15 Most Probable AFib Causes

2. High Blood Pressure

High blood pressure is one of the most common factors linked to atrial fibrillation. When your blood pressure stays high for a long time, your heart must work harder to move blood through your body. This constant strain can cause the upper chambers of the heart to stretch and stiffen, disrupting the normal rhythm of your heartbeat.

As these changes progress, the heart’s electrical system may weaken, making irregular rhythms more likely to occur. Many people do not notice symptoms at first because high blood pressure develops slowly. Some may feel tired or short of breath during activity, while others may not notice anything until their heartbeat becomes irregular.

Normal readings below 120/80 mm Hg help support a stable rhythm. When your blood pressure rises, even small increases can influence how smoothly your heart maintains its pattern. Once levels reach 130/80 mm Hg or higher, the added pressure significantly raises the likelihood of developing atrial fibrillation.

3. Infection

Infections can cause inflammation that affects your heart’s rhythm. When your body works to fight off illness, it releases chemicals that make your heart work harder. This added stress may trigger electrical changes in the heart’s upper chambers, leading to atrial fibrillation (AFib).

Respiratory infections such as pneumonia, influenza, or COVID-19 are among the most common triggers because they can lower oxygen levels and increase strain on the heart. Fever, dehydration, and widespread inflammation during a severe illness can further raise the likelihood of developing AFib. Other serious conditions, including sepsis or severe urinary tract infections, may also disrupt the balance of electrolytes like potassium and sodium.

These shifts can interfere with the electrical signals that keep your heartbeat steady, making irregular rhythms more likely. Older adults and people with heart disease face a higher chance of experiencing AFib during or after an illness, and even a brief episode signals added strain on the heart.

4. Heart Disease

Heart disease can play a major role in the development of atrial fibrillation. When the heart’s structure or function changes, the electrical signals that control your heartbeat may become disrupted, making irregular rhythms more likely.

Coronary artery disease, where plaque narrows the arteries, can reduce blood and oxygen flow to the heart muscle. This can weaken the heart over time and increase the likelihood of rhythm problems. Heart valve disease may have a similar effect by forcing the heart to work harder to circulate blood.

A history of heart attack or ongoing heart failure raises the risk even more. These conditions can scar or stretch heart tissue, making it harder for electrical signals to travel normally through the upper chambers of the heart. Long-term high blood pressure adds to this strain by thickening or enlarging parts of the heart.

Common treatments for heart disease, such as therapies that lower blood pressure or control cholesterol, can reduce the stress on your heart. Managing weight, avoiding tobacco, and staying active also protect your heart’s health.

5. Lung Disease

Lung diseases can increase your risk of developing atrial fibrillation. When your lungs are not working well, your heart must work harder to move oxygen through your body. This added strain can disturb the heart’s normal rhythm and lead to irregular electrical signals.

Chronic lung conditions such as chronic obstructive pulmonary disease (COPD), pulmonary embolism, or sleep apnea can reduce oxygen flow or raise pressure in the lung’s blood vessels, which affects how efficiently the heart can pump. Serious lung infections like pneumonia can also contribute to AFib by causing inflammation, fever, and low oxygen levels that add stress to the heart.

People with long-term lung disease often develop high pressure in the lung’s blood vessels, which can enlarge parts of the heart. This structural change creates an environment where AFib can occur more easily. Treating lung disease, maintaining healthy oxygen levels, and reducing inflammation can help lower the chance of developing this condition.

6. Sleep Apnea

Sleep apnea is a sleep disorder that slows or briefly stops your breathing while you sleep. The most common form, obstructive sleep apnea (OSA), happens when your airway becomes blocked by relaxed throat muscles or excess tissue. These pauses in breathing can occur many times a night and lower your oxygen levels.

When your oxygen drops, your heart works harder to restore blood flow, which can put strain on your heart and raise your risk of atrial fibrillation (AFib). Repeated episodes of low oxygen also affect how your heart’s electrical signals work, making it easier for an irregular rhythm to develop. Common signs that others may notice include loud snoring and episodes of choking or gasping during sleep.

