The evaluation of AFib involves diagnosis, determination of the cause of the arrhythmia, and classification of the arrhythmia. A minimal evaluation should be performed in all individuals with AF. This includes a history and physical examination, ECG, transthoracic echocardiogram, and routine blood work. The goal of this evaluation is to determine the general treatment regimen for the individual. If results of the general evaluation warrant it, further studies may be then performed. Certain individuals may benefit from an extended evaluation which may include an evaluation of the heart rate response to exercise, exercise stress testing, a chest x-ray, trans-esophageal echocardiography, and other studies. AFib screening is not generally performed, although a study of routine pulse checks or ECGs during routine office visits found that the annual rate of detection of AF in elderly patients improved from 1.04% to 1.63%; selection of patients for prophylactic anticoagulation would improve stroke risk in that age category. This estimated sensitivity of the routine primary care visit is 64%. This low result probably reflects the pulse not being checked routinely or carefully. The most commonly used tools to diagnose AFib include: History & Physical Exam: Most of the patients will have symptoms of fast irregular heart beats. The history of the individual's AFib episodes is likely the most important part of the evaluation. On physical exam they have irregularly irregular heart beat upon palpation and auscultation. Distinctions should be made to those who are entirely asymptomatic (silent AFib) when they are in AF (in which case the AF is found as an incidental finding on an ECG or physical examination) and those who have gross and obvious symptoms due to AF and can pinpoint whenever they go into AF and revert to sinus rhythm. Evaluating the cumulative burden and assessing the need for anticoagulation is a challenge in patients who have silent AFib. Routine blood work: While many cases of AF have no definite cause, it may be the result of various other problems (see below). Hence, renal function and electrolytes are routinely determined, as well as thyroid-stimulating hormone (commonly suppressed in hyperthyroidism and of relevance if amiodarone is administered for treatment) and a blood count. In acute-onset AF associated with chest pain, cardiac troponins or other markers of damage to the heart muscle or congestive heart failure may be ordered. Coagulation studies (INR/aPTT) are usually performed, as anticoagulant medication may be commenced. Electrocardiogram (ECG): The ECG draws a picture on thermal graph paper of the electrical impulses traveling through the heart muscle. Instead of a regular rhythm, AF records a chaotic and irregular rhythm. Atrial fibrillation is diagnosed on an electrocardiogram (ECG), whenever irregular heart beat is suspected. Characteristic findings are the absence of P waves, with unorganized electrical activity in their place, and irregularity of R-R interval due to irregular conduction of impulses to the ventricles Ambulatory Holter monitor: If paroxysmal AFib is suspected but an ECG during an office visit only shows a regular rhythm, AF episodes may be detected and documented with the use of ambulatory Holter monitoring (e.g. for a day or two). A small external recorder, worn over the chest for a short period, usually 24 to 72 hours. Electrodes (sticky pads) are placed on the skin of your chest. Wires are attached from the electrodes to the monitor. The electrical impulses are continuously recorded and stored in the monitor. After the monitor is removed, a technician uses a computer to analyze the data to evaluate the heart rhythm. . In individuals with symptoms of significant shortness of breath with exertion or palpitations on a regular basis, a holter monitor may be of benefit to determine if rapid heart rates (or unusually slow heart rates) during atrial fibrillation are the cause of the symptoms. Transthoracic echocardiogram: This is the ultrasound test of the heart which provides structural and functional details of the heart. A non-invasive transthoracic echocardiogram (TTE) is generally performed in newly diagnosed AF, as well as if there is a major change in the patient's clinical state. This ultrasound-based scan of the heart may help identify valvular heart disease (which may increase the risk of stroke manifold), left and right atrial size (which indicates likelihood that AF may become permanent), left ventricular size and function, peak right ventricular pressure (pulmonary hypertension), presence of left ventricular hypertrophy and pericardial disease. Significant enlargement of both the left and right atria is associated with long-standing atrial fibrillation and, if noted at the initial presentation of atrial fibrillation, suggests that the atrial fibrillation is likely of a longer duration than the individual's symptoms. An extended evaluation is generally not necessary in most individuals with atrial fibrillation, and is only performed if abnormalities are noted in the limited evaluation, if a reversible cause of the atrial fibrillation is suggested, or if further evaluation may change the treatment course.