Syncope is a transient loss of consciousness and usually occurs when there is a reduction in the flow of blood to the brain.
It is common, with 4 in 10 patients experiencing syncope at least once in their life and 1 in 40 emergency department visits being due to it.
There are a number of different causes of syncope. In most cases it is due to fainting (otherwise known as vasovagal syncope), which occurs because of problems with the way the body controls blood pressure and pulse and is not usually serious but can of course lead to injury.
However, there are a number of rarer causes of syncope that need important treatment and full assessment is important. In some cases, it may arise because of a serious rhythm problem with the heart. The other group of causes are structural problems such as a narrowed heart valve.
This is the most commonly reason for fainting, particularly in young patients. It occurs when reflexes that control heart rate and blood pressure fail temporarily leading to a reduction in blood supply to the brain.
It can occur in certain situations when the body overreacts to a trigger such as severe pain, distress, or standing for prolonged periods. It can also occur following certain actions such as coughing, swallowing, or even laughing. In some patients, it can occur due to stimulation of sensors in the neck (carotid sinus) which help regular blood pressure. This type of fainting usually occurs following certain neck movements, wearing tight collared shirts, or shaving.
Orthostatic syncope occurs as a result of the reduction in blood pressure when you stand up and is related to posture. This cause is usually clear because the collapses occur when moving from a sitting to a standing position. The body normally has mechanisms to stabilize blood pressure when standing, but in some cases the fall in blood pressure can be enough to cause syncope. The causes include dehydration, medications (particularly some prostate drugs, antidepressants and blood pressure medications) and some underlying health conditions such as diabetes, multiple sclerosis, or Parkinson's disease
A variety of rhythm problems can cause syncope including the heart being too fast (ventricular tachycardia, supraventricular tachycardia) or too slow (atrioventricular block, sick sinus syndrome). Patients may complain of palpitations before they lose consciousness. In some patients there may be a history of cardiac problems, or a family history of rhythm problems with the heart.
In some cases the shape or function of the heart is abnormal and this can limit the blood flow out of the heart to the brain. This may be more apparent during exercise. This may be due to a valvular problem such as aortic stenosis, or a problem with the heart muscle such as hypertrophic cardiomyopathy. In some cases of heart failure the output of the heart can be so low as to cause syncope, but this can co-exist with rhythm problems.
If the symptoms are very suggestive of fainting (i.e. neurocardiogenic syncope) then no tests may be required. Blood tests to look for anaemia or thyroid problems are suggested and an electrocardiogram (ECG) to look for conduction problems with the heart is often useful.
If the patient’s symptoms are not suggestive of fainting then investigation with 24-hour ECG (to look for intermittent arrhythmias) and an echocardiogram (to look for problems with the shape or function of the heart) are recommended. If the syncope is thought to be due to other causes such as coronary artery disease then other tests may be required.
If the syncope is due to fainting, then the measures below may be helpful.
In other cases, the syncope is due to another causes and this requires specific assessment and treatment. The treatment may include a pacemaker (if the heart rate is too slow), anti-arrhythmic drugs or ablation (if the heart rate is too fast) and even surgery to replace narrowed a narrowed heart valve.
Syncope is common and in many cases is an isolated problem which doesn’t have long-term consequences. However, there are important causes which require treatment and a thorough assessment is suggested. Our expert Consultant Cardiologists are fully trained in evaluating syncope and are available for consultation on any day of the week and weekends as well.
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