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Heart block is an arrhythmia (or “abnormal heart rhythm) in which electrical signals traveling from the atria to the ventricles are stopped or delayed, causing the heart to beat very slowly.
The electrical system of the heart is made up of several parts that communicate with one another to tell the heart muscle fibers when to contract. The sinoartrial (SA) node starts the signal causing the atria to contract. This signal travels through the atrioventricular (AV) node and on to the bundle of His, bundle branches, and Purkinje fibers causing the ventricles to contract. The flow of electrical signals is what produces a normal heartbeat.
In heart block, the normal electrical signals are either delayed or stopped as they travel from the SA node through the atria to the AV node and the ventricles. As a result, the heart may beat too slowly. These very slow heart rhythms may cause lightheadedness, dizziness, or loss of consciousness.
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