A number of different arrhythmias may potentially affect the heart of a child.

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.

The sinus node is the pacemaker of the heart. It is responsible for generating the electrical impulses that stimulate the heart muscle to contract. Sinus bradycardia refers to a  slower than normal heart rate.

The sinus node is the pacemaker of the heart. It is responsible for generating the electrical impulses that stimulate the heart muscle to contract. Sinus tachycardia refers to a faster than normal heart rate.