Atrial fibrillation is a common heart rhythm problem that causes an irregular and often fast heartbeat. People with atrial fibrillation may feel palpitations, fatigue, shortness of breath, or lightheadedness, and some have no symptoms. It can come and go or be long-lasting, and risk rises with age and heart disease. Atrial fibrillation raises the risk of stroke and heart failure, but the outlook is often good with treatment. Care usually includes blood thinners to lower stroke risk and medicines or procedures to steady the rhythm and rate.
Overview
Atrial fibrillationSymptoms
Atrial fibrillation symptoms often include a fast, fluttering, or irregular heartbeat, chest discomfort, shortness of breath, fatigue, or lightheadedness. Some feel heart pounding during rest or exercise. Many with atrial fibrillation have no symptoms and discover it during a checkup.
Outlook and prognosis
Many living with atrial fibrillation do well with timely care. Medicines, procedures, and heart‑healthy habits can reduce episodes, protect against stroke, and support an active life. Outlook varies by age, triggers, other heart conditions, and how consistently treatment is followed.
Causes and risk factors
Atrial fibrillation can follow heart or valve disease, high blood pressure, thyroid imbalance, or sleep apnea. Age, family history, obesity, diabetes, alcohol, stimulants, smoking, endurance sports, infections, surgery, and stress raise risk; knowing early symptoms of atrial fibrillation helps.
Genetic influences
Genetics plays a meaningful role in atrial fibrillation, especially when it appears at a younger age or without clear triggers. Variations in several genes can raise risk by affecting heart electrical signaling. Family history modestly increases lifetime risk.
Diagnosis
Atrial fibrillation is usually diagnosed with an electrocardiogram (ECG) showing an irregular, often rapid heartbeat. If episodes come and go, doctors may use wearable monitors and echocardiography or blood tests to support the diagnosis of atrial fibrillation and check causes.
Treatment and drugs
Atrial fibrillation treatment aims to steady your heart rhythm, control heart rate, and lower stroke risk. Care often combines medicines (rate or rhythm control plus blood thinners), lifestyle changes, and procedures like cardioversion, catheter ablation, or left atrial appendage closure.
Symptoms
A racing or flip-flopping heartbeat can make everyday tasks—like climbing stairs or holding a conversation—feel unexpectedly hard. Atrial fibrillation can bring on episodes of an irregular pulse along with breathlessness, chest discomfort, or fatigue. Symptoms vary from person to person and can change over time. Early symptoms of atrial fibrillation are sometimes subtle, so you might notice only brief flutters or getting winded more easily at first.
Fluttering, thumping, or skipped beats may come on suddenly. Episodes can last seconds to hours and then settle. During atrial fibrillation, the rhythm often feels irregular rather than steady.
The heart can race even at rest. You may feel a strong pounding in your chest or throat. Bursts can leave you feeling breathless or uneasy.
Breathing can feel harder with activity or when lying down. Climbing stairs or carrying groceries may feel unusually taxing. In atrial fibrillation, the heart’s squeeze is less efficient, which can add to breathlessness.
Pressure, tightness, or pain can occur during an episode. Seek urgent care if chest pain is severe or paired with sweating, nausea, or spreading pain. These signs can signal a heart emergency and need prompt evaluation.
How people usually first notice Atrial fibrillation?
Many people first notice atrial fibrillation when their heart suddenly feels “off”—a fluttering, racing, or pounding in the chest that may come and go, sometimes with lightheadedness, shortness of breath, chest discomfort, or unusual fatigue. For some, the first signs of atrial fibrillation show up during a routine checkup or on a smartwatch alert, where an irregular pulse is picked up even if they feel fine. Others discover it after a trigger like stress, alcohol, illness, or exercise brings on an episode, prompting an ECG in urgent care or the emergency department that confirms the irregular rhythm.
Types of Atrial fibrillation
Atrial fibrillation (AFib) has a few well-recognized patterns that describe how often it happens and how long episodes last. These patterns matter because symptoms and day-to-day impact can differ, and treatment plans may shift over time. The balance of symptoms can shift over time. Knowing the main types of atrial fibrillation can help you and your care team match therapy to what you experience.
