A Comparison of Rate Control and Rhythm Control in Patients with Atrial Fibrillation
A Comparison of Rate Control and Rhythm Control in Patients with Atrial Fibrillation – The Atrial Fibrillation Follow-Up Investigation of Rhythm Management (AFFIRM) Investigators – published in the New England Journal of Medicine on December 5 2002
Atrial fibrillation is the most common sustained cardiac arrythmia. Most symptoms during atrial fibrillation are caused by poorly controlled or irregular ventricular rate. Two different treatment approaches: 1. Rhythm control: use of antiarrythmic drugs (amiodarone, sotalol, flecainide, etc) in order to convert to sinus rhythm. Theoretical benefits include less symptoms, better exercise tolerance, decreased stroke risk, potential to come off long-term anticoagulation and a better quality of life. 2. Rate control: use of AV nodal blockage (beta blockers, calcium channel blockers diltiazem or verapamil, digoxin) to control the ventricular response rate.
This was a randomized multi-center comparison study conducted out of the University of Washington but included 213 clinical sites. This was an intention to treat study. They recruited atrial fibrillation patients who were either over age 65 or had other risk factors for stroke or death. They also needed clinical judgement to decide if they were likely to be in recurrent a fib, that their a fib was likely to cause death, that they needed long-term anticoagulation and that they did not have any contraindications to anti-coagulation. Once randomized, the physician could choose which drug to use and they could use multiple agents as needed. Only after failing two trials were they allowed to consider non-pharmalogical treatment (ablation). Everyone was put on warfarin with an INR goal 2-3. – Rhythm control: 2/3 chose amiodarone, sotalol was the next most popular. Electrical cardioversion is an option. – Rate control: 1/2 chose beta-blockers, diltiazem was the next most popular. Goal HR <80 at rest and <110 during 6-minute exercise test.
Primary endpoint = mortality Composite endpoint = death, disabling stroke, disabling anoxic encephalopathy, major bleeding and cardiac arrest
They enrolled 4060 patients into the study. On average they were followed for 3.5 years. 70% had HTN, 40% had CAD. For 1/3 of the patients, this was their first episode of atrial fibrillation. The mean age was 70. 40% were women and 11% were an ethnic minority.
For the rate control group: in 5 years 35% were in sinus rhythm, 80% had adequate rate control. 250 patients crossed over between groups (usually due to uncontrolled symptoms of a fib or CHF). 85% were compliant with their anticoagulation.
For the rhythm control group: in 5 years 62% were in sinus rhythm. 594 patients had crossed over (either because they were unable to get into a sinus rhythm or they had side effects from the anti-arrythmic drugs).
Overall there was no statistically significant difference in either mortality or the composite outcome between the two groups. Overall there was a 1% stroke rate for each group, and usually occured in patients who were either not on anticoagulation or were subtherapeutic on their INR. Measurement of cognition and quality of life were the same between the two groups.
However, the rhythm group did have a statistically significant increase in the number of hospitalizations and were more likely to have drug side effects.
Take home point: rate control should be considered as a primary approach to treatment!