Sinus bradycardia

Sinus bradycardia can be the result of many things including good physical fitness, medications, and some forms of heart block. Sinus bradycardia is common in athletes but also can be caused by hypothyrodism.

"Sinus" refers to the sinus node, the heart's natural pacemaker which creates the normal regular heartbeat.

Bradycardia is the medical term for a slow heart rate. The normal resting heart rate range for a healthy adult is between 60 and 100 beats per minute. In a person with bradycardia, the heart beats fewer than 60 times per minute due to some type of blockage or slowing of the natural electrical signals in the heart. It may caused by a slowed signal from the sinus node (sinus bradycardia), by a pause in the normal activity of the sinus node, or by blocking of the electrical impulse on its way from the atria to the ventricles.

In sinus bradycardia, the heart rate is slow, but the rhythm normal with each atrial beat (small rise) followed by a ventricular beat (spike).
Sinus bradycardia