Known risk factors for atrial fibrillation include age, male sex, valvular heart disease, systolic/diastolic dysfunction, hypertension, and diabetes. Patients with nonvalvular afib and presence of other risk factors have a five-fold increase risk for stroke. In contrast, patients with valvular heart disease and afib have an even higher risk for stroke up to 17-fold. At least four large clinical trials have clearly demonstrated that anticoagulation with aspirin and/or warfarin can decrease the risk of stroke by 50-80%. (NEJM study).

Atrial fibrillation may be secondary to reversible causes, and treatment of the underlying diseases usually terminates the arrhythmia. Some of those most common etiologies include alcohol intake (holiday heart syndrome), infectious state, myocardial infarction, hyperthyroidism, and pulmonary embolism (Table 1). If none of those causes can be identified in a patient less than 60 year of age, the arrhythmia is referred to as lone afib.

More frequently, atrial fibrillation will be associated with an underlying structural heart disease such as valvular problems, heart failure with chamber dilatation, coronary artery disease, congenital heart disease, hypertrophic or dilated cardiomyopathy, and atrial septal defect. Other conditions causing a restrictive cardiomyopathy such as amyloidosis, hemochromatosis, endomyocardial fibrosis, and tumor have also been associated with an increase risk for afib.

Table 1. Etiologies of Atrial Fibrillation
1. Atrial pressure elevation (leading to dilatation)
    Valvular disease: mitral/tricuspid regurgitation or stenosis,
    mitral valve prolapse
    Systolic or diastolic dysfunction
    Hypertrophic cardiomyopathy (HCM)
    Pulmonary hypertension (COPD with cor pulmonale)
    Pulmonary embolism
    Intracardiac thrombi or tumor
2. Inflammatory and infiltrative process
    Age induced atrial fibrosis
3. Infectious process
    Any infections and fever
4. Endocrine disorders
5. Neurogenic
    Subarachnoid hemorrhage
6. Atrial ischemia
    Myocardial infarction
7. Drugs
    Alcohol (holiday heart)
8. Idiopathic
    Lone afib if less than 60 years old
9. Familial

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