Is rate more important than rhythm in treating atrial fibrillation? No

doi:10.1136/bmj.b3174

Published 21 August 2009, doi:10.1136/bmj.b3174
Cite this as: BMJ 2009;339:b3174

Head to Head

Is rate more important than rhythm in treating atrial fibrillation? No

Andrew R J Mitchell, consultant cardiologist

¹ Jersey Heart and Lung Unit, General Hospital, St Helier, Jersey JE1 3QS

mail{at}jerseycardiologist.com

Timothy Betts (doi:10.1136/bmj.b3173) argues that focusing onrate will cause less harm to patients, but Andrew Mitchell believesthat achieving sinus rhythm will have better long term results

The number of patients with atrial fibrillation continues torise, partly because of the increasing size and age of the populationbut also because of the large number of patients surviving withother potentially arrhythmogenic conditions.¹ Atrial fibrillationhas been shown to be an independent predictor of mortality withodds ratio of 1.5 (95% confidence interval 1.2 to 1.8) in menand 1.9 (95% confidence interval 1.6 to 2.3) in women.² Restoringsinus rhythm is more important than a rate control strategyin persistent atrial fibrillation, and most patients shouldbe offered the chance to have normal rhythm restored.

Rate versus rhythm

Three large randomised trials (Atrial Fibrillation Follow-upInvestigation of Rhythm Management (AFFIRM), Rate Control versusElectrical Cardioversion (RACE), and Strategies of Treatmentof Atrial Fibrillation (STAF)) showed no clear mortality benefitof rhythm control over rate control in patients with relativelyasymptomatic atrial fibrillation during two to three years offollow-up.³ ⁴ ⁵ Another randomised trial showed no differencein mortality between rhythm and rate control in patients withadvanced heart failure and atrial fibrillation.⁶

There is no doubt that rate control is easier, less time consuming,and cheaper than rhythm control, and this has led to some doctorsabandoning sinus rhythm as a goal for patients with atrial fibrillation.At one US centre the rates of referral for cardioversion andablation for rate control fell sharply after publication ofthe AFFIRM study.⁷ Rate control with β blockers, calciumchannel blockers, or digoxin can improve symptoms, but the drugshave potential side effects.⁸ Left ventricular function candeteriorate and left atrial size increase, irrespective of ventricularrate control, with acceptance of permanent atrial fibrillation.⁹¹⁰

Sinus rhythm versus atrial fibrillation

The rate versus rhythm studies discussed above are in fact intentionto treat studies of different drug strategies for the managementof atrial fibrillation rather than randomised studies of sinusrhythm versus atrial fibrillation. As an example, after fiveyears in the rhythm control limb of AFFIRM, the number of patientsin sinus rhythm was only 63%.³ An on-treatment analysis of AFFIRMsubsequently showed that the two predictors of reduced mortalitywere the maintenance of sinus rhythm and the use of warfarin.¹¹The use of antiarrhythmic drugs (particularly amiodarone) inthe rhythm control group of AFFIRM may have counterbalancedthe favourable mortality benefits of restoring sinus rhythm.The risk of non-cardiovascular death was increased 1.5-foldin the rhythm group, largely driven by increased death fromcancer and pulmonary disorders.

Several other studies point towards the benefits of sinus rhythm.In the STAF study⁵ all the mortality occurred in patients whowere in atrial fibrillation and patients with heart failurein sinus rhythm in the RACE study had reduced mortality.¹² Restoringand maintaining sinus rhythm has been shown to improve ejectionfraction,¹⁰ reduce left atrial size,¹³ improve exercise capacity,¹⁴and improve quality of life.¹⁵ The Stockholm Cohort of AtrialFibrillation Study examined the outcome of patients after cardioversion,with those maintaining sinus rhythm having an improved longterm prognosis.¹⁶ Two randomised trials of antiarrhythmic drugs(dofetilide and amiodarone) in patients with heart failure andatrial fibrillation found that patients whose sinus rhythm wasrestored had significantly reduced mortality.¹⁷ ¹⁸ A more recentrandomised trial of dronedarone found reduced cardiovasculardeath rates and hospital admissions, largely by reducing recurrenceof atrial fibrillation.¹⁹

Role of non-drug treatment

Non-pharmacological techniques for managing atrial fibrillationare now widely available. Repeated early external cardioversionis a quick and effective method of restoring sinus rhythm, particularlyin patients taking anticoagulants who have relatively infrequentepisodes of persistent atrial fibrillation.²⁰ Early cardioversionmay reduce or reverse atrial remodelling, increasing the timespent in sinus rhythm between episodes of atrial fibrillation.Internal cardioversion is effective when external cardioversionis unsuccessful.

Most cardiac centres are now offering left atrial ablation forpatients with recurrent atrial fibrillation. Radiofrequencyablation reduces recurrences by about 65% at one year comparedwith drugs²¹ and has been shown to improve cardiac function,²²patient outcomes,²³ and quality of life.²⁴ In the most recentinternational guidelines, ablation has moved up alongside amiodaronein the treatment ladder.²⁵ The procedure can, however, takeseveral hours, with many patients requiring repeat ablationand risks include a 1 in 1000 risk of death and higher risksof stroke and pericardial tamponade.

Sinus rhythm remains the goal

Atrial fibrillation is a heterogeneous condition with multipleunderlying causes and triggers and cardiologists should tailoradvice to the patient. Patients with severe symptoms will benefitsymptomatically from the restoration of sinus rhythm. Antiarrhythmicdrugs should be offered to patients with recurrent atrial fibrillation,backed up by electrical cardioversion to restore and maintainsinus rhythm. In addition to making the patient feel better,the restoration of sinus rhythm may reduce the risk of emergencyhospital admission and stroke, improve the ejection fraction,reduce atrial remodelling, improve exercise capacity, and improveoutcome.

Cite this as: BMJ 2009;339:b3174

Competing interests: None declared.

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