Syncope pathophysiology
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Overview
Blood pressure is the main determinant for the presentation of syncope. Blood pressure is determined by cardiac output and total peripheral vascular resistance, and hence, any disturbances with any of these variables may lead to the presentation of syncope.
Pathophysiology
Syncope is an entity in which loss of conscience due to cerebral hipoperfusion presents. There are several pathways to explain its pathophysiology, depending if it is either reflex syncope, orthostatic intolerance, or cardiovascular syncope.
Reflex Syncope
Reflex syncope presents when there is a failure of body's normal compensation of cardiac reflexes in response to a trigger. It can be manifested as 4 categories, whose pathophysiology differs:
- Vasovagal syncope
- Situtational syncope
- Carotid sinus syncope
- Atypical forms
Each of these categories has different triggers that lead to the presentation of syncope. Shown below a table for each syncope form and its triggers. Note that in any trigger, different mechanisms may be involved in its presentation, such as in micturition, where different pathways participate.
| Syncope |
Triggers: |
| Vasovagal |
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| Situational |
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| Carotid Sinus |
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| Atypical forms |
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Orthostatic Intolerance
Orthostatic intolerance is caused by a chronic autonomic nervous system failure (ANF). This ANF causes a deficient vasoconstriction and ultimately decreased blood pressure, leading to the manifestation of syncope. Syncope is a symptom of orhtostatic intolerance.