Last updated on July 10, 2024

What Is a Dangerous Heart Rate with Afib?

In atrial fibrillation (Afib), the heart’s rhythm becomes irregular, causing beats that can be too fast or too slow. Knowing what is a dangerous heart rate with AFIB is essential for managing this condition. Whether it’s the risks of a consistently fast heartbeat or the effects of a slow heartbeat, understanding these thresholds is vital for treatment and a better life quality.

Understanding Normal Heart Rates

A normal resting heart rate for adults ranges from 60 to 100 beats per minute (bpm). Various factors such as age, fitness level, and activity can influence this rate. Athletes might have a lower resting heart rate, while stress or physical activity can increase it. A consistently high or low heart rate outside this range, particularly when coupled with symptoms, may indicate an underlying health issue that requires medical attention. Monitoring heart rate in atrial fibrillation is essential to keep yourself healthy.

Heart Rates and Atrial Fibrillation

In atrial fibrillation, the upper chambers of the heart (atria) beat irregularly and out of sync with the lower chambers (ventricles). This irregularity can cause heart rates to vary significantly. When atrial fibrillation occurs, the heart rate can increase dramatically, often exceeding the normal range. In AFib, the atria beat irregularly, but in atrial flutter, the atria beat regularly but faster than usual and more often than the ventricles.

Types of AFIB

Atrial fibrillation (AFib) is categorized into five main types based on the duration and pattern of irregular heartbeats.

  • Paroxysmal Atrial Fibrillation involves episodes that start and stop suddenly, usually within 24 hours but can last up to a week.
  • Persistent AFib has episodes lasting more than a week, requiring medical intervention to restore normal rhythm.
  • Long-standing persistent AFib is continuous, lasting more than 12 months.
  • Permanent AFib is a chronic condition where normal rhythm cannot be restored or is not attempted.
  • Nonvalvular AFib occurs without a related heart valve issue and can be present in any of the other types.

What Happens in Afib?

  • Irregular Heart Rhythm: The abnormal heart rhythm leads to rapid and chaotic electrical signals.
  • Increased Rate: The ventricular rate can rise significantly, sometimes reaching 100-175 bpm or higher during an episode.

Signs of Dangerous Heart Rates in AFIB

Rapid Heart Rate (Tachycardia)

  • Persistent Heart Rate Over 100 bpm at Rest: Consistently elevated heart rates can be alarming and may require medical attention.
  • Sudden Increases Above 150 bpm: Rapid increases in heart rate can be a sign of a dangerous episode.

Symptoms of High Heart Rates

  • Chest Pain or Discomfort: This can indicate that the heart is struggling to cope with the increased rate.
  • Shortness of Breath: Difficulty breathing can occur as the heart rate spikes.
  • Dizziness or Lightheadedness: A rapid heart rate can reduce blood flow to the brain.
  • Fainting (Syncope): Severe tachycardia can cause a drop in blood pressure, leading to fainting.
  • Palpitations: Feeling of a pounding or fluttering heart.

Slow Heart Rate (Bradycardia)

  • Heart Rate Below 60 bpm: While this can be normal for some, in the context of Afib, it may indicate a problem.
  • Extreme Fatigue: Low heart rates can cause a lack of energy and persistent tiredness.
  • Confusion or Memory Problems: Reduced blood flow to the brain can affect cognitive function.
  • Weakness: General muscle weakness can occur due to insufficient blood flow.

Severe Signs of AFIB

Stroke Symptoms

Sudden numbness or weakness, especially on one side of the body, trouble speaking, or sudden vision loss can indicate a stroke, a serious complication of Afib.

Heart Disease Symptoms

Persistent coughing or wheezing, shortness of breath, swelling in the legs, ankles, and feet, or rapid weight gain from fluid retention.

Risk Factors of Uncontrolled Heart Rates with Atrial Fibrillation

Complications of high/low heart rates in atrial fibrillation can lead to serious health risks: 

Increased Stroke Risk

Rapid heart rates can cause blood to pool in the heart, forming clots that may lead to stroke if they travel to the brain.

