From the Guidelines
Syncope is primarily caused by a temporary reduction in cerebral perfusion, resulting from decreased cardiac output, reduced peripheral vascular resistance, or both, and can be classified into cardiac, noncardiac, and reflex syncope, with vasovagal syncope being the most common type. The causes of syncope can be diverse, including:
- Cardiac syncope, which is caused by bradycardia, tachycardia, or hypotension due to low cardiac index, blood flow obstruction, vasodilatation, or acute vascular dissection 1
- Noncardiac syncope, which includes reflex syncope, orthostatic hypotension, volume depletion, dehydration, and blood loss 1
- Reflex syncope, which is caused by a reflex that leads to vasodilation, bradycardia, or both, and can be further classified into vasovagal syncope, carotid sinus syndrome, and other types 1 Other less common causes of syncope include:
- Cardiovascular conditions such as cardiac tamponade, constrictive pericarditis, and pulmonary embolus 1
- Infiltrative diseases such as amyloidosis and hemochromatosis 1
- Infectious diseases such as myocarditis and Lyme disease 1
- Neuromuscular disorders such as myotonic dystrophy and Friedreich ataxia 1
- Anatomic abnormalities such as cardiac tumors and anomalous coronary artery 1 It is essential to identify the underlying cause of syncope to provide appropriate management and treatment, which may include lifestyle modifications, medications, and interventions such as pacemaker implantation or surgery 1.
From the Research
Causes of Syncope
The causes of syncope can be categorized into:
- Cardiovascular causes, which can be further subdivided into structural heart disease, coronary heart disease, and arrhythmia 2
- Non-cardiovascular causes, including neurological, metabolic, psychiatric, and other disorders 2
- Unexplained causes, with many patients experiencing neurally mediated (i.e., neurocardiogenic or vasovagal) syncope 2
Cardiovascular Causes
Cardiovascular causes of syncope may be structural (mechanical) or electrical 3. The second most frequent category of syncope is cardiac syncope, with bradyarrhythmias or tachyarrhythmias being the most common causes 4.
Non-Cardiovascular Causes
Non-cardiovascular causes of syncope include:
- Orthostatic hypotension, which is caused by an abnormal drop in systolic blood pressure upon standing 3
- Reflex syncope, which can be categorized into vasovagal syncope, situational syncope, carotid sinus syncope, and atypical reflex syncope 3
- Neurogenic orthostatic hypotension, which can present with syncope or severe recurrent presyncope 5
Other Causes
Other causes of syncope include:
- Vasovagal syncope, which can be associated with painful or emotionally stressful situations, prolonged standing, or specific trigger situations 2
- Situational syncope, which is due to specific situational stressors 3
- Carotid sinus syncope, which is caused by pressure on the carotid sinus 3
- Atypical reflex syncope, which is characterized by episodes of syncope or reflex syncope that cannot be attributed to a specific trigger or syncope with an atypical presentation 3