ATRIAL FIBRILLATION

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• Atrial fibrillation (AF) - AF is a supraventricular tachyarrhythmia with uncoordinated atrial activation and ineffective atrial contraction. It is caused by repetitive sporadic atrial depolarizations initiated by abnormal foci, typically originating in the pulmonary veins of the left atrium. [22]

• Subclinical atrial fibrillation - the AHA defines subclinical AF as asymptomatic AF identified by implanted devices (pacemakers, defibrillators, or implantable loop recorders) or wearable monitors in individuals without ECG-documented AF. The EHRA defines subclinical AF as an AHRE lasting greater than 6 minutes and less than 24 hours detected with continuous ECG monitoring (intracardiac) and without prior diagnosis (ECG or Holter monitoring) of AF. See stroke prevention in subclinical AF for more. [20,22]

• Atrial high-rate episode (AHRE) - the EHRA defines AHREs as atrial tachyarrhythmia episodes with a rate > 190 beats/min detected by cardiac implantable electronic devices. See stroke prevention in AHREs for more. [20]

• Paroxysmal atrial fibrillation - AF that is intermittent and terminates within 7 days of onset [22]

• Persistent atrial fibrillation - AF that is continuous for more than 7 days and requires intervention. Patients with persistent AF who become paroxysmal with therapy should still be considered persistent. [22]

• Nonvalvular atrial fibrillation - AF that occurs in the absence of mitral valve disease or a prosthetic heart valve

• Atrial flutter - Atrial flutter, which is sometimes seen with AF, is a reentry tachyarrhythmia typically involving the tricuspid annulus that produces a characteristic sawtooth pattern on ECG [22]

• Atrioventricular (AV) node - the AV node is a bundle of specialized cells that conducts depolarization from the atria into the ventricles (see Illustration of cardiac conduction)

• Sinoatrial (SA) Node - the SA node is a bundle of specialized cells that initiates depolarization of the atria, functioning as the heart's normal pacemaker (see Illustration of cardiac conduction).

• Cryptogenic stroke - cryptogenic strokes, also called "strokes of undetermined source," are strokes without an identifiable source of thrombosis that account for about 30% of all strokes.

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• Atrial Fibrillation (AF) is the most common heart arrhythmia, with an estimated worldwide prevalence of 0.4 - 1.0%. Age is the most important risk factor, with the following prevalences observed in studies:
• Age (years): prevalence
• 65 - 69: 3 - 7%
• 70 - 74: 5 - 11%
• 74 - 79: 9 - 16%
• 80 - 84: 13 - 23%
• 85 - 89: 16 - 29% [1,21]

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• Overview
• Atrial fibrillation can lead to strokes that cause significant morbidity and mortality. Symptoms of AF vary widely, and many patients do not realize they have the condition; up to 30% of cryptogenic strokes are caused by undetected AF. Because it can go unnoticed and effective treatments are available, there has been much interest in screening for the condition.


• Studies
• A study that screened adults aged 75 to 76 years with an intermittent ECG for 2 weeks found that screening led to a slight decrease in the composite outcome of stroke, systemic embolism, bleeding leading to hospitalization, and all-cause death over 7 years (absolute risk reduction 1.1%, p=0.045). [PMID 34469764]
• A study that screened high-risk patients with an implantable loop recorder did not find a benefit over 5.3 years. [PMID 34469766]
• A study that screened people 70 and older using a 14-day single-lead continuous ECG patch found no benefit of screening over a median follow-up of 15.3 months. [PMID 39230544]


• Professional recommendations
• The USPSTF states that there is insufficient evidence to make a recommendation for or against AF screening with ECG

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• Age (most important)
• Age (years): prevalence
• 65 - 69: 3 - 7%
• 70 - 74: 5 - 11%
• 74 - 79: 9 - 16%
• 80 - 84: 13 - 23%
• 85 - 89: 16 - 29% [21]
• Male sex
• Race (White > Black > Asian)
• Heart disease
• Coronary artery disease
• Acute heart attack
• Pericarditis
• Myocarditis
• Cardiomyopathies
• Congestive heart failure
• Left ventricular hypertrophy
• Valvular heart disease (most often mitral valve)
• Hypertension
• Wolff-Parkinson-White syndrome
• Heavy alcohol intake (see alcohol reduction study below)
• Obesity
• Obstructive sleep apnea
• Genetic/familial
• Hyperthyroidism
• Fish oil
• Cardiac surgery (postoperative AF)
• Electrocution
• Pulmonary embolism [1]
• Physical activity - risk is increased in people with a sedentary lifestyle and in those who exercise intensely (elite athletes) [18,22]

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• Atrial fibrillation is a heart arrhythmia marked by repetitive sporadic atrial depolarizations initiated by abnormal foci, typically originating in the pulmonary veins of the left atrium. The abnormal electrical activity overrides the normal SA node, causing atrial contractions to be uncoordinated and unproductive. The AV node transmits the disorganized charges from the atria to the ventricles, creating an irregular ventricular rhythm. The heart rate in AF can range from slow to fast, depending on the responsiveness of the AV node to the irregular discharges. Very rapid rates (>120 bpm) can hamper ventricular filling and lead to heart failure. Over time, AF induces chemical, electrical, and structural remodeling that facilitates AF occurrence and promotes thromboembolism.
• Disorganized atrial activity allows blood to pool and clot in the heart. The most common site for thrombus formation is the left atrial appendage (see atrial appendage), an outpocketing in the left atrium that is believed to be the source of > 90% of AF-induced thrombi. If the clot breaks free, it can travel to the brain and cause a stroke. [10]


