Causes of Syncope
| Mechanism | Subtype | Comment |
|---|---|---|
| Reflex (neurally-mediated) | Vasovagal | Typically follows pain, emotional distress or prolonged standing. Diagnose when there are no features suggesting an alternative diagnosis, and the clinical features are concordant (Table 9.2). |
| Situational | Diagnose when there are no features suggesting an alternative diagnosis and syncope occurred in typical circumstances (e.g. micturition while standing, or a prolonged bout of coughing). | |
| Carotid sinus hypersensitivity(CSH) | Diagnose in patients aged 60 and over with TLoC, when there are no features suggesting an alternative diagnosis, and testing for CSH (Table 9.4) is positive. | |
| Atypical form | Diagnose when there no features suggesting an alternative diagnosis, testing for CSH is negative, and tilt-table testing provokes symptoms. | |
| Orthostatic hypotension | Primary autonomic failure | For example in multiple system atrophy, Parkinson's disease with autonomic failure. |
| Secondary autonomic failure | For example in diabetes mellitus or amyloidosis. | |
| Drug-induced | Many drugs may cause or contribute to orthostatic hypotension, including alpha blockers, antidepressants, antihypertensive agents, drugs for Parkinson's disease and diuretics. | |
| Volume depletion | See Chapter 2. | |
| Cardiovascular | Bradyarrhythmia | See Chapter 44. |
| Tachyarrhythmia | See Chapters 40, 41, 42, 43. | |
| Structural cardiac disease | This includes valve disease (notably severe aortic stenosis; see Chapter 51), congenital heart disease and cardiomyopathies. ECG and echocardiography typically show characteristic abnormalities. | |
| Acute myocardial ischaemia | See Chapters 45 and 46. | |
| Aortic dissection | See Chapter 50. | |
| Pulmonary embolism | See Chapter 57. | |
| Severe pulmonary hypertension | May result in exertional syncope. There may be clinical signs of right ventricular failure (e.g. elevated jugular venous pressure). ECG and echocardiography typically show characteristic abnormalities. |