There are many causes of syncope.
- If blood does not circulate the way it should
- The autonomic nervous system does not work properly
- Changes in blood pressure
- Changes in heart rate
- Heart problems
- Metabolic abnormalities
Types of Syncope
There are a number of types of syncope.
Blood Pressure Drops Suddenly
This is the most common type of syncope and occurs when your blood pressure drops suddenly, reducing blood flow to your brain. When you stand up, gravity causes blood to pool in the lower part of your body, below the diaphragm. In response, the heart and autonomic nervous system (ANS) react to maintain your blood pressure.
Triggered by Particular Situations
This is a type of vasovagal syncope that takes place only during particular situations. Certain situations "trigger" an exaggerated neurological reflex. These can include such things as dehydration, intense emotional stress, anxiety, fear, pain, hunger, the sight of blood or use of alcohol or drugs. Hyperventilation associated with panic or anxiety also can cause syncope. Other triggers may include coughing forcefully, turning the neck or wearing a tight collar.
Blood Pressure Drops Suddenly Due to Quick Position Change
This occurs when your blood pressure drops suddenly due to a quick change in position, such as from lying down to standing. Postural syncope can be related to certain medications or dehydration.
Heart or Blood Vessel Problem Interferes with Blood Flow to Brain
This involves a loss of consciousness due to a heart or blood vessel problem that interferes with blood flow to your brain. Among these are an abnormal heart rhythm (arrhythmia), obstructed blood flow in the heart or blood vessels, valve disease, aortic stenosis, blood clot, or heart failure. Syncope caused by heart problems can be life-threatening.
Triggered by Neurological Condition
This is the result of a neurological condition such as stroke, transient ischemic attack (TIA) or seizure.