• An electrocardiogram should already have been done to confirm the diagnosis of atrial fibrillation. An electrocardiogram may also indicate a possible underlying cause (such as old myocardial infarction, left ventricular hypertrophy, or a pre-excitation syndrome).
• Do the following tests:
• Thyroid function tests (to exclude hyperthyroidism).
• Full blood count (to exclude anaemia).
• Blood urea and electrolytes, calcium, and glucose measurement (to exclude electrolyte disturbances, which may precipitate atrial fibrillation).
• Liver function tests and a clotting screen (to assess suitability for warfarin).
• Chest radiography (to assess a suspected lung abnormality, such as lung cancer; this test may also help to detect heart failure).
• For people not being referred to a cardiologist, consider organizing transthoracic echocardiography if:
• There is a high risk or a suspicion of underlying heart disease (for example signs of heart failure or a cardiac murmur).
• Information on cardiac structure or function is needed to make a decision about starting antithrombotic treatment.
• Most decisions about starting antithrombotic treatment should be based on clinical judgement. Do not routinely organize echocardiography solely for risk stratification if the person meets the clinical criteria to start warfarin.

These recommendations are based on the National Institute for Health and Clinical Excellence (NICE) guideline Atrial fibrillation: National clinical guideline for management in primary and secondary care [National Collaborating Centre for Chronic Conditions, 2006] and published expert opinion [MeReC, 2002; NHS Scotland, 2005; Fuster et al, 2006a; ICSI, 2008].

• NICE does not give specific recommendations on when to refer for echocardiography in those people who present to primary care with atrial fibrillation (AF).
• After reviewing good-quality evidence (29 studies) on the ability of echocardiographic findings to predict outcomes in AF (such as recurrence of AF after cardioversion, stroke, or vascular death), NICE gave general advice on which people should undergo echocardiography.
• NICE states that the decision to start appropriate antithrombotic treatment can be made clinically. However, the risk may be unclear in some people (such as those with suspected left ventricular dysfunction without overt heart failure), in which case echocardiography may be useful in refining their risk for stroke.