Heart Block

Heart block is a disorder of the heartbeat. It occurs when electrical impulses can't pass from the atria (upper chambers of the heart) to the ventricles (the heart's lower chambers). This may keep the contractions of the atria from coordinating with the contractions of the ventricles, and may cause a very slow heart rate.

There are various degrees of heart block:

• In first-degree block, the passage of impulses is delayed but there are no symptoms.
• In second-degree heart block, some of the atrial impulses fail to reach the ventricles and cause the pulse to become slow or irregular.
• In third-degree block (complete heart block), no atrial impulses reach the ventricles and the ventricles beat very slowly. This may have a serious effect on the heart's pumping ability so that not enough oxygenated blood flows to the brain and the rest of the body, which can cause a range of symptoms.

The most common cause of heart block is aging of the heart. It may also be a congenital (birth defect) problem. Many times, a heart block is a symptom of heart disease. Heart blocks may be caused by:

• heart attacks
• coronary artery disease
• rheumatic fever
• overdose of certain heart drugs
• infectious diseases of the heart, such as endocarditis.

A block that has existed for a long time may not mean that there is a problem. A block that appears suddenly may be a sign of a new heart problem or worsening of an existing one. Sometimes heart block can come and go.

First degree heart block is fairly common. It can sometimes be found in teenagers, young adults and in well-trained athletes. The condition may be caused by rheumatic fever, some types of heart disease and by some drugs. First-degree heart block causes no symptoms.

Second degree heart block may not cause symptoms. Second degree block can sometimes progress to third-degree.

Third degree heart block is a serious condition that usually affects the heart's ability to pump blood effectively. Symptoms include:

• fainting
• dizziness
• tiredness
• low blood pressure on standing
• shortness of breath
• sudden heart failure.

Heart blocks can be diagnosed with a test called an electrocardiogram (ECG), which measures the heart's electrical activity. Heart blocks have a certain pattern, which the ECG machine records. In some instances, a special test called an electrophysiologic study (EPS) uses probes placed into the heart to measure the flow and direction of electricity. A test called a Holter monitor can also diagnose the problem.

Treatment depends on the degree of heart block you have. Many times heart block is not treated at all. In some cases, the block becomes so severe that the heart can no longer beat at the proper pace and symptoms develop. When this occurs, usually you will need an artificial pacemaker implanted in your chest.

Treatment of other heart problems reduces the risk of the block getting worse.