A 12-lead ECG showing atrial fibrillation at approximately 132 beats per minute Diagram of normal sinus rhythm as seen on ECG. In atrial fibrillation the P waves, which represent depolarization of the top of the heart, are absent. The evaluation of atrial fibrillation involves a determination of the cause of the arrhythmia, and classification of the arrhythmia. Diagnostic investigation of AF typically includes a complete history and physical examination, ECG, transthoracic echocardiogram, complete blood count, and serum thyroid stimulating hormone level. Screening Numerous guidelines recommend opportunistic screening for atrial fibrillation in those 65 years and older. These organizations include the: • European Society of Cardiology, • National Heart Foundation of Australia and the Cardiac Society of Australia and New Zealand • European Heart Rhythm Society, • AF-SCREEN International Collaboration, • Royal College of Physicians of Edinburgh • European Primary Care Cardiovascular Society, and • Irish Health Information and Quality Authority. Single timepoint screening detects undiagnosed AF, which is often asymptomatic, in approximately 1.4% of people in this age group. A Scottish inquiry into atrial fibrillation estimated that as many as one-third of people with AF are undiagnosed. Despite this, in 2018, the United States Preventive Services Task Force found insufficient evidence to determine the usefulness of routine screening. Given the importance of having a pathway to treatment, general practice is potentially an ideal setting to conduct AF screening. General practice was identified as a 'preferred' setting for AF screening by the AF-SCREEN international collaboration report due to the availability of nursing support and the natural pathway to treatment. Screening in primary care has been trialled in a number of countries. These include: a recent Canadian study conducted in 184 general practices; a screening program conducted alongside influenza vaccinations in 10 Dutch practices; and several Australian studies showed that opportunistic screening in primary care by GPs and nurses using eHealth tools was feasible. Minimal evaluation In general, the minimal evaluation of atrial fibrillation should be performed in all individuals with AF. The goal of this evaluation is to determine the general treatment regimen for the individual. If the results of the general evaluation warrant it, further studies may then be performed. History and physical examination The history of the individual's atrial fibrillation episodes is probably the most important part of the evaluation. Distinctions should be made between those who are entirely asymptomatic 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 or revert to sinus rhythm. Routine bloodwork While many cases of AF have no definite cause, it may be the result of various other problems. Hence, kidney 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 may be ordered. Coagulation studies (INR/aPTT) are usually performed, as anticoagulant medication may be commenced. Electrocardiogram ECG of atrial fibrillation (top) and normal sinus rhythm (bottom). The purple arrow indicates a P wave, which is lost in atrial fibrillation. Atrial fibrillation is diagnosed on an electrocardiogram (ECG), an investigation performed routinely whenever an irregular heartbeat is suspected. Characteristic findings are the absence of P waves, with disorganized electrical activity in their place, and irregular R–R intervals due to irregular conduction of impulses to the ventricles. At very fast heart rates, atrial fibrillation may look more regular, which may make it more difficult to separate from other supraventricular tachycardias or ventricular tachycardia. QRS complexes should be narrow, signifying that they are initiated by normal conduction of atrial electrical activity through the intraventricular conduction system. Wide QRS complexes are worrisome for ventricular tachycardia, although, in cases where there is a disease of the conduction system, wide complexes may be present in A-fib with a rapid ventricular response. If paroxysmal AF is suspected, but an ECG during an office visit shows only a regular rhythm, AF episodes may be detected and documented with the use of ambulatory Holter monitoring (e.g., for a day). If the episodes are too infrequent to be detected by Holter monitoring with reasonable probability, then the person can be monitored for longer periods (e.g., a month) with an ambulatory event monitor. Echocardiography In general, a non-invasive transthoracic echocardiogram (TTE) is performed in newly diagnosed AF, as well as if there is a major change in the person's clinical state. This ultrasound-based scan of the heart may help identify valvular heart disease (which may greatly increase the risk of stroke and alter recommendations for the appropriate type of anticoagulation), left and right atrial size (which predicts the likelihood that AF may become permanent), left ventricular size and function, peak right ventricular pressure (pulmonary hypertension), presence of left atrial thrombus (low sensitivity), 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 to be of a longer duration than the individual's symptoms. Extended evaluation In general, an extended evaluation is not necessary for most individuals with atrial fibrillation and is performed only 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. Chest X-ray In general, a chest X-ray is performed only if a pulmonary cause of atrial fibrillation is suggested, or if other cardiac conditions are suspected (in particular congestive heart failure). This may reveal an underlying problem in the lungs or the blood vessels in the chest. In particular, if underlying pneumonia is suggested, then treatment of the pneumonia may cause the atrial fibrillation to terminate on its own. Transesophageal echocardiogram A regular echocardiogram (transthoracic echo/TTE) has a low sensitivity for identifying blood clots in the heart. If this is suspected (e.g., when planning urgent electrical cardioversion), a transesophageal echocardiogram/TEE (or TOE where British spelling is used) is preferred. The TEE has much better visualization of the left atrial appendage than transthoracic echocardiography. This structure, located in the left atrium, is the place where a blood clot forms in more than 90% of cases in non-valvular (or non-rheumatic) atrial fibrillation. TEE has a high sensitivity for locating thrombi in this area and can also detect sluggish blood flow in this area that is suggestive of blood clot formation. If a blood clot is seen on TEE, then cardioversion is contraindicated due to the risk of stroke, and anticoagulation is recommended. Ambulatory Holter monitoring A Holter monitor is a wearable ambulatory heart monitor that continuously monitors the heart rate and heart rhythm for a short duration, typically 24 hours. In individuals with symptoms of significant shortness of breath with exertion or palpitations regularly, a Holter monitor may be of benefit to determine whether rapid heart rates (or unusually slow heart rates) during atrial fibrillation are the cause of the symptoms. Exercise stress testing Some individuals with atrial fibrillation do well with normal activity but develop shortness of breath with exertion. It may be unclear whether the shortness of breath is due to a blunted heart rate response to exertion caused by excessive atrioventricular node-blocking agents, a very rapid heart rate during exertion, or other underlying conditions such as chronic lung disease or coronary ischemia. An exercise stress test will evaluate the individual's heart rate response to exertion and determine whether the AV node blocking agents are contributing to the symptoms. Classification +Classification system AF category Defining characteristics First detected only one diagnosed episode Paroxysmal recurrent episodes that stop on their own in less than seven days Persistent recurrent episodes that last more than seven days Longstanding Persistent recurrent episodes that last more than twelve months Permanent AF that has been accepted, and for which a solely rate control strategy has been decided upon. The American College of Cardiology (ACC), American Heart Association (AHA), and the European Society of Cardiology (ESC) recommend in their guidelines the following classification system based on simplicity and clinical relevance. All people with AF are initially in the category called first detected AF. These people may or may not have had previous undetected episodes. If a first detected episode stops on its own in less than seven days and then another episode begins, later on, the category changes to paroxysmal AF. Although people in this category have episodes lasting up to seven days, in most cases of paroxysmal AF, the episodes will stop in less than 24 hours. If the episode lasts for more than seven days, it is unlikely to stop on its own and is then known as persistent AF. In this case, cardioversion can be attempted to restore a normal rhythm. If an episode continues for a year or more, the
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