Therapeutic Options for Atrial Fibrillation
Atrial fibrillation is the most common heart rhythm disorder. This may cause heart diseases (for example: hypertension, valvular) or extra-cardiac causes (for example: hyperthyroidism, alcohol consumption). As a mechanism of the atrial fibrillation it is due to electrical microcircuits at the atria levels (atria – the upper chambers of the heart).
Depending on the duration of an episode of atrial fibrillation, we talk about:
paroxysmal atrial fibrillation: pass spontaneously in less than 1 week;
persistent atrial fibrillation: does not go away, requiring cardioversion (recovery of sinus rhythm – the normal rhythm of the heart – through medical therapy, or the application of external electric shock);
Permanent atrial fibrillation: cannot or do not want cardioversion.
Consequence of atrial fibrillation is the loss of normal atrial contraction. In atrial fibrillation, the atria contracts disorganized, chaotic. This slows down the blood flow to the heart, with the possibility of formation of thrombi (blood clots) in the left atrium or left atrial of the ear level. For this reason, there is an increased risk of a stroke, the migration of these blood clots at the level of left atrium.
This risk is quantified by several scores
CHADS2 score: the cardiomyopathy, hypertension, age over 75, diabetes each worth 1 point and the existence of a history of a stroke is worth 2 points. If CHADS2 score more than you need anticoagulant treatment.
CHA2DS2-VASC score uses the following criteria: heart failure = 1 point, hypertension = 1 point, age over 75 years = 2 points, diabetes = 1 point, the existence of a stroke or thromboembolic event = 2 points, cardiac or peripheral vascular disease = 1 point, age between 65 and 74 years = 1 point, female sex = 1 point. High risk is defined CHA2DS2-VASC score higher or equal to 2.
HAS scores – BLED takes into account seven parameters: uncontrolled hypertension (SBP = 160 mmHg) = 1 point, liver or kidney function alterated = 1 point, a history of stroke = 1 point, bleeding or predisposition to bleeding = 1 point, poor control of INR = 1 point over 65 years = 1 point, treatment with platelet aggregation inhibitors or anti-inflammatory medications (aspirin, clopidogrel) = 1 point, alcohol consumption (more than 8 alcoholic drinks / week) = 1 point.
According to these scores, the presence of other systemic disease or other cardiac disease, and depending on the type of permanent atrial fibrillation, persistent or paroxysmal, there are several treatment options:
Control of heart rate involves the conversion to sinus rhythm and prevents recurrence of atrial fibrillation. It can be done if paroxysmal atrial fibrillation (which is converted spontaneously to sinus rhythm) or with persistent atrial fibrillation (by electrical or drug).
Control heart rate when you cannot or do not want cardioversion.
Although there are few studies in the specialty literature that support the heart rate control therapy does not reduce mortality compared with control therapy in heart rate by maintaining sinus rhythm may prevent or slow cardiac remodeling, it can reduce the symptoms of failure heart and improve quality of life. Normally the first approach of an atrial fibrillation is the conversion sinus rhythm, if it cannot be obtained we are opting for heart rate control therapy, often accompanied by anticoagulant therapy. When possible, it must be done atrial fibrillation treatment (for example: hyperthyroidism) and is also important treatment of other associated cardiac pathologies.
Conversion of atrial fibrillation to sinus rhythm can be achieved
a) Products using the following active substances:
Amiodarone in intravenous administration or oral administration, in the last case necessitating the administration of a loading dose. It is preferable if there is a structural heart disease,
Other antiarrhythmic drugs: flecainide, propafenone, orally or intravenously, and vernakalant, intravenous ibutilide when there is no structural cardiac disease.
b) Elective: by applying external electric shock energy of 150-200 Joules, under general anesthesia, usually with propofol.
c) Combined method: the most commonly used conversion therapy, usually involves administering a variable period of time of an antiarrhythmic, followed later by electro conversion.
To remember, an important predictor of maintaining sinus rhythm after cardioversion is the size of the left atrium measured by cardiac ultrasound.
For paroxysmal atrial fibrillation, new treatment guidelines describe an approach of the type “pill in the pocket”. When the patient is aware of the occurrence of an episode of atrial fibrillation, he may self-inject to convert to sinus rhythm like flecainide or propafenone antiarrhythmic. It has been shown that administration of 450-600 mg of propafenone or flecainide 200-300 mg is a safe and effective option in the treatment of paroxysmal atrial fibrillation, sinus rhythm with a conversion rate of 94%. But before recommending this approach, screening should be done to the individual patient regarding indications and contraindications, efficacy and safety of self-administration of these antiarrhythmic.
Regardless of what method of conversion is used, it must respect the following principle, to avoid the maximum stroke or other embolic events. So it should not be tempted cardioversion before it is performed:
3 weeks of effective anticoagulation or
Transesophageal ultrasound to exclude the presence of thrombus at the level of the left atrium.
There are three exceptions to this rule, when you must immediately realize the conversion to sinus rhythm:
uncomplicated atrial fibrillation, heart healthy, with onset of less than 24-48 hours;
Atrial fibrillation in a patient already properly anticoagulated;
Atrial fibrillation poorly tolerated by the patient which justified an emergency cardioversion.
