Sudden drop in heart rate and dizziness

Medically Reviewed by James Beckerman, MD, FACC on August 17, 2022

  • Heart Basics
  • Symptoms
  • When to See a Doctor
  • Causes
  • Diagnosis
  • Treatment

Generally, it is normal to have a slower heart rate when you’re resting. It can be a sign of good health. But if it’s too slow, it could be a symptom of a condition called bradycardia.

Normally, your heart beats 60 to 100 times a minute when you’re at rest. But with bradycardia, it goes down to less than 60 beats a minute.

This might not cause a problem for some people. But it could be a clue that you have an issue with the electrical system in your heart. You need to see a doctor who can figure out why it’s beating slowly and if you should get treatment.

Electrical signals travel through the heart’s four chambers -- two on the top called the atria and below them, the two ventricles. These signals prompt it to beat in a steady rhythm. But pulses don’t always fire off as they should.

This creates what’s called arrhythmias, or abnormal heartbeats.

Some conditions cause the heart to beat too fast or to flutter. With bradycardia, it’s the opposite. The electrical problem slows down the time in between heartbeats.

You may simply have a slower-than-normal heart rate that doesn’t cause any symptoms. The electrical activity may be working fine, just a little slower than it does in most people. You wouldn’t even be diagnosed with this condition.

And even with bradycardia, you may never notice any symptoms or need treatment. But that’s not always the case.

The biggest concern is your heart isn’t doing well enough at pumping blood to all the organs and tissues that need it. When this happens, the following may develop:

You may also find that you tire out easily with even just a little activity.

If you check your heart rate and it’s regularly below 60 beats per minute, be aware of those symptoms.

If you have no other symptoms, you probably don’t need to see a doctor right away. You may exercise a lot, and a slow heart rate could be a sign of how fit you are. But, bring it up at your next appointment.

If you or a loved one notices mild to medium symptoms, go to a doctor quickly.

If you or a loved one faints, has chest pains or trouble breathing, call 911.

Tiredness, trouble concentrating, or breathing harder may just seem like part of growing older. But sometimes it’s more than that.

Be sure to tell your doctor about all your symptoms. If you wear out more easily now than you did a month or year ago, let them know.

The chances of getting bradycardia increase as you get older, though that’s true of most heart conditions. The causes of bradycardia can vary greatly from one person to the next.

The abnormal rhythm can show up after a heart attack or as a side effect of heart surgery. Other things that can lead to it:

  • Certain medications, such as those to treat high blood pressure and other arrhythmias, or abnormal heartbeats
  • A congenital defect, or problem you’re born with
  • Thyroid disease, an imbalance of hormones in the body
  • Obstructive sleep apnea, when your breathing pauses many times throughout the night

Bradycardia can be a little hard for doctors to figure out, because it’s not always present all the time. Your heart can go in and out of slow rhythms.

Your doctor will be able to make the diagnosis if you’re having a bout of bradycardia during a test called an electrocardiogram. Often called an EKG, it’s a way to measure your heart’s electrical system.

If your heart rate appears normal, but you have had symptoms of bradycardia, your doctor may have you wear a 24-hour monitor.

Your doctor will ask about your personal and family health histories, as well as any symptoms you’ve had.

If your doctor decides that you have bradycardia, the treatment plan will be based on the likely cause of the problem.

For instance, if the cause is hypothyroidism, or low thyroid function, treating that may take care of the heart rate issue.

If there is no clear physical cause, your doctor may change medications that might be slowing your heart. Beta blockers are sometimes prescribed to relax your heart muscle. But if they cause you to have a really slow heart rate, your doctor might lower the dosage or give you a different drug.

If these approaches don’t work and your condition is serious enough to put your brain and other organs at risk, you may need a pacemaker.

A surgeon will put this small device into your chest. It has thin, flexible wires, called leads, which extend to the heart. They carry small electrical charges that help keep the heart pumping at a steady rate.

If you have been given a pacemaker, listen to your doctor’s instructions about how it operates and any signs it might not be working.

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Take this information with you to a physician that specializes in heart rhythm disorders by using our international specialist directory.

Atrial fibrillation (AFib) is the most common abnormal heart rhythm. In a normal heart, the four chambers of the heart beat in a steady, rhythmic pattern. With AFib, the atria (upper chambers of the heart) fibrillate (quiver or twitch quickly) and create an irregular rhythm.

