Atrial Fibrillation and Atrial Flutter
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This topic covers both atrial fibrillation (AFib) and atrial flutter (AFlut).
- 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 bpm).
- AFlut: Paroxysmal or continuous supraventricular tachyarrhythmia with rapid but organized atrial electrical activity. The atrial rate is typically between 250 and 350 bpm 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 bpm.
- AFib and AFlut are related arrhythmias, sometimes seen in the same patient. Distinguishing the two is important, as there may be implications for management.
- Clinical classifications:
- Paroxysmal: self-terminating episodes, usually <7 days
- Persistent: sustained >7 days, usually requiring pharmacologic or DC cardioversion to restore sinus rhythm
- Permanent: Sinus rhythm cannot be restored or maintained. It is a shared decision between patient and clinician as to when to cease further attempts to restore and/or maintain sinus rhythm.
- Nonvalvular AFib: absence of rheumatic mitral stenosis, a mechanical or bioprosthetic heart valve or mitral valve repair
- Lone AFib occurs in patients <60 years (with possible genetic predisposition) who have no clinical or echocardiographic evidence of cardiovascular disease, including hypertension (HTN).
- Incidence/prevalence increases significantly with age.
- Young patients with AFib, particularly lone AFib, are most commonly males.
- AFib: from <0.1%/year <40 years to >1.5%/year >80 years
- Lifetime risk: 25% for those ≥40 years
- AFlut is less common.
- Estimated at 0.4–1% in general population, with 2.7 million patients in America
- Increase with age, up to 8% in those ≥80 years
Etiology and Pathophysiology
- Cardiac: HTN, ischemic heart disease, heart failure, 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
- Endocrine: hyperthyroidism, diabetes
- Postoperative: cardiac, pulmonary, or esophageal
- Idiopathic: lone AFib
- 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. This is often subclinical and usually not detectable with current cardiac imaging techniques but plays an important role in the pathogenesis of the arrhythmia.
- 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.”
Familial forms are rare but do exist. There are ongoing efforts to identify the genetic underpinnings of such cases.
Age, HTN, and obesity are the most important risk factors for both AFib and AFlut.
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 in some.
Commonly Associated Conditions
HTN and other cardiac diseases