• Illustration of the mechanism of atrial fibrillation

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• Symptoms
• AF has a wide range of symptoms. Some people have no symptoms and are unaware that they have it, while others have overt heart failure. Some people are not aware they have AF until they have a stroke.
• AF can start suddenly and then revert to sinus rhythm on its own, or it can be persistent
• Symptoms of AF include:
• Irregular heartbeat
• Rapid heartbeat
• Palpitations
• Heart failure in susceptible patients
• Chest pain in susceptible patients
• Stroke

• Physical exam
• A cardiac exam will reveal an irregular heartbeat and pulse
• Signs of heart failure (e.g., edema, dyspnea) may be present in susceptible individuals

• Diagnostic workup
• The AHA recommends the following:
• ECG
• Transthoracic ECHO
• Labs: CBC, CMP, TSH
• In select cases, the following may be indicated:
• Holter monitor
• Transesophageal ECHO - if cardioversion is being considered
• Exercise testing - to evaluate adequacy of rate control
• Electrophysiological study - in patients who are considering ablation [1]

• Electrocardiogram (ECG)
• ECG findings consistent with AF include wavy, nondistinct p-waves with ventricular depolarizations (QRS complexes) occurring at irregular intervals. If the ventricular response rate is rapid, only repetitive, nonuniformly-spaced QRS complexes may be present. See AF ECG illustration for more.

• Cardiac monitoring
• Since AF is often intermittent, cardiac monitoring over extended periods may be necessary to detect it. Over the last 20 years, devices that provide continuous tracings for months to years have been introduced. Examples of these devices are listed below.


• Implatable defibrillators and pacemakers - implantable defibrillators and pacemakers provide contiunous tracings that can detect AF
• Implantable loop recorder - small device implanted under the skin of the chest that can record and transmit heart rhythms for up to 3 years
• External loop recorder - device worn on the chest that records a continuous ECG while the patient is wearing it. Most external loop recorders are worn for 4 - 6 weeks.
• Zio® patch - small waterproof patch that provides a continuous reading for up to 2 weeks
• Smart watches - a number of smart watches now have the ability to detect AF (e.g. Apple Watch, Fitbit)
• Holter monitor - external device with cardiac leads that can monitor the heart rhythm for up to 48 hours

• Heart echocardiogram (ECHO)
• All patients with newly diagnosed AF should have a heart ECHO to detect valvular heart disease, which is a risk factor for AF
• Transthoracic ECHO is suitable in most patients, while a transesophageal ECHO (TEE), which provides better images of the left atrium and left atrial appendage, may be preferred in patients who have suffered a stroke or plan to undergo cardioversion. If a clot is detected on TEE, cardioversion should be delayed (see cardioversion recs). [1]

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• Overview
• Patients with AF may be treated with a rate control (medications to maintain a heart rate < 100 bpm) or rhythm control (therapies to maintain sinus rhythm) strategy. The AHA gives the following general guidance on choosing a method: patients without heart failure, limited symptoms, and low AF burden may be managed with rate control, while those with heart failure, frequent symptoms, and high AF burden may benefit from rhythm control.
• Factors to consider when choosing a strategy, AHA recommendations, and two studies that compared the approaches are reviewed below

• AHA 2023 rate vs rhythm control recommendations
• In patients with AF, shared decision-making with the patient is recommended to discuss rhythm- versus rate-control strategies (taking into consideration clinical presentation, comorbidity burden, medication profile, and patient preferences), discuss therapeutic options, and for assessing long-term benefits (see factors to consider when choosing a strategy)
• In patients with reduced LV function and persistent (or high burden) AF, a trial of rhythm control should be recommended to evaluate whether AF is contributing to the reduced LV function.
• In patients with symptomatic AF, rhythm control can be useful to improve symptoms
• In patients with a recent diagnosis of AF (<1 year), rhythm control can be useful to reduce hospitalizations, stroke, and mortality
• In patients with AF and heart failure, rhythm control can be useful for improving symptoms and improving outcomes, such as mortality and hospitalizations for HF and ischemia
• In patients with AF, rhythm-control strategies can be useful to reduce the likelihood of AF progression [22]

• Summary
• In the AFFIRM study, rate control was noninferior to rhythm control with antiarrhythmic drugs for overall mortality. The rhythm control group had more hospitalizations and adverse events, and twice as many people in the rhythm control group crossed over to rate control than vice versa.
• In the EAST-AFNET 4 trial, an early rhythm control strategy that mainly used antiarrhythmic medications (86.8%) was slightly superior to a rate control strategy for a composite of CVD outcomes (absolute risk difference of 1.1%). The number needed to treat for one person to benefit from a rhythm control strategy was 91.

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• Overview
• AHA recommendations for rate control strategy are provided below, along with a study that compared a strict (< 80 bpm) to a lenient (> 110) target

• AHA 2023 recommendations
• Target heart rate
• In patients with AF without heart failure who are candidates for select rate-control strategies, heart rate target should be guided by underlying patient symptoms, in general aiming at a resting heart rate of < 100 to 110 bpm
• Medications
• In patients with AF, beta blockers or nondihydropyridine calcium channel blockers (diltiazem, verapamil) are recommended for long-term rate control with the choice of agent according to underlying substrate and comorbid conditions
• In patients with AF and heart failure symptoms, digoxin (target level < 1.2 ng/ml) is reasonable for long-term rate control in combination with other rate-controlling agents, or as monotherapy if other agents are not preferred, not tolerated, or contraindicated
• In patients with AF and LVEF <40%, nondihydropyridine calcium channel–blocking drugs should not be administered given their potential to exacerbate heart failure
• In patients with permanent AF who have risk factors for cardiovascular events, dronedarone should not be used for long-term rate control [22]

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• Overview
• Rhythm control can be achieved with electrical cardioversion, pharmacological cardioversion (antiarrhythmic medications), and catheter ablation. Reviews of each modality are provided below, along with AHA recommendations and studies comparing ablation to antiarrhythmics.

