Atrial fibrillation Bedford guidelines for investigation and management
Atrial fibrillation is the commonest sustained arrhythmia. It is present in 10 % of the population over 70 years of age. It can be classified as PAROXYSMAL(spontaneously cardioverts), PERSISTENT(requires intervention to cardiovert) or PERMANENT(often >1 year duration and does not cardiovert to sinus rhythm).
Common causes
Valve disease, hypertension, ischaemic heart disease and thyrotoxicosis.
Investigations
12 lead ECG is essential to confirm diagnosis
Blood tests: FBC, U&E, glucose, TSH.
Echocardiogram is usually necessary to identify valve disease and assess chamber dimensions (open access in patients with AF by GP referral to the cardiologist). This will help in accessing the likely success of DC cardioversion, and the need for WARFARIN anticoagulation.
Treatment
Rhythm control 1: Drug or electrical conversion to sinus rhythm
Refer to cardiologist.
It is essential to identify and treat the cause otherwise specific therapy directed at rhythm control may be ineffective. If the onset of atrial fibrillation is within 48hrs the patient should be admitted to hospital for cardioversion. Otherwise outpatient referral is appropriate for anticoagulation and arrangement for DC cardioversion. Cardioversion is often ineffective in the elderly, those with structural heart disease or prolonged AF (>1year).
Treatments of choice: If acute onset (<48 hours) drugs can be used first: FLECAINIDE iv (except in presence of structural or ischaemic heart disease) or AMIODARONE orally.
Sotolol, digoxin and calcium channel blockers are ineffective.
DC cardioversion is indicated when drug therapy has not been effective or atrial fibrillation has been present for more than 48 hours.
Rhythm control 2: Drugs for maintenance of sinus rhythm after cardioversion, or in paroxysmal AF
Referral usually required.
Paroxysmal and treated persistent AF recurs in 90% of patients within a year and may be asymptomatic. Therefore assessment of recurrence requires a careful history for symptoms of rapid and irregular palpitation as well as ECG evidence, either during an attack or by repeated ambulatory monitoring. Treatment should be considered in those with prolonged, frequent and/or symptomatic attacks. It is rarely easy to control.
Treatments of choice: FLECAINIDE 50-100mg bd (except in presence of structural or ischaemic heart disease), ATENOLOL 25-50mg od (hypertension, ischaemia or hyperthyroidism), AMIODARONE 200mg daily, after loading (CCF), DISOPYRAMIDE (vagally mediated e.g. nocturnal AF due to sinus bradycardia).
Digoxin is not effective in maintaining sinus rhythm
Rate control for permanent AF
Referral not required.
Patients treated in this way have an equivalent mortality, quality of life and functional status as those treated more aggressively by rhythm control (AFFIRM). Target heart rate at rest should be 60-80bpm and during exercise 90-115bpm.
DIGOXIN 62.5-250mcg od is effective at controlling the ventricular rate at rest, but less effective at controlling the heart rate on exercise.
BETA-BLOCKERS (Atenolol 25-50mg od) either alone or in combination with digoxin, are better at controlling inappropriate tachycardia on exercise.
VERAPAMIL 40-80mg tds (not the slow-release preparations) can be used alone or in combination with digoxin. Can be used when b blockers are contraindicated, but not with b blockers.
Stroke prevention
Referral not required.
The risk of stroke is similar for all forms of AF and increases with associated risk factors. Each patient should have a risk-benefit analysis but in general those with no risk factors can be managed with ASPIRIN and the rest should be warfarinised unless there is a contraindication.
WARFARIN (70% risk reduction) for: ASPIRIN (22% risk reduction) for:
all over 75 the others
all over 60 with CAD or diabetes
and those with heart failure, hypertension,
impaired LV or thyrotoxicosis
and no contraindications
Those patients referred for DC cardioversion should be therapeutically anti-coagulated (INR>2) for >3/52 prior to cardioversion. The warfarin should only be discontinued after one month post-cardioversion if none of the above risk factors are present and there has not been any recurrence of AF.
SH, ICC, JPC Nov 2003