Written by Dimitrios Vrachatis, Specialist Cardiologist, PhD, National and Kapodistrian University of Athens.
What is fainting?
Transient loss of consciousness is a distressing experience. It is brief and involves loss of memory for the event, reduced responsiveness and loss of motor control. It may result from syncope, a seizure or a psychogenic episode.
Which doctor assesses fainting?
Loss of consciousness always requires urgent medical assessment, often involving several specialties, starting with cardiology.
The cardiologist assesses syncope: transient loss of consciousness with sudden onset, spontaneous complete recovery and reduced blood supply to the brain.
What happens during syncope?
Oxygenated blood supply to the brain falls. Six to eight seconds of low aortic pressure, approximately 50–60 mmHg, corresponding to cerebral arterial pressure of 30–45 mmHg, can be sufficient.
What is presyncope?
Presyncope is the state preceding fainting, though it does not always progress to loss of consciousness. It is usually described as feeling about to faint, severe dizziness or dimming vision.
How is syncope classified?
It is classified as:
- Cardiac
- Orthostatic
- Neurally mediated or reflex
Why is prompt assessment important?
Without medical care, approximately 10% of cases are followed by a major adverse event within 7–30 days.
Presyncope is reported to carry similar subsequent risk. Finding the cause can be difficult, and a definite diagnosis is not always reached.
Which tests may be needed?
Basic assessment includes:
- A detailed history
- Examination, including standing blood pressure testing and/or carotid sinus massage when indicated
- A resting ECG and/or 24-hour Holter recording
- Echocardiography
- An exercise test
- Blood tests
Prolonged monitoring with an implantable loop recorder may be needed. Findings may lead to coronary angiography or an electrophysiology study. Investigations proceed stepwise according to individual characteristics and diagnostic algorithms.
What causes cardiac syncope?
Potential causes span much of cardiovascular medicine:
- Acute coronary syndromes, reducing coronary blood flow
- Electrical conduction disorders
- Pulmonary embolism
- Acute aortic dissection
- Valve disease
- Dangerous arrhythmias
- Channelopathies
- Congenital heart disease
Is cardiac syncope dangerous?
Many causes are life-threatening. They may arise suddenly, such as myocardial infarction or complete heart block, or reflect a pre-existing diagnosed or undiagnosed condition, such as severe aortic stenosis or chronic coronary disease. Urgent diagnosis and appropriate treatment are required.
How is cardiac syncope treated?
Treatment depends on the cause. An acute myocardial infarction requires angiography and probably angioplasty. Severe irreversible bradycardia may require a permanent pacemaker. Severe aortic stenosis requires valve replacement. Dangerous rapid arrhythmias may require ablation and/or an ICD. These are examples rather than an exhaustive list.
Are non-cardiac forms equally dangerous?
Orthostatic and reflex syncope are benign forms. Behavioural changes are usually the main treatment:
- Avoid standing suddenly from sitting.
- Recognise warning symptoms and sit or lie down before fainting.
- Learn physical counter-pressure exercises for prolonged standing.
- Stay well hydrated.
- Avoid very hot showers.
- Avoid or protect against known triggers, such as severe pain, fear or prolonged standing.
The treating doctor may adjust medicines that worsen the problem. In selected cases, specific medicines such as fludrocortisone or midodrine are used.
What is the prognosis?
It depends on the cause. Because possibilities range from harmless to very dangerous, specialist assessment is always needed rather than self-diagnosis.
When is the risk higher?
Every episode of loss of consciousness needs prompt medical advice. Higher-risk features include:
- Severe chest pain, abdominal pain or headache
- Cold sweats
- A markedly fast or slow heartbeat
- Persistently low blood pressure
- Known heart failure, coronary disease, valve disease, cardiomyopathy or a serious arrhythmia
- Older age
- Injury during the episode
- Occurrence during exercise
- Repeated episodes
- A family history of sudden death at a young age