Causes of Syncope - Differential Diagnosis Algorithm

Cardiac - Arrhythmia:

 • Tachyarrhythmia

 • Bradyarrhythmia

 • Supraventricular Tachycardia

 • Sick-Sinus Syndrome

 • Second/Third Degree Atrioventricular Block

Cardiac - Outflow Obstruction:

 • Aortic Stenosis

 • Hypertrophic Obstructive Cardiomyopathy

 • Pulmonary Embolus

 • Other

Orthostatic:

 • Dehydration

 • Hypovolemia

 • Medications

Central:

 • Emotional

Peripheral/Situational:

 • Bladder Emptying

 • Pain

 • Reduced Effective Arterial Blood Volume

 • Carotid Sinus Syncope

 • Tussive

 • Defecation



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