Prevention of Atrial Fibrillation
Management of acute atrial fibrillation: see Management of Acute Atrial Fibrillation
Essentials
- Prophylactic treatment for atrial fibrillation (AF) should be considered if the arrhythmia is ill tolerated by the patient. Without treatment it will recur in 80-90% of patients within one year.
- Prophylactic treatment should be planned individually for each patient, bearing in mind the need to control any predisposing factors, e.g. the correction of electrolyte or endocrinological disturbances as well as good treatment of heart diseases and other primary diseases.
- Antiarrhythmic drugs are only seldom able to totally eliminate episodes of AF and, therefore, symptom relief and more infrequent episodes should be considered as realistic treatment goals.
- If there is no response to drug treatment, the patient should be referred to a cardiologist specialized in rhythmology to assess the need of catheter ablation or other invasive treatments.
Drug therapy
- The patient's co-existing (heart) diseases and their medication play an integral part in the choice of prophylactic medication against AF (picture 1).
- The initiation of actual antiarrhythmic drugs (Class I and III agents) should be carried out by a specialist physician, but primary care physicians may manage the follow-up treatment in accordance with guidelines provided by the specialist.
- Objective evidence regarding the efficacy of the medication may be obtained, for example, with ambulatory ECG monitoring and clinical exercise testing. Enough time must be allowed for the effect of the medication to stabilise before assessing the effectiveness of the drug.
- In primary care, the first choice drug for the prevention of AF is a beta-blocker.
- Beta-blockers are particularly suited for patients with hypertension, coronary heart disease or heart failure or in whom the arrhythmia is precipitated by physical exercise or stress.
- In heart failure, the treatment should be started cautiously with a small dose.
- When combined with other antiarrhythmic agents, beta-blockers enhance their action and reduce their proarrhythmic effects.
- In vagally mediated AF the arrhythmia occurs when the heart rate slows down, e.g. after a meal or at night when the patient is asleep. In this type of AF, beta-blockers may, however, even aggravate the situation.
- Beta-blockers may eliminate the symptoms of AF by controlling the ventricular rate. This may, in turn, hamper the assessment of treatment results.
- Even though the differences between various beta-blockers are likely to be small, it is advisable to favour products that are administered once daily and for which there is strongest evidence in the treatment of associated diseases (bisoprolol 5-10 mg once daily, metoprolol 50-200 mg once daily)
Calcium-channel blockers
- Calcium-channel blockers (verapamil and diltiazem) do not prevent the recurrence of AF but, as with beta-blockers, they do offer symptom relief by controlling the ventricular rate. They also enhance the efficacy, and reduce the proarrhythmic effects, of other antiarrhythmic agents.
Digoxin
- Digoxin does not prevent the recurrence of AF, and it may even increase the frequency and duration of AF episodes. However, digoxin may prevent a rapid ventricular response to recurrent AF, which justifies its use in patients with heart failure.
- The impact of digoxin on the prognosis of patients with AF is in dispute.
- At present the most popular drugs in the prevention of AF are the Class IC drug flecainide as well as the Class III drugs amiodarone and dronedarone.
- Flecainide (100-200 mg once daily) is effective and safe in the treatment of lone AF, but it is contraindicated in patients with myocardial infarction, heart failure or another structural heart disease.
- The use requires careful examination of the patient and exclusion of other heart diseases before commencing the treatment as well as close monitoring during the treatment (picture 2).
- Pre-treatment investigations such as echocardiography and, if needed, exercise stress test can be carried out in a hospital outpatient clinic and there is usually no need to admit the patient to hospital to start the treatment.
- Follow-up can be carried out in primary care.
- Should any signs or symptoms suggestive of structural heart disease be detected during a follow-up visit, the patient should be referred to a cardiologist for further investigations and possible change of medication.
- Flecainide must be stopped immediately if the patient suffers a myocardial infarction, develops severe heart failure or shows other signs or symptoms suggestive of structural heart disease.
- Continuation of the medication is also contraindicated if the patient develops a bundle branch block.
- In order to reduce the risk of proarrhythmia, a Class IC drug should preferably be co-administered with a beta-blocker or another drug that slows down atrioventricular (AV) conduction.
- Amiodarone is more effective against the recurrence of AF than other antiarrhythmic agents. However, its long-term use is hampered by several non-cardiac adverse effects and drug interactions (for example with warfarin, direct anticoagulants), which makes it an unsuitable choice for the initial treatment of AF.
