Is rate more important than rhythm in treating atrial fibrillation? YesBMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b3173 (Published 21 August 2009) Cite this as: BMJ 2009;339:b3173
- Timothy R Betts, consultant cardiologist and electrophysiologist
Both sides of the debate on whether to control rhythm or rate agree that sinus rhythm is better than atrial fibrillation.1 If a strategy to control rhythm could guarantee to be efficacious, cost effective, and have no risk of adverse events, there would be no argument. Unfortunately, this is rarely the case. Rhythm control is difficult to achieve and initially requires the use of potentially toxic drugs. If the objective is to “first do no harm,” rate control is more important.
Six randomised controlled trials comparing rate and rhythm control have clearly shown that mortality (whether as a primary or composite end point) is not reduced with rhythm control.2 3 4 5 6 7 In the two largest of these there was even a trend to increased mortality in the rhythm control group.3 4 This is probably because of the potential toxicity of rhythm control drugs and the inappropriate withdrawal of warfarin in the rhythm control group leading to an increase in thromboembolic events.
The rhythm control arms in comparative studies show how challenging it is to maintain sinus rhythm. Even with a variety of antiarrhythmic drugs and repeated external cardioversions, only 37-65% of patients maintain sinus rhythm.3 8 Up to 25% of patients prescribed amiodarone, the most effective of the antiarrhythmic drugs, will discontinue it because of unacceptable side effects.9 In contrast, the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study reported that 85% of patients initially assigned to a rate control strategy maintained this for the duration of the trial.10
In a few people, rate control drugs may be ineffective or may exacerbate sinus node and atrioventricular node dysfunction. In these instances, ablation of the atrioventricular node and implantation of a pacemaker (which also has the advantage of regularising the ventricular rate) has been shown to control rate effectively.11
Quality of life
Although atrial fibrillation may be asymptomatic, most affected people present with symptoms ranging from palpitations, breathlessness, chest pain, and dizzy spells to fatigue and reduced exercise capacity. The goal of treatment is to reduce symptoms and improve quality of life. Somewhat surprisingly, despite the fact that drugs to control heart rate do not tackle the irregularity of the pulse or the loss of atrial contractility, all comparative studies to date have shown similar quality of life scores in rate and rhythm control groups.12 13 This is probably a consequence of patient selection and the ineffectiveness and more pronounced side effects of rhythm controlling drugs.
Thromboembolic stroke is the most important consequence of atrial fibrillation. Ideally, a rhythm control strategy should completely abolish atrial fibrillation, reducing the risk of stroke and avoiding the need for anticoagulation. Unfortunately, this is impossible to guarantee. Even if symptomatic episodes no longer occur, electrocardiographic monitoring has shown that asymptomatic episodes often continue.14 If a patient has a high enough risk score to justify anticoagulation with warfarin in the presence of atrial fibrillation, this should be continued regardless of whether a rate or rhythm control strategy is pursued, even if a rhythm control approach seems to be successful.
Tachycardia mediated cardiomyopathy may occur in a small proportion of susceptible patients with persistent atrial fibrillation and ventricular rates constantly in excess of 110 beats per minute. For this to happen, individuals must be relatively asymptomatic so that the onset of atrial fibrillation goes unnoticed. Fortunately, the cardiomyopathy is reversible once adequate rate control (through drugs, atrioventricular node ablation and pacemaker, or the restoration of sinus rhythm) is achieved. As rhythm control is rarely effective and patients are unable to detect the arrhythmia, a rate control approach is vital for susceptible patients to prevent recurrence of cardiomyopathy.
Both AFFIRM and the Rate Control versus Electrical Cardioversion (RACE) study showed that rate control is less costly than rhythm control.15 16 The use of rhythm control drugs is associated with an increased number of hospital admissions.17 Even if a rhythm control strategy reduces the frequency or duration of atrial fibrillation episodes, it is not uncommon for additional, rate controlling drugs such as β blockers, calcium channel blockers, or digoxin to be prescribed to reduce symptoms during attacks.
A rate control strategy is more important than a rhythm control strategy because it is effective for the majority of patients with atrial fibrillation, uses less toxic drugs, reduces the risk of harm from tachycardia mediated cardiomyopathy, and reminds the doctor and patient of the need for appropriate thromboprophylaxis. This is particularly important as atrial fibrillation primarily affects elderly people, who often have other conditions. However, in an important minority of patients, particularly younger and physically active people and those in whom the loss of atrial contractile function rather than rapid irregular ventricular rate causes severe symptoms, a rhythm control strategy may be preferred. The advent of radiofrequency ablation techniques such as pulmonary vein isolation, have made this possible in carefully selected patients.18 Ablation and the development of less toxic, more effective antiarrhythmic drugs such as dronaderone may encourage the pursuit of sinus rhythm for a broader spectrum of patients.19 Until rhythm control strategies are more effective, however, rate control is the most important initial objective for most people with atrial fibrillation.
Cite this as: BMJ 2009;339:b3173
Competing interests: TRB has received funding from Medtronic for research into catheter ablation for atrial fibrillation.