Can Anesthesia Cause Atrial Fibrillation (AFib)?

Anesthesia can play a part in atrial fibrillation (AFib), but it is seldom the main reason an irregular heartbeat appears around surgery. The bigger trigger is the stress the whole operation puts on the body, especially in an older or already strained heart.¹ This rhythm problem is the most common one linked to surgery.² An episode in hospital is usually treatable and often passes, but it is worth following up after you go home.

How Often AFib Happens Around Surgery and When It Starts

AFib can begin after any operation. After surgery that isn’t on the heart, between 2 and 30 people in 100 develop it.³ Heart surgery carries a higher rate, and valve operations carry the greatest risk.⁴ In one large group of heart surgery patients, about 1 in 4 developed it.⁵

That range is so wide because the type of operation matters. Big chest and abdominal operations sit at the high end, and older patients have a higher rate in any type of surgery. Closer monitoring also finds more short episodes, which pushes the numbers up.

It most often appears 2 to 4 days after surgery.⁶ Most episodes therefore begin after the anesthetic drugs have long since worn off.

During AFib the heart beats fast and unevenly instead of in a steady rhythm. Some people feel fluttering, a pounding chest, breathlessness or lightheadedness. Many feel nothing, and tiredness after surgery can hide the symptoms that do occur, so many episodes are found only on a heart monitor.⁷ In patients after major non-heart surgery, continuous wireless monitoring found it in 6.5% of patients, about twice as many as staff noticed.⁸

After major surgery, many patients are connected to a heart monitor for the first days. AFib shows up on it as an irregular line with no clear repeating pattern between beats. An episode can last minutes or hours and then stop by itself, so someone checked only once in a while can easily be missed. If a nurse tells you the monitor showed an irregular rhythm, that is a finding to follow up, and it does not by itself mean you are in danger at that moment.

What Anesthesia Itself Does to the Heart

Many anesthetic drugs change the tiny electrical channels that time each heartbeat.⁹ In lab tests on human heart cells, the gases halothane and isoflurane weakened the calcium signals of the heart’s upper chambers by about a fifth to a third.¹⁰ That can shorten the heart’s recovery time between beats, which may make rhythm problems easier to start.¹¹ The gas xenon had almost no such effect, and these effects went away fully once the drug was removed.¹²

Those results came from isolated cells in a dish, not from a whole person’s heart during an operation. In real patients the drugs are given in controlled doses and the team watches the heart rhythm throughout.

Drug effects matter most in people with heart disease, inherited rhythm conditions, salt imbalances, or unstable blood pressure.¹³ These blood salts are minerals such as potassium and magnesium, and they help keep the heartbeat steady. After keyhole lung surgery, people given ketamine had AFib slightly more often, about 2.9% compared with 2.2%.¹⁴ The sedative dexmedetomidine, on the other hand, lowered AFib after heart surgery by roughly a fifth.¹⁵

Comparisons like these can mislead. When one group is given a drug and another is not, the groups often differ in age, health and type of operation, and those differences can account for part of the result. The ketamine gap is small in absolute terms.

In people having a heart valve replaced through a catheter, those under full general anesthesia had new AFib about 3 times as often within a year as those sedated.¹⁶ But the general anesthesia group also more often went to intensive care, so sicker patients may explain part of the gap.

General anesthesia puts you fully to sleep and usually needs a breathing tube. Sedation and nerve blocks let you breathe on your own and use fewer drugs. Your anesthesiologist can tell you which options fit your surgery.

Numbing the chest with an epidural gives mixed results. In one trial of bypass surgery, adding a chest epidural cut rhythm problems from about 24% to 3%.¹⁷ Pooled bypass trials found no clear benefit,¹⁸ and after lung surgery, an epidural made no difference to AFib risk.¹⁹ No anesthetic choice reliably prevents AFib.

The Bigger Triggers Pain Stress and Inflammation

A surge in the body’s fight-or-flight response is considered the main trigger.²⁰ Pain, alcohol or drug withdrawal, low blood count, low oxygen, low blood sugar, thyroid problems and fluid shifts all drive it up.²¹ Blood loss during surgery also releases stress hormones that upset heart rhythm.²²

Pain raises heart rate and releases stress hormones that can irritate the upper chambers of the heart. Asking for pain relief early is reasonable, not a nuisance to staff, because good control lowers a trigger.

Withdrawal works the same way. Someone who drinks heavily every day and suddenly can’t drink in hospital can go into withdrawal within a day or two, which sharply revs up the stress response. This can happen to people who don’t think of themselves as heavy drinkers, so telling the team your honest usual intake lets them plan for it.

Blood loss and a low blood count add strain of their own. With a low count the blood carries less oxygen, so the heart beats faster to compensate. That extra workload, combined with stress hormones released during bleeding, can push a vulnerable heart into an irregular rhythm.