- The use of amiodarone requires careful patient selection and monitoring in order to identify disturbances in the function of e.g. thyroid gland, liver or lungs. On the other hand, amiodarone seldom causes proarrhythmia, and it can also be used in patients with myocardial infarction and heart failure.
- In order to avoid the emergence of adverse effects, the loading dose (e.g. 600 mg/day for 2 weeks) should be followed by the lowest possible maintenance dose (100-200 mg/day).
- When assessing the efficacy of amiodarone it should be remembered that it may take several weeks before its effect is fully stabilised.
- In order to avoid bleeding complications, the dose of warfarin should be halved when amiodarone is started, and INR values should be checked more frequently.
- Dronedarone is a derivative of amiodarone. It does not contain iodine, and a methyl-sulfonamide group has been added to lower its lipophilicity. Even if dronedarone due to these structural changes is probably causes fewer severe adverse effects than amiodarone, its use requires careful patient selection and regular follow-up (picture 3).
- The efficacy of dronedarone (400 mg twice daily) in the prevention of atrial fibrillation has been verified in extensive studies. Its antiarrhythmic effect does not, however, equal that of amiodarone and several other antiarrhythmic agents.
- Dronedarone is particularly suitable for the prevention of atrial fibrillation associated with coronary heart disease, but due to serious adverse effects it is contraindicated in heart failure and in permanent atrial fibrillation as well as in patients who have been diagnosed with liver or lung toxicity during amiodarone treatment. Concomitant use with dabigatran is also contraindicated.
- Sotalol is a beta-blocker but if administered at high doses (> 160 mg/day) it prolongs the QT time, as is the case with the Class III drugs.
- After electrical or pharmacological cardioversion, sotalol prevents the recurrence of both paroxysmal and persistent AF more effectively than placebo, but due to the risk of torsade de pointes its use has significantly declined in the recent years.
- Other arrhythmic agents are not often used as prophylaxis against AF. Class IA agents quinidine and disopyramide (that may require special permission for compassionate use) particularly prevent so-called vagal AF. However, due to the risk of proarrhythmia they should be prescribed by a cardiologist.
- Catheter ablation prevents the recurrence of AF, on average, in 70-85% of patients with lone, paroxysmal AF that has proved to be medically refractory, but more knowledge is required on its effect on the prognosis of the patients.
- The primary indication for catheter ablation is highly symptomatic (EHRA score 3-4) drug-refractory AF. Most suitable patients for ablation treatment are those with
- paroxysmal AF
- no diagnosis of major heart disease
- transverse diameter of the left atrium < 5 cm
- frequent premature atrial complexes on the T wave.
- Ablation may be considered as the first-line treatment option in highly symptomatic patients with lone paroxysmal AF.
- Catheter ablation is a complicated electrophysiological procedure which is associated with a small risk of serious complications (e.g. cardiac tamponade, pulmonary vein stenosis, thromboembolic complications, oesophageal perforation).
- If AF is triggered by another supraventricular arrhythmia, such as atrioventricular nodal re-entrant tachycardia or tachycardia associated with WPW, catheter ablation of the triggering arrhythmia also prevents AF.
- Rapid AF associated with WPW syndrome is life-threatening: these patients should absolutely undergo catheter ablation of the accessory conducting pathway.
- Catheter ablation in atrial flutter may reduce AF but does not eliminate it completely.
- The insertion of a pacemaker to prevent the recurrence of AF is in practice only suitable for patients who present with conventional indications for pacing, such as a dysfunction of the sinus node.
- In sick sinus syndrome, atrial pacing reduces the incidence of AF, thromboembolic complications as well as mortality (see Sick Sinus Syndrome).
- A maze procedure or surgical ablation therapy performed in association with other cardiac surgery effectively prevents recurrence of AF.
- A surgical approach is considered for the treatment of AF mainly in patients who require open heart surgery for other reasons or when other treatment modalities have proved ineffective or are contraindicated.
- Identification and treatment of risk factors, together with a healthy life-style (exercise, weight management, cessation of smoking), are important in the prevention of AF.
- Special attention should be paid on the treatment of hypertension, obesity and heart failure.
- ACE inhibitors and angiotensin-II receptor antagonists appear to reduce the occurrence of AF in heart failure and hypertension, but there is no evidence on their efficacy in the prevention of lone AF.
- Research findings regarding the effect of statins and fish oils on AF are controversial, and their routine use is not recommended.
- Fish oils may increase the risk of bleeding when used concomitantly with anticoagulation therapy.