A slow heart rate, a condition known as bradycardia, occurs when the heart beats fewer than 60 beats per minute for most non-trained athletes, according to the Mayo Clinic. Bradycardia can be a serious condition because a slow heart rate can deprive the organs of the body, including the brain, of oxygen-rich blood. A slow heart rate can produce symptoms throughout the body including dizziness, weakness, fatigue, shortness of breath, chest pains, memory impairment and fainting. There are many factors that can interfere with the normal electrical impulses in the heart causing the heart rate to be slow.
Medications
Taking some prescription medications, especially those prescribed to treat other heart-related conditions, can cause a slow heart rate. Beta-adrenergic blockers, such as acebutolol, metoprolol and atenolol, are medications prescribed to treat high blood pressure and abnormal heart rhythms. By binding to beta receptors they block adrenaline and therefore reduce the nerve impulses traveling through the heart, according to the Texas Heart Institute. These actions can result in bradycardia.
Some calcium channel blocker medications, such as diltiazem and verapamil, prescribed to treat high blood pressure can also cause a slow heart rate by slowing the rate at which calcium passes into the heart muscle.
Hypothyroidism
The thyroid gland is responsible for producing thyroid hormone which regulates the function of cells throughout the body. Thyroid hormone is important for the normal function of the heart muscle. In those who have hypothyroidism, a condition of low thyroid hormone, the heart muscle is weak and not able to contract as strongly or as fast, resulting in a slow heart rate.
Electrolyte Imbalance
The normal function of the heart is dependent upon a delicate balance of electrolytes including calcium, sodium and potassium. The heart rhythm is regulated by the natural pacemaker, called the sinus node, located in the right atrium. The sinus node initiates electrical impulses which then travel from the atria to the ventricles to trigger contraction. In order for the electrical impulses to be generated, electrolytes are needed to move across cell membranes. If the levels are not high enough, or there is too much of one mineral and not enough of another, these impulses are inhibited resulting in a slow heart rate.
Heart Damage
Damage to the tissues of the heart, from illnesses such as rheumatic fever, birth defects or injury, such as from a heart attack, can cause a slow heart rate. Damage to the right atria can damage the sinus node causing it to discharge electrical impulses at a slower-than-normal rate. Damage to the tissue between the atria and ventricle, known as the AV node, can block or partially block the electrical impulse from reaching the ventricle. The ventricle is the main pumping chamber but without adequate electrical impulse it cannot contract, resulting in a slow heart rate.
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