Paroxysmal AFib
Episodes start and stop on their own, often lasting minutes to hours but less than 7 days. People may feel sudden flutters, breathlessness, or a pause in energy, then return to normal rhythm between episodes. Some notice triggers like stress, alcohol, or poor sleep.
Persistent AFib
Irregular rhythm lasts more than 7 days and usually needs treatment to get back to normal rhythm. Symptoms can be steadier—like exercise intolerance, fatigue, or shortness of breath. Daily activities may feel harder because the heart stays out of rhythm for longer.
Long-standing persistent
AFib continues for 12 months or more without returning to a normal rhythm. Symptoms may become a new baseline, ranging from noticeable palpitations to quieter fatigue. Treatment often focuses on either restoring rhythm or controlling rate long term.
Permanent AFib
AFib is accepted as ongoing, and the plan focuses on heart-rate control and stroke prevention. People may still feel palpitations or tiredness, but some feel few symptoms once the rate is controlled. Types of atrial fibrillation like this guide expectations for long-term management.
What genetics can tell you about symptoms
Some people inherit changes in heart-ion channel or structural genes (like KCNQ1, SCN5A, MYH6) that make heart cells fire or conduct electricity unevenly, triggering atrial fibrillation episodes. Others have variants near the PITX2 gene that subtly alter atrial development, raising lifelong AF risk.
Causes and risk factors
Atrial fibrillation often starts when the heart’s electrical system is strained by other health issues. Older age and high blood pressure are key risks for atrial fibrillation. Heart valve or coronary disease, heart failure, and thyroid imbalance can set the stage. Obesity, sleep apnea, diabetes, kidney or lung disease, and family history add to risk, and some gene changes can as well. Alcohol binges or heavy use, smoking, stimulant drugs, acute illness, or recent surgery may trigger episodes, and some risks are modifiable (things you can change), others are non-modifiable (things you can’t).
Environmental and biological risk factors
Atrial fibrillation can start quietly and make daily routines feel a bit off, from climbing stairs to concentrating at work. Doctors often group risks into internal (biological) and external (environmental). Because early symptoms of atrial fibrillation can be subtle, knowing which factors add to risk can help you and your care team stay alert. Below are environmental and biological risks linked with this heart rhythm problem.
Age-related changes in the heart's electrical pathways increase the chance of rhythm problems. Risk rises steadily with advancing age.
Long-term pressure load thickens and stiffens the heart’s upper chambers. This structural stress makes atrial fibrillation more likely.
Leaky or narrowed valves strain the atria. The extra stretch and scarring can set the stage for atrial fibrillation.
Enlarged, stressed atria and shifts in pressure promote erratic signaling. People with heart failure often develop atrial fibrillation during flare-ups.
Genetic risk factors
Atrial fibrillation can run in families, and in some people, DNA changes play a major role. Researchers have mapped several genetic risk factors for atrial fibrillation, from rare single-gene variants to clusters of common markers that add up. Carrying a genetic change doesn’t guarantee the condition will appear.
Family history: Having a close relative with atrial fibrillation raises your chance, especially if several relatives are affected. The pattern can be stronger when atrial fibrillation starts at a younger age.
Single-gene variants: Rare changes in one gene can directly increase risk in some families. Examples include variants in KCNQ1, SCN5A, or LMNA.
Ion channel genes: Changes that alter sodium or potassium flow in heart cells can trigger rhythm problems. These variants can make atrial fibrillation more likely, sometimes at a younger age.
Structural-heart genes: Variants in proteins that build the heart muscle, such as TTN or MYH6, can stretch or stress the atria. This can set the stage for atrial fibrillation, sometimes alongside a cardiomyopathy.
PITX2 region variants: Common DNA markers near PITX2 on chromosome 4q25 are strongly linked to atrial fibrillation. On their own they raise risk modestly, but together with other markers the effect adds up.
Other risk regions: Variants near genes such as ZFHX3 and KCNN3 also nudge risk upward. These are common in the population and do not cause atrial fibrillation by themselves.
Polygenic background: Dozens to hundreds of small DNA differences can combine to meaningfully shift lifetime risk. People with a high combined burden of markers have a higher chance of atrial fibrillation.
