ABC of Atrial Fibrillation: ATRIAL FIBRILLATION IN GENERAL AND HOSPITAL PRACTICE

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Abstract
General practice Despite the considerable interest in atrial fibrillation in epidemiological and hospital studies, little information exists on the prevalence and management of atrial fibrillation in general practice. In a recent audit of a general practice list of about 10000 patients, we found 67 patients who were currently in atrial fibrillation or who were known to have had past episodes of the arrhythmia. Role of general practitioner To identify patients with new onset atrial fibrillation To assess thromboembolic risk and to start early treatment with antithrombotic drugs—warfarin will be needed for most patients, while aspirin may be suitable for patients aged <65 years with no cardiac risk factors or structural heart disease To help to monitor treatment with anticoagulants To refer appropriate patients to a cardiologist for further assessment (including echocardiography) and consideration of cardioversion To be aware of potential drug interactions and toxicity with antiarrhythmic drugs and anticoagulants This prevalence increased with age, rising from 1.5% in people in their 60s to 8% in those aged over 90. A third of the 67 patients had paroxysmal atrial fibrillation. Only two thirds were currently receiving anticoagulant treatment, and an echocardiogram had been obtained in only a third. Of the 30 patients under 75 years, 10 had mitral valve disease, while only one patient aged over 75 had mitral valve disease. A general practitioner typically has 10-15 patients with atrial fibrillation on his or her list From the stroke prevention in atrial fibrillation study, major clinical risk factors for stroke and thromboembolism were congestive heart failure, hypertension, and previous thromboembolism. We found that at least one of these risk factors was present in three quarters of patients seen in general practice with atrial fibrillation (and in 84% of those aged over 75). View larger version: In this window In a new window Prevalence of atrial fibrillation by age in a general practice population. The general population is aging—that is, the proportion of elderly people is increasing—and by the year 2000 the proportion of people over 70 in Britain will constitute 20-25% of the total population. Atrial fibrillation will therefore be an increasingly common cause of stroke, thromboembolism, and heart failure, emphasising that atrial fibrillation is an important public health problem. Many patients will also be taking antiarrhythmic drugs and anticoagulants. As many elderly patients have other medical conditions, the problem of side effects and drug interactions will become increasingly common. For example, hypokalaemia secondary to the use of high doses of loop diuretics may result in dangerous arrhythmias in patients taking digoxin. The use of antiarrhythmics such as amiodarone may result in drug interactions with warfarin and digoxin with consequent toxicity. Such possibilities emphasise the need for concurrent treatments to be fully recorded and for a high index of suspicion for drug interactions. Non-compliance by patients because of inadequate understanding or supervision may also be dangerous. Careful monitoring of requests for repeat prescriptions is therefore essential. When to refer patients with atrial fibrillation to a cardiologist Age <30 Atrial fibrillation resistant to “usual” drugs for rate control Patient suitable for cardioversion Further assessment needed—for example, valvar heart disease Patient with moderate to severe heart failure Patient with resistant heart failure Frequent attacks of paroxysmal atrial fibrillation Syncopal attacks due to atrial fibrillation Drugs that may interact with oral anticoagulants Gastrointestinal tract Potentiating drugs—Antacids (magnesium salts); cimetidine; liquid paraffin and other laxatives Antagonistic drugs—Cholestyramine; colestipol Cardiovascular system Potentiating drugs—Amiodarone; clofibrate; dextrothyroxine; diazoxide; dipyridamole; ethacrynic acid; quinidine; sulphinpyrazonexyiAntagonistic drugs—Cholestyramine; colestipol; spironolactone Respiratory system Antagonistic drugs—Antihistamines Central nervous system Potentiating drugs—Chloral hydrate and related compounds; chlorpromazine; dextropropoxyphene; dichloralphenazone (initial); diflunisal; mefenamic acid; monoamine oxidase inhibitors; triclofos sodium; tricyclic antidepressants Antagonistic drugs—Barbiturates; carbamazepine; dichloralphenazone—late; haloperidol; phenytoin; primidone Infections Potentiating drugs—Aminoglycosides; ampicillin (oral); cephalosporins; chloramphenicol; co-trimoxazole; cycloscrine; erythromycin; isoniazid; ketoconazole; metronidazole; miconazole; nalidixic acid; penicillin G (large doses)—intravenous; quinine salts; streptotriad; sulphonamides (long acting); tetracyline Antagonistic drugs—Griscofulvin; rifampicin Endocrine system Potentiating drugs—Anabolic steroids; chlorpropamide; corticosteroids; danazol; glucagon; metoclopramide; propylthiouracil; sulphonyl urea; thyroxine; tolbutamide Antagonistic drugs—Oral contraceptives Malignant disease and immunosuppression Potentiating drugs—Cyclophosphamide; mercaptopurine; methotrexate; immunosuppressant drugs; tamoxifen Musculoskeletal and joint disease Potentiating drugs—Allopurinol; aspirin and the salicylates; azapropazone; diflunisal; fenclofenac; fenoprofen; feprazone; fluefenamic acid; flubiprofen; indomethacin; ketoprofen; mefenamic acid; naproxen; paracetamol (high daily doses (with dextropropoxyphene distalgesic/coproxamol)); piroxicam; sulindac; sulphinpyrazone Nutrition and blood Potentiating drugs—Alcohol (dose dependent potentiator) Antagonistic drugs—Vitamin K; alcohol Ear, nose, and oesophagus Antagonistic drugs—Antihistamines; phenazone Skin Antagonistic drugs—Antihistamines Alcoholism Potentiating drugs—Disulfiram...