heart block

a condition describing a failure in the conduction of electrical impulses from the natural PACEMAKER (the SINOATRIAL NODE ) through the HEART , which can lead to slowing of the pumping action. There are three types: 1. In first degree (partial or incomplete) heart block, there is a delay in conduction between atria (see ATRIUM ) and VENTRICLES , but this does not cause slowing. 2. In second degree heart block, there is intermittent slowing because not all the impulses are conducted between atria and ventricles. 3.In third degree (or complete) heart block, there is no electrical conduction, the heartbeats are slow, and the ventricles beat at their own intrinsic slow rhythm. This causes blackouts and can lead to heart failure. Heart block is more common in elderly people where degenerative changes have occurred. It may, however, also be CONGENITAL or may result from other forms of heart disease, such as MYOCARDITIS , CORONARY THROMBOSIS , CARDIOMYOPATHY and VALVE DISEASE . For second and third degree heart block, treatment involves use of an artificial pacemaker.