The heart is a muscular pump with four chambers, two upper (left and right atria) and two lower (left and right ventricles). These contract and pump blood. Special tissue in the heart produces and sends electrical impulses to get the muscle to contract. Normal electrical signals start from the sinoatrial (SA) node in the wall of the right atrium. From there the signal goes to the left atrium and reaches the atrioventricular (AV) node between the atria and ventricles. The signal then goes to the left and right bundle branches and finally the ventricles. There it stimulates ventricles to contract.
Heart block refers to a disturbance of these impulses. Thirddegree heart block, or complete heart block, is one of three types (first-and second-degree blocks are the others). In complete heart block, no impulses from the atria reach the ventricles. Signals are completely blocked at the AV node.
The exact cause is often unknown. Complete heart block isn’t contagious or passed from generation to generation. It usually occurs in elderly people and may be the result of aging. Heart conditions including coronary artery disease, myocardial infarctions (heart attacks), heart valve disease, and congestive heart failure can cause complete heart block. Other causes are diseases, such as sarcoidosis, rheumatoid arthritis, or Lyme disease, and some medicines (e.g., digoxin, beta-blockers, and calcium channel blockers).
Symptoms can vary and include dizziness, lightheadedness, shortness of breath, chest pain, and fainting. Many people may have no symptoms.
The health care provider makes a diagnosis from the medical history and a very slow pulse at a physical examination.
The health care provider will order electrocardiography (ECG) to measure the heart’s electrical activity.
If additional tests are needed to confirm the diagnosis, a 24-hour recording of the heartbeat (Holter monitor) while following usual daily activities will be done. Sometimes, admission to a hospital is needed for constant monitoring in preparation for treatment.
No drugs can treat complete heart block. If excessive doses of a drug is the cause, stopping the drug is required. The best treatment for complete heart block not caused by drugs is insertion of a pacemaker. Pacemakers are small, electrical devices put into the heart to tell it to beat to stimulate the heart to beat in a normal fashion.
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