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Atrioventricular conduction disorders (AV block)


AV conduction disorders are caused by delays or inability to conduct exertion from atriums to ventricles. Depending on the severity of the conduction disorder, there are three levels of AV block.

The atrioventricular block I° (AV block I°) is characterized by prolongation of the PR interval on the ECG, each P wave being monitored by a QRS complex.

The AV block II ° represents the intermittent inability of the AV to conduct impulse from an atrium to a ventricle so that the QRS complex disappears. There are two types of this block.

The AV block II° type  Mobitz I (or Wenckebach periodics) is characterized by progressive prolongation of the PR interval from cycle to cycle, so that every third, fourth or fifth QRS complex is blocked.

The AV block II° type Mobitz II PR interval always remains constant and the individual QRS complexes are blocked, most often in a specific relationship (4:3, 3:2, 2:1).

At a complete atrioventricular block (AV block III°) no impulse from the atriums reaches the ventricles. The atriums work their rhythm, and the ventricles independently of the atriums work at their own pace under the influence of their guide.

Causes:

  • Rheumatic carditis or other myocardial damage (AV block I)
  • Myocardial infarction, Prinzmetal’s angina pectoris, myocarditis, cardiomyopathies, specific heart muscle diseases, Lev’s disease (AV block II and III)
  • Digitalis intoxication, antiarrhythmic drugs and hyperkalaemia can cause AV blocks.
  • A complete AV block can be congenital, and can also occur during surgical interventions at the heart.

Symptoms:

  • Symptomatology of patients with AV block I° belongs to the underlying disease
  • Patients with AV block II° if the frequency of the ventricles is normal or somewhat reduced, they are usually without specific symptomatology.
  • Symptoms of the complete block vary from dyspnoea (difficulty breathing) or angina in the physical effort – to cardiac failure or shock during rest (depending on the balance between the degree of bradycardia and changes in the myocardium and/or coronary arteries)
  • In the elderly, episodes of expressed bradycardia may cause weakness, confusion, or fainting.

Diagnosis:

  • Anamnesis, physical examination, ECG

Treatment:

  • With AV block I and II degree directed to the treatment of the cause
  • Medical therapy
  • Temporary introduction of a pacemaker – electrode (to increase heart rate and hemodynamic repair)
  • Permanent implantation of a pacemaker (for a chronic form of the complex heart block or AV block II with frequent blocking of the impulse from atriums to ventriclees)

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