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heart block n incoordination of the heartbeat in which the atria and ventricles beat independently due to defective transmission through the bundle of His and which is marked by decreased cardiac output often with cerebral ischemia
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a condition in which conduction of the electrical impulses generated by the natural pacemaker of the heart (the sinoatrial node) is impaired, so that the pumping action of the heart is slowed down. In partial or incomplete heart block conduction between atria and ventricles is delayed (first degree heart block) or not all the impulses are conducted from the atria to the ventricles (second degree heart block). In third degree or complete heart block no impulses are conducted and the ventricles beat at their own slow intrinsic rate (20-40 per minute).
Heart block may be congenital or it may be due to heart disease, including myocardial infarction, myocarditis, cardiomyopathy, and disease of the valves. It is most frequently seen in the elderly as the result of chronic degenerative scarring around the conducting tissue. There may be no symptoms, but when very slow heart and pulse rates occur the patient may develop heart failure or Stokes-Adams syndrome. Symptoms may be abolished by the use of an artificial pacemaker.
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impairment of conduction of an impulse in heart excitation, either permanent or transient and due to anatomical or functional impairment. It is subclassified as first, second, or third degree heart block and is frequently used specifically to denote atrioventricular block.Medical dictionary. 2011.