• Electrical cardioversion
• Electrical cardioversion is a procedure where the patient is sedated and given a heart shock, which sometimes converts AF to normal sinus rhythm. Cardioversion can be performed emergently (e.g., unstable patients, short AF duration) or on an outpatient elective basis. Success rates for cardioversion vary depending on the study and patient population. In general, 50 - 90% of patients convert to sinus rhythm during the initial procedure, of which 50% maintain sinus rhythm for at least one year. [23] See anticoagulation for cardioversion for recommendations on anticoagulant therapy before and after cardioversion.
• STUDY
  A study (N=427) published in 2019 compared early vs delayed cardioversion in stable patients presenting to the ER with AF for < 36 hours. The delayed group was given rate control medications and observed for 48 hours to see if the AF would resolve, while the early group received immediate cardioversion. In the delayed group, spontaneous conversion to sinus rhythm occurred in 69% of patients within 48 hours. The primary outcome of sinus rhythm at 4 weeks was not significantly different between groups (Early - 94% | Delayed - 91%). [PMID 30883054 ]

• AHA 2023 electrical cardioversion recommendations
• In patients with hemodynamic instability attributable to AF, immediate electrical cardioversion should be performed to restore sinus rhythm
• In patients with AF who are hemodynamically stable, electrical cardioversion can be performed as initial rhythm-control strategy or after unsuccessful pharmacological cardioversion [22]

• Pharmacological cardioversion
• Antiarrhythmics can be used acutely to convert AF to sinus rhythm (pharmacological cardioversion) and chronically for sinus rhythm maintenance. They are most effective when initiated within 7 days of AF onset and can maintain sinus rhythm in about 50% of patients. During pharmacological cardioversion, patients are at increased risk of stroke and should receive appropriate anticoagulation (see anticoagulation for cardioversion)
• STUDY
  A study (N=396) comparing procainamide infusion to electrical cardioversion in patients presenting to the ER with acute AF found that procainamide restored sinus rhythm in 52% of patients compared to 92% with cardioversion. [PMID 32007169]

• AHA 2023 pharmalogical cardioversion recommendations
• Cardioversion
• For patients with AF, pharmacological cardioversion is reasonable as an alternative to electrical cardioversion for those who are hemodynamically stable or in situations when electrical cardioversion is preferred but cannot be performed
• For patients with AF, ibutilide is reasonable for pharmacological cardioversion for patients without depressed LV function (LVEF < 40%)
• For patients with AF, intravenous amiodarone is reasonable for pharmacological cardioversion, although time to conversion is generally longer than with other agents (8-12 hours)
• For patients with recurrent AF occurring outside the setting of a hospital, the “pill-in-the-pocket” (PITP) approach with a single oral dose of flecainide or propafenone, with a concomitant atrioventricular nodal blocking agent, is reasonable for pharmacological cardioversion if previously tested in a monitored setting [22]
• Maintenance
• For patients with AF and HFrEF (≤ 40%), therapy with dofetilide or amiodarone is reasonable for long-term maintenance of sinus rhythm
• For patients with AF and no previous MI, or known or suspected significant structural heart disease, or ventricular scar or fibrosis, use of flecainide or propafenone is reasonable for long-term maintenance of sinus rhythm
• For patients with AF without recent decompensated HF or severe LV dysfunction, use of dronedarone is reasonable for long-term maintenance of sinus rhythm
• For patients with AF without significant baseline QT interval prolongation or uncorrected hypokalemia or hypomagnesemia, use of dofetilide is reasonable for long-term maintenance of sinus rhythm, with proper dose selection based on kidney function and close monitoring of the QT interval, serum potassium and magnesium concentrations, and kidney function.
• For patients with AF and normal LV function, use of low-dose amiodarone (100-200 mg/d) is reasonable for long-term maintenance of sinus rhythm but, in view of its adverse effect profile, should be reserved for patients in whom other rhythm control strategies are ineffective, not preferred, or contraindicated. [22]

• Catheter ablation
• The area in the left atrium surrounding the entrance of the pulmonary veins is a frequent initiator of ectopic atrial foci, and ablating this tissue has been shown to reduce AF occurrence. The studies below compared various procedural techniques.


