Atrial Fibrillation

KEY FEATURES

Essentials of Diagnosis

• Presents as an irregularly irregular heart rhythm on examination and electrocardiogram (ECG)

  • Prevention of stroke should be considered in all patients with risk factors for stroke, such as

    • Heart failure (HF)

    • Hypertension

    • Age 65 or older

    • Diabetes mellitus

    • Prior history of stroke or transient ischemic attack (TIA)

    • Vascular disease

  • Heart rate control with beta-blocker or calcium channel blockers generally required

• Restoration of sinus rhythm with cardioversion, antiarrhythmic medications, or catheter ablation in symptomatic patients

General Considerations

• The most common chronic arrhythmia, with an estimated global prevalence of 50 million individuals

  • Rarely life-threatening

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

  • In patients with heart disease, atrial fibrillation can be caused by

    • Rheumatic and other forms of valvular heart disease

    • Dilated cardiomyopathy

    • Hypertension

    • Coronary heart disease

    • Thyrotoxicosis

• In patients without heart disease, paroxysmal episodes can be caused by

  • Pericarditis

  • Chest trauma

  • Thoracic or cardiac surgery

  • Thyroid disorders

  • Obstructive sleep apnea

  • Pulmonary disease

  • Electrolyte disturbances

  • Acute alcohol excess or withdrawal

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

• Untreated, the rate of stroke is approximately 5% per year

• Patients with the following factors are at substantially higher risk (up to nearly 20% per year in patients with multiple risk factors)

  • Significant obstructive valvular disease

  • Chronic HF or left ventricular (LV) dysfunction

  • Diabetes mellitus

  • Hypertension

  • Age over 75 years

  • History of prior stroke or other embolic events

• In patients presenting with cryptogenic stroke, a substantial portion of them will have asymptomatic or "subclinical" atrial fibrillation

  • Can be detected with implantable loop recorders

CLINICAL FINDINGS

Symptoms and Signs

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

• Atrial fibrillation is the only common arrhythmia in which the ventricular rate is rapid and the rhythm very irregular

• Pulse deficit: a difference between the apical rate and the pulse rate; this deficit is greater when the ventricular rate is high

  • Often occurs paroxysmally before becoming the established rhythm

  • Those who are older or have inactive lifestyles may have relatively few symptoms

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

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, LV 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 ...