Daily Archive 12.02.2019

Pharmacological cardioversion for atrial fibrillation

Means for intravenous administration. With recent atrial fibrillation (AF) (ejection fraction (AF) up to 7 days old), sinus rhythm can be restored with the help of intravenous administration of flekine, propafenone, sotalol or amiodarone. In patients with heart failure or drastically reduced pumping function of the ventricles, only amiodarone must be used for this purpose: other drugs may worsen myocardial contractility and cause ventricular arrhythmias. Sinus rhythm recovery is possible in no more than 2/3 of cases. The relief effect of amiodarone may require waiting up to 24 hours.

Flankaine and propafenone in some cases do not restore sinus rhythm, but reduce the frequency of atrial activity and, thus, transform AF in TP or atrial tachycardia. Paradoxically, the lower frequency of atrial activity can lead to a noticeable increase in the frequency of ventricular contractions due to the fact that the AV node is able to conduct most or all of the atrial impulses on the ventricles, which sometimes makes it necessary to perform emergency electrical cardioversion.

Dofetilide and ibutilide are newer drugs with class III antiarrhythmic drugs. They are moderately effective as a means of stopping a newly emerging AF (there are more chances for success with TA). However, when they are used, there is a significant risk of developing tirade de pointes. In the UK, these drugs are currently unavailable.

One of the means of a new group of drugs that have a selective effect on the electrophysiological properties of atrial myocardium is vernacalant. It has been shown that with recent AF, intravenous administration of the drug restores sinus rhythm within a few minutes in about 50% of patients.

It should be borne in mind that almost half of the episodes of recent atrial fibrillation (AF) for 8 hours spontaneously stop. Therefore, strictly speaking, the introduction of antiarrhythmic drugs is not necessary in order to restore sinus rhythm in each case!

Ineffective drugs. Digoxin is ineffective as a means of restoring sinus rhythm, and there is evidence that it can actually contribute to the preservation of arrhythmia by shortening the refractory period of atrial myocardium. BAB and calcium channel blockers, although they have the ability to effectively reduce the frequency of ventricular contractions in AF, do not restore sinus rhythm.

Drugs for oral administration. Flekainid and propafenone have moderate efficacy in preventing recurrences of AF and have the same contraindications for use as with intravenous administration. They should not be prescribed to patients with myocardial dysfunction or ischemic heart disease, and if TP occurs, which can lead to a significant increase in the frequency of ventricular contractions, ideally should be combined with BAB or calcium channel blockers. The author of these lines gives preference to flekainid and, with normal ventricular function, recommends it as a first-line agent.

BAB rarely prevent atrial fibrillation (AF), but if the medical history suggests that arrhythmia is provoked by exercise or due to hyperthyroidism, they are the drugs of choice. Some (but not all) studies have shown that sothalol, a class III antiarrhythmic drug, is more effective in preventing AF, compared with other BABs, but should be avoided in patients with a prolonged QT interval.

The most effective means of preventing recurrence of atrial fibrillation (AF) is amiodarone, but due to the high incidence of undesirable effects, the drug should only be used as a backup for treating patients with severe symptoms if the other drugs listed above have been ineffective or cannot be prescribed. Amiodarone is the drug of choice in treating patients with heart failure.

Dronedarone, a derivative of amiodarone, due to reports of a large number of cardiac and extracardiac adverse effects, is currently recommended only as a second-line drug for maintaining sinus rhythm in adult clinically stable patients with paroxysmal AF or persistent AF after successful cardioversion.

For the prevention of paroxysmal atrial fibrillation for many years used quinidine. However, a meta-analysis of research data showed that taking the drug is associated with a significant increase in mortality (presumably due to its proarrhythmic action), so it is no longer used to prevent recurrence of AF.

Digoxin shortens the refractory period of the atrial myocardium and thus increases the susceptibility to AF. There is no evidence that it prevents arrhythmia.