Bradycardia and its causes

Bradycardia just means a slowing of the heart rate. Slow heart rates are quite common in sleep as the body’s energy requirements are low. It is also normal in well trained athletes. This type of bradycardia develops due to endurance training in athletes. Athlete’s bradycardia and can be reversed by deconditioning. Deconditioning is done by stopping exercise training for a period.

Low heart rate can occur with intake of certain medications e.g. beta blocker medications like metoprolol. These medications lower the effect of sympathetic nervous system. Sympathetic nervous system is responsible for increasing the heart rate with exercise and stress.

Heart rate can be low in certain disorders of the brain due to defective control from the brain. Bradycardia can also be due to increased pressure within the skull cavity. Another important cause of slow heart rate is reduced functioning of the thyroid gland. Thyroid is a gland situated in the front of neck.

The heart rate can be slow due to poor functioning of the sinus node. Sinus node is the natural pacemaker of the heart. This disorder is known as sick sinus syndrome. Heart rate can also be slow if the signals from the heart are not conducted well to the lower chambers. This occurs when there is disease of the conduction system of the heart. This condition is known as complete heart block. Both these conditions require the implantation of an artificial pacemaker to increase the heart rate.

Assessment of bradycardia

Simple method to assess if the low heart rate is very dangerous or not is to see the response to exercise. If the heart rate steadily increases with graded exercise, the bradycardia is unlikely to be dangerous. The response of heart rate to exercise can be measured in a scientific way with a treadmill exercise test.

Another simple way to assess bradycardia is to see its response to medications which can increase heart rate like atropine. But this can be done only in a hospital setting as the medicine has to be given as an injection.

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