There are three types, or degrees, of<unk> : (1) first-degree, (2) second-degree, and (3) third-degree, with third-degree being the most severe. An ECG is used to differentiate between the different types of<unk> s. However, one important consideration when diagnosing<unk> s from ECGs is the possibility of pseudo-<unk> s which are due to concealed junctional extrasystoles. It is important to diagnose<unk> s precisely because unnecessary pacemaker placement in patients with pseudo-AV blocks can worsen symptoms and create complications. First-degree<unk>  First-degree<unk>  occurs when there is a delay, but not disruption, as the electrical signal moves between the atrium and the ventricles through the AV node. On ECG, this is defined by a PR interval greater than 200 msec. Additionally, there are no dropped, or skipped, beats. Second-degree<unk>  __TOC__ Second-degree<unk>  occurs when the electrical signal between the atria and ventricles is even more impaired than in a first-degree<unk> . In a second-degree<unk> , the impairment results in a failure to conduct an impulse, which causes a skipped beat. Mobitz I Mobitz I is characterized by a progressive, yet, reversible block of the AV node. On ECG, this is defined by progressive prolongation of the PR interval, with a resulting dropped beat (the PR interval gets longer and longer until a beat is finally dropped, or skipped). Some patients are asymptomatic; those who have symptoms respond to treatment effectively. There is a low risk of a Mobitz I<unk>  leading to heart attack and complete heart block. Mobitz II Mobitz II is caused by a sudden, unexpected failure of the His-Purkinje cells to conduct the electrical impulse. On ECG, the PR interval is unchanged from beat to beat, but there is a sudden failure to conduct the signal to the ventricles, and resulting in random skipped beat. The risks and possible effects of Mobitz II are much more severe than Mobitz I in that it can lead to severe heart attack. Third-degree<unk>  Third-degree<unk>  occurs when the signal between the atria and ventricles is completely blocked, and there is no communication between the two. None of the signals from the upper chambers makes it to the lower chambers. On ECG, there is no relationship between P waves and QRS complexes, meaning the P waves and QRS complexes are not in a 1:1 ratio. Third-degree<unk>  is the most severe of the<unk> s. Persons suffering third-degree<unk>  need emergency treatment including but not limited to a pacemaker.
Atrioventricular block
Left bundle branch block
Right bundle branch block
Sinoatrial block
Ectopic beat
Bundle branch block
Sinus arrhythmia
Junctional tachycardia