Features February 2019 Issue

Should You Be Concerned If Your Heart Rate Is Too Fast or Too Slow?

Both scenarios can put you at risk for problems.

In the doctor's office, a nurse measures your heart rate by putting fingers on your wrist or neck and looking at a watch. Do you know why this is done?

Most people probably don't give it a second thought, but measuring your heart rate regularly allows your doctor to spot when your heart is not functioning like it should.

"We are looking for a heart rate that is too fast or too slow. Both of these can lead to problems," says Cleveland Clinic cardiologist Chad Raymond, DO.

What Your Heart Rate Means

Heart rate-sometimes called pulse-is the number of times your heart beats every minute.

It is different from blood pressure, which measures the force of blood against the walls of your arteries.

A normal, healthy resting heart rate is between 60 and 100 beats per minute (BPM). Because that span is wide, measuring your pulse over time allows your doctor to determine what BPM is normal for you-and know when your pulse is too slow or too fast.

Slow Heart Rate Risks

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Heart rates that are consistently slow or fast prevent the heart from working as well as it should and produce a variety of symptoms.

In some people, a heart rate on the lower end of normal is a sign their heart is working efficiently. This means it isn't working too hard to pump blood effectively throughout the body. Athletes in great cardiovascular health often have slow heart rates.

A heart rate that becomes too slow, however, is another matter. The condition, called bradycardia, is usually diagnosed when a resting heart rate is less than 60 BPM or, in some cases, 50 BPM.

A below-normal heart rate can cause insufficient blood flow to the brain, resulting in unexplained lightheadedness, fatigue or fainting. "Fainting is a common symptom of bradycardia and can lead to falls and bone fractures," says Dr. Raymond.

A heart that is beating too slowly may try to compensate by trying to pump harder. This can lead to high blood pressure or, over time, heart failure. However, a slow heart rate does not normally increase the risk of coronary artery disease.

Treating a Slow Pulse

If you have bradycardia with no other symptoms, you may not need treatment. But if you start fainting or experiencing frequent episodes of lightheadedness or chest pain, tell your doctor.

Sometimes, bradycardia is a side effect of medications such as beta-blockers or digoxin. Adjusting the dosage usually restores the heart rate to normal.

Low thyroid hormone levels can cause heart rate to slow down, as well. Increasing the dose of thyroid hormone often fixes the problem.

Many times, bradycardia is caused by a problem with the heart's sinoatrial (SA) node. This so-called "natural pacemaker" is a cluster of cells in the right atrium that sends electrical signals to help control the heartbeat. An SA that does not work properly can cause the heart rate to slow down, speed up or become inconsistent. Sometimes, a pacemaker is required. A pacemaker that detects bradycardia sends a signal to the heart that restores a healthy rate.

Faster Is Not Better

People who have a consistently fast heart rate are more likely to develop heart failure or, in the case of atrial fibrillation or flutter, blood clots. However, the cause-and-effect relationship is unclear. "We're not sure whether a fast heart rate causes these problems, or is just a sign of what's going on," says Dr. Raymond.

A faster heart rate also increases the risk of premature cardiac death. A large study found that people with a resting heart rate on the high end of normal (80 BM to 90 BPM) had a 40 percent shorter lifespan than those with a heart rate of 60 BPM to 69 BPM.

Many times, all it takes to lower a fast heart rate is exercise. "Fifteen to 30 minutes of moderate exercise, such as brisk walking, every day can help lower a heart rate and the increased cardiac death rate that accompanies it," says Dr. Raymond.

The real danger comes with a heart rate that is so rapid that it prevents the upper and lower chambers of the heart from contracting in sync. This prevents the heart from pumping blood efficiently, causing palpitations, shortness of breath, chest pain, dizziness or fainting. This condition, called tachycardia, can cause heart failure, stroke or sudden cardiac death if left untreated.

Although the right treatment for tachycardia depends on the specific type, there are medications and treatments such as ablation to slow a rapid or irregular heart rhythm and restore the heart rate to normal.

How and When to Measure Pulse

To measure your resting heart rate, pick a time when you feel relaxed. Sit quietly for about five minutes. Then place two fingers on the thumb side of your wrist between the bone and tendon over your radial artery. If you can't feel your pulse, place your fingers on your neck below and slightly in front of your ears. Count the number of beats for 15 seconds and then multiply that number by four to get the BPM.

If you have heart disease or risk factors for it, ask your doctor what your target heart rate should be. Measure your resting heart rate several times a day. "Be sure to tell your doctor if you notice a change. It may not be serious-but then, it may be a sign your heart is not working like it should," says Dr. Raymond.

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