Heart Block- Symptom, Causes, Treatment of Heart Block

Heart Block is the disturbance of heart rhythm resulting from blockage of the transmission of electrical impulses through the specialised muscle that forms the con ducting tissue of the heart. In healthy people the heart rate is controlled by the sinoatrial node (pace maker) situated in the right atrium (upper chamber of the heart), which discharges regular impulses that are conducted throughout the upper chambers and to the ventrides (lower chambers of the heart) to stimulate their contraction.

Normally the ventrcles contract about 0.2 seconds (depending on the heart rate) after the atria. In heart block this interval is increased beyond 0.22 seconds. This very slight delay may decrease the heart's ability to pump blood efficiently.

There are varying degrees of heart block. In first degree heart block, the interval between atrial and ventricular contraction is prolonged. though this does not cause any problem and is believed to be normal in well-trained athletes.

In second degree heart block, not all atrial contractions are followed by ventricular contractions, which results in missed beats. In complete heart block, no impulses are conducted from the atria to the ventrides. Although the atria continue to contract at a rate controlled by the pacemaker according to the patient's activities, the ventrides contract independently at a rate of about 40 beats per minute. In severe second degree and complete heart block, the heart rate cannot increase in response to exercise and other circum stances (such as fever) that increase demands on the circulation. This can have serious consequences for the patient

Causes of Heart Block

Heart block may be caused by damage to the heart's conducting tissue resulting from coro naryartery disease (narrowing of the arteries supplying the heart musde), heart attack, myocarditis (inflammation of the heart musde), rheumatic fever, or overdosage of some drugs (especially digoxin). Congenital heart block is due to an inborn defect of the heart's conducting tissue.

Symptoms of Heart Block

Fainting, dizziness, weakness, fatigue and breathlessness on exertion are common in com plete heart block. Acute heart failure is a possibility.

Treament of Heart Block

If the cause of heart block cannot be corrected, an artificial pacemaker is fitted.

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