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You are here : 3-RX.com > Medical Encyclopedia > Diseases and Conditions > Heart Block
      Category : Health Centers > Heart Diseases

Heart Block

Alternate Names : Atrioventricular Block, AV Block, Bundle Branch Block, Complete Heart Block, First-Degree Heart Block, Second-Degree Heart Block, Third-Degree Heart Block, Cardiac Conduction Defect, Infranodal Block, Intraatrial Block, Intraventricular Block, Sinoatrial Block

Overview, Causes, & Risk Factors | Symptoms & Signs | Diagnosis & Tests | Prevention & Expectations | Treatment & Monitoring

Heart block is a disruption in the relay of electrical signals that control activity of the heart muscle.

What is going on in the body?

The heart beats by using electric impulses. These impulses follow a specific route through the heart. These routes or pathways are sometimes grouped together into specialized areas called nodes and bundles.

Bundles send out little fibers that go into the muscle of the heart. The nodes, bundles, and fibers are responsible for the unified beating of the heart and the rate at which it beats. A defect along any of these pathways can cause a heart block. This does not mean the blood flow or blood vessels are blocked.

There are many kinds of heart block. Each type depends on where the damage has occurred in the electrical pathway.

  • First-degree heart block. This type occurs when the electrical impulse passes through the heart slower than normal, but heartbeat and rhythm are still within a healthy range. This type of block does not mean there is anything really wrong with the heart.
  • Second-degree heart block. This occurs when some of the electrical signals from the upper chamber of the heart, called the atrium, don't reach the lower chamber of the heart, called the ventricle. This results in what are called "dropped beats."
  • Complete heart block.This is the worst form of heart block. In this condition, no electrical impulses pass from the upper to the lower parts of the heart, so the lower part starts beating on its own, but at a much slower rate than is healthy. When this occurs, the lower part of the heart may not beat fast enough or regularly enough to keep blood flowing to the vital organs.
  • What are the causes and risks of the disease?

    Many times, heart block is a symptom that the person has another type of heart disease. Heart blocks are common in people who have:

  • history of heart attacks
  • coronary artery disease
  • infectious diseases of the heart, such as endocarditis
  • hereditary defect of the heart, called congenital heart block
  • Certain medicines can also cause heart block if the levels in the body build up too much. Some examples include:

  • beta blockers, such as propanolol or pindolol
  • calcium channel blockers, such as verapamil or diltiazem
  • digitalis glycosides, such as digoxin
  • Highly-trained athletes may also have the less severe forms of heart block, but will most likely have no symptoms other than a slow heartbeat.

    A block that has existed for a long time may pose no problem. A block that appears suddenly may be due to a new heart problem or the worsening of an old one. A change in the heart block can alert the doctor to a change in the status of the heart.


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    Heart Block: Symptoms & Signs

    Author: Eric Berlin, MD
    Reviewer: Kathleen A. MacNaughton, RN, BSN
    Date Reviewed: 09/17/02

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