Fainting (syncope) is caused by the blood supply to the brain being interrupted for a variety of reasons. When this is neurally mediated, it related to the nervous system comprising of the brain, nerves and spinal cord. There are 3 types if neurally mediated syncope (also called reflex syncope): vasovagal, situational and carotid sinus syncope.
Vasovagal syncope occurs when a temporary malfunction in the autonomic nervous system occurs. The autonomic nervous system is part of the nervous system responsible for regulating many of the body's automatic functions, including heart beat and blood pressure. When there is increased activity of one of the main nerves in this system called the vagus nerve, a drop in blood pressure and heart rate occurs, leading to temporary interruption in the bran's blood supply and causing syncope.
Vasovagal syncope may be caused by:
Standing for long periods of time
Spending a long time in a hot environment
Sudden intense stress, emotional upset, fear or anxiety
Situational syncope is also a type of fainting related to the nervous system. It occurs when a bodily function places a sudden strain on the autonomic nervous system. Causes include: • Coughing • Sneezing • Swallowing • Laughing • Passing stools • Urinating
Carotid Sinus Syndrome
The carotid sinus is a collection of sensors in the carotid artery, located in the neck. The carotid sinus heps regulate the blood flow into the brain through the carotid artery. Some people develop a hypertensive carotid sinus that results in any physical stimulus of the carotd sinus causing the sensors to suddenly trigger a drop in blood pressure and heart rate- this is known as carotid sinus syndrome. Examples of the type of stimulation include: • Turning your head to one side quickly • Shaving over the carotid sinus area in the neck • Wearing a tight collar It can be simulated by massaging the carotid sinus while the patient is connected to a heart monitor to detect the blood pressure and heart rate drop. This condition is more common in older patients.
An ECG will help detect any drop in heart rate (an ambulatory 24 hour monitor can also sometimes help) and a blood pressure monitor can detect drops too. Carotid sinus massage as described above can also be carried out in a controlled environment. Tilt table testing can help rule out orthostatic hypotension (a drop in blood pressure resulting in fainting when one suddenly stands up, usually as a result of dehydration, anti-hypertensive mediation, diabetes or neurological conditions like Parkinson's disease).
Treating the underlying cause or avoiding specific triggers is usually the easiest and most effect way of avoiding further vasovagal and situational syncope episodes. Maintaining adequate hydration and cutting back on antihypertensive medications under your cardiologist's guidance will also help with orthostatic hypotension. Carotid sinus syncope however may require a pacemaker insertion to ensure the heart beat does not drop to levels low enough to cause syncope.