Heart block: A blockage in the conduction of the normal electrical impulses in the heart. Heart block is not uncommon and is detected with an electrocardiogram. Heart block occurs from degeneration or scarring of the electrical pathways in the heart muscle, either naturally or as a result of disease. Heart block typically requires no treatment, but can be a factor in the decision of whether or not to put a pacemaker in a heart that is failing or irregularly beating.
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