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Atrial Fibrillation

Practice Essentials

Atrial fibrillation (AF) has strong associations with other cardiovascular diseases, such as heart failure, coronary artery disease (CAD), valvular heart disease, diabetes mellitus, and hypertension. It is characterized by an irregular and often rapid heartbeat (see the first image below). The exact mechanisms by which cardiovascular risk factors predispose to AF are not understood fully but are under intense investigation. Catecholamine excess, hemodynamic stress, atrial ischemia, atrial inflammation, metabolic stress, and neurohumoral cascade activation are all purported to promote AF.

Ventricular rate varies from 130-168 beats per min

Ventricular rate varies from 130-168 beats per minute. Rhythm is irregularly irregular. P waves are not discernible.

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The image on the right is a reconstructed 3-dimensional image of the right atrium in a patient undergoing atrial fibrillation ablation. The figure on the left was created with a mapping catheter using Endocardial Solutions mapping technology. It represents the endocardial shell of the right atrium and is used as the template during left atrial ablation procedures.

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Signs and symptoms

The clinical presentation of AF spans the entire spectrum from asymptomatic AF with rapid ventricular response to cardiogenic shock or devastating cerebrovascular accident (CVA). Unstable patients requiring immediate direct current (DC) cardioversion include the following:

Patients with decompensated congestive heart failure (CHF)

Patients with hypotension

Patients with uncontrolled angina/ischemia

Initial history and physical examination include the following:

Documentation of clinical type of AF (paroxysmal, persistent, long-standing persistent or permanent)

Assessment of type, duration, and frequency of symptoms

Assessment of precipitating factors (eg, exertion, sleep, caffeine, alcohol use)

Assessment of modes of termination (eg, vagal maneuvers)

Documentation of prior use of antiarrhythmics and rate-controlling agents

Assessment of presence of underlying heart disease

Documentation of any previous surgical or percutaneous AF ablation procedures

Airway, breathing, and circulation (ABCs)

Vital signs (particularly heart rate, blood pressure, respiratory rate, and oxygen saturation)

Evaluation of head and neck, lungs, heart, abdomen, lower extremities, and nervous system

See Clinical Presentation for more detail.

Diagnosis

Findings from 12-lead electrocardiography (ECG) usually confirm the diagnosis of AF and include the following:

Typically irregular ventricular rate (QRS complexes)

Absence of discrete P waves, replaced by irregular, chaotic F waves

Aberrantly conducted beats after long-short R-R cycles (ie, Ashman phenomenon)

Heart rate (typically 110-140 beats/min, rarely >160-170 beats/min)

Preexcitation

Left ventricular hypertrophy

Bundle-branch block or intraventricular conduction delay

Acute or prior myocardial infarction (MI)

Transthoracic echocardiography (TTE) is helpful for the following applications:

To evaluate for valvular heart disease

To evaluate atrial and ventricular chamber and wall dimensions

To estimate ventricular function and evaluate for ventricular thrombi

To estimate pulmonary systolic pressure (pulmonary hypertension)

To evaluate for pericardial disease

Transesophageal echocardiography (TEE) is helpful for the following applications:

To evaluate for atrial thrombus (particularly in the left atrial appendage)

To guide cardioversion (if thrombus is seen, cardioversion should be delayed)

See Workup for more detail.

Management

The cornerstones of AF management are rate control and anticoagulation,
as well as rhythm control for those symptomatically limited by AF. The clinical decision to use a rhythm-control or a rate-control strategy requires integrated consideration of the following:

Degree of symptoms

Likelihood of maintaining sinus rhythm after successful cardioversion

Presence of comorbidities

Candidacy for AF ablation

Anticoagulation

The 2014 American College of Cardiology (ACC)/American Heart Association (AHA)/Heart Rhythm Society (HRS) guidelines on anticoagulation for patients with nonvalvular AF include the following
:

No risk factors: No anticoagulation or antiplatelet therapy

One moderate-risk factor: Aspirin 81-325 mg/day, or anticoagulants

Any high-risk factor or more than one moderate-risk factor: Anticoagulants

Risk factors for thromboembolism in AF are as follows:

High-risk factors: Prior stroke or transient ischemic attack (TIA), systemic thromboembolism, or age 75 years or older

Moderate-risk factors: Age 65-74 years, female sex, hypertension, diabetes mellitus, heart failure, arterial disease (prior myocardial infarction, peripheral arterial disease, aortic plaque)

Anticoagulation is indicated as follows:

Patients with newly diagnosed AF and those awaiting electrical cardioversion can be started on intravenous (IV) heparin or low-molecular-weight heparin (LMWH) (1 mg/kg twice daily)

Concomitantly, patients can be started on warfarin in an inpatient setting while awaiting a therapeutic international normalized ratio (INR) value of 2-3

Newer oral anticoagulants present an alternative to warfarin in patients with nonvalvular AF; their onset of action is almost immediate and eliminates the need for bridging with heparin/LMWH.

Newer oral anticoagulants that have been approved by the US Food and Drug Administration (FDA) include the following:

One direct thrombin inhibitor: Dabigatran

Three factor Xa inhibitors: Rivaroxaban, apixaban, edoxaban

Risk of bleeding

Optimal long-term strategies for AF management should be based on a thoroughly integrated consideration of patient-specific factors and the likelihood of success. Selection of an appropriate antithrombotic regimen should be balanced between the risk of stroke and the risk of bleeding.

Factors that increase the risk of bleeding with anticoagulation include the following:

History of bleeding (the strongest predictive risk factor)

Age older than 75 years

Liver or renal disease

Malignancy

Thrombocytopenia or aspirin use

Hypertension

Diabetes mellitus

Anemia

Prior stroke

Fall risk

Genetic predisposition

Supratherapeutic INR (for warfarin)

For patients with clinical indications for anticoagulation who are at an unacceptably high risk of clinically significant bleeding, two treatment alternatives exist:

Left atrial appendage isolation using the catheter-based WATCHMAN device (the only FDA device currently approved in the United States)

Left atrial appendage ligation using the LARIAT epicardial/endocardial suture system

Rate control strategies

Medications (non-dihydropyridine calcium channel blockers, beta-blockers, digoxin [rarely as monotherapy], amiodarone [mainly for patients who are intolerant of, or unresponsive to, other agents])

Atrioventricular node modification with placement of a permanent pacemaker (invasive procedure indicated in patients when other rate and rhythm control alternatives have been exhausted)

Rhythm control strategies

Electrical cardioversion (generally employed as a the first-line management strategy in young symptomatic patients)

Medications (flecainide, propafenone, dofetilide, amiodarone, sotalol)

Ablation (catheter based, surgical, or hybrid)

Catheter ablation is recommended in the 2014 ACC/AHA/HRS AF guidelines for the following indications
:

It is useful for patients with symptomatic paroxysmal AF who are intolerant of, or whose condition is refractory to, rhythm-control medications.

It is reasonable as a treatment for patients with symptomatic persistent AF who are intolerant of, or whose condition is refractory to, a rhythm-control strategy using medications.

It is a reasonable alternative for patients with recurrent symptomatic paroxysmal AF who have not tried a rhythm-control medication.

See Treatment and Medication for more detail.

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