New England Journal of Medicine December 05, 2002

A Comparison of Rate Control and Rhythm Control in Patients with Atrial Fibrillation

The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) Investigators

Bottom Line

The AFFIRM trial demonstrated that a rhythm-control strategy offered no survival advantage over a rate-control strategy in patients with atrial fibrillation and high cardiovascular risk, and was associated with more adverse drug effects and hospitalizations.

Key Findings

1. After a mean follow-up of 3.5 years, there were 356 deaths in the rhythm-control group compared to 310 deaths in the rate-control group (mortality at 5 years: 23.8% vs. 21.3%; hazard ratio 1.15, 95% CI 0.99-1.34, P=0.08) [4.1.1].

2. Hospitalization rates were significantly higher in patients assigned to the rhythm-control strategy compared to the rate-control strategy (80.1% vs. 73.0%, P < 0.001).

3. Adverse drug events, including torsades de pointes (0.8% vs. 0.2%, P=0.007), were more frequent in the rhythm-control group.

4. The incidence of ischemic stroke was similar between the groups, with the majority of strokes in both groups occurring when warfarin had been stopped or the international normalized ratio (INR) was subtherapeutic.

Study Design

Design

Randomized Controlled Trial

Open-Label

Sample

4,060

Patients

Duration

3.5 yr

Median

Setting

Multicenter, North America

Population Patients aged 65 years or older, or with other risk factors for stroke or death, who had atrial fibrillation likely to be recurrent and in whom both rate-control and rhythm-control therapies were considered appropriate.

Intervention Rhythm-control strategy using antiarrhythmic drugs and cardioversion to maintain sinus rhythm.

Comparator Rate-control strategy using atrioventricular nodal blocking agents (beta-blockers, calcium channel blockers, digoxin) to achieve target heart rates, allowing atrial fibrillation to persist.

Outcome Overall mortality (all-cause mortality).

Study Limitations

• The study population was primarily older (mean age 69.7) and relatively asymptomatic; results may not generalize to younger patients or those with severe symptoms driven by atrial fibrillation [4.1.1].

• The rhythm-control strategy relied primarily on older antiarrhythmic drugs with known systemic and proarrhythmic toxicities, and preceded the modern era of widespread catheter ablation.

• There was a significant rate of crossover between the two treatment arms (e.g., due to drug failure in rhythm control), which can dilute differences in an intention-to-treat analysis.

Clinical Significance

The AFFIRM trial caused a major paradigm shift in cardiology by overturning the assumption that attempting to maintain sinus rhythm inherently improves survival. It established rate control as an equivalent, and often preferred, first-line strategy for asymptomatic or mildly symptomatic older patients with atrial fibrillation. Importantly, it highlighted that stroke risk persists regardless of rhythm strategy, dictating that anticoagulation should be guided by clinical stroke risk factors rather than the apparent presence of sinus rhythm.

Historical Context

Prior to AFFIRM, prevailing medical dogma asserted that preserving sinus rhythm was fundamentally superior, reducing heart failure, stroke, and death. Although physiological arguments favored sinus rhythm, it was unknown if the benefits outweighed the toxicity of available therapies. The AFFIRM trial, alongside contemporaneous trials like RACE, settled the issue by demonstrating that whatever benefits sinus rhythm provided were fully offset by the adverse effects of the antiarrhythmic drugs required to maintain it.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

Why did patients in the rhythm control group of the AFFIRM trial continue to have ischemic strokes despite being ostensibly in sinus rhythm, and what does this teach us about the pathophysiology of atrial fibrillation?

Key Response

This highlights that AFib is not just a mechanical rhythm issue but a marker of underlying atrial myopathy and systemic hypercoagulability. Because asymptomatic recurrences of AFib are common, stroke risk remains high, demonstrating that restoring sinus rhythm does not eliminate the need for anticoagulation in high-risk patients.

Resident

Based on the AFFIRM trial, how should you counsel a highly symptomatic 68-year-old patient with hypertension and recurrent AFib regarding the choice between rate and rhythm control strategies?

Key Response

The resident must balance the AFFIRM trial's finding that rhythm control offers no survival benefit and has higher adverse effects with the need for symptom relief. AFFIRM established rate control as a non-inferior, safer default for asymptomatic patients, but symptom management remains the primary indication for pursuing rhythm control. Crucially, anticoagulation must continue regardless of the chosen strategy.

Fellow

How does the emergence of catheter ablation as a primary modality for rhythm control challenge the applicability of the AFFIRM trial's findings to modern electrophysiology practice, particularly considering recent trials like CABANA and EAST-AFNET 4?

Key Response

Fellows must contextualize classic literature with modern advancements. AFFIRM used highly toxic antiarrhythmic drugs which likely offset any physiological benefits of sinus rhythm. Modern rhythm control utilizes early ablation and safer strategies (as seen in EAST-AFNET 4), which have shown improved cardiovascular outcomes compared to the delayed, drug-centric approach evaluated in AFFIRM.

Attending

Given that the AFFIRM trial demonstrated a higher incidence of adverse drug events and hospitalizations in the rhythm control arm, how do we systematically avoid the trap of 'treating the monitor instead of the patient' in our clinical practice?

Key Response

Attendings must emphasize the concept of therapeutic illusion and iatrogenesis. The drive to achieve normal sinus rhythm can lead to the aggressive use of toxic antiarrhythmics. