Per UWorld:
"In 3rd degree AV block, electrical impulses coming from SA node are blocked before being transmitted to the ventricles; the point of blockade is usually within the AV node or His bundle.
The cells located immediately distal to the blockade (e.g. in the His bundle in this patient) never receive the impulse from the SA node and therefore begin generating their own pacemaker impulse that is transmitted to the ventricles.
On ECG, the SA node impulses continue to march out as P waves, and the His bundle impulses generate QRS complexes (an escape rhythm) at the intrinsic rate of the His bundle pacemaker (eg 40-60/min). Because the atria and ventricles are not communicating, the P waves and QRS complexes have no relation to one another."
AV node being pacemaker doesn't make sense...how could it transmit the SA's signal to the ventricles if there's a complete blockade at the level of the AV node or below it?