• Ablation vs Sham procedure - a small study (N=126) comparing pulmonary vein isolation with cryoablation to a sham procedure found that ablation lowered the AF burden by 60% over 6 months compared to 35% in the sham group (p <0.001). [PMID 39221629]
• Ablation techniques - tissue ablation is typically performed with radiofrequency energy (thermal ablation) or freezing (cryoablation). Studies comparing these techniques have found them to be equivalent. [PMID 27042964, PMID 31630538] A third ablation technique using high-voltage electrical fields (pulsed field ablation) has also been shown to be as effective. [PMID 37634148]
• Left atrial fibrosis ablation - left atrial fibrosisis is a hallmark of atrial myopathy and has been associated with a higher risk of AF recurrence after ablation. Theoretically, ablating the fibrosis may lower the risk of recurrent AF. A study (N=843) published in 2022 compared the effects of adding MRI-guided fibrosis ablation to standard ablation on atrial arrhythmia recurrence in patients with persistent AF. There was no significant difference between the groups during the 12 - 18 month follow-up period. [PMID 35727277]
• Left atrial posterior wall isolation - persistent AF is less responsive to ablation than paroxysmal AF. Some experts have theorized that left atrial posterior wall conductive anomalies may be the reason, and adjunctive ablation of this area has risen in popularity. A study published in 2023 compared pulmonary vein isolation to pulmonary vein isolation + left atrial posterior wall isolation in symptomatic patients with persistent AF. At 12 months post-ablation, no significant difference was found for the primary outcome of freedom from any documented atrial arrhythmia. [PMID 35727277]
• Vein of Marshall ablation - the vein of Marshall, which runs along the left atrium and drains into the coronary sinus, has been identified as a potential source of ectopic foci. A study comparing standard ablation to standard ablation with vein of Marshall ablation (performed by perfusing ethanol into the vein) found that the addition of vein of Marshall ablation improved success rates. [PMID 33107945] A second similar study that included vein of Marshall ablation as part of a linear ablation strategy also found a benefit. [PMID 39556379]
• Ablation with left atrial appendage ligation to reduce AF recurrence - a study (N=404) evaluated the effects of adding percutaneous left atrial appendage ligation to ablation in patients with nonparoxysmal AF. At 12 months, there was no significant difference in atrial arrhythmia recurrence between patients who received ligation and those who did not (63.3% vs 59.9%, respectively). [PMID 38563835]
• Ablation with left atrial appendage occlusion - a study (N=202) evaluated the effects of performing ablation before or after left atrial appendage occlusion (Watchman device) during a combined procedure. After a median follow-up of 2.5 years, the primary outcome (a composite of thromboembolic events including stroke or transient ischemic attack, device-related thrombus, clinically relevant bleeding, and cardiovascular rehospitalization or death) was significantly lower in the occlusion-first group (16.5% vs 28.9%), as was AF recurrence (22.7% vs 36.5%). [PMID 39546313]
• Periprocedural anticoagulants - Most patients continue taking their current anticoagulant when they have an ablation procedure done. Two studies have compared the safety of direct-acting oral anticoagulants (rivaroxaban and dabigatran) to warfarin for procedural anticoagulation. Both drugs were found to be equivalent to warfarin. [PMID 25975659, PMID 28317415]
• Ablate and pace - In patients with severely symptomatic AF, an approach called "ablate and pace" is sometimes performed. Ablate and pace involves ablating the AV node and then pacing the ventricles with a biventricular pacemaker. A small study (N=133) found that this approach was superior to pharmacological rate control in patients with severe AF and heart failure. [PMID 34453840]

• Efficacy in preventing AF
• Depending on the study and the method used to detect AF, catheter ablation has a success rate of about 57 - 70% for preventing recurrent AF at one year post-ablation. At 2 years, success (defined as no atrial arrhythmia) has dropped to less than 50% in some trials. Repeat ablation is necessary in about 12 - 20% of patients. [4,9,11,17]
• The EARLY-AF trial comparing initial treatment with cryoablation to antiarrhythmics found that ablation was superior to antiarrhythmics for preventing AF reoccurrence at 1 year (42.9% vs 67.8%)
• A small study published in 2020 (N=302) found that the addition of renal denervation to catheter ablation increased the success rate of catheter ablation at 12 months (72% with vs 56% without). [PMID 31961420]

• Efficacy (clinical outcomes)
• The CABANA study comparing ablation to antiarrhythmics for a number of clinical outcomes (death, disabling stroke, serious bleeding, cardiac arrest) found no clear benefit of ablation over meds
• Two small studies among patients with significant HFrEF (CASTLE-AF and CASTLE HTx) found that ablation was superior to medical therapy for a number of CVD outcomes.

• AHA 2023 catheter ablation recommendations
• Initial therapy
• In patients with symptomatic AF in whom antiarrhythmic drugs have been ineffective, contraindicated, not tolerated or not preferred, and continued rhythm control is desired, catheter ablation is useful to improve symptoms
• In selected patients (generally younger with few comorbidities) with symptomatic paroxysmal AF in whom rhythm control is desired, catheter ablation is useful as first-line therapy to improve symptoms and reduce progression to persistent AF
• In patients with symptomatic or clinically significant atrial flutter, catheter ablation is useful for improving symptoms
• In patients (other than younger with few comorbidities) with symptomatic paroxysmal or persistent AF who are being managed with a rhythm-control strategy, catheter ablation as first-line therapy can be useful to improve symptoms
• In selected patients with asymptomatic or minimally symptomatic AF, catheter ablation may be useful for reducing progression of AF and its associated complications [22]
• Heart failure
• In appropriate patients with AF and HFrEF who are on guideline-directed medical therapy, and with reasonable expectation of procedural benefit, catheter ablation is beneficial to improve symptoms, QOL, ventricular function, and cardiovascular outcomes
• In appropriate patients with symptomatic AF and HFpEF with reasonable expectation of benefit, catheter ablation can be useful to improve symptoms and improve quality of life [22]
• Recurrence
• In patients with recurrent symptomatic AF after catheter ablation, repeat catheter ablation or antiarrhythmic drug therapy is useful to improve symptoms and freedom from AF [22]
• Anticoagulation during procedure
• In patients on warfarin who are undergoing catheter ablation of AF, catheter ablation should be performed on uninterrupted therapeutic anticoagulation with a goal INR of 2.0 to 3.0
• In patients on a DOAC who are undergoing catheter ablation of AF, catheter ablation should be performed with either continuous or minimally interrupted oral anticoagulation [22]
• STUDIES
  Two studies comparing the safety of DOACs (rivaroxaban and dabigatran) to warfarin for procedural anticoagulation found that DOACs were equivalent to warfarin. [PMID 25975659, PMID 28317415]

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• Overview
• A study that found significant weight loss lowered AF symptom burden and occurrence is described below, along with AHA recommendations on weight loss and exercise


