Atrial Fibrillation and Atrial Flutter

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This topic covers both atrial fibrillation (AFib) and atrial flutter (AFlut).

Description

  • AFib: paroxysmal or continuous supraventricular tachyarrhythmia typically originating from the left atrium characterized by rapid, uncoordinated atrial electrical activity and an irregularly irregular ventricular response. The ventricular rate can become 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. In typical AFlut, the atrial rate is between 250 and 350 beats/min and is often manifested as “saw-tooth” flutter (F) waves on the ECG, inverted in the inferior leads and upright in V1. AFlut can have a regular ventricular response and commonly occurs with 2:1 or 3:1 AV block, but also can have an irregular ventricular rate when there is variable AV block.
  • 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: Long standing AFib where sinus rhythm cannot be restored/maintained.
    • Nonvalvular AFib: absence of moderate-to-severe mitral stenosis or a mechanical heart valve
  • Lone AFib occurs in patients <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 of age to >1.5%/year >80 years of age
  • Lifetime risk: 25% for those ≥40 years of age
  • AFlut is less common.

Prevalence

  • Estimated at 0.4–1.0% in general population, with 8.6 million patients in North America
  • Increases with age, up to 8% in those ≥80 years of age

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 and sleep apnea
  • Idiopathic: lone AFib
  • Postsurgical: cardiac and noncardiac surgery
  • Patients with paroxysmal episodes are usually associated with premature atrial beats and/or bursts of tachycardia, originating in pulmonary veins.
  • 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, obesity, sleep apnea, and type 2 DM are the most important risk factors for both AFib and AFlut.

General Prevention

AHA guidelines (1)[C], based on strong class 1 evidence recommend comprehensive lifestyle and risk factor modification, including weight loss, exercise, smoking cessation, alcohol reduction, and optimal blood pressure control as central to both primary and secondary prevention of AFib.

Commonly Associated Conditions

HTN, stroke and other cardiac diseases

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