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- Transient loss of consciousness characterized by unresponsiveness, loss of postural tone, and spontaneous recovery; usually caused by cerebral hypoxemia
- System(s) affected: Cardiovascular; Nervous
- Up to 20% of adults will have ≥1 episode by age 75; 15% of children <18 years of age
- Accounts for 1–6% of hospital admissions and ~3% of emergency room visits
- Epidemiological study showed yearly prevalence of fainting spells resulting in medical evaluation was 9.5/1,000 inhabitants (1).
In institutionalized elderly (>75 years), 6%
- Heart disease
- Vasodilators (including calcium channel blockers, ACE inhibitors, and nitrates)
Specific cardiomyopathies and arrhythmias may be familial (i.e., long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy).
See “Risk Factors.”
- In some cases, vagal response leads to decreased heart rate.
- Systemic hypotension secondary to decreased cardiac output and/or systemic vasodilation leads to a drop in cerebral perfusion and resulting loss of consciousness.
- Cardiac: Obstruction to outflow:
- Aortic stenosis
- Hypertrophic cardiomyopathy
- Pulmonary embolus
- Anomalous coronary artery origin resulting in cardiac ischemia
- Cardiac arrhythmias:
- Sustained ventricular tachycardia (VT)
- Supraventricular tachycardia (atrial fibrillation, atrial flutter, re-entrant SVT)
- 2nd- and 3rd-degree AV block
- Sick-sinus syndrome
- Pacing-induced infranodal block
- H-V interval >100 ms
- Reflex-mediated vasovagal (neurocardiogenic/neurally mediated), situational (micturition, defecation, cough, hair combing)
- Orthostatic hypotension
- Neurologic: Seizures; transient ischemic attack (can in theory cause syncope, but presentation usually markedly clinically different from pure syncope)
- Carotid sinus hypersensitivity
Commonly Associated Conditions