• RCT
  Effect of Weight Loss on AF Burden and Occurrence, JAMA (2013) [PubMed abstract]
• Design: Randomized, controlled trial (N=150 | length = 15 months) in overweight patients (average BMI 33) with symptomatic AF
• Treatment: Weight loss intervention vs Control
• Primary outcome: Atrial Fibrillation Severity Scale scores: symptom burden and symptom severity (scale 3.25 [best] - 30 [worst])
• Results:
• Weight loss: Intervention - 31 lbs, Control - 8 lbs
• Primary outcome (point reduction): Intervention - 11.8, Control - 2.6 (p<0.001)
• Mean AF episodes on 7-day Holter: Intervention - 0.62, Control - 2.0 (p<0.001)
• Mean duration of AF on 7-day Holter (minutes): Intervention - 491, Control - 1546 (p<0.001)
• Findings: In this study, weight reduction with intensive risk factor management resulted in a reduction in atrial fibrillation symptom burden and severity and in beneficial cardiac remodeling. These findings support therapy directed at weight and risk factors in the management of atrial fibrillation.


• AHA 2023 recommendations
• Weight loss
• In patients with AF who are overweight or obese (with body mass index [BMI] >27 kg/m2), weight loss is recommended, with an ideal target of at least 10% weight loss to reduce AF symptoms, burden, recurrence, and progression to persistent AF [22]
• Exercise
• In individuals with AF unrelated to excessive exercise, moderate-to-vigorous exercise training to a target of 210 minutes per week is recommended to reduce AF symptoms and burden, increase maintenance of sinus rhythm, increase functional capacity, and improve quality of life. [22]

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• Overview
• A study that found alcohol abstinence lowered AF burden is detailed below, along with AHA recommendations on alcohol intake


• RCT
  Alcohol Abstinence vs Continue Alcohol for Atrial Fibrillation Control, NEJM (2020) [PubMed abstract]
• Design: Randomized controlled trial (N=140 | length = 6 months) in patients with symptomatic paroxysmal or persistent AF who consumed ≥ 10 alcoholic drinks per week
• Treatment: Abstain from alcohol vs Continue usual alcohol consumption
• Primary outcomes: Two primary endpoints were freedom from recurrence of atrial fibrillation (after a 2-week “blanking period”) and total atrial fibrillation burden (proportion of time in atrial fibrillation) during 6 months of follow-up
• Results:
• Primary outcome (freedom from recurrence): Abstinence - 47%, Continue - 27% (p=0.005)
• Primary outcome (median % time in AF): Abstinence - 0.5%, Continue - 1.2% (p=0.01)
• Average alcohol intake during study: Abstinence - 2.1 drinks/week, Continue - 13.2 drinks/week
• Findings: Abstinence from alcohol reduced arrhythmia recurrences in regular drinkers with atrial fibrillation.


• AHA 2023 recommendations
• Patients with AF seeking a rhythm-control strategy should minimize or eliminate alcohol consumption to reduce AF recurrence and burden [22]

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• CHA2DS2-VASc score
• The CHA2DS2-VASc score is the recommended stroke risk assessment tool for patients with AF. Score criteria and annual stroke risk based on score are provided in the tables below.

• Sum the scores for each criterion the patient meets
• Reference [12]

CHA2DS2-VASc risk criteria	Score
Prior stroke, TIA, or thromboembolism	2
Age ≥ 75	2
Hypertension	1
Diabetes	1
Heart Failure	1
Vascular disease (CAD or PVD)	1
Age 65 - 74	1
Female sex	1

• Reference [12]

Annual risk of stroke based on CHA2DS2-VASc score
CHA2DS2-VASc SCORE	Annual Stroke Rate
0	0%
1	1.3%
2	2.2%
3	3.2%
4	4.0%
5	6.7%
6	9.8%
7	9.6%
8	6.7%
9	15.2%

• CHADS2 score
• The CHADS2 score, which preceded the CHA2DS2-VASc score, is no longer recommended because CHA2DS2-VASc has been shown to be superior. However, some guidelines still incorporate CHADS2 scores, so the criteria and annual stroke risk based on score are provided below.

• Sum the scores for each criterion the patient meets
• Reference [1,2]

CHADS2 risk criteria	Score
Prior stroke, TIA, or thromboembolism	2
Age ≥ 75	1
Hypertension	1
Diabetes	1
Heart Failure	1

• Reference [1]

Annual risk of stroke based on CHADS2 score
CHADS2 score	Annual Stroke Rate
0	1.9%
1	2.8%
2	4%
3	5.9%
4	8.5%
5	12.5%
6	18.2%

• Stroke prevention during cardioversion
• During electrical and pharmacological cardioversion, the sudden shift to sinus rhythm can promote thromboembolism both from preexisting thrombi and acute changes in atrial mechanics. To help prevent a treatment-induced stroke, imaging and anticoagulation are recommended, depending on the patient scenario.


• AHA 2023 cardioversion thromboembolism prevention recommendations
• In patients with AF duration of ≥ 48 hours, a 3-week duration of uninterrupted therapeutic anticoagulation or imaging evaluation to exclude intracardiac thrombus is recommended before elective cardioversion
• In patients with AF undergoing cardioversion, therapeutic anticoagulation should be established before cardioversion and continued for at least 4 weeks afterwards without interruption to prevent thromboembolism
• In patients with AF in whom cardioversion is deferred due to left atrial appendage thrombus detected on precardioversion imaging, therapeutic anticoagulation should be instituted for at least 3 to 6 weeks, after which imaging should be repeated before cardioversion
• In patients with reported AF duration of < 48 hours (not in the setting of cardiac surgery) and who are not on anticoagulation, precardioversion imaging to exclude intracardiac thrombus may be considered in those who are at elevated thromboembolic risk (CHA2DS2-VASc score ≥ 2 or equivalent)
• In patients with low thromboembolic risks (CHA2DS2-VASc 0-1 or equivalent) and AF duration of < 12 hours, the benefit of precardioversion imaging or pericardioversion anticoagulation is uncertain given the low incidence of pericardioversion thromboembolic events in this population
• STUDY
  A study (N=2199) comparing edoxaban to enoxaparin-warfarin in patients undergoing electrical cardioversion for AF found that edoxaban was noninferior for CVD event prevention and bleeding risk. [PMID 27590218]
• Patients with left atrial appendage occlusion
• In patients with AF and previous left atrial appendage occlusion who are not on anticoagulation, imaging evaluation to assess the adequacy of left atrial appendage occlusion and exclude device-related thrombosis before cardioversion may be reasonable
• In patients with AF and previous left atrial appendage occlusion with residual leak, pericardioversion anticoagulation may be considered and continued thereafter [22]