Early-onset AF: When atrial fibrillation begins before about age 60, inherited factors are more likely to play a major role. In this situation, a genetics specialist may discuss testing or family screening.
Lifestyle risk factors
Atrial fibrillation (AF) often develops and progresses alongside daily habits, so targeting modifiable behaviors can lower risk and reduce episodes. The lifestyle risk factors for atrial fibrillation most often relate to alcohol, weight, physical activity patterns, diet quality, sleep, and stress. Addressing these areas can lessen AF symptom burden, cut recurrence after treatment, and improve heart rhythm control.
Regular heavy drinking and binge episodes increase AF risk and can trigger same‑day episodes (“holiday heart”). Cutting alcohol meaningfully reduces AF episodes and recurrence after ablation.
Higher body fat enlarges and scars the atria, raising the chance of AF and its progression. Gradual, sustained weight loss reduces AF burden and improves treatment success.
Low cardiorespiratory fitness is linked to higher AF risk and worse symptom control. Building moderate aerobic fitness lowers incidence and reduces episode frequency.
Very high volumes of endurance training can remodel the atria and raise AF risk. Balancing training load and adding recovery days may reduce episodes in susceptible athletes.
Risk prevention
Atrial fibrillation risk can be lowered by tending to heart health every day and working with your care team. Prevention is about lowering risk, not eliminating it completely. For many, that means taming common triggers, treating underlying conditions, and catching changes early before they snowball. Small, steady steps can make episodes less likely and may delay a first event.
Keep blood pressure in a healthy range to reduce strain on the upper heart chambers. Home checks and regular visits help catch changes early.
Heavy or frequent drinking can spark irregular rhythms, especially binge episodes. If you drink, keep it light and spread out.
Extra weight raises the chance of atrial fibrillation by stressing the heart and lungs. Gradual weight loss and waist reduction can lower risk.
Brisk walking, cycling, or swimming improves heart conditioning and blood pressure. Aim for steady, moderate activity most days rather than extreme endurance.
Transmission
Atrial fibrillation isn’t contagious, so it can’t be transferred from one person to another. You can’t catch atrial fibrillation from close contact, coughing, kissing, sex, sharing utensils, or through blood or organ donation.
Some families do see more cases of atrial fibrillation, and in rare situations certain inherited changes can raise risk, but there isn’t a single, predictable pattern for how atrial fibrillation is inherited. For most people, atrial fibrillation develops from a mix of age, heart strain, and other health conditions rather than genetic transmission of atrial fibrillation.
When to test your genes
Atrial fibrillation is a progressive/acquired heart rhythm condition; gene testing isn’t routine for most people. Consider genetic testing if AFib began young (under ~60), there’s a strong family history, or you have AFib plus cardiomyopathy or sudden death in relatives. Results may guide screening, medication choices, and family risk.
Diagnosis
Atrial fibrillation is usually picked up when irregular heartbeats or related symptoms lead to a focused heart evaluation. For some, routine check-ups reveal the first clues. Understanding how atrial fibrillation is diagnosed can help you know what to expect. Testing aims to confirm the rhythm, look for triggers, and check heart structure and overall health.
Your clinician asks about palpitations, breathlessness, chest discomfort, lightheadedness, and fatigue. They’ll note when episodes happen, how long they last, and possible triggers like alcohol, caffeine, or illness.
A pulse check may reveal an irregular, often rapid rhythm. Your provider also listens for valve problems and looks for signs of fluid build-up or thyroid issues.
A brief, in-office electrical tracing can confirm atrial fibrillation during an episode. It shows a characteristic irregular pattern and helps rule out other abnormal rhythms.
Portable monitors worn for 24 hours to several weeks can catch intermittent episodes you don’t feel. Options include Holter, event, or patch monitors, which record your rhythm during daily life.
Stages of Atrial fibrillation
In atrial fibrillation, “stages” usually refer to how often the irregular rhythm shows up and how long it lasts, rather than how severe it feels. Many people feel reassured knowing what their tests can—and can’t—show. Knowing the pattern helps tailor decisions about medicines, procedures, and stroke prevention. Early symptoms of atrial fibrillation may be brief and easy to miss, which is why tracking when episodes start and stop can be useful.
