Pacemaker

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Pacemaker
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A pacemaker (cardiac stimulator) is a small device that generates weak electric impulses. These impulses force the heart to contract, when it is “lazy” – when the patient suffers from bradycardia.

When is a pacemaker implanted?

The heart has a cluster of cells called the sinus node. The node generates electric impulses which spread through specific paths and force the atria of the heart and later the ventricles to contract. However, prior to entering into the ventricles, the impulse is slightly delayed in another node called atrioventricular node.

Generation of the impulses in the sinus node may be disturbed by atherosclerosis, heart defects, heart diseases, hypertension and other diseases. Therefore the sinus node dysfunction may occur – the heart rate decreases or stops for a few seconds. Bradycardia occurs when the heart rate becomes less than 60 beats/min.

The spread of the impulse may be impaired in the atrioventricular node as well. This condition is called atrioventricular block. That may also cause a decrease in the heart rate and irregular heart activity. The implantation of a pacemaker is considered when the heart rate is 40 beats/min or less, or when the heart stops for 3 seconds. Bradycardia may cause weakness, hypotension and loss of consciousness (MAS, Morgagni - Adams - Stokes – syndrome).

Do we always need a pacemaker when bradycardia is present?

Bradycardia may be caused by certain drugs, infectious diseases and etc. In these cases the patient is observed until the heart rate becomes normal.

Is it a complex surgery?

A pacemaker is a thick device that weights only several tens of grams. It is implanted in the collarbone area under the skin. Wires from the pacemaker are passed through the largest blood vessels into the heart’s atria and ventricles. This surgery is performed by cardiac surgeons. Local anesthesia is usually sufficient.

What does the pacemaker do?

Modern pacemakers regularly check the heart’s electric activity and if the heart is beating at a normal speed or faster it does nothing. The pacemaker does not protect the heart from faster heart rate – tachycardia, or arrhythmias. Depending on the type of bradycardia, the pacemaker may stimulate only atria, only ventricles, or both of them.

   

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