What Is A Dangerous Heart Rate?

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Most adults have experienced a racing heart rate at some point in their lives, be it the result of an intense workout or stressful job interview. While a normal heart rate does fluctuate, a heart that’s consistently beating too fast or too slowly can be cause for concern.

To determine whether your heart rate is considered “dangerous,” it’s best to assess your resting heart rate, which should generally fall between 60 and 100 beats per minute. Read on to learn about potential health risks associated with a resting heart rate that regularly sits outside that range, as well as when you should reach out to your health care provider.

Dangerous Heart Rate

A heart rate below 60 beats per minute or above 100 beats per minute is often considered dangerous when a person is at rest (and awake) but can be normal in other states. During sleep, for instance, a person’s heart rate may often drop below 60 beats per minute. Meanwhile, heart palpitations exceeding 100 beats per minute can be caused by non-dangerous conditions as well, such as a rigorous run or temporary stress.

An abnormally high or low heart rate is considered worrisome when it occurs for multiple hours or days. It may also be considered dangerous when it’s accompanied by other symptoms.

When Your Heart Rate Is Too High

If you just completed a tough workout or navigated a stressful experience, your heart rate may temporarily exceed 100 beats per minute, but it shouldn’t remain above that threshold consistently.

“Having palpitations doesn’t [always] mean there’s actually something horribly wrong,” explains Alon Ronen, M.D., a cardiologist at Bridgeport Hospital, part of Yale New Haven Health in Connecticut. “Many things can trigger palpitations, including stress, anxiety and panic. Sleep pattern changes, poor sleep habits and other lifestyle changes can trigger palpitations as well.”

Dr. Ronen reiterates that a fast heart rate tends to only be problematic when it’s consistent for an extended period of time or when it presents alongside other symptoms, such as chest pain, shortness of breath and dizziness.

If your heart rate consistently measures above 100 beats per minute, it’s classified as tachycardia, a condition marked by a rapid heart rate.

There are several main types of tachycardia:

  • Sinus tachycardia (ST) is a fast heart rhythm that results from faster-than-normal electrical impulses generated from the sinus node. A rare subset of sinus tachycardia is inappropriate sinus tachycardia, when the heart beats quickly for no clear reason.
  • Supraventricular tachycardia (SVT) is a fast heartbeat that originates from the heart’s upper chambers. There are a wide variety of supraventricular tachycardias, the most notable of which is atrial fibrillation, as it is the most common sustained arrhythmia worldwide.
  • Junctional tachycardia (JT) originates from the junction, an area between the upper and lower chambers of the heart.
  • Ventricular tachycardia (VT) occurs when the lower chambers of the heart beat very quickly.​​ It’s often more serious than SVT.

Causes of Tachycardia

Each of the different types and subtypes of tachycardia stem from different causes.

Sinus tachycardia is often caused by:

  • Anxiety
  • Infection
  • Fever
  • Pain
  • Sleeplessness
  • Anemia
  • Blood volume depletion
  • Hypoxia (low oxygen levels)
  • Thyroid disease
  • Other types  of heart disease
  • Exposure to stimulants
  • Specific medications or withdrawal from them

SVT causes are varied but may be precipitated by the above via mechanisms related to re-entry, higher automaticity or triggered activity. Structural heart disease or other changes in the body’s homeostasis can be contributing factors as well.

Meanwhile, VT can be caused by:

  • A lack of blood flow through the coronary arteries
  • Side effects of medication or illicit substances
  • Cardiomyopathy, a condition that makes it harder for the heart muscles to pump blood
  • Infiltrative heart diseases
  • Congenital heart diseases

When Your Heart Rate Is Too Low

If your heart rate consistently sits under 60 beats per minute when you’re awake, you could be diagnosed with bradycardia, a lower-than-average heart rate.

On its own, a low heart rate isn’t cause for concern. “Elite athletes can often have resting heart rates as low as 40 beats per minute,” notes Nick West, M.D., chief medical officer and division vice president of global medical affairs of Abbott’s Vascular Business in San Francisco. “However, if you’re not an athlete and have such a low pulse at rest, it can be an early sign of deterioration in the heart’s natural conducting system.”