• Switching from warfarin to DOAC
• DOACs offer several advantages over warfarin (e.g., no lab monitoring or dosage adjustments, slightly better outcomes in some trials), raising the question of whether warfarin-treated patients should be switched to one. While this practice has not been studied extensively, a trial (N= 1330) published in 2023 found that switching frail elderly patients (age ≥ 75) with AF to a DOAC from warfarin led to more bleeding complications and no reduction in thromboembolic events compared to continuing warfarin. [PMID 37634130]

• Anticoagulant + antiplatelet therapy
• Patients with atrial fibrillation who have coronary artery disease have indications for both anticoagulation and antiplatelet therapy. Recommendations for treating these patients are covered at the links below
• Antithrombotic therapy after acute coronary syndrome (myocardial infarction or unstable angina)
• Antithrombotic therapy in stable coronary artery disease

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• Overview
• The left atrial appendage, an outpocketing in the left atrium where blood tends to pool and form clots (see atrial appendage), is believed to be the source of > 90% of thromboses in AF
• The Watchman device, which is inserted during a procedure similar to a heart cath, closes off the appendage and prevents blood from pooling. It was approved for stroke prevention in AF in 2009, and a second-generation device called Watchman FLX was released in 2020. A third occlusion device, Amplatzer Amulet, became available in 2021. The appendage can also be surgically occluded or excised during heart surgery.
• Studies comparing closure to anticoagulation for stroke prevention in different clinical scenarios are detailed below

• RCT
  PRAGUE-17 trial - Atrial Appendage Closure vs Apixaban in High-risk Patients with AF, J Am Coll Cardiol (2020) [PubMed abstract]
• Design: Randomized controlled trial (N=402 | length = median 19.9 months) in high-risk AF patients with high-risk defined as history of bleeding requiring intervention or hospitalization, a history of a cardioembolic event while taking an anticoagulant, and/or a CHA₂DS₂-VASc of ≥ 3 and HAS-BLED of > 2
• Treatment: Atrial appendage closure (Amulet - 61% | Watchman - 36% | Watchman FLX - 2.8%) vs Direct oral anticoagulant (96% received apixaban)
• Primary outcome: Composite of stroke, TIA, systemic embolism, cardiovascular death, major or nonmajor clinically relevant bleeding, or procedure-/device-related complications
• Results:
• Primary outcome: Atrial appendage closure - 11%/year, Apixaban - 13.4%/year (p=0.44)
• There were no differences between groups for the components of the composite endpoint: all-stroke/TIA (HR: 1.00, 95%CI [0.40 to 2.51]), clinically significant bleeding (HR 0.81, 95%CI [0.44 to 1.52]) and cardiovascular death (HR 0.75, 95%CI [0.34 to 1.62])
• Findings: Among patients at high risk for stroke and increased risk of bleeding, left atrial appendage closure was noninferior to apixaban in preventing major atrial fib-related cardiovascular, neurological, and bleeding events

• RCT
  LAAOS III - Atrial Appendage Occlusion vs No Occlusion During Cardiac Surgery, NEJM (2021) [PubMed abstract]
• Design: Randomized controlled trial (N=4770 | length = average 3.8 years) in patients with AF (average CHA₂DS₂-VASc score 4.2) undergoing cardiac surgery for another indication
• Treatment: Occlusion of the left atrial appendage vs No occlusion. Most occlusions were performed surgically (> 80%) and not with devices. Anticoagulation was continued during follow-up in both groups.
• Primary outcome: Occurrence of ischemic stroke (including transient ischemic attack with positive neuroimaging) or systemic embolism
• Results:
• Primary outcome: Occlusion - 4.8%, No occlusion - 7% (p=0.001)
• Findings: Among participants with atrial fibrillation who had undergone cardiac surgery, most of whom continued to receive ongoing antithrombotic therapy, the risk of ischemic stroke or systemic embolism was lower with concomitant left atrial appendage occlusion performed during the surgery than without it.

• RCT
  OPTION Trial - Left Atrial Appendage Closure vs Anticoagulation after Ablation for Atrial Fibrillation, NEJM (2024) [PubMed abstract]
• Design: Randomized, open-label trial (N=1600 | length = 36 months) in patients with atrial fibrillation (average CHA₂DS₂-VASc score 3.5) who had undergone catheter ablation
• Treatment: Left atrial appendage closure (WATCHMAN FLX) vs Oral anticoagulation (95% of patients received DOACs). In the closure group, patients received oral anticoagulants and aspirin for 90 days, followed by aspirin alone until 12 months after randomization.
• Primary outcome: Safety: Non-procedure-related major bleeding or clinically relevant nonmajor bleeding; Efficacy: composite of death from any cause, stroke, or systemic embolism
• Results:
• Primary outcome (safety): Left atrial appendage closure - 8.5%, Oral anticoagulation - 18.1% (p<0.001 for superiority)
• Primary outcome (efficacy): Left atrial appendage closure - 5.3%, Oral anticoagulation - 5.8% (p<0.001 for noninferiority)
• At the 36-month follow-up, 10.1% of patients in the device group (left atrial appendage closure) were still receiving oral anticoagulation
• Findings: Among patients who underwent catheter-based atrial fibrillation ablation, left atrial appendage closure was associated with a lower risk of non-procedure-related major or clinically relevant nonmajor bleeding than oral anticoagulation and was noninferior to oral anticoagulation with respect to a composite of death from any cause, stroke, or systemic embolism at 36 months.

