[Epidemiology, risk factors, and pathogeny of atrial fibrillation and atrial flutter].
Atrial fibrillation is a frequent arrhythmia which has a high prevalence after 65 years of age, thus the typical patient's age is about 75. There are two atrial fibrillation predictors: traditional factors of cardiovascular risk (age, male sex, high blood pressure, diabetes), and structural heart disorders (heart failure, valvular heart disease). All preventive measures to reduce atrial fibrillation incidence, must be directed towards these factors. Additionally, left atrial size, ejection fraction and ventricular hypertrophy are echocardiographic predictors. Atrial fibrillation doubles the mortality rate and is related to an annual stroke rate of 4.5%. The stroke risk factors are: age, hypertension, diabetes, previous stroke, congestive heart failure, coronary heart disease, mitral stenosis, prosthetic heart valves and thyrotoxicosis. Left atrial size and ventricular disfunction are echocardiographic stroke risk factors. Each patient's risk can be stratified on the basis of these factors. All of this information is essential to handle the arrhythmia appropriately; this arrhythmia may be more important than has been thought. Atrial flutter is not very frequent and so it is less studied; however it is an arrhythmia with a similar clinical context to atrial fibrillation, although, probably, with a smaller embolic risk.