Regardless of your athletic status, experts advise visiting your health care provide if a low heart rate is accompanied by any of the following:

  • Dizziness
  • Fainting
  • Fatigue
  • Confusion
  • Trouble breathing

There are several main types of bradycardia:

  • Sinus bradycardia simply occurs when the heart rate is less than 60 beats per minute, which, as mentioned above, can be considered normal in healthy, athletic people. It’s unlikely to lead to complications unless the heart rate is regularly less than 40 beats per minute and/or causes other symptoms.
  • Sick sinus syndrome occurs when the sinus node (the heart’s natural pacemaker) fails to function properly. Sinus pauses, a type of bradycardia in which the heart slows down because the sinus node isn’t activating the electrical system throughout the rest of the heart correctly, may occur in this setting. Various arrhythmias or combinations of arrhythmias can present in people with sick sinus syndrome. Many individuals with sick sinus syndrome, particularly those with frequent sinus pauses and/or with symptoms, may require an artificial pacemaker.
  • Tachycardia-bradycardia syndrome, also called tachy-brady syndrome, often occurs in people with atrial fibrillation who also have sinus node dysfunction. Sometimes the heart sometimes beats too quickly while other times it beats too slowly.
  • Heart block is an abnormality in the way electricity passes through the heart, “blocking” the electrical impulse on its normal path and resulting in a slower heart rate. There are multiple forms of heart block, with each differing in severity and corrective treatment.
  • Ectopic bradycardia occurs when a focus other than the sinus node functions as the natural pacemaker for the heart. It can occur in the atria, termed ectopic atrial bradycardia, in the junction, called junctional bradycardia, or in the ventricles, dubbed idioventricular rhythm.

Causes of Bradycardia

Bradycardia has many causes, ranging from mild to severe. Sleep apnea is a common cause, as well as one of the least concerning. Bradycardia is remedied in 90% of treated sleep apnea cases, according to research in Trends in Cardiovascular Medicine.

Some forms of bradycardia are caused by structural heart problems, including the degeneration of the electrical conduction system.

Sinus node damage or dysfunction, or the inability of the sinoatrial node to produce an adequate heart rate, often leads to bradycardia as well.

Dangerous Heart Rate for Adults

Whether a heart rate is considered “dangerous” does vary with age, as well as the presence of other symptoms a patient may be experiencing.

“Heart rate alone isn’t always an indicator of danger,” says Dr. West. “However, reduced or elevated heart rates in conjunction with symptoms, such as dizziness, blackouts or collapse [episodes] (syncope), or chest pain, suggest medical attention should be sought urgently.”

There isn’t a set range for when a heart rate is deemed dangerous, but Dr. Ronen says a heart rate above 100 beats per minute or in the 50s or lower while resting is often a cause for concern. However, a cardiologist should consider the degree of danger on a case-by-case basis. For example, Dr. Ronen has seen a 76-year-old with a resting heart rate of 36 beats per minute not because he had an underlying problem, but because he was an avid cyclist.

When to See a Doctor About Your Heart Rate

It can be tricky to know when to see a doctor about your heart rate.

“Even if there’s an obvious reason why your heart rate is low or high, it can still be hard to know when you should see your health care provider,” says Katie E. Golden, M.D., a medical editor at GoodRx. “But if you’re worried about your heart rate, it’s best not to delay medical evaluation.”

A heart rate measurement is also a normal element of an annual physical exam. If your provider notices anything abnormal with your heart rate during this exam, they may order more tests or refer you to a specialist.

What You Can Do to Stabilize Your Heart Rate

If you’re in an emergency situation, the best way to stabilize your heart rate is to seek immediate medical attention.

In a non-emergency situation, consider exploring stress-relieving tools like mindfulness and meditation, modifying your diet and incorporating more movement into your daily routine. One of the most common and effective ways to stabilize your heart rate is to exercise consistently. Meanwhile, eating a heart-healthy diet, such as the Mediterranean diet, can also help stabilize your heart rate.

Spending time in nature is an underrated way to help stabilize your heart rate, according to John La Puma, M.D., the clinical director and founder of Chef Clinic in Santa Barbara, California. “Even looking at nature can relax your physiology,” he says. “Real nature has mixed effects—for some people, it relaxes you, and for others, it excites you. Either way, nature-based therapies are important heart health tools.”