Learn More About Skipped Beats

Learn More About Slow Heartbeat

Learn More About Syncope (Fainting)


The heart muscle is responsible for circulating blood throughout the body. When the heart does not operate as it is supposed to and develops an abnormally slow heart rate that is less than 60 beats per minute, the condition is known as bradycardia.

Bradycardia can be life threatening if the heart is unable to maintain a rate that pumps enough oxygen-rich blood throughout the body.

The main symptom of bradycardia is a heart rate below 60 beats per minute. This abnormally low heart rate can cause the brain and other organs to become oxygen-deprived, which can lead to symptoms such as:

  • Fainting
  • Dizziness
  • Fatigue
  • Weakness
  • Shortness of breath
  • Chest pain
  • Confusion
  • Memory difficulties
  • Quickly tiring during physical activity

In rare cases when bradycardia goes undiagnosed for an extended period of time, the following complications can occur:

  • Cardiac arrest
  • Angina
  • High blood pressure

Causes and Risk Factors

Bradycardia is caused by a disruption in the heart's electrical system that controls the heart rate. This disruption can come from four possible causes:

  • Sinoatrial node problems - the sinoatrial node, often referred to as the sinus node, is considered to be the natural pacemaker of the heart. This group of cells triggers electrical impulses to the heart, causing it to contract. When this node isn’t working properly it can trigger much slower electrical impulses causing the heart to beat slower.
  • Dysfunctional conduction pathways - electrical impulses travel in the heart via conduction pathways. When these pathways do not work properly, the heart rate is affected — a condition often referred to as an atrioventricular block or heart block, of which there are three forms:
  • First degree - all of the electrical signals from the atria reach the ventricles, although they are transmitted slower than normal.
  • Second degree - only some of the electrical signals from the atria reach the ventricles. When a signal does not reach the ventricles, the heart beat it was meant to trigger does not occur.
  • Third degree - none of the electrical impulses make it from the atria to the ventricles. When this happens, a natural pacemaker in the ventricles may step in to take over regulating the heartbeat, although at a rate that is slower than normal.

Other risk factors that may contribute to a disruption of the electrical impulses associated with bradycardia include:

Bradycardia can affect patients of all ages, genders and ethnicities. However, older patients are at an increased risk as well as patients with the following risk factors:

  • High blood pressure (hypertension)
  • Smoking
  • Heavy alcohol use
  • Use of recreational drugs
  • Psychological stress or anxiety

Diagnosis of bradycardia will generally begin with the physician taking a medical history and performing a physical exam. During the physical exam, the physician will listen to the patient's heart to detect if there is an abnormal heart rate. Patients are also asked for a detailed description of their symptoms. Symptoms may suggest the presence of bradycardia. If so, or if an abnormal heart rate is observed, the physician may order an electrocardiogram to confirm it. An EKG is a painless procedure that records the electrical activity of the heart.

If the abnormal heart rhythm is intermittent, the patient may need to wear a Holter monitor. This portable device allows the medical team to observe the patient's heart over a longer period of time and helps diagnose the condition if the abnormal rhythm happens while the patient is not at the hospital.

Depending on the patient's symptoms and the results of the other diagnostic tests, an echocardiom may be prescribed. This noninvasive procedure uses a machine called a transducer that bounces sound waves off the heart and back into the transducer. These echoes are then translated into visual images.

Other diagnostics may include the tilt table test and exercise test to look at the relationship between the patient’s heart rate and physical position (sitting or standing), as well as how exercise affects the heart rate. Electrophysiology studies may also be used to look at the heart's electrical system.

Treatment of bradycardia will vary from one patient to another and will depend on the type, severity and cause of their condition. In some cases, when the abnormal heart rhythm is caused by an underlying condition, such as hypothyroidism, treatment may focus on addressing that underlying condition. Treatment options may include adjusting current medication and sometimes surgery.

Because medications that are used to control blood pressure and other conditions — such as beta blockers or calcium channel blockers — may cause bradycardia, a patient's medications may be adjusted.

In some cases, surgery may be needed to implant a pacemaker if other treatment options do not adequately address the condition.

The knowledgeable and highly trained staff at the Cedars-Sinai Heart Institute will work with each patient to determine the best treatment option.

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