Atrioventricular block

An AV block ( atrioventricular block ) is a common heart rhythm disorder. The conduction between the atria and the ventricles at the atrioventricular node ( AV node) has delayed the heart, temporarily or permanently suspended.

Milder forms of AV block may go unnoticed and require no treatment. More severe forms lead to an excessively slow heart rate (bradycardia, bradyarrhythmia ). In extreme cases, it may even come to a complete halt of the chambers, then what an emergent drug and pacemaker treatment needs.

  • 2.1 Congenital heart block
  • 2.2 Acquired AV block 2.2.1 chronic degenerative
  • 2.2.2 idiopathic
  • 2.2.3 Other damage

Molding

All forms of AV block can be detected by electrocardiogram ( ECG).

Atrioventricular block, first degree

Here, the conduction is delayed and there is a delayed onset of contraction of the ventricles. This disorder is ( 200 ms) in the ECG or to a shortening of the distance between the resulting during filling of the left ventricle D and A-wave in the echo identified by a prolongation of the PQ time. They often remains subjective unnoticed and usually does not require treatment.

AV - block II degree

The conduction fails partially. There are several possibilities:

  • The PR interval gets longer. Finally, it is so long that an atrial excitation is no longer transferred and a single ventricular contraction fails. The subsequent ventricular contraction is again transferred normally. Then the PQ interval prolongation begins anew ( Wenckebachperiodik ). The scientific definition of a Wenckebach block states that a P-wave is not conducted and the AV time of the P wave is longer before failure than the AV time of the P wave after the failure.
  • Sudden and unexpected absence of a ventricular response to an atrial excitation without the PQ interval must have been extended before. It can also regularly only every 2nd, 3rd or 4th atrial action be transferred to the chamber ( 2:1 - or 3:1 - or 4:1 block). This localized mostly in the His bundle block form is called Mobitz block. The forecast is compared to the Wenckebach block unfavorable, because of the risk that the rhythm goes into a total AV block.

In the English -speaking world the Wenckebach block is also called Mobitz Type I, the Mobitz block Mobitz Type II or as Hay.

AV block III. degree

Complete failure of conduction between atrium and ventricle. The chamber remains behind or fails in a slow escape rhythm asynchronous further to the atria, which is generated by the secondary node (AV node ) or the tertiary pacemaker ( His bundle, Tawaraschenkel and Purkinje fibers ). The frequency of these pacemaker cells is between 20 and 40/min. A complete heart block. Degree can interfere with normal QRS complexes ( AV escape rhythm ) or widened QRS complexes ( ventricular escape rhythm ) occur.

A total AV block is a typical indication for implantation of a pacemaker.

Causes and frequency

Congenital heart block

A congenital heart block is rare with an incidence of 1:20,000. Causes are about one-third

  • Congenital heart disease,
  • Idiopathic, possibly lack of fusion of the conduction system or
  • Flammable, for example, in autoimmune disease of the mother.

Acquired AV block

A variety of causes can lead to AV block. The plurality of cases based on chronic degenerative changes (see below) in the context of cardiac disorders. 40-60 % of cases are caused by an idiopathic fibrosis (see below). Most common reversible cause are drugs. All antiarrhythmic drugs that cause conduction delay, may, especially in overdose or combination of each other, cause AV block. In clinical practice, cardiac glycosides and beta-blockers are the most common triggers. Damage caused by medical intervention or heart attack (see below) may be reversible.

Chronic degenerative

  • Infections endocarditis
  • Lyme disease
  • Chagas disease
  • Other bacterial, viral, rickettiale, fungal infections
  • Neuromuscular diseases Myotonic dystrophy
  • Kearns -Sayre syndrome
  • Limb-

Sinus node 1 - 2 AV node

Important structures are linked graphics

  • Infiltrative diseases amyloidosis
  • Sarcoidosis
  • Hemochromatosis
  • Carcinoid
  • Neoplastic disease primary tumor
  • Metastases
  • After radiotherapy
  • Collagen Systemic Lupus Erythematosus
  • Sjogren's Syndrome
  • Scleroderma
  • Rheumatoid arthritis

Idiopathic

  • Lev 's disease: fibrosis of the proximal conduction system with bilateral bundle-branch block
  • Lenègre disease: From occurs distally on the middle portions of the conduction system in the proximal progressing to total AV block fibrosis, the more likely in younger people.

Other damage

  • Circulatory disturbance of the AV node coronary heart disease
  • Trans Coronary ablation of septal hypertrophy in HOCM
  • Radio frequency ablation AV node, for example, in refractory atrial fibrillation tachykardem
  • Accessory pathway in AV nodal reentrant tachycardia
  • Endocardial radiofrequency ablation of septal hypertrophy in HOCM

Therapy

  • Medical therapy with atropine or adrenaline for a short time as a bridge to definitive treatment with a pacemaker. Long-term therapy with drugs is uncertain, many side effects and is regarded as outdated.
  • Transitory or permanent pacemaker in symptomatic patients each cue type and in asymptomatic patients with complete heart block. Degree or second degree Mobitz type.
Cardiac dysrhythmia Mitochondrial disease Emery–Dreifuss muscular dystrophy Bilateralism Bundle branch block Epinephrine Sinoatrial block
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