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 ...