Under normal circumstances, the heart rate is controlled by a natural electric stimulator consisting of a group of special cells in the wall of the right atrium. Electric impulses, that are transmitted from this stimulator to two atriums, and then into ventricles, cause the rhythmic shrinkage of the heart muscle; this is waht we call a heartbeat. A heart block occurs when – due to interference in the impulse system – a congestion delay occurs, so that the rhythm of the atrium does not correlate with the rhythm of the ventricle.
At the beginning (e.g. the first stage of blockage), slow heart rate impulses do not produce any symptoms. In the second stage, some of the atrium beats do not reach the ventricle, and the pulse is irregular. In a disturbance called a third-degree heart block, the pulses do not reach the ventricle, and they continue to beat, regardless of the stimulator and the atriums. The speed of heart beat, which is actually the rate of the ventricle, is usually increased to overcome the burden or excitement. But, due to the heart block, the rate will not increase. Because of this, the heart does not pump enough oxygenated blood into the brain and other parts of the body when they need increased supply.
A heart block may occur for no apparent reason, but is often associated with coronary thrombosis. Excess doses of some drugs, especially those that affect the heart, can also cause a heart block.
There are often no symptoms. If you are moving a little and if you are not exposed to emotional excitement, you may not even know that you have this disorder. However, a complete cardiac block (third-degree block) sometimes causes symptoms of cardiac decompensation.
The most severe symptoms occur at so-called Stokes-Adams syndrome. The main symptom is a sudden loss of consciousness, often accompanied by spasms. Such seizures may occur if the ventricle, which beat without the control of the stimulator cells, significantly slows the pulse or misses a few beats, and the heart does not pump enough blood for a few seconds to maintain normal brain function.
In the UK, a heart block affects about one in every 3000 people per year. Disease equally affects both men and women.
A lower heart rate will not cause serious consequences. Before the appearance of artificial heart stimulators (pacemakers), people with a complete heart block had only 50% chances of the survival for more than one year. The mortality of people with Stokes-Adams syndrome is still relatively high, but it slowly decreases with the development of artificial heart stimulants.
What to do?
General weakness and loss of breath are the symptoms of many forms of heart diseases, including the heart block. If you feel these symptoms – especially if you occasionally lose consciousness – talk to your doctor immediately.
Many forms of heart block do not require treatment, and even a complete heart block if you are older and if you have no symptoms. A heart block associated with coronary thrombosis or Stokes-Adams syndrome is generally treated with an artificial heart stimulator (pacemaker), an electrical device that takes over the work of a defective natural stimulator, heart, and a pulse delivery system.