Atrial Fibrillation

KEY FEATURES

Essentials of Diagnosis

• Presents as an irregularly irregular heart rhythm on examination and 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, affecting approximately 9% of individuals aged > 65

• Rarely life-threatening

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

• 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 heart failure 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 has asymptomatic, intermittent 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)

• 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

• 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 beta-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, 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 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