ecorder ECG in those with symptomatic episodes more than 24 hours apart.[2] Blood tests: TFTs, FBC (anaemia may precipitate heart failure), renal function and electrolytes (abnormal serum potassium levels can potentiate arrhythmias, especially if the patient is taking, or about to start, digoxin), LFTs and coagulation screen (pre-warfarin).CXR (may indicate cardiac structural causes of AF, such as