonary stenosis, pulmonary embolus, left atrial myxoma, and pericardial tamponade.

C. Orthostatic Syncope (Postural Syncope):

This refers to a low blood pressure after suddenly getting up from a laying position or from standing for a long period of time.

The heart rate slows and the blood vessels in the legs dilate causing a pooling of blood in the legs, leading to a lowering of blood pressure. This can decrease the blood flow to the brain and cause a syncopal episode.

The causes of orthostatic hypotension include blood or fluid loss, illnesses affecting the nervous system (i.e. diabetes, Parkinson disease), alcohol, carotid sinus hypersensitivity, and certain medications used to treat arrhythmias and lower blood pressure.

These medications include:

Angiotensin Converting Enzyme (ACE) Inhibitors
Beta Blockers
Calcium Channel Blockers
Tricyclic Antidepressants


D. Other Causes:


Other causes of syncope include low blood sugar, anemia, hyperventilation, seizures, heart attack, cardiac tumor, or pulmonary embolism.


Differential Diagnosis of a syncopal attack:



Adrenal Insufficiency/Crisis
Abdominal Aortic Aneurysm
Acute Massive Myocardial Infarction
Aortic Dissection


Aortic Stenosis
Atrial Fibrillation


Brugada Syndrome
Subarachnoid Hemorrhage
Obstructive Cardiomyopathy
Heart block


Left Atrial Valve Thrombus or Myxoma
Antidepressant Toxicity
Long QT Syndrome
Antiarrhythmic Toxicity
Mitral Stenosis
Beta-Blocker Toxicity
Multifocal Atrial Tachycardia
Calcium Channel Blocker Toxicity
Pulmonary Embolism
Cocaine Toxicity
Pulmonary Valvular Stenosis
Tricyclic Antidepressant Toxicity
Pulmonary Hypertension
Sinus Bradycardia
Sick Sinus Syndrome
Tetralogy of Fallot
Torsade de Pointes
Wolff-Parkinson-White Syndrome

How is it diagnosed?

Dr. Jamnadas will better understand your syncope based around 3 parameters.
These parameters include: Patient History, Physical Examination, and Testing.
A. Patient History:
Obtaining patient history is the most important diagnostic tool in syncope. 85% of the diagnosis comes from the history given from the patient.
  • Dr. Jamnadas  will ask of the events which occurred before, during, and after a syncopal attack.
  • You will be asked of precipitating factors such as sleep or food deprivation, if you were in a warm atmosphere, if alcohol was consumed, if u had any pain, or had strong emotional stress before the occurrence of syncope.
  • Warning signs before the attack might be discussed such as sweating or dizziness, which gives a clue towards a vasovagal syncopal attack.
  • If the event was sudden without warning signs, it is more likely to be a heart rhythm problem.
  • If the syncopal attack occurred during exertion, it is most likely an obstructive cause.
  • If the event occurred after postural changes or standing for a long period of time.
  • Details may be given from a witness present at the time of syncope and be able to estimate the duration of unconsciousness.
  • A witness may also provide history of how you were after the episode. If postevent confusion was present, it is a clue to determining whether the episode was syncope or a seizure. Postevent confusion is suggestive of a seizure.
  • You will also be asked if you have any preexisting medical conditions like heart disease or diabetes.
  • History will be taken from patients who have taken medication prior to the event, including blood pressure lowering drugs.
  • You will also be asked of any other personal and family history of cardiac disease.
B. Physical Examination:
  • During a physical examination, your vitals will be taken. Vitals include taking your pulse, blood pressure, and temperature. Blood pressure may be taken more than once, in the laying and sitting position.
  • Dr. Jamnadas will listen to the sounds of your heart to determine whether any high-grade valvular defects are present. They will also listen for any carotid artery bruits, indicating a narrowing of the blood vessel supplying the brain.
  • Carotid sinus massage may be done. The carotid artery (artery in the neck) is firmly massaged while your heart rate is monitored. This can help in diagnosing a condition known as carotid sinus syncope.
  • You will also be examined for any injuries that may have been sustained secondary to syncopes such as head injury, lacerations, or fractures.
C. Testing:
A number of medical tests can help determine the cause of syncope. These tests include:
Laboratory investigations:
  • Blood Analysis– this includes a CBC to reveal signs of anemia, serum glucose levels, electrolytes and renal function tests. Cardiac enzymes may be checked in patients whom cardiac origin is high.
  • Urine Analysis– to search for bacteria causing urinary tract infection, which may precipitate syncope.
Diagnostic Studies:
  • Electrocardiogram (EKG) – this is a common and easy test to perform which records the electrical activity of the heart. This detects any irregular heart rhythms and may show evidence of a preexisting heart attack.
  • 24-Hour Holter monitor– records the electrical events of the heart during your normal daily activities. This helps in detecting signs of arrhythmias. It is important to accurately record your activities and symptoms so Dr. Jamnadas can compare them to the Holter monitor findings.
  • Event monitor– If symptoms of arrhythmia are infrequent and do not occur within 24 hours, an event recorder may be ordered for you for up to 30 days.
  • Echocardiogram (ECHO) – shows images of the heart determining the size and shape of the heart, and shows whether the heart walls and pumping activity are normal or performing weakly.
  • Tilt Table Test– In this test you will be asked to lay flat on a table. The table will be tilted in various angles while your heart rate and blood pressure are monitored. This test is useful in revealing abnormal cardiovascular reflexes that produce syncope.
  • Stress test– helps access the blood flow to the heart at rest and during stress. Will detect if any areas are receiving less blood flow.
Other Studies:
  • Chest x-ray– to assess the size and shape of the heart in congestive cardiac failure, infections within the lung causing pneumonia, or any fluid or mass can be seen in the lungs.
  • Computerized tomography (CT scan) – to look for signs of abdominal aortic aneurysm or aortic dissection.
  • T-wave alternans test (TWA)– detects abnormalities in electrical conduction that predicts sudden death.

