When Is Heart Rate “Too Slow?”

By Stephen T. Sinatra, M.D., F.A.C.C., F.A.C.N., C.N.S., C.B.T.

It can be frightening to learn that your heart isn’t beating normally, especially when it’s racing or quivering. But what about bradycardia, a heartbeat that’s slower than normal?

What’s considered “too slow” can vary from person to person, depending on age and physical condition. But generally speaking, bradycardia is defined as a resting heart rate of fewer than 60 beats per minute (BPM).

Slow heart rate is not necessarily a bad thing. Many healthy, physically active people—particularly athletes—have a resting heart rate well below 60 BPM. In these cases, a slow heart rate is a sign of good health and means that the heart is very efficient at pumping blood throughout the body. A slow heart rate is also completely normal during sleep.

Additionally, bradycardia becomes more common with age. In the absence of symptoms, though, it’s really nothing to be concerned about. For these reasons, cardiologists usually don’t worry too much about it.

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In certain situations, though, bradycardia can become problematic…

Bradycardia Symptoms

When the heart rate becomes so slow that the heart isn’t able to pump enough blood to meet the body’s needs, bothersome symptoms can develop. Bradycardia symptoms that indicate insufficient blood flow include:

  • Fatigue
  • Weakness
  • Dizziness/lightheadedness (especially with exertion)
  • Fainting or near-fainting
  • Shortness of breath
  • Confusion

If left untreated, severe or abnormal bradycardia can lead to complications like heart failure, chest pain, high blood pressure, or orthostatic hypotension (severe drop in blood pressure that occurs when you stand up from sitting or lying down).

If you have any of these symptoms, you need to work with a cardiologist to determine the type and cause of your bradycardia. 

Types and Causes of Bradycardia

The two most common types are sinus bradycardia and heart block.

Despite a name that says otherwise, sinus bradycardia has nothing to do with your nasal passages. It actually refers to the sinus node (also called sino-atrial node), which is a small group of cells located at the top of the right atrium that sends out signals instructing your body to pump more blood. The sinus node is sometimes called your “intrinsic” or “natural pacemaker.”

The sinus node should send out a signal about 60 to 100 times per minute. But if it works too slowly or fails to work at all, sinus bradycardia can result.

The condition may be so mild that you never notice symptoms. But in more serious cases, you might notice the symptoms mentioned above.

A number of conditions can injure or incapacitate your sinus node, thus resulting in bradycardia. Some of them include:

Additionally, certain drugs can cause bradycardia. Some of the usual suspects are medications used to control arrhythmias and high blood pressure. Slow heart rate is a common side effect of beta blockers, for example, and sometimes the dosage will need to be reduced or discontinued if bradycardia symptoms develop.

With a heart block (also called atrioventricular, or AV, block), the flow of signals from the sinus node down to another group of cells, called the AV node, is compromised.

Mild forms of this type of bradycardia cause no symptoms, but more serious forms may require emergency care.

Heart blocks may be caused by congenital heart defects, but most often they are the result of heart attack, inflammation of the heart muscle, and/or heart disease.

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Bradycardia Treatment

Bradycardia treatment depends on the type, cause, and severity of symptoms.

If you have no symptoms, treatment usually isn’t necessary.

If you have an underlying problem that is causing the bradycardia—such as sleep apnea or a thyroid disorder—your doctor will likely address that. Often, resolving those issues restores your resting heart rate into the normal range.

If you’re taking a medication that could be affecting your heart rate, finding an alternative or adjusting dosage may correct the problem.

To see if the slow heart rate is indeed the cause of your bradycardia symptoms, your doctor may have you wear a 24-hour monitor for a week or so. 

And finally, if all else fails and your doctor believes your bradycardia needs to be treated, s/he may recommend a pacemaker. This small device gets implanted under your collarbone, and wires are threaded through your veins and hooked up to your heart. A pacemaker monitors your heart rate and, when necessary, sends electrical impulses so that you maintain an appropriate number of beats per minute.

The Bottom Line on Bradycardia

In healthy young people, and even in older people who are in good physical shape, a slow heart rate—even as low as 40 or 50 BPM—is pretty typical.  Bradycardia is only considered a real issue if your heart rate is too slow to meet your body’s needs and you start developing symptoms. If that’s the case, your cardiologist can come up with a treatment plan that’s appropriate for you.

Otherwise, he/she will simply monitor your heart rate and follow up with you periodically to make sure your bradycardia is not starting to affect or bother you in any way.

© Stephen Sinatra, MD. All rights reserved.

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