• AHA 2023 atrial appendage closure recommendations
• Percutaneous closure
• In patients with AF, a moderate to high risk of stroke (CHA2DS2-VASc score ≥ 2), and a contraindication (see below) to long-term oral anticoagulation due to a nonreversible cause, percutaneous left atrial appendage occlusion is reasonable
• In patients with AF and a moderate to high risk of stroke and a high risk of major bleeding on oral anticoagulation, percutaneous left atrial appendage occlusion may be a reasonable alternative to oral anticoagulation based on patient preference, with careful consideration of procedural risk and with the understanding that the evidence for oral anticoagulation is more extensive
• During cardiac surgery
• In patients with AF undergoing cardiac surgery with a CHA2DS2-VASc score ≥ 2 or equivalent stroke risk, surgical left atrial appendage exclusion, in addition to continued anticoagulation, is indicated to reduce the risk of stroke and systemic embolism
• In patients with AF undergoing cardiac surgery and left atrial appendage exclusion, a surgical technique resulting in absence of flow across the suture line and a stump of < 1 cm as determined by intraoperative transesophageal echocardiography should be used.
• In patients with AF undergoing cardiac surgery with CHA2DS2-VASc score ≥ 2 or equivalent stroke risk, the benefit of surgical left atrial appendage exclusion in the absence of continued anticoagulation to reduce the risk of stroke and systemic embolism is uncertain [22]
• Contraindications to long-term anticoagulation
• Severe bleeding due to a nonreversible cause involving the gastrointestinal, pulmonary, or genitourinary systems
• Spontaneous intracranial/ intraspinal bleeding due to a nonreversible cause
• Serious bleeding related to recurrent falls when cause of falls is not felt to be treatable [22]

• Summary
• Device closure vs anticoagulants
• In the PROTECT AF study, the Watchman device was noninferior to warfarin, and in the PRAGUE-17 trial, the Watchman and Amulet devices were noninferior to apixaban. A study comparing the first-generation Watchman and Amulet devices showed similar safety and efficacy profiles. [PMID 34459659] Together, these studies show that atrial appendage device closure is a safe and effective alternative to anticoagulation for stroke prevention in patients with AF.


• Device closure vs anticoagulants after ablation
• The OPTION trial found that following catheter ablation for AF, the Watchman device was superior to anticoagulation for safety (bleeding events) and noninferior for efficacy (death from any cause, stroke, or systemic embolism). This study makes a strong case for concomitant left atrial appendage device closure during ablation, particularly in patients who wish to discontinue anticoagulation.


• Closure during cardiac surgery
• In the LAAOS III study, left atrial appendage occlusion during cardiac surgery, primarily using surgical techniques, was superior to no occlusion for preventing strokes and systemic embolism in patients with AF.

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• Overview
• Traditionally, AF has been diagnosed with ECGs, telemetry, or holter monitors that provide days of tracings. In the past 20 years, new implantable devices (e.g., loop recorders, implantable defibrillators, pacemakers) have been introduced that give continuous readings over months to years. Longer tracings can detect asymptomatic episodes of atrial tachyarrhythmias that have undetermined clinical significance. Two events that have been loosely defined are atrial high-rate episodes (AHRE) and subclinical AF. While criteria aren't standardized across professional organizations, the following definitions are often seen:


• AHRE - atrial tachyarrhythmia episodes with a rate > 170 beats/min (> 190 in some guidelines) detected by cardiac implantable electronic devices
• Subclinical AF - an asymptomatic AHRE lasting greater than 6 minutes and less than 24 hours


• Observational studies have found these events are associated with a higher-than-normal but less-than-AF stroke risk, spurring researchers to evaluate the effects of antithrombotics in affected patients. The first study below examined edoxaban in AHREs, while the second one compared apixaban to aspirin in subclinical AF.

• AHA 2023 recommendations
• For patients with a device-detected atrial high-rate episode (AHRE) lasting ≥ 24 hours and with a CHA2DS2-VASc score ≥ 2 or equivalent stroke risk, it is reasonable to initiate oral anticoagulation within a shared-decision making framework that considers episode duration and individual patient risk.
• For patients with a device-detected AHRE lasting between 5 minutes and 24 hours and with a CHA2DS2-VASc score ≥ 3 or equivalent stroke risk, it may be reasonable to initiate anticoagulation within a shared-decision making framework that considers episode duration and individual patient risk
• Patients with a device-detected AHRE lasting < 5 minutes and without another indication for oral anticoagulation should not receive oral anticoagulation. [22]

• Summary
• The studies above do not support anticoagulation for AHRE or subclinical AF. In both control groups, most of the patients (54% in NOAH-AFNET 6 and 100% in ARTESIA) were receiving aspirin, which may have reduced the effect size of anticoagulation, as some studies have found antiplatelet therapy reduces stroke risk in AF.
• Over the course of both studies, a significant number of subjects met AF diagnostic criteria (18% in NOAH-AFNET 6 and 24% in ARTESIA), underpinning the importance of continued close monitoring.

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• Overview
• Antiplatelet therapy is widely used for the secondary prevention of ischemic stroke. Its efficacy in AF was evaluated in the four studies below.

