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| | Rush Copley Adam Encyclopedia |
 | | The electrical impulse that signals the heart to contract in a synchronized manner begins in the sinoatrial node (SA node), which is the body's natural pacemaker. |
 | | The incidence of tachycardia and bradycardia varies greatly, depending on the condition of the heart itself, the history of prior heart attack, blood chemistry imbalance, or endocrine abnormalities. |
 | | Electrical "shock" (defibrillation or cardioversion), the implantation of a temporary pacemaker to interrupt the arrhythmia, or antiarrhythmic drugs may be used. |
| www.rushcopley.com /adam/Ency_Article.asp?GenContentID=001101 (735 words) |
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