The work-up for AF involves careful history taking and physical examination, laboratory studies (including a CBC, serum electrolyte tests, toxicology screening, and thyroid function tests), ECG, chest radiography, and echocardiography. The patient's history should include the time of onset, the frequency of episodes, any associated symptoms, and any history of treatment for AF. Laboratory studies may be useful in determining possible etiologies of AF. The WBC count may help in finding an underlying infection, and the hemoglobin concentration may demonstrate anemia. Electrolyte levels, such as magnesium and potassium, may be abnormal, and an elevated creatinine value may indicate renal insufficiency.
Certain illicit drugs can cause a rapid heart rate; therefore, a toxicology screening may be useful when indicated.
Hyperthyroidism can predispose patients to AF. For this reason, an evaluation of thyroid function with measurement of the patient's thyroid-stimulating hormone level is warranted.
AF can be diagnosed when the ECG shows an irregular rhythm with the absence of P waves. In addition, examine the patient for any signs of left ventricular hypertrophy, bundle branch blocks, and atrioventricular nodal blocks, as well as for evidence of cardiac ischemia or previous myocardial infarction. Chest radiographs may be useful in evaluating the cardiac silhouette for cardiomegaly and the lung fields and vasculature for evidence of airspace disease or pulmonary edema.
A transthoracic echocardiogram should be obtained to identify the size and motion of the atria, ventricles, and cardiac valves, and it can reveal pericardial disease. Transesophageal echocardiography is more sensitive than transthoracic echocardiography for diagnosing left atrial thrombus or left atrial appendage thrombus.
Rate control is important in patients who present with rapid AF of more than 72 hours' duration, and beta-blockers (metoprolol) or calcium-channel blockers (diltiazem) are recommended in patients who do not have an accessory pathway. Digoxin and amiodarone are the drugs of choice for controlling rapid AF in patients with left ventricular failure and no accessory pathway; however, digoxin should be loaded over 24 hours.
Anticoagulation treatment is also recommended for most patients with AF to help reduce the risk for stroke. The CHADS2 and CHA2DS2-VASc scores can help determine risk and help make decisions about anticoagulation treatment. These scores use such components as age; sex; and associated conditions, including hypertension, congestive heart failure, diabetes, vascular disease, or a prior stroke.
Anticoagulation is typically achieved with warfarin (dosed to maintain an international normalized ratio of 2-3) or one of the new novel oral anticoagulants (NOAC), such as dabigatran, rivaroxaban, or apixaban. In patients considered to be at low risk for thromboembolism or in patients who have a contraindication to the use of warfarin or NOACs, aspirin can be administered.
Conversion to sinus rhythm may be achieved with pharmacologic agents or with synchronized external electrical cardioversion. Conversion should be done only when the risk for thromboembolism is limited, as in patients with an onset of symptoms less than 72 hours before presentation, in those who received anticoagulation for 4 weeks, or in those in whom transesophageal echocardiography rules out a left atrial or left atrial appendage thrombus. For patients with chronic symptomatic AF, catheter-based ablation (via pulmonary vein isolation) is used to decrease the burden.
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