heart block

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A condition in which faulty transmission of the impulses that control the heartbeat results in a lack of coordination in the contraction of the atria and ventricles of the heart.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun pathology A disease in the electrical system of the heart, opposed to coronary artery disease, which is disease of the blood vessels of the heart.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun recurrent sudden attacks of unconsciousness caused by impaired conduction of the impulse that regulates the heartbeat