First diagnosed
This is the first time atrial fibrillation is recorded, no matter how long it lasts. It tells your care team they’re at the starting line of understanding your pattern.
Paroxysmal AF
Episodes come and go on their own, usually within 7 days, often within 24–48 hours. Symptoms may flare during an episode and then settle when the heartbeat returns to normal.
Persistent AF
The irregular rhythm lasts more than 7 days or needs treatment to reset it. Doctors may discuss rhythm-control options and stroke prevention in more detail at this stage.
Long-standing persistent
Atrial fibrillation continues without a break for over 12 months. Care often focuses on symptom relief, heart protection, and weighing rhythm versus rate-control strategies.
Permanent AF
Atrial fibrillation is ongoing and you and your doctor decide not to try to restore normal rhythm. Care centers on rate control, stroke prevention, and feeling as well as possible day to day.
Outlook and prognosis
Looking at the long-term picture can be helpful. For many people with atrial fibrillation, the outlook depends on how often episodes happen, how fast the heart races, and whether other conditions—like high blood pressure, sleep apnea, diabetes, or heart disease—are also in the mix. Some notice brief, occasional flutters that come and go; others have a steady irregular rhythm most of the time. When episodes are frequent or the heart rate stays high, fatigue, shortness of breath, and reduced stamina can build up over months.
Prognosis refers to how a condition tends to change or stabilize over time. The biggest long-term risks of atrial fibrillation are stroke and heart failure, but both can be reduced with the right care. Blood thinners lower stroke risk substantially, and rate or rhythm treatments—medications, cardioversion, ablation—can improve symptoms and exercise capacity. In large studies, people with well-managed atrial fibrillation live longer and feel better than those who go untreated. Mortality is higher when atrial fibrillation is combined with advanced heart disease or unmanaged risk factors, but many living with atrial fibrillation maintain good quality of life for years.
Many people ask, “What does this mean for my future?”, especially when early symptoms of atrial fibrillation interrupt sleep or make stairs harder. Early care can make a real difference by preventing clots, keeping the heart from overworking, and addressing triggers like alcohol, thyroid problems, or untreated sleep apnea. Over time, most people find a steady plan—medicines, possible ablation, and lifestyle steps such as blood pressure control, healthy weight, and regular activity—keeps flares less frequent and complications less likely. Talk with your doctor about what your personal outlook might look like, including your stroke risk score and whether treatments like ablation or anticoagulation fit your goals.
Long-term effects
Atrial fibrillation can affect health over years, and the outlook depends on age, heart health, and treatment choices. Long-term effects vary widely and can change over time. Some remember the early symptoms of atrial fibrillation as brief flutters or fatigue, but the bigger concerns in the long run often involve stroke risk, heart strength, and day-to-day stamina.
Atrial fibrillation can let blood pool in the heart and form clots that travel to the brain. This raises the chance of stroke, especially with age or other conditions. Blood-thinning treatment can lower this risk.
Years of fast, irregular beats can strain the heart and weaken the pumping muscle. This can lead to breathlessness, ankle swelling, or needing extra pillows to sleep. Heart function may improve if the rhythm and rate are controlled.
The long-term risk of memory or thinking problems is higher in atrial fibrillation. Small, silent strokes and reduced blood flow may play a role. Preventing strokes helps protect brain health.
Many people notice getting tired faster and needing more breaks with atrial fibrillation. Walking up stairs or doing chores may feel harder. Energy levels can fluctuate from day to day.
How is it to live with Atrial fibrillation?
Living with atrial fibrillation can feel unpredictable: some days are quiet, and other days a sudden flutter, thump, or breathlessness interrupts work, exercise, or sleep. Many notice limits on stamina, the need to pace activities, and the mental load of tracking pulse, medications, and appointments, all while staying alert for red-flag symptoms like chest pain or fainting. With good treatment—rhythm or rate control, anticoagulation to lower stroke risk, and heart-healthy routines—most people regain a steady rhythm to daily life, even if the heartbeat remains irregular. Partners, family, and coworkers often become allies, learning when to pause, offering rides after procedures, and helping create calm, predictable routines that make living with AFib safer and easier.