In case of conversion to sinus rhythm is then necessary to consider a medicinal treatment to prevent recurrence of atrial fibrillation. For this purpose you can use the following classes of medications:
beta-blockers (for example: metoprolol, carvedilol, bisoprolol) have modest effectiveness in preventing recurrence of atrial fibrillation, atrial fibrillation except in the context of hyperthyroidism or exercise-induced;
Flecainide, propafenone (Class IC antiarrhythmic medicinal products). Flecainide doubles the chances of maintaining the sinus rhythm. Both flecainide and propafenone can be safely administered in patients without other cardiac pathologies, but should be avoided in case of existence of concomitant coronary artery disease or if a low ejection fractions. Their management should be associated with atrioventricular node blockers because it is possible to convert atrial fibrillation to atrial flutter quickly lead to the ventricles.
Amiodarone (class III antiarrhythmic) prevents recurrence of atrial fibrillation more effective than sotalol or propafenone. Can be administered safely to patients with atrial fibrillation associated with structural cardiac disease including heart failure.
sotalol prevents recurrence of atrial fibrillation in patients with coronary artery disease equally effective as Amiodarone, but sotalol administration should be avoided in women, in patients with ventricular hypertrophy, severe bradycardia, ventricular arrhythmias, renal dysfunction, hypokalemia because of the risk of inducing other arrhythmias.
Dronedarone similar to propafenone and flecainide, have efficacy in preventing recurrence of atrial fibrillation of lower Amiodarone.
Rate control is required in most patients with atrial fibrillation, except in the case of a slow spontaneous atrial fibrillation allure. Current recommendations concerning the heart rate in case when atrial fibrillation is 60-80 b/min at rest, and 90-115 b/min at moderate effort. The following medicines can be used to control heart rate:
Beta-blockers (for example: metoprolol, carvedilol, bisoprolol) are useful when there is an increased sympathetic tone, or in the presence of myocardial ischemia associated with atrial fibrillation. Represents a safe and effective choice in the long-term control of heart rate;
Nondihydropyridine calcium channel blockers (for example: verapamil, diltiazem) are effective in controlling acute and chronic heart rate but should be avoided in patients with systolic heart failure (ejection fraction decreased) due to their inotropic effect (decrease myocardial contractility);
Digoxin – is effective in controlling heart rate at rest, and not effort. But can cause life-threatening side effects, so they must be administered with caution, and also has many medicinal interactions;
Dronedarone – is effective in controlling heart rate both at rest and during exercise, but at the moment it is not approved its administration in permanent atrial fibrillation;
Amiodarone – is an antiarrhythmic with high-efficiency, typically used in intravenous and oral administration to control heart rhythm. It is rarely given due to chronic long-term adverse extra-cardiac (thyroid dysfunction, bradycardia).
To be mentioned:
There are patients in whom atrial fibrillation shows a slow heart rate, which is the only therapeutic option pacemaker implant;
There are patients on which medicinal strategies to control the heart rate are not successful. For them atrioventricular node ablation may be proposed and subsequent pacemaker implant.
Curative treatment of atrial fibrillation can be achieved:
Interventional: by ablation using radiofrequency current at the level of atrial microcircuits. This is an invasive procedure that usually addresses symptomatic patients for whom other methods had failed conversion to sinus rhythm. The benefit of radiofrequency stream ablation of atrial fibrillation in asymptomatic patients has not been demonstrated. Recent studies have shown a success rate of this procedure by 77% compared to 52% in terms of antiarrhythmic drugs to treat atrial fibrillation.
Surgical (Maze procedure) involves making incisions in the atria in order to fragment the electrical microcircuits involved in atrial fibrillation. Although this intervention shows a 75-95% success rate in preventing recurrence of atrial fibrillation in 15 years, associated surgical risks are high, which is why it is not used routinely.
Other interventional methods: cryoablation, using high intensity ultrasound producing local necrosis blocking atrial microcircuits.
Anticoagulation in atrial fibrillation is recommended according to CHADS2 score:
for CHADS2 score greater than 2 is shown with Antivitamins K anticoagulant therapy (acenocoumarol, warfarin) maintaining INR between 2 and 3;
for CHADS2 score equal to 1 is recommended anticoagulation therapy Antivitamins K maintaining INR between 2 and 3, or aspirin 250 mg / day if bleeding risk is high;
For CHADS2 score equal to 0 is recommended Aspirin 250 mg / day or anything.
Be mentioned that there are other special situations where anticoagulation is or not recommended and indication of the treatment should be agreed with the treating physician considering all patient related pathologies.
For patients without valvular disease (valvular heart disease) there is an alternative of the treatment, anticoagulation with Antivitamins K:
Closing the left atrium ear: an interventional procedure is performed and aims to prevent thromboembolic events, the starting point is at ear level of the left atrium. The effectiveness of this procedure for patients non valvular proved to be superior to warfarin anticoagulation in terms of stroke prevention.
Using a new class of anticoagulants (dabigatran, rivaroxaban, apixaban) they have proven effective in preventing stroke in patients without valvular disease. Their use can be recommended in patients who have an increased risk of intracranial hemorrhage, or patients for INR monitoring are poor.