Atrioventricular block (AVB) is a cardiac arrhythmia in which there is a change in the transmission of electrical impulses between the heart chambers, the atria and the ventricles. In second-degree AVB, one or more atrial impulses are not transmitted to the ventricles (not all P waves are followed by a QRS on the electrocardiogram).
There are two types:
- Type I - Möbitz I or Wenckebach
- Type II - Möbitz II
In second-degree Möbitz II AVB, there is an intermittent block in the electrical impulse generated in the atria, which is not transmitted to the ventricles.
The most common cause is inadequate blood supply to the heart muscle cells, known as ischaemic heart disease.
It manifests as weakness, shortness of breath, chest pain, loss of consciousness and sudden cardiac arrest.
The diagnosis is based on a clinical history and physical examination. It is confirmed by an electrocardiogram, which shows the blockage of electrical conduction.
In symptomatic cases, the patient needs to be stabilised with drugs that speed up the heart rate. If the symptoms are severe or the arrhythmia is causing organ failure, a temporary pacemaker should be fitted until a permanent pacemaker can be implanted.
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