Atrial fibrillation

Atrial fibrillation can be either persistent or paroxysmal. When dealing with new onset atrial fibrillation (AF), generally we tend to wait for at least a week before labelling it as persistent AF. The treatment of persistent AF is either rate-control or rhythm-control. When we choose the rate-control strategy, we allow the arrhythmia to persist (atrial rate in AF is more than 350 per minute) but we use drugs to prevent the ventricular rate from exceeding a particular limit (below 90/min at rest and below 110/min during usual activity).

When we choose the rhythm-control strategy, we take measures to change the AF to sinus rhythm. We do this either with drugs (usually Class 1C or Class 3 antiarrhythmic drugs) or by electrical means. Research on atrial fibrillation has told us that both the rate-control and rhythm-control strategies are fine provided patients on rate-control are on adequate long term anticoagulation. It does seem a bit illogical that allowing a fast atrial arrhythmia to remain intact has the same outcomes as changing it back to its normal rhythm. The answer lies in knowing that long term use of antiarrhythmic drugs is not completely safe because they have a pro-arrhythmic effect and can provoke ventricular arrhythmias which lead to complications.

We also know that if we can control the ventricular rate adequately, we can prevent tachycardia-induced cardiomyopathy from developing.

For those who have paroxysmal AF, the treatment options are not so clearly defined even though we know that long term anticoagulation is necessary for them too. Patients with paroxysmal AF tend to be treated with antiarrhythmic drugs. Another option for such patients is catheter-ablation therapy, a procedure where the pulmonary veins in the left atrium are electrically isolated by using radio-frequency energy. All invasive procedures have risks and catheter ablation for AF can lead to strokes (by dislodging microemboli from the left atrium) and cardiac tamponade (by piercing the atrial wall).

A recent study in the New England Journal of Medicine tells us that both drug therapy and catheter ablation are effective for patients with paroxysmal AF and that there is no strong evidence yet that one is better than the other even though we know that those who undergo catheter ablation have less recurrence of AF after two years.