Atrioventricular Block (AV Block)

1. Definition

1.1. Atrioventricular (AV) block is partial or complete interruption of impulse transmission from the atria to the ventricles. The most common cause is idiopathic fibrosis and sclerosis of the conduction system. Diagnosis is by ECG; symptoms and treatment depend on degree of block, but treatment, when necessary, usually involves pacing.

1.2. -

2. Third degree AV block

2.1. -

3. First degree AV block

3.1. -

3.2. -

3.3. PR interval > 0.2 sec.

3.4. symptomatic

3.5. further investigation

3.6. not related between P wave with QRS complex

4. Second degree AV block

4.1. Some normal P waves are followed by QRS complexes, but some are not. Two types exist.

4.1.1. Mobitz type I

4.1.1.1. 2nd-degree AV block, the PR interval progressively lengthens with each beat until the atrial impulse is not conducted and the QRS complex is dropped (Wenckebach phenomenon); AV nodal conduction resumes with the next beat, and the sequence is repeated

4.1.1.2. occurs at the AV node in about 75% of patients with a narrow QRS complex

4.1.1.3. pacemaker inserted

4.1.2. -

4.1.3. Mobitz type II

4.1.3.1. 2nd-degree AV block, the PR interval remains constant. Beats are intermittently nonconducted and QRS complexes dropped, usually in a repeating cycle of every 3rd (3:1 block) or 4th (4:1 block)

4.1.3.2. always pathologic

4.1.3.3. occurs at the His bundle in 20% of patients and in the bundle branches in the rest.