You might not notice these symptoms yourself, but a bed partner or family member may. Other signs you may experience include daytime fatigue and morning headaches. Treatment options range from lifestyle changes like weight loss and exercise to nighttime breathing devices or mouthpieces for more severe cases.

7. Heart Surgery

Heart surgery can raise your chances of developing atrial fibrillation, especially right after the operation. This is most common after procedures such as coronary artery bypass grafting or valve repair and replacement. When your body reacts to surgery, it can place stress on the heart tissue and affect how your heartbeat is regulated.

The heart’s upper chambers may become irritated or swollen, which can interrupt the electrical signals that normally keep your heartbeat steady. As a result, some people develop brief, irregular episodes of AFib shortly after surgery. AFib occurs in up to one-third of patients following bypass surgery and in about half of those who undergo valve operations.

The risk can vary depending on your age, overall health, and type of procedure. During recovery, your heart rhythm is closely monitored. Treatments may include medications to control heart rate or blood thinners to reduce the risk of blood clots.

8. Emotional Stress

Emotional stress can affect your heart rhythm by triggering the body’s natural “fight or flight” response. When you feel anxious, angry, or overwhelmed, your body releases stress hormones that increase your heart rate and blood pressure. Over time, this can disturb the electrical signals that control your heartbeat, raising your risk of developing atrial fibrillation (AFib).

You might notice your heart racing, irregular beats, or shortness of breath during stressful moments. These changes are often temporary, but chronic stress can gradually strain the heart and make rhythm problems more likely. In addition, people under significant stress may sleep poorly, smoke, or turn to unhealthy foods or alcohol for relief.

These behaviors can raise blood pressure or increase inflammation, both of which may contribute to AFib. Managing daily stress through rest, physical activity, or even talking with supportive people can make a measurable difference in how your heart responds over time.

9. Weakened Immune System

A weak immune system can make you more likely to experience health conditions that stress your heart, which may increase your risk of atrial fibrillation (AFib). When your immune defenses are low, infections can last longer and place added stress on the heart, affecting its normal rhythm.

Illnesses such as pneumonia or other serious infections can raise body temperature and inflame heart tissue. People may notice their heart racing or skipping beats due to this extra strain. Conditions that cause chronic inflammation, such as autoimmune diseases, can also interfere with the heart’s electrical signals, and over time this makes episodes of AFib more likely.

Certain treatments, such as immune-suppressing drugs, long-term steroid use, or chemotherapy, can weaken the immune system and make it harder for the body to fight infections. A weakened immune system can also slow healing, increase oxidative stress, and contribute to nutritional deficiencies during prolonged illness, which may further disrupt heart rhythm.

10. Sick Sinus Syndrome

Sick sinus syndrome happens when your heart’s natural pacemaker, the sinus node, does not create signals properly. The sinus node controls how fast and steady your heart beats. When it fails, your heart rate can become too slow, pause for several seconds, or sometimes switch between slow and fast beats.

You are more likely to develop this condition if you are older than 50, though it can appear at any age. The main cause is usually scar-like damage in the heart’s electrical system that develops over time. In children, past heart surgery involving the upper chambers can also lead to this problem.

You might notice tiredness, dizziness, fainting, or shortness of breath when the heart cannot pump blood well. At other times, you may have no symptoms until an irregular rhythm shows up on a heart test. Some medicines that slow heart rate, such as certain calcium channel blockers, beta blockers, or antiarrhythmics, may worsen your rhythm problems.

11. Previous Heart Surgery and Heart Problems

If you have had heart surgery or other heart conditions, your risk of atrial fibrillation (AFib) can be higher. Procedures on the heart may alter how electrical signals travel, and scarring that forms during healing can interfere with normal rhythm. People who develop AFib after surgery may notice irregular heartbeats or shortness of breath during recovery.

