Complete heart block, also referred to as third-degree heart block, or third-degree atrioventricular (AV) block, is a disorder of the cardiac conduction system where there is no conduction through the AV node as shown below:
Atria & ventricle completely ignoring each other. . .
When you see this, emergently place temporay pacing in a hospital setting where plans for permanent pacer and cardiovascular consult can be obtained.