The term bradycardia refers to a slow heart rate. Normal electrical conduction in a child's heart involves the generation of electricity in the sinus node in the upper right portion of the heart. Electricity then travels through both atrium to the AV node in the middle of the heart. From here, electricity is spread out through both ventricles. As electricity moves through the ventricles, heart muscle contracts.
What is Bradycardia?
Bradycardia simply means a slow heart rate. A normal heart rate in children varies quite a bit based on age as well as activity level. In a normal teenager, a resting heart rate is typically between 60 and 100 beats per minute. With activity, the heart rate may get as high as 200 beats per minute. During sleep, the heart rate can occasionally drop as low as 30-40 beats per minute.
Bradycardia Causes
The most common cause of bradycardia in children and teenagers is sinus bradycardia. This simply means that the sinus node is firing at a slow rate. Most of the time sinus bradycardia is a normal physiologic response. For example, a healthy, well conditioned athlete may have a slow resting heart rate. In addition, the heart rate normally slows during rest or sleep. Abnormal sinus bradycardia is fairly uncommon in children and seem most commonly following heart surgery. It can also be seen as a secondary problem in infants, especially premature babies.
Other causes of bradycardia include certain forms of AV block. In second degree AV block, transmission of electricity from the top part of the heart to the bottom part of the heart is intermittently blocked. In complete heart block, or complete AV block, transmission of electricity from the atria to the ventricles is completely interrupted. With complete heart block, some other area below the AV node must take over and become responsible for generating electricity for the heart. Usually this happens at a much slower rate than normal, resulting in bradycardia.
Bradycardia Symptoms
Most children with sinus bradycardia do not have any symptoms whatsoever. Abnormal bradycardias, for example those caused by sinus node dysfunction or complete heart block, can present with a number of different symptoms. Often the child may feel excessively fatigued or tired. This may be worse during times of exercise or activity. Occasionally syncope or fainting may occur. In younger children, frequent or worsening nightmares can be a sign of significant bradycardia.
Bradycardia Treatment
Treatment of bradycardia depends on the underlying cause. Physiologic bradycardia in a child requires no treatment whatsoever. Pathologic bradycardia, for example that associated with complete heart block often requires a pacemaker.