A site for medical students - Practical,Theory,Osce Notes

Syncope due to reflex affecting heart

Vasovagal syncope

It  is a very common cause of dizziness or syncope that  is characteristically seen in response to the following.
  • Fear
  • Sudden emotional stress
  • Anxiety
  • Physical or mental exhaustion
  • Pregnancy 
  • Anaemia. 
Vasovagal syncope is always preceded by warning symptoms such as nausea. weakness, sweating, epigastric discomfort, blurred vision, headache, tinnitus, difficulty  in concentrating, sighing and dizziness.

The heart rate decreases, and the patient appears pale. The syncope is transient,and  last a few seconds to a few minutes, and this may be prevented by immediately lying down. Rarely, this type of syncope can occur when the patient is recumbent.

Orthostatic hypotension
Orthostatic hypotension produces dizziness on arising or after prolonged standing and this can be related to reduction  in effective blood volume, autonomic nervous system dysfunction, or rarely, to circulating vasodilator substances.

Causes are 
  • Drugs-antihypertensive or antidepressant medications, vasodilators, and beta blockers
  • Diabetic autonomic neuropathy
  • Anaemia
  • Low blood volume
  • Large varicose veins
  • Pregnancy
  • Addison's disease (rare cause)
  • Secondary hypertension-pheochromocytoma.
Hypersensitive carotid sinus
It is suspected when the patient describes dizziness or syncope after hyperextension of the neck, turning of the head, or pressure over the area of the carotid sinus from a necktie or during shaving. The syncope is evanescent, with rapid and complete recovery.