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Atrial fibrillation
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Atrial fibrillation

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Contributors: Ryan Hoefen MD, PhD, Lowell A. Goldsmith MD, MPH
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Synopsis

Atrial fibrillation is the result of disordered electrical activity within the atria, resulting in a lack of coordinated atrial contraction. The atrioventricular (AV) node, which is bombarded with electrical activity, acts as an electrical filter and prevents conduction of all these electrical stimuli. The ventricles are activated with an irregular, random rhythm with an overall rate that is dependent on the electrical conductivity of the AV node. Patients without significant AV node disease who are not on AV nodal blocking medications will generally have significant tachycardia with the onset of atrial fibrillation.

The initiation of the electrical wavelets that cause atrial fibrillation is usually induced by an underlying mechanical irritation of the atria through stretching (increased atrial filling pressures), infiltration, or inflammation. Proximate causes may include valvular heart disease, hypertension, hypertrophic cardiomyopathy, ischemia, congestive heart failure, congenital heart disease, pulmonary embolism, hyperthyroidism, infection, or surgery. Other reported contributing factors include obesity, diabetes, the metabolic syndrome, chronic kidney disease, family history, electrolyte abnormalities (ie, low serum magnesium), alcohol, caffeine, and certain medications (eg, theophylline, adenosine, digitalis, and bisphosphonates). In some cases, no underlying cause is apparent.

Episodes of atrial fibrillation may spontaneously resolve, with restoration of normal sinus rhythm within seconds to days. In other cases, it may be persistent if medical intervention is not performed. When restoration of normal sinus rhythm is indicated, electrical or pharmacologic cardioversion may restore normal sinus rhythm.

Atrial fibrillation is a very common cardiac arrhythmia, carrying a lifetime risk of approximately 25%. It may occur at any age, but is increasingly prevalent with advancing age. The prevalence also increases with underlying heart disease. There is a slightly higher prevalence in males than females in all age groups.

In many patients, the ventricular rate is rapid, producing sudden onset of symptoms that may include palpitations, dizziness, lightheadedness, or near syncope. Particularly in those with coexistent cardiac or systemic illness, the extreme tachycardia can also result in hypotension, subendocardial ischemia, congestive heart failure, or frank syncope. In patients with slower AV node conduction, the ventricular rate may be relatively normal and the patient may be completely asymptomatic. In such patients, atrial fibrillation may be an incidental physical exam or ECG finding.

Patients with ventricular preexcitation (Wolff-Parkinson-White syndrome) require special attention. In patients with a bypass tract allowing conduction of fibrillation potentials from the atrium to the ventricle at a rapid rate, thus bypassing the AV node, the ventricular rate may become extremely fast, destabilizing the ventricle and resulting in ventricular fibrillation. AV nodal blocking medications should not be used in these patients, since they may actually enhance conduction down a bypass tract, increase the ventricular rate, and further destabilize the ventricle.

Patients with atrial fibrillation are at increased risk of arterial thromboembolism such as an embolic stroke due to increased hemostasis in the left atrium lacking coordinated contractility. The risk of such events complicating atrial fibrillation increases with age, coexistent congestive heart failure, hypertension, diabetes, and prior history of a stroke. All patients with atrial fibrillation should be risk stratified for the possibility of thromboembolism, and treatment with antiplatelet and/or anticoagulant medications should be considered. In some cases, a stroke or other thromboembolic event may be the initial presentation of atrial fibrillation.

Pediatric Patient Considerations:
Although rare among children, atrial fibrillation is nearly always an indicator of underlying structural heart disease in young patients.

Codes

ICD10CM:
I48.91 – Unspecified atrial fibrillation

SNOMEDCT:
49436004 – Atrial fibrillation

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

Best Tests

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Management Pearls

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Therapy

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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References

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Last Updated: 08/29/2016
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Atrial fibrillation
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Atrial fibrillation : Chest pain, Fatigue, Delirium, Heart palpitations, Syncope, Dyspnea, Generalized weakness
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