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Heart block or Atrioventricular (AV) block is a disorder, that is associated with the electrical system of the heart. It can either be partial or complete. The electrical impulses that are transported from the atria to the ventricles, produce heartbeats (contractions of the heart muscles). This impulse is blocked between the atrium and the ventricle. Due to the slow moving impulse, skipped beat (irregular heartbeat) or weak heartbeat is noticed. Based upon the severity, a heart block is classified into three categories:

First Degree AV Block: This occurs when there is a considerable increase in the conduction time of an impulse.
Second Degree AV Block: Also referred as partial heart block, this occurs when some atrial impulses are not transferred.
Third Degree AV Block: This occurs when no atrial impulses are transferred.

Causes

Drugs and Stimulants: Certain medications affect the normal beating of the heart. For example, beta blockers slow down the heart rate while the consumption of ephedrine, that is used as an appetite suppressant or as a medication to treat asthma, bronchitis, etc., can lead to tachycardia (high heart rate) or cardiac arrhythmias (irregular heartbeat). Calcium channel blockers may also be the contributing factors that affect the heart. The medicine 'digitalis' slows down the transfer of impulses from the atrium to the ventricle. Therefore, people should be extremely cautious while taking more than one medicine at a time. They should discuss the side effects of the medicines with their doctor, to avoid serious conditions. The consumption of stimulants like caffeine, nicotine, and cocaine also leads to rapid beating of the heart.

Heart Diseases: Cardiomyopathy (heart muscle diseases) or a myocardial infarction (heart attack) can make the heart muscles weak. Coronary artery diseases can also affect the transfer of impulses in the heart. A defect in the heart valve and diseased sinus node (pacemaker) can lead to disturbed heartbeats.

Genetic Disorder: Genetic disposition is many times responsible for structural defects in the heart, that lead to impaired conduction of impulses. Congenital heart diseases are quite common. Structural abnormalities of atrioventricular node can lead to this disorder.

Other Diseases and Disorders: Diseases like arthritis, diabetes, atherosclerosis, ischemic heart disease, hyperkalemia, high cholesterol levels, inflammation of the heart, and electrolyte imbalance can result in an AV block. Increased tone of the vagus nerve can lead to second degree blockage. High blood pressure, bacterial or viral infection of the heart, development of a scar tissue after surgery, and congenital heart defects can also contribute to the blockage.

Intensive Exercise: Athletes who train rigorously or sports persons who undergo endurance training can get affected by this disorder.

Symptoms

Second degree AV block usually does not exhibit any symptoms. However, as the condition worsens symptoms such as abnormally slow heart rate, cardiac arrhythmia, fainting, seizures, dizziness, breathlessness (shortness of breath), and chest pain can be experienced. Nausea can also be experienced along with chest pain and breathing difficulty.

When the impulses of the heart do not reach the ventricles, the condition becomes more serious. A pacemaker helps correct abnormal or slow heartbeat. Third degree blockage can be permanent (chronic) or temporary (transient). Degenerative changes of the heart or effects of a heart attack are usually responsible for a chronic heart block, which significantly affects the capacity of the heart to pump blood. It can result in serious situations such as cardiac arrest and cardiac death. If you notice any symptoms of a weak heart or AV block, you should immediately consult your physician. Prompt medication and treatment can help avoid worsening of the situation.

ECG (Electrocardiogram), Electrophysiologic study (EPS) (a type of cardiac catheterization), and Implantable Loop Recorder (ILR) are the tests performed to diagnose the affected conduction of electrical impulses in the heart. Doctors may prescribe medicines and place a pacemaker to alleviate the symptoms. The patient has to take proper care and rest. Follow-ups at regular intervals are very important for these patients. Consumption of alcohol, drugs, or smoking can worsen the situation. Even excessive emotional stress can affect the conduction of these impulses. A healthy diet and regular exercise can help prevent all unwanted situations that come along with heart diseases.

Disclaimer: This Buzzle article is for informative purposes only, and should not be used as a replacement for expert medical advice.