All About Heart Rate Changes and What Is Normal

The heart beats to circulate the blood around the body. It has four chambers: two upper chambers called the atria, and two lower chambers called the ventricles. Oxygen-depleted blood flows into the right atrium, then continues to the right ventricle and into the lungs, where it gets reoxygenated. From the lungs, it flows to the left atrium and into the left ventricle. The left ventricle pushes the blood back out into the body.

Many things can cause an elevated heart rate. While some indicate a health problem, others are more situational. For example, you may experience an elevated heart rate after drinking caffeinated beverages or if you have a fever. Physical activity also makes the heart rate go up, and generally, the more vigorous the exercise, the higher the heart rate.

An elevated heart rate can indicate a number of health problems, including high or low blood pressure, anemia, or overactive thyroid. Other causes that can be dangerous are an imbalance of electrolytes, medication side effects, and the use of stimulant drugs, like methamphetamine or cocaine.

Just as everyone's resting heart rate varies, so does their low heart rate. Generally, anything less than 60 beats a minute is considered a low heart rate, but this does not apply to everyone all the time. A low heart rate is normal in some cases. It might fall below 60 during sleep, and active adults, especially athletes, can have resting heart rates as low as 40 beats per minute.

Abnormal causes of low heart rate include problems with the electrical system in the heart, hypothyroidism, and damage from aging, surgery, or disease. Other causes are congenital heart defects, electrolyte imbalances, sleep apnea, and inflammatory diseases.

Some medications for high blood pressure or abnormal heart rhythms can also cause a low heart rate.

Factors that affect heart rate can also be environmental, like air temperature and humidity. The heart pumps a little faster when it is hot outside, but this is usually not a substantial change, adding only 10 beats per minute or so.

Heart rate elevates slightly when moving from lying or sitting to standing, as well, and stress and anxiety can also raise the pulse, sometimes significantly.

Learning how to check your heart rate can help you monitor your heart health. Your pulses are where you can feel the force of the blood entering the body from the left ventricle with every heartbeat. The best places to check your pulse are on the wrists, elbows, and sides of your neck. Place your fingers gently over your pulse, then count the number of beats for a full minute. Your pulse will be slowest when sitting, lying down, or relaxing and highest after physical activity.

It is normal for the heart rate to change based on activity level, but a heart rate with an abnormal rhythm can indicate a problem in the heart.

Heart failure, coronary artery disease, and heart valve problems can all cause abnormal rhythms, as can drugs, birth defects, and age-related changes.

When an irregular heart rate is detected, tests can determine the underlying issue. Electrocardiography is a graphic representation of the heart rate and rhythm, showing the path of the electrical impulses through the heart. Some arrhythmias cause the heart to beat too fast, while others cause it to beat too slow.

Treatment for heart rate issues varies depending on the cause. Fast heart rates that require treatment usually respond to medication to regulate the rhythm. Pacemakers commonly treat low heart rates, but they can also treat a fast heart rate by delivering an electric shock to regulate the pace and rhythm.