Thursday, 16 September 2010

MRCP revision battle 13.3: Long PR interval

The PR interval represents the time taken for the electrical impulse to travel from the sino-atrial node and through the atrioventricular node to the ventricles.

Normal range is 0.12 to 0.2 milliseconds (= 3 to 5 small squares)

A long PR = first degree heart block.

Causes of a long PR ( can be remembered as DRIP SAL, easier to remember if you have a drippy friend called Sally):
  • Drugs (beta blockers, calcium channel blockers, digoxin)
  • Rheumatic fever
  • IHD (anterior MIs in particular can prolong the PR interval)
  • Potassium - either high or low levels
  • Sarcoidosis
  • Aortic root pathology
  • Lyme disease

So that was short and sweet.  Onto another brief battle that should be familiar, cauda equina syndrome...