How is it treated?

Syncope is treated depending on the underlying cause. The goal of treatment is to prevent recurrences and the progression of serious problems.
Vasovagal syncope:
Vasovagal syncope can be treated by educating the patient of the precautions to be taken as well as avoiding potential triggers to minimize the potential risk of harm.
For example:
  • If you have carotid sinus syncope, you will be instructed to not wear tight collars, to use a razor instead of electric razor, and drink plenty of fluids.
  • If you usually faint at the sign of blood, Lie Down immediately and elevate the legs once you feel any symptoms of syncope. If you are unable to lie down, sit down with your head between your knees.
Cardiac Syncope:
Cardiac syncope is treated with antiarrhythmic drugs or pacemaker/ ICD placement. A pacemaker is a small device that is implanted under the skin of the chest. This connects wires to the heart which transmits impulses to regulate the heart rate and rhythm.
Patients with life-threatening ventricular arrhythmias may need an implantable cardioverter defibrillator (ICD). This does the same as the pacemaker, but also administers an electric shock to correct the electrical problem that can prevent a person from dying.
Cardiac outflow obstruction can be treated with Beta Blockers to decrease the workload of the heart. Cardiovascular intervention procedures may be required or valvular correction surgeries.
Orthostatic Syncope:
Orthostatic syncope treatment also involves patient education. Certain techniques are designed to decrease the pooling of blood in the legs that allows blood pressure to drop once you stand. These techniques include the contraction of the leg muscles before and during standing. You will also be instructed to and rise slowly, in stages to stand.
Additional therapy may be given such as increasing salt in your diet, foot exercises, compression stockings for the legs, and consumption of plenty of fluids can be useful in the treatment of syncope.
It is important to Stay Hydrated.
Antihypertensive medications, especially diuretics are notorious for causing orthostatic syncope and many need adjustment.
Medications used:
  • Fludrocortisone– can be given to increase the amount of blood volume.
  • Midodrine– is a medication that can also be given to constrict the blood vessels to increase the blood volume.

What is the prognosis?

Vasovagal syncope and orthostatic syncope have an excellent prognosis and do not increase the risk of death.

Patients with cardiac syncope may be restricted from their daily activities.

Without treatment, the prognosis for people with cardiac conditions is usually poor and has a mortality of 25%.

How can I prevent this?

Patient education is very important!
Education may have a vital impact on prevention and recurrence of syncope.
Certain maneuvers can be tried which may stop or delay vasovagal syncope.
These maneuvers include:
– Crossing the legs while tensing the leg muscles, abdominal muscles, and buttock
– Clenching your fists or gripping a stress ball
– Gripping your arms while trying to pull them apart
  • Avoid standing up too quickly
  • Sit near the aisle so you can leave if you feel faint
  • Increase your salt and potassium intake
  • Drink plenty of fluids
  • Do not skip meals
  • Do not stand for a long period of time
  • Avoid alcohol and caffeine
  • Review your medications with your doctor
Safety Issues:
Patients who present with syncope are instructed not to drive until cleared by the doctor to do so.
This is recommended mostly for patients with no warning signs of syncope.