Bradycardia: Symptoms, Causes, and Resources

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Structure of the Heart

The human heart consists of two upper chambers (the right atrium and left atrium, known collectively as the atria) and two lower chambers (the left ventricle and right ventricle). The rhythm of a person’s heart is usually controlled by the sinus node, a cluster of cells located in the right atrium that produces electrical impulses. From the sinus node, these electrical impulses travel across the atria, causing it to contract and pump blood into the ventricles. The electrical impulses then arrive at the atrioventricular node, a cluster of cells that transmits the signal to another collection of cells (the bundle of His). From the bundle of His, the electrical signal is transmitted to the left and right ventricles, causing them to contract and pump blood to the lungs and body. The right ventricle pumps oxygen-poor blood to the lungs, and the left ventricle pumps oxygen-rich blood to the body.

What is the normal heart rate in a resting adult? In a typical adult at rest, the heart usually beats at a rate of 60 to 100 times per minute. In general, bradycardia refers to a heart condition in which the heart rate is lower than 60 beats per minute, and tachycardia refers to a heart condition in which the heart rate is higher than normal, which would be over 100 beats per minute in a resting adult.

What is Bradycardia?

Regular aerobic exercise conditions the heart, causing it to beat at a slower rate. Thus, a slow heartbeat may be a sign of good physical condition, with healthy young adults and athletes commonly having heartbeats of less than 60 beats per minute. Unhealthy bradycardia, however, occurs when there is an abnormality in the electrical pathway, delaying or blocking the passage of electrical impulses from the atria to the ventricles. This can occur due to a malfunction with respect to the sinus node or the AV node. Malfunctions are caused or contributed to by congenital heart defects, degeneration of heart tissue due to aging, diseases that damage the heart’s electrical system or slow electrical impulses, inflammatory diseases, high blood pressure and even various medications.

How is Bradycardia Diagnosed?

Bradycardia is diagnosed with an ECG (electrocardiogram), either in the doctor’s office or hospital, or with a portable type which the person can wear like a pocketbook, taking it along during a typical day to measure heart rate through electrodes which are fastened to the chest. When the doctor reviews the recorded heartbeat, even the type of bradycardia can be determined, whether atrial bradycardia, atrioventricular nodal bradycardia, or ventricular bradycardia. Sick sinus syndrome, when the sinus node malfunctions, causing irregular heartbeat, includes bradycardia-tachycardia syndrome, wherein sometimes the heart beats too slowly and other times it beats too quickly.

Symptoms of Bradycardia

While healthy bradycardia does not produce any symptoms, for a person with unhealthy bradycardia, his or her brain and other organs may not obtain the necessary oxygen supply. In this case, a number of symptoms may be experienced, including dizziness, near fainting or fainting, fatigue, weakness, shortness of breath, chest pains, sleep interruption and confusion. If left untreated, complications may exist including frequent fainting spells, heart failure, cardiac arrest and death. Complications will vary depending on how slow the heart rate is, where the electrical problem occurs and prior damage to heart tissue.

What causes bradycardia?

Bradycardia is a slow beating of the heart. In adults, this means that the heart is beating at less than 60 beats per minute, unlike the usual 60 to 100 beats per minute. Due to the fact that the heart is beating slower, less oxygen arrives to nourish the cells of the body. The body responds to the lack of oxygen with weakness, fatigue, a feeling of being about to faint when standing or taking part in physical activity, chest pains, or disturbed sleep.

It is worth noting that more than half of professional athletes who are in very good shape have bradycardia, due to the heart having built up a more efficient way of pumping the same amount of blood with fewer contractions. This is known as benign sinus bradycardia, and for athletes, this is normal, not pathological.

In infants, whose heartbeat is normally between 120 and 160 beats per minute, bradycardia is defined as less than 100 beat per minute. This is more common in premature babies, but stroking the baby gently or rocking the bassinet can get the heart beating faster.

The causes of bradycardia are divided up into those which are caused by heart problems and those which are not. The ones caused by underlying heart problems include degenerative primary electrical disease, ischemic heart disease, vascular heart disease, or valvular heart disease. Bradycardia which is not due to problems of the heart is often triggered by high blood pressure, an under-active thyroid gland, prolonged bed rest, or as a side effect of medication taken for other conditions. Once the cause of bradycardia is known, solutions can be proposed to eliminate it. For example, if the underlying cause is high blood pressure, this can be brought under control with lifestyle changes or medication. If, on the other hand, the cause is due to mediation, having the doctor cut down on the dosage or change to a different medication might help.

If lifestyle changes are not enough to improve bradycardia or if it is not caused by the above-mentioned factors, there are other options. A pacemaker can be surgically implanted, and it will both monitor heart rate and send electrical impulses to get the heart to beat faster. Atropine administered intravenously can bring about temporary improvement as well.

How to Prevent Bradycardia

Ways to prevent bradycardia in the first place are to maintain heart health by eating a diet that’s low-fat, and high in fruits, vegetables, and whole grains. As heart disease increases with being overweight, regular exercise and keeping one’s weight down are important in not putting extra stress on the heart. High blood pressure and high cholesterol should be avoided, as reflex bradycardia is a type of decreased heart rate in response to too high blood pressure. Other behaviors which increase the risk of bradycardia, as well as a number of other diseases and general poor health, are smoking, illegal drugs, and too much alcohol consumption. If heart disease is already present, the person should be sure to keep all medical appointments and follow the doctor’s orders, letting the doctor know if symptoms change or if new symptoms develop.

More resources about Bradycadia

University of Rochester’s Information about Bradycardia

More information about Bradycadia

Resources about Bradycardia

Bradycardia: Causes, Diagnosis, and Prevention Resources

Amy Scholten, MPH information about bradycardia (Pronounced: Bray-dee-car-dee-uh ) at the NYU Cardiac & Vascular Institute

Columbia.edu’s Cardiac Center

Bradycadia or Tachycardia

During exercise, a heart may speed up to 160 to 180 or more beats per minute. This is normal. Unhealthy tachycardia occurs, however, when an abnormality in atria and ventricles produce rapid electrical signals and an increased heart rate. Common types of unhealthy tachycardia include atrial fibrillation, atrial flutter, supraventricular tachycardia, ventricular tachycardia and ventricular fibrillation. Factors that can cause or contribute to such abnormalities include high blood pressure, smoking, heavy alcohol and caffeine consumption, medications, drug abuse, damage to heart tissue from heart disease, congenital heart defects, imbalance of electrolytes and an overactive thyroid.

Symptoms of Tachycardia

When the heart beats too quickly, the ventricles do not have enough time to fill with blood and, thus, are unable to pump sufficient amounts of blood to the rest of the body, depriving organs and tissues of oxygen. In this case, a number of symptoms may be experienced, including the heart skipping a beat, heart palpitations, dizziness, blackouts, fainting or near fainting, rapid pulse rate and chest pain. If left untreated, complications from unhealthy tachycardia may exist, including blood clots, heart failure, frequent fainting spells and sudden death (usually only associated with ventricular tachycardia or ventricular fibrillation).

Resources about Tachycardia

Tachycardia Overview from the University of Maryland Medical Center

Atrial Tachycardia overview from Columbia.edu

Resource by F.Rosseti

I am a teacher in Michigan. I grew up in Florida and have lived here in MI for close to 15 years. I enjoy writing and skiing in my spare time.

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