First degree AV block
See brief interpretation of 12 lead EKG above
– PR interval > 0.22 sec and all P waves conduct to the ventricles
First degree heart block (or first degree atrioventricular, AV, block) is characterized by PR prolongation more than 0.22 seconds, but all P waves conduct to the ventricles. The conduction from the atria to the ventricles are delayed and the lesion is most often located at the AV node.
A detail from the EKG above:
Note that the prolongation may be so marked, that the P wave is integrated in the preceding T wave or is mistaken for an U wave.
First degree heart block is considered a benign condition and a minor prolongation may be seen in normal individuals and athletes, though it is also associated with electrolyte disturbances, digitalis intoxication, myxedema and myocardial infarction.