Surgery also sets off inflammation throughout the body, and strong evidence links it to AFib.²³ It can come from conditions you had before surgery, from the operation itself, and from healing afterward.²⁴ Heart surgery adds strain from the heart-lung machine and the heart being stopped and restarted.²⁵

Low potassium or magnesium can trigger AFib during and after surgery.²⁶ Fluid shifts and body positioning on the table can also set it off.²⁷ Correcting blood salts is a key way to prevent it after non-heart surgery.²⁸

On day two or three these triggers can stack up. Pain medicine is being reduced just as pain peaks, fluids given during surgery shift back into the blood, and poor sleep, low appetite and missed medicines add stress. Each alone may be harmless, but combined they can tip a vulnerable heart.

Who Is Most at Risk

Advanced age is the main risk factor in both heart and non-heart surgery.²⁹ The aging heart changes in structure and function in ways that favor AFib.³⁰ High blood pressure and an enlarged heart also raise risk.³¹ A past episode of AFib strongly predicts another after surgery.

Risk factors add up, so someone who is older with high blood pressure and a previous irregular rhythm is in a different position from someone with one factor alone. Still, most people with risk factors don’t get AFib after surgery, and most who do have it treated and recover.

Before surgery, tell your team about any past irregular heartbeat, even a brief one, and about heart, thyroid or kidney conditions. Mention your usual alcohol use, since withdrawal can trigger AFib, and list all your medicines, especially heart and blood pressure pills. You can also ask whether you will be on a heart monitor after surgery, whether your blood salts will be checked, and whether to keep taking a beta-blocker on surgery day.

How Doctors Treat AFib in the Hospital

The team first checks blood pressure and whether the heart is coping.³² Unstable means low blood pressure, chest pain or signs the heart isn’t pumping enough blood. In that case waiting for medicine to work is unsafe, so a timed electric shock resets the rhythm.³³ It is delivered while the patient is sedated, so it isn’t felt.

In stable patients, they first look for bleeding, low oxygen and blood salt problems.³⁴ Then they slow the heart with beta-blockers or similar drugs, aiming for under 110 beats a minute.³⁵ In AFib the lower chambers can race, leaving too little time to fill with blood, which can cause breathlessness or low blood pressure. Slowing the rate is often enough, because the rhythm frequently returns to normal once the triggers settle.

People with a weak heart receive amiodarone instead of certain calcium blockers.³⁶ Some calcium blockers weaken the heart’s pumping, which is dangerous if the heart is already weak. That is one reason the team checks how well the heart is working early on.

AFib often returns to normal rhythm on its own.³⁷ Still, after heart surgery, if it lasts beyond 24 hours, doctors usually start a blood thinner, called an anticoagulant.³⁸ After non-heart surgery, blood thinners are considered when it lasts over 48 hours in higher-risk people.³⁹

From the bed, this means extra monitor stickers and frequent blood draws, with medicine through the drip or by mouth. Going home may be delayed a little. Often within a day or two, someone tells you the rhythm is back to normal.

Does AFib After Surgery Affect Long-Term Health

People who had AFib after surgery have a higher risk of stroke soon after and in later years.⁴⁰ The stroke link was stronger after non-heart surgery, about double the risk.⁴¹ In older adults after heart surgery, AFib was more than twice as likely to return.⁴² Stroke is uncommon in absolute terms, so doubling a small risk still leaves most people free of stroke.

After non-heart surgery, people with AFib had a stroke risk similar to people whose AFib started without surgery.⁴³ Surgery may uncover AFib that was likely to appear anyway. If it carries the same stroke risk, it is reasonable to treat it as real AFib and not a harmless blip.

In one follow-up clinic, about 1 in 10 heart surgery patients had AFib return.⁴⁴ Only about 1 in 5 of those had symptoms.⁴⁵ Feeling fine is therefore not proof the rhythm is normal, and a monitor, not just how you feel, is the way to find out.

After going home, ask whether you need a heart monitor worn for one to two weeks. Learn the symptoms to report: racing heart, breathlessness and dizziness. Check your blood pressure regularly, and know the stroke signs: face droop, arm weakness and slurred speech.

Wearable heart monitors can catch short, silent episodes that a brief ECG misses. A smartwatch alert is a prompt to see a doctor, not a diagnosis, and recorded readings are worth bringing to your appointment.

Can You Lower Your Risk Before Surgery

Before heart surgery, beta-blockers cut the odds of AFib by about two-thirds.⁴⁶ Amiodarone, magnesium and pacing wires also lowered it.⁴⁷ Adding amiodarone to beta-blockers lowered risk further than beta-blockers alone.⁴⁸ If you are having heart surgery, ask whether a preventive medicine is planned.

This is mostly a heart surgery strategy. The evidence comes from operations where AFib is common enough that preventive treatment is worth the side effects. After non-heart surgery, AFib is less common, so doctors tend to focus on triggers and individual risk rather than giving everyone a preventive drug.

Keep taking prescribed heart medicines unless told to stop. Stopping a beta-blocker suddenly can make the heart race and raise rhythm problems, so any change should be agreed with the team. Your anesthesiologist or surgeon will tell you which pills to take on the morning of surgery, and asking is better than guessing.

Treating thyroid problems and anemia ahead of time removes triggers, and reporting pain early after surgery keeps it controlled. Heavy drinkers who stop abruptly can have dangerous withdrawal, including a racing heart and seizures, so cutting back should be done with medical advice. Cutting back helps most when it starts weeks before surgery, not in the last day or two.