An atrioventricular (AV) block is a cardiac arrhythmia in which the conduction of electrical stimulus between the different chambers of the heart, the atria and ventricles, is altered.
In a second-degree AV block, one or more atrial stimuli are not sent to the ventricles (not all p waves are followed by QRS in the electrocardiogram).
There are two types: type I (Mobitz I or Wenckebach) and type II (Mobitz II).
In the Mobitz I or Wenckebach second-degree AV block, a PR interval prolongation (the time in which the electric stimulus is carried from the atria to the ventricles is progressively elongated) is produced until a beat is blocked and fails to be conducted to the ventricles.
It can occur in normal subjects and athletes with no underlying heart disease. Its possible aetiologies include: congenital diseases, ischemic cardiopathy (infarctions), medication, and previous cardiac surgery.
Most patients are asymptomatic. If symptoms appear, they are: fatigue, dizziness, loss of consciousness, thoracic pain, and feeling out of breath.
It is diagnosed with the medical history and a physical exploration. Typically, an electrocardiogram and a thoracic X-ray are done to complete the study.
Treatment will be conducted to correct the cause of it and treat the symptoms. If the blockage progresses, it could be necessary to place a pacemaker.
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