Description

• AFib: paroxysmal or continuous supraventricular tachyarrhythmia characterized by rapid, uncoordinated atrial electrical activity and an irregularly irregular ventricular response; in most patients, the ventricular rate is rapid because the atrioventricular (AV) node is bombarded with very frequent atrial electrical impulses (400 to 600 beats/min).
• AFlut: paroxysmal or continuous supraventricular tachyarrhythmia with rapid but organized atrial electrical activity; the atrial rate is typically between 250 and 350 beats/min and is often manifested as “saw-tooth” flutter (F) waves on the ECG, particularly in the inferior leads and V₁. AFlut commonly occurs with 2:1 or 3:1 AV block, so the ventricular response may be regular and typically at a rate of 150 beats/min.
• AFib and AFlut are related arrhythmias, sometimes seen in the same patient. Distinguishing the two is important because there may be implications for management.
• Clinical classifications:
  • Paroxysmal: self-terminating episodes, usually <7 days
  • Persistent: sustained >7 days, usually requiring pharmacologic or electrical cardioversion to restore sinus rhythm
  • Permanent: Sinus rhythm cannot be restored or maintained.
  • Nonvalvular AFib: absence of moderate-to-severe mitral stenosis or a mechanical heart valve
• Lone AFib occurs in patients aged <60 years (with possible genetic predisposition) who have no clinical or echocardiographic evidence of cardiovascular disease, including hypertension (HTN).

Epidemiology

• Incidence/prevalence increases significantly with age.
• Young patients with AFib, particularly lone AFib, are most commonly males.

Incidence

• AFib: from <0.1%/year <40 years to >1.5%/year >80 years
• Lifetime risk: 25% for those aged ≥40 years
• AFlut is less common.

Prevalence

• Estimated at 0.4–1% in general population, with 2.7 million patients in America
• Increases with age, up to 8% in those ≥80 years

Etiology and Pathophysiology

• Cardiac: HTN, acute coronary syndrome (ACS), congestive heart failure (CHF), valvular heart disease, cardiomyopathy, pericarditis, and infiltrative heart disease
• Pulmonary: pulmonary embolism (PE), chronic obstructive pulmonary disease (COPD), obstructive sleep apnea, pneumonia
• Ingestion: ethanol, caffeine, nicotine
• Endocrine: hyperthyroidism, diabetes mellitus (DM)
• Obesity
• Postoperative: cardiac, pulmonary, or esophageal
• Idiopathic: lone AFib
• Iatrogenic: amiodarone
• Patients with paroxysmal episodes are usually associated with premature atrial beats and/or bursts of tachycardia, originating in pulmonary vein ostia or other sites.
• Many patients with AFib are thought to have some degree of atrial fibrosis or scarring.
• Autonomic (vagal and sympathetic) tone may play a role in triggering the arrhythmia.
• The presence of AFib is associated with electrical and structural remodeling processes that promote arrhythmia maintenance in the atria, termed “AFib begets AFib.”

Genetics
Familial forms are rare but do exist. There are ongoing efforts to identify the genetic underpinnings of such cases.

Risk Factors

Age, HTN, and obesity are the most important risk factors for both AFib and AFlut.

General Prevention

Adequate control of HTN may prevent development of AFib due to hypertensive heart disease and is the most significant modifiable risk factor for AFib. Weight reduction may decrease the risk of AFib in obese patients. Ethanol consumption may trigger AFib.

Commonly Associated Conditions

HTN, stroke, and other cardiac diseases