Third-degree AV block
Third-degree AV block (ie, complete heart block) exists when there are more P waves than QRS complexes and there is no relationship between them (ie, no conduction). The conduction block may be at the level of the AVN, the bundle of His, or the bundle-branch Purkinje system. In most cases (approximately 61%), the block occurs below the His bundle. Block within the AV node accounts for approximately one fifth of all cases, whereas block within the His bundle accounts for slightly fewer than one fifth of all cases.