A slow pulse rate can be caused by a disruption of the electrical system of the heart, reports WebMD. Slow pulse rates may indicate an extremely healthy heart, but if uncommon or accompanied by other symptoms, may require a medical evaluation to determine the cause, states Healthline.
Having a slow pulse rate is called bradycardia, reports WebMD. A normal heart rate falls between 60 and 100 beats per minute while a person is at rest. Athletes and healthy younger people frequently have heart rates below 60 beats per minute. In severe cases of bradycardia, the heart may not be pumping enough blood to sustain normal body functions.
Bradycardia can be the result of aging, but can also be caused by coronary artery disease, heart attacks or infections such as endocarditis and myocarditis, according to WebMD. Other conditions that disrupt electrical impulses to the heart include low thyroid levels and too much potassium in the blood. Medications such as beta-blockers, anti-arrhythmics and digoxin also can cause the pulse rate to drop. Another cause is a damaged heart muscle or a congenital heart defect.
Heart failure, an enlarged heart and an overactive thyroid gland are also common causes of bradycardia, MedlinePlus explains. External causes include alcohol, caffeine or stimulant drugs taken in excessive amounts. Some heart, blood pressure and depression medicines also cause arrhythmia.
An electrocardiogram or other tests may be necessary to accurately diagnose the cause of bradycardia, states Healthline. Bradycardia is treated medically if the cause is an effect of medication or other toxins; in other cases, a pacemaker is installed to regulate the heart rate.