From the Guidelines
Syncope is primarily caused by cardiac issues, neurally mediated causes, orthostatic hypotension, and other conditions that lead to insufficient blood flow to the brain, as stated in the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1. The main causes of syncope can be categorized into several groups, including:
- Cardiac causes, such as arrhythmias, structural heart problems, and cardiac output obstruction
- Neurally mediated causes, including vasovagal syncope, situational syncope, and carotid sinus hypersensitivity
- Orthostatic hypotension, often related to dehydration, medication side effects, or autonomic nervous system dysfunction
- Other causes, such as neurological conditions, metabolic disorders, and psychiatric conditions According to the European Heart Journal guidelines on management of syncope, the diagnosis of the cause of syncope can be made based on the initial evaluation, including the patient's history, physical examination, and eyewitness observation, if available 1. The evaluation of syncope should also include an assessment for structural heart disease and ischemia, as well as less common causes of syncope that are associated with sudden death, such as Wolff-Parkinson-White syndrome and inherited cardiac ion channel abnormalities 1. Identifying the specific cause of syncope is crucial for appropriate treatment, which may include medication adjustments, lifestyle changes, or addressing underlying conditions, and can help improve the quality of the patient's life and prevent injury to the patient or others 1.
From the Research
Causes of Syncope
The causes of syncope are diverse and can be associated with significantly different prognoses 2. Some of the possible causes of syncope include:
- Cardiac causes, such as dysrhythmia and obstruction 3
- Vasovagal causes, which are characterized by a sudden loss of consciousness due to a lack of cerebral perfusion 4
- Orthostatic causes, which occur when there is a sudden drop in blood pressure upon standing 3
- Neurologic causes, such as cerebrovascular disease and intracerebral hemorrhage 3
- Medication-related causes, which can occur due to the side effects of certain medications 3
- Idiopathic causes, which are cases where the cause of syncope is unknown 3
Vascular Causes of Syncope
Vascular causes of syncope can be deadly and include conditions such as:
- Pulmonary embolism 3, 4
- Subclavian steal 3
- Aortic dissection 3
- Cerebrovascular disease 3
- Intracerebral hemorrhage 3
- Carotid/vertebral dissection 3
- Abdominal aortic aneurysm 3
Structural Heart Disease and Syncope
The presence of structural heart disease in patients with syncope is associated with a poor prognosis and may be a predictor of sudden cardiac death 5. It is essential to consider the presence of structural heart disease and primary electrophysiological disorders in patients who present with syncope.
Life-Threatening Causes of Syncope
Cardiac syncope is associated with an elevated risk of mortality, and includes both primary arrhythmic and obstructive etiologies 6. Identification of individuals with life-threatening causes of syncope is contingent on careful clinical assessment and judicious use of diagnostic investigations.