Treatment and drugs
Atrial fibrillation treatment focuses on preventing stroke and managing the heart’s rhythm and rate so you feel better day to day. Most people take a blood thinner to lower stroke risk; options include warfarin (with regular blood tests) or newer direct oral anticoagulants, and your doctor will help choose based on age, kidney function, bleeding risk, and other conditions. To control symptoms, some start with rate-control medicines like beta blockers or calcium channel blockers, while others use rhythm-control strategies such as antiarrhythmic drugs, electrical cardioversion, or catheter ablation to restore and maintain a steady heartbeat. Treatment plans often combine several approaches, and may also include treating triggers like high blood pressure, sleep apnea, excess alcohol, or thyroid problems, plus heart-healthy habits and weight management. If first-line treatments don’t help, specialists may try second-line options such as repeat ablation, device therapy, or surgical procedures in selected cases.
Non-drug treatment
Living with atrial fibrillation can affect your energy, sleep, and confidence to be active. Alongside medicines, non-drug therapies can improve symptoms, reduce episodes, and lower stroke risk. Some supports are lifestyle-based, while others are procedures that do not rely on pills. Noticing early symptoms of atrial fibrillation can help you and your care team tailor which options to try first.
A brief, controlled shock under sedation can reset the heart’s rhythm. It may quickly restore a normal rhythm in atrial fibrillation.
A specialist threads thin tubes to the heart to quiet the spots that trigger irregular beats. Many people with atrial fibrillation have fewer episodes and better quality of life afterward.
A small device can be placed in the heart to block the area where clots often form. This may reduce stroke risk for people with atrial fibrillation who cannot take long‑term blood thinners.
Losing excess weight can lessen strain on the heart and lower AF episodes. Structured programs, like supervised nutrition and activity plans, can help changes stick.
Your genes may have an impact on how drugs work for you
Medicines for atrial fibrillation can work differently from one person to the next because gene differences affect how fast your body processes a drug or how strongly your heart’s receptors respond. Doctors may use pharmacogenetic testing or careful dose trials to tailor therapy safely.
Pharmacological treatments
Medicines for atrial fibrillation aim to do three things: prevent blood clots and stroke, slow a fast heartbeat, and restore or maintain a normal rhythm. Choices depend on your symptoms, heart and kidney health, and stroke risk. Not everyone responds to the same medication in the same way. For some, early symptoms of atrial fibrillation—like a racing heartbeat or shortness of breath—help guide which drugs are tried first.
Apixaban, rivaroxaban, dabigatran, and edoxaban lower stroke risk by preventing blood clots. Doses may be adjusted for kidney function and bleeding risk.
This long‑used blood thinner prevents clots and strokes. It needs regular INR blood tests and has food and drug interactions, but vitamin K can reverse its effect in emergencies.
Metoprolol, atenolol, and bisoprolol slow the heart rate to ease palpitations and breathlessness. They can cause fatigue or low blood pressure and may not suit asthma.
Diltiazem and verapamil slow the heart rate when beta blockers aren’t a good fit. They may cause ankle swelling or constipation and are avoided in some heart failure.
Genetic influences
Genes can influence who develops atrial fibrillation, especially when episodes start at a younger age or there’s a strong family pattern. Family history is one of the strongest clues to a genetic influence. For most people, risk comes from a combination of many small gene changes working together, which raises the chance of atrial fibrillation but doesn’t make it certain. In a small number of families, a single gene change affecting the heart’s electrical signaling can lead to early-onset atrial fibrillation and sometimes other rhythm issues. These inherited tendencies often interact with age, high blood pressure, sleep apnea, alcohol, and other triggers, so relatives with the same background may have very different symptoms and timing. If several close relatives have atrial fibrillation, or if you were diagnosed at a younger age (for example, before 60), asking about genetic counseling or testing for genetic causes of atrial fibrillation may help guide care.
Is Atrial fibrillation genetic?
Genetics plays a meaningful role in atrial fibrillation, especially when it appears at a younger age or without clear triggers. Variations in several genes can raise risk by affecting heart electrical signaling. Family history modestly increases lifetime risk.
