AV Blocks - First Degree Blocks
A 
first degree heart
block indicates that there is a delay
in conduction between the atria and bundle of His. The cause may
be due to either an interruption in either the atria or AV node
itself. It is indicated on the ECG as having a prolonged P-R
interval of >0.20 seconds duration indicating that depolarization
is taking longer to travel through the AV node. Among the causes
of first degree heart block are digitalis intoxication,
beta-blockers, Calcium channel blockers and hyperkalemia (excess
potassium in the blood). The electrical impulse will eventually
get to the ventricles, so this type of heart block is actually a
delay, not a true block of electrical activity.
first degree heart
block indicates that there is a delay
in conduction between the atria and bundle of His. The cause may
be due to either an interruption in either the atria or AV node
itself. It is indicated on the ECG as having a prolonged P-R
interval of >0.20 seconds duration indicating that depolarization
is taking longer to travel through the AV node. Among the causes
of first degree heart block are digitalis intoxication,
beta-blockers, Calcium channel blockers and hyperkalemia (excess
potassium in the blood). The electrical impulse will eventually
get to the ventricles, so this type of heart block is actually a
delay, not a true block of electrical activity.