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For further information, see CMDT Part 10-32: Atrial Fibrillation

Key Features

Essentials of Diagnosis

  • Presents as an irregularly irregular heart rhythm on exam and ECG

  • Two main treatment strategies for long-term management of atrial fibrillation are rate control or rhythm control, although they are not mutually exclusive

    • Rate control with β-blocker or calcium channel blockers generally required

    • Restoration of sinus rhythm with electrical cardioversion, antiarrhythmic medications, or catheter ablation

  • The CHADS2 score and the CHA2DS2-VASc score are risk assessment tools that can guide anticoagulation decisions

General Considerations

  • The most common chronic arrhythmia, affecting approximately 9% of individuals older than age 65

  • The incidence increases significantly with age starting in the 7th decade of life

  • Rarely life-threatening

  • If the ventricular rate is rapid enough, it can precipitate hypotension, myocardial ischemia, or myocardial dysfunction

  • Approximately 60% of patients with a first episode will revert to sinus rhythm within 24 hours

  • Substantial portion of the aging population with hypertension has asymptomatic or "subclinical" atrial fibrillation, which is also associated with increased risk of stroke

Clinical Findings

Symptoms and Signs

  • Irregularly irregular pulse (harder to distinguish with more rapid heart rates)

  • Often occurs paroxysmally before becoming the established rhythm

  • Older or inactive individuals may have relatively few symptoms

  • However, some patients are made uncomfortable by the irregular rhythm due to palpitations or fatigue

  • In patients with heart disease, rheumatic disease, and other valvular heart disease, atrial fibrillation can be caused by

    • Dilated cardiomyopathy

    • Atrial septal defect

    • Hypertension

    • Coronary heart disease

    • Thyrotoxicosis

  • In patients with normal hearts, paroxysmal episodes can be caused by

    • Pericarditis

    • Chest trauma

    • Thoracic or cardiac surgery

    • Thyroid disorders

    • Obstructive sleep apnea

    • Pulmonary disease (pneumonia, pulmonary embolism)

    • Electrolyte disturbances

    • Acute alcohol excess or withdrawal

    • Medications, such as β-adrenergic agonists, inotropes, bisphosphonates, and certain chemotherapeutics

Diagnosis

  • ECG

    • Surface ECG typically demonstrates erratic, disorganized atrial activity between discrete QRS complexes occurring in an irregular pattern

    • Atrial activity may be very fine and difficult to detect on the ECG, or quite coarse and often mistaken for atrial flutter

  • Echocardiography

    • Provides assessment of chamber volumes, left ventricular size and function, or the presence of concomitant valvular heart disease

    • Should be performed in all patients with a new diagnosis of atrial fibrillation

  • Transesophageal echocardiography is the most sensitive imaging modality to identify thrombi in the left atrium or left atrial appendage prior to any attempt at chemical or electrical cardioversion

  • Ambulatory ECG monitoring or event recorders are indicated when paroxysmal atrial fibrillation is suspected

  • Obtain thyroid-stimulating hormone level to exclude thyrotoxicosis as a potential cause

Treatment

Medications

  • If atrial fibrillation persists for > 1 week

    • Spontaneous conversion is unlikely

    • Management consists of rate control and anticoagulation

  • Rate control

    • Rate control ...

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