• AHA 2023 recommendations
• In patients with AF who are candidates for anticoagulation and without an indication for antiplatelet therapy, aspirin either alone or in combination with clopidogrel as an alternative to anticoagulation is not recommended to reduce stroke risk
• In patients with AF without risk factors for stroke, aspirin monotherapy for prevention of thromboembolic events is of no benefit

• Summary
• Antiplatelet therapy is clearly inferior to anticoagulation for stroke prevention in AF

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• Stopping anticoagulation after cardioversion or ablation
• After successful cardioversion or catheter ablation, the question arises as to whether patients can stop anticoagulation. Unfortunately, there are no good studies providing guidance on this issue. Only about 50% of patients treated with cardioversion maintain sinus rhythm at one year, and approximately 50% of patients who undergo ablation have AF recurrence within 5 years. The decision to stop anticoagulation after cardioversion or catheter ablation is based on individual factors and the patient's willingness to accept unknown risks. AHA recommendations for stopping anticoagulation after ablation are provided below. [19]


• AHA 2023 recommendations for stopping anticoagulants after ablation
• In patients who have undergone catheter ablation of AF, oral anticoagulation should be continued for at least 3 months after the procedure with a longer duration determined by underlying risk
• In patients who have undergone catheter ablation of AF, continuation of longer-term oral anticoagulation should be dictated according to the patients' stroke risk (eg, CHA2DS2-VASc score ≥ 2) [22]

• Periprocedural recommendations
• See periprocedural antithrombotic recommendations

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• Overview
• Atrial fibrillation is a common complication of cardiac surgery, occurring in 20 - 50% of patients. Fortunately, 90% of patients return to sinus rhythm within days. The ideal treatment of postoperative AF has not been defined. The study below compared rate control to rhythm control in patients with postoperative AF after CABG and/or heart valve surgery.

• AHA 2023 postoperative AF recommendations
• In postoperative cardiac surgery patients, beta blockers are recommended to achieve rate control for AF unless contraindicated or ineffective in which case a nondihydropyridine calcium channel blocker is recommended
• In hemodynamically stable cardiac surgery patients with postoperative AF, rate-control (target heart rate, < 100 bpm) and/or rhythm-control medications are recommended as initial therapy, with the choice of strategy according to patient symptoms, hemodynamic consequences of the arrhythmia, and physician preference
• In patients who develop poorly tolerated AF after cardiac surgery, direct current cardioversion in combination with antiarrhythmic drug therapy is recommended, with consideration of imaging to rule out left appendage thrombus before cardioversion in those patients in whom AF has been present > 48 hours and who have not been on anticoagulation
• In patients who develop postoperative AF after cardiac surgery, it is reasonable to administer anticoagulation when deemed safe in regard to surgical bleeding for 60 days after surgery unless complications develop and to reevaluate the need for longer term anticoagulation at that time
• In patients who develop AF after cardiac surgery and who are treated with rate-control strategy, at 30- to 60-day follow-up it is reasonable to perform rhythm assessment and, if AF does not revert to sinus rhythm spontaneously, consider cardioversion after an adequate duration of anticoagulation [22]

• Summary
• In the CTSN study, neither a rate nor rhythm strategy was superior to the other for managing postoperative AF. One takeaway from the trial is that anticoagulation was started and continued for at least 60 days if AF persisted for more than 48 hours. This offers some guidance on when and how to anticoagulate these patients. Stroke and TIA events were low in both groups (<1%).
• STUDIES
  A 2021 study (N=420) found that posterior left pericardiotomy (to prevent pericardial effusion) after cardiac surgery significantly reduced the risk of postoperative AF (17% vs 32%). [PMID 34788640] Another study (N=430) found that partial cardiac denervation (cutting off the ligament of Marshall and resecting the fat pad along the Waterston groove) after CABG also reduced the incidence of postoperative AF (18.1% vs 31.6%). [PMID 39550720]

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• 1 - PMID 16908781 AHA 2006 AF GL
• 2 - PMID 22315257 ACCP GL on thrombosis
• 3 - PMID 22858728 AHA 2012 update on oral antithrombotics
• 4 - PMID 22168644 NEJM review of ablation
• 5 - PMID 22869839 Bleeding study with combined therapy
• 6 - PMID 21177058 2011 AHA focused update
• 7 - PMID 12466506 AFFIRM study
• 8 - PMID 20231232 RACE II study
• 9 - PMID 20103757 Ablation vs meds
• 10 - PMID 19683639 PROTECT AF
• 11 - PMID 24549549 RAAFT-2
• 12 - PMID 24682348 AHA 2014 AF GL
• 13 - PMID 24682347
• 14 - PMID 24682348 AHA 2014 AF GL
• 15 - PMID 25399274 PROTECT-AF follow-up
• 16 - PMID 30686041 2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation
• 17 - PMID 33197159 Cryoablation or Drug Therapy for Initial Treatment of Atrial Fibrillation, NEJM (2020)
• 18 - PMID 34253538 - Risk of atrial fibrillation in athletes: a systematic review and meta-analysis, Br J Sports Med (2021)
• 19 - PMID 28506916 - 2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation, Heart Rhythm (2017)
• 20 - PMID 28934408 - Device-detected subclinical atrial tachyarrhythmias: definition, implications and management-an European Heart Rhythm Association (EHRA) consensus document, Europace (2017)
• 21 - PMID 36780164 - Prevalence and Incidence of Atrial Fibrillation Among Older Primary Care Patients, JAMA Netw Open (2023)
• 22 - PMID 38033089 - 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines, Circulation (2023)
• 23 - PMID 20003371 - Short-term and long-term success of electrical cardioversion in atrial fibrillation in managed care system, Int Arch Med (2009)