Pharmacogenetics—how genetics influence drug effects
In atrial fibrillation, genes can influence how your body processes blood thinners and rhythm or rate medicines, affecting the dose that works well and your chance of side effects. For warfarin, differences in genes such as CYP2C9 and VKORC1 can mean you need a lower or higher starting dose, so some teams use genotype-guided dosing to reach a safe blood‑thinning level more smoothly. Not every difference in response is genetic, but small gene effects have been seen with some newer blood thinners; at this time, routine genetic testing isn’t recommended for them. Genes that affect the CYP2D6 enzyme can also change levels of certain rhythm drugs (like flecainide or propafenone) and some beta‑blockers, so doctors may start with a different dose or choose another option if you’re likely to process them slowly. Genetics won’t change early symptoms of atrial fibrillation, but they can shape which medication and dose is safest and most effective for you. If you’ve had bleeding on a low warfarin dose, needed unusually high doses, or felt significant side effects on flecainide or propafenone, it’s reasonable to ask whether pharmacogenetic testing could help tailor your treatment.
Interactions with other conditions
Atrial fibrillation often travels with high blood pressure, sleep apnea, diabetes, kidney disease, and heart failure, and each can make the rhythm problem harder to control. Doctors call it a “comorbidity” when two conditions occur together. For example, untreated sleep apnea or an overactive thyroid can trigger episodes, while heart failure and atrial fibrillation can each worsen the other’s symptoms, like breathlessness and fatigue. Stroke risk from atrial fibrillation rises further if you also have high blood pressure, vascular disease, or diabetes, so blood thinners are often considered, though they need extra care if you have stomach ulcers, liver problems, or a high risk of falls. Some medications for other illnesses can interact with atrial fibrillation treatment—for instance, certain inhalers or decongestants may speed the heart, and anti-inflammatory pain relievers can increase bleeding when combined with anticoagulants. If you have these conditions, noticing early symptoms of atrial fibrillation—like a racing, irregular heartbeat or new shortness of breath—and treating triggers such as sleep apnea and thyroid issues can lower flare-ups and help you live well.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
History
Throughout history, people have described sudden “fluttering” in the chest, spells of weakness, and faintness that came and went—episodes we now recognize as atrial fibrillation. A village healer might have felt an irregular pulse at the wrist and advised rest; a clerk in a cold office might have noticed their heart racing after an illness or too much coffee. These lived experiences were the first clues, long before machines could record the rhythm.
From early theories to modern research, the story of atrial fibrillation reflects how tools changed what doctors could see. In the 18th and 19th centuries, clinicians learned to read the pulse and heart sounds, noting beats that were “irregularly irregular.” The arrival of the electrocardiogram (ECG) in the early 1900s transformed those bedside impressions into tracings on paper. Wavy baselines without clear atrial beats, paired with irregular spacing between heartbeats, became the hallmark ECG pattern. Initially understood only through symptoms, later the rhythm’s electrical roots were mapped in more detail.
As medical science evolved, treatments followed. Early care focused on easing symptoms with rest and digitalis from foxglove plants. Mid-20th-century medicines aimed to slow the heart or restore regular rhythm. Electrical cardioversion—brief, controlled shocks—offered a way to reset the heartbeat. In recent decades, awareness has grown that atrial fibrillation raises stroke risk, prompting the careful use of blood thinners to protect the brain. Procedures also advanced: catheter ablation uses targeted energy to quiet the short-circuits that keep the upper chambers quivering.
Once considered rare, now recognized as common, atrial fibrillation is seen more often as populations live longer and as monitoring improves. Portable ECG devices and smart wearables can flag an irregular pulse at home, bringing people to care earlier. Genetics has added another layer, showing that while age, high blood pressure, and heart disease matter most, some families carry changes in genes that slightly raise risk.
Historical differences highlight why definitions and goals have shifted over time. The focus moved from chasing a perfectly normal rhythm to also prioritizing safety—preventing stroke, easing symptoms, and respecting how atrial fibrillation varies from person to person. Some live with brief, occasional episodes; others have a rhythm that stays irregular most of the time. Today’s approach blends the old art of listening to how someone feels with modern tools that see the rhythm in real time. Looking back helps explain why early symptoms of atrial fibrillation were easy to miss, and why today’s mix of monitoring, medicines, and procedures offers more options—and more reassurance—than ever before.