Rules for Third Degree Block (Complete Heart Block)
Regularity: R-R interval will be regular. P-P interval will also be regular.
Rate: The atrial rate will be regular and normally be 60-100. Rate of the QRS complexes is dependent on the focus. If the focus is ventricular, the rate will be 20-40. If the focus is junctional, the rate will be 40-60.
P WAVE: P waves are upright and uniform. There will be more P waves than QRS complexes. PRI: PRI is not measured because there is no relationship between P waves ad QRS complexes. QRS: Usually measures more than 0.12 seconds, however if the focus producing the QRS complex is junctional, it will be less than 0.12 seconds. 