An atrioventricular block (AVB) is a cardiac arrhythmia in which there is a disturbance in the conduction of the electrical stimulus between the different chambers of the heart, atria and ventricles. In second-degree AVB, one or more atrial stimuli are not conducted to the ventricles (not all P waves are followed by QRS on the electrocardiogram).
There are two types: type I (Mobitz I or Wenckebach) and type II (Mobitz II).
In second-degree Mobitz I or Wenckebach AVB, there is a progressive lengthening of the passage time of the electrical stimulus from the atria to the ventricles (increased PR interval), until a beat is blocked and does not lead to the ventricles.
It can occur in healthy subjects and athletes without underlying cardiac disease. Among the most frequent causes are: congenital diseases, ischemic heart disease (infarction), medication and previous cardiac surgery.
Most cases do not manifest symptoms. When symptoms do occur, they include fatigue, dizziness, loss of consciousness, chest pain and shortness of breath.
It is diagnosed by clinical history and physical examination. An electrocardiogram and chest X-ray are usually performed to complete the study.
Treatment will be aimed at correcting the cause and treating the symptoms. If the degree of blockage progresses, it may be necessary to place a pacemaker.
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