Heart problems such as heart failure, valve disease, or coronary artery disease can also contribute to AFib. These conditions can weaken or enlarge parts of the heart. When the heart has to work harder, the upper chambers can become stressed, which increases the likelihood of AFib.

Other conditions, including heart infections, inflammation, or previous heart attacks, may further raise your risk by damaging heart tissue and disrupting how the heart times each beat. If you have a history of heart disease, early detection can help manage AFib episodes and reduce the chance of them becoming long-term.

12. Hyperthyroidism

Hyperthyroidism happens when your thyroid gland makes too much thyroid hormone. This hormone controls how fast your body uses energy. The thyroid gland can become overactive for several reasons. Graves’ disease is the most common cause. Thyroid nodules or too much iodine intake can also trigger the gland to release more hormones than the body needs.

High thyroid hormone levels speed up the heart’s electrical activity, which can lead to an irregular rhythm that feels like fluttering or pounding in your chest. You might notice symptoms such as a fast heartbeat, nervousness, sweating, or unexplained weight loss. Some people also feel shaky or have trouble sleeping. These symptoms can develop slowly or appear suddenly, making them easy to confuse with other conditions.

When hyperthyroidism is left untreated, this ongoing strain raises the risk of developing AFib. Treatment usually focuses on lowering thyroid hormone levels and stabilizing heart rhythm.

13. Atrial Flutter

Atrial flutter is an abnormal heart rhythm that affects the upper chambers of your heart, called the atria. It happens when the electrical signals in the atria move in a circular pattern instead of following the normal pathway. This causes your heart to beat faster than usual but in a more regular pattern than atrial fibrillation.

You might experience a fluttering feeling in your chest or notice that your heartbeat feels quick or steady but forceful. Some people also feel tired, dizzy, or short of breath. Atrial flutter can sometimes occur along with atrial fibrillation, and the two conditions may alternate.

Several health problems can increase the chance of atrial flutter, including high blood pressure, heart valve disease, and heart failure. Aging, past heart surgery, and lung disease can also make it more likely. Treatment may involve controlling the heart’s rhythm or rate or taking blood-thinning medications to help prevent stroke.

14. Pneumonia

When you develop pneumonia, the infection and inflammation in your lungs can place heavy stress on your body. Your heart works harder to maintain oxygen and blood flow. This extra strain can sometimes disturb the heart’s electrical signals and trigger atrial fibrillation (AFib).

Pneumonia causes a strong immune response that releases chemicals called inflammatory mediators, which can change how heart cells conduct electricity. Fever, low oxygen levels, and fluid buildup can further increase the likelihood of developing an irregular heartbeat.

People who already have heart disease, high blood pressure, or are older often face a higher chance of developing AFib during pneumonia. Even if the irregular rhythm starts only during the infection, studies show that it can return later.

Treating pneumonia effectively and managing AFib early both help reduce complications. You may receive oxygen therapy, fluids, and medicines such as heart rate controllers or anticoagulants, depending on your individual situation.

15. Risk Factors

Your risk for atrial fibrillation (AFib) can rise with a mix of health conditions, age, and lifestyle habits. Some risks build up over many years, while others relate to lifestyle choices. Age is one of the strongest influences. As you get older, your heart’s structure and electrical signals may change, making AFib more likely.

High blood pressure also plays a major role because it forces your heart to work harder, which can strain the heart’s chambers. Several other medical issues can contribute, including diabetes, heart failure, heart valve disease, ischemic heart disease, and thyroid disorders. Chronic kidney problems and obesity can also add to the strain on your heart.

When multiple conditions occur together, your chances of developing AFib increase further. Lifestyle habits such as smoking, heavy drinking, long-term stress, poor sleep, and lack of physical activity can also disturb your heart rhythm and weaken your heart over time. Some people also inherit genetic traits that increase their likelihood of developing rhythm problems.