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Syncope, a transient loss of consciousness and postural tone due to reduced cerebral blood flow, is associated with spontaneous recovery.


Cerebral blood flow can be maintained if cardiac output and systemic arterial vasoconstriction compensate, but when these adjustments fail, hypotension which results in cerebral Perfusion to less than half of normal results in syncope.

Causes of syncope

  1. Disorders of vascular tone or blood volume
    Orthostatic hypotension
  2. Cardiovascular disorders
    1. Structural and obstructive causes
      1. Pericardial constriction or tamponade
      2. Aortic outflow tract obstruction
      3. Aortic valvular stenosis
      4. HOCM
    2. Cardiac arrhythmias
      1. Bradyarrhythmias
      2. Tachyarrhythmias
  3. Cerebrovascular Disease
  4. Vertebrobasilar insufficiency
  5. Basilar artery migraine
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Differential diagnosis

  1. Anxiety attacks
  2. Hyperventilation syndrome
  3. Seizures
  4. Hypoglycemia
  5. Hysterical Fainting

Diagnostic Tests

  1. Electrocardiogram.
  2. Invasive cardiac electrophysiologic testing provides diagnostic and prognostic information regarding sinus node function, AV conduction, and supraventricular and ventricular arrhythmias.
  3. Upright tilt table testing (AIIMS May 2007) is the most important tests in orthostatic hypotension. 
  4. The echocardiogram is the “gold standard” for the diagnosis of hypertrophic cardiomyopathy and atrial myxoma.

Note: Carotid sinus massage should generally be avoided, unless carotid ultrasound is negative for atheroma, because its diagnostic specificity is unknown and it may provoke a transient ischemic attack (TIA) or stroke in individuals with carotid atheromas.

Rx Syncope


The treatment of syncope is directed at the underlying cause.

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