Is a Low Heart Rate Dangerous?

A low heart rate can lead to fainting and falls if you’re not a highly trained athlete, but the condition is often treatable.

low heart rate dangerous

Health risks can develop from a low heart rate—a condition called bradycardia.

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A low heart rate may be a sign of an efficiently working heart. Or, if the rate becomes too low, it could be a sign of health complications down the road.

A normal or healthy resting heart rate for an adult is between 60 and 100 beats a minute. A heart rate near the lower end of that range is considered a good sign. Your heart isn’t working too hard to pump blood effectively throughout the body. It’s one indication of cardiovascular fitness. A very rapid heart rate, on the other hand, raises your risk of heart failure, blood clots, and other problems.

But health risks can develop if a low heart rate gets too low—a condition called bradycardia. Bradycardia is usually diagnosed when your resting heart rate is less than 60 beats per minute (BPM). In some cases, the threshold is less than 50 BPM. Those numbers are guidelines. You may experience heart-related complications if your resting heart rate is 65 or 70 BPM. Or, you may be fine with a resting heart rate that is less than 60 BPM. Long-distance runners and other athletes in top cardiovascular health often have a resting heart rate that is under 60 BPM.

If you’re not training for a marathon or swimming dozens of laps every day, you should talk with your doctor if you notice a low heart rate.

When to Worry About a Low Heart Rate

One complication related to bradycardia is a condition called syncope. It means a loss of consciousness (fainting), usually due to insufficient blood flow to the brain. A low pulse rate can compromise your circulation. Your heart may not pump fast enough to keep a healthy flow of blood up to your brain and throughout your body. Fainting, of course, can lead to dangerous falls and bone fractures.

The most common symptoms of a low heart rate, according to the American Heart Association, are fatigue, confusion, dizziness, shortness of breath, especially during exercise.

To compensate for a slowly beating heart, your heart muscle might try to pump harder to keep up with your body’s demand for oxygenated blood. This can lead to high blood pressure (hypertension) and even heart failure, if your heart muscle works overtime for too long a period. A low pulse rate is also paired sometimes with low blood pressure, a condition known as hypotension. Low blood pressure is also a cause of syncope.

However, research suggests that bradycardia does not increase the risk of cardiovascular disease—the precursor to a heart attack. A study led by Ajay Dharod, MD, an internal medicine specialist with Wake Forest Baptist Medical Center, found that a low heart rate by itself does not suggest an inevitable slide toward heart disease. “For a large majority of people with a heart rate in the 40s or 50s, who have no symptoms, the prognosis is very good,” Dr. Dharod says. “Our results should be reassuring for those diagnosed with asymptomatic bradycardia.”

Treatment

If you have bradycardia, but not other symptoms, you may not need any treatment. But if you do start to experience fainting or even frequent episodes of feeling lightheaded, or you start to experience chest pain, tell your doctor. If treatment is necessary, your doctor will need to determine the cause first.

In many cases, bradycardia is caused by problems with the sinoatrial (SA) node. This is sometimes referred to as the heart’s “natural pacemaker.” The SA node is a cluster of cells in the upper part of the heart that sends out electrical signals that help control the beating of your heart. If the SA node is damaged or is otherwise not working properly, your heart rate can slow down, speed up, or become inconsistent. An abnormal heart rate of any type is called an arrhythmia. If the problem is serious enough, you may require a pacemaker. This small device is implanted in the chest. When it detects an arrhythmia, it sends an electrical signal to the heart to help restore a healthy rate.

Common causes and risk factors of bradycardia are old age, heart block, and damage from heart disease or heart attack. Another common cause is thyroid disease. Low thyroid function (hypothyroidism) can cause a number of health problems, including low heart rate. Controlling your thyroid disease with medication and lifestyle changes may help correct bradycardia.

A low heart rate may also be a side effect of certain medications, such as digoxin, a common drug used to treat heart failure. Beta blockers, which are often prescribed to treat high blood pressure or tachycardia (abnormally fast heart rate), may also cause your heart to beat too slowly. “Bradycardia may be problematic in people who are taking medications that also slow their heart rate,” Dr. Dharod says. “Further research is needed to determine whether this association is casually linked to heart rate or to the use of these drugs.”

Adjusting your medication dosage may be enough to reset your heart rate.

Measuring Your Heart Rate

Checking your resting heart rate isn’t difficult. Start by sitting quietly for five minutes or so. Then, place two fingers on the thumb side of your wrist, between the bone and the tendon over your radial artery. Once you feel a pulse, count the number of beats for 15 seconds. Then multiply that number by four. That will give you your beats per minute.

It’s a good idea to do this every so often, just to have a baseline number. If you notice a change—up or down—tell your doctor at your next appointment. You should also talk with your doctor about your target heart rate, particularly if you are an older adult or you have risk factor for cardiovascular problems, such as diabetes, family history of heart disease, smoking, obesity, a sedentary lifestyle, or high blood pressure.

Keep in mind that your heart rate should go up when you exercise and then return to a normal resting heart rate soon after you stop. If your heart rate doesn’t rise very much or takes a long time to return to normal, tell your doctor. It may be a sign of a heart that isn’t working optimally. It may not be serious, but it is worth a discussion with your physician.

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This article was originally published in 2018. It is regularly updated. 

As a service to our readers, University Health News offers a vast archive of free digital content. Please note the date published or last update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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Jay Roland

Jay Roland has been executive editor of Massachusetts General Hospital’s Mind, Mood & Memory since 2017. Previously, he held the same position with Cleveland Clinic’s Heart Advisor, since 2007. In … Read More

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