Heart Failure

Prolonged high heart rates can weaken the heart muscle over time, leading to heart failure where the heart cannot pump blood effectively. Coronary artery disease, heart valve disease, and heart problems present at birth increase the risk of AFib

Reduced Quality of Life

Symptoms such as fatigue, dizziness, and shortness of breath can significantly impact daily activities and overall well-being.


Persistent irregular heart rhythms can contribute to other complications such as cardiomyopathy, which affects the heart’s structure and function. Early intervention and management are crucial to mitigate these risks.

Dangerous Heart Rates in Afib

A heart rate that is too high or too low can be dangerous, particularly in the context of Afib.

High Heart Rates

  • Over 100 bpm at Rest: Persistent heart rates over 100 bpm at rest, known as tachycardia, can be dangerous. It may increase the risk of stroke, heart failure, and other complications.
  • Above 150 bpm: Rates above 150 bpm are particularly concerning and may lead to severe symptoms such as chest pain, shortness of breath, and fainting.

Low Heart Rates

  • Below 60 bpm: While a lower heart rate can be normal for well-conditioned athletes, a heart rate below 60 bpm (bradycardia) in others, particularly if symptomatic, can indicate a problem with the heart’s electrical system.

Managing Heart Rates in Afib

The importance of managing heart rate in AFIB patients can reduce symptoms and prevent complications.


  • Beta-Blockers: These help to slow the heart rate.
  • Calcium Channel Blockers: These also aid in reducing heart rate.
  • Antiarrhythmic Drugs: Used to maintain a normal heart rhythm.

Lifestyle Changes

  • Diet and Exercise: A heart-healthy diet and regular exercise can improve overall cardiovascular health.
  • Stress Management: Techniques such as yoga, meditation, and deep breathing can help manage stress, which can trigger Afib episodes. Maintaining this can increase heart attack survival rate.

Medical Procedures

  • Cardioversion: A procedure to restore normal heart rhythm.
  • Ablation: A minimally invasive procedure to destroy small areas of heart tissue causing abnormal electrical signals.
  • Pacemakers: Used in cases of bradycardia to regulate the heart rate.

When To See a Doctor About AFIB Heart Rate?

See a doctor immediately if you experience chest pain, severe shortness of breath, fainting, or symptoms of a stroke (sudden numbness, difficulty speaking).

Consult a healthcare provider if your Normal Sleeping Heart Rate exceeds 100 bpm at rest or drops below 60 bpm with accompanying symptoms.

Your provider will start by gathering your health history, family history, and symptoms you’ve noticed related to AFib. Regular check-ups are crucial for ongoing Afib management.

Atrial Fibrillation FAQS

What is considered a dangerous heart rate for someone with atrial fibrillation?

A heart rate consistently over 100 beats per minute (bpm) at rest is considered dangerous for someone with atrial fibrillation (Afib). Additionally, sudden spikes above 150 bpm or a heart rate below 60 bpm, particularly if accompanied by symptoms, can also be dangerous.

Why are extremely high or low heart rates dangerous for people with AFIB?

Extremely high heart rates can lead to complications like stroke and heart failure by putting excessive strain on the heart. Low heart rates (bradycardia) can result in insufficient blood flow to organs, causing dizziness, fatigue, and even fainting, which can compromise overall health and well-being. 

What are the symptoms of a dangerous irregular heartbeat with Afib?

Symptoms of dangerous heartbeats with Afib include chest pain, severe shortness of breath, dizziness, fainting, palpitations, extreme fatigue, and confusion. In severe cases, symptoms of stroke, such as sudden numbness or difficulty speaking, may occur.

How is a dangerous heart rate in AFIB treated?

Treating a dangerous heart rate in Afib involves medications like beta-blockers and calcium channel blockers to control the heart rate, and antiarrhythmic drugs to maintain a normal rhythm. Cardioversion, catheter ablation, and implantable devices like pacemakers or ICDs may be used for more severe cases. Lifestyle changes and anticoagulation therapy to prevent strokes are also critical components of atrial fibrillation treatment.


This blog is for informational & educational purposes only and does not intend to substitute any professional medical advice or consultation. For any health-related concerns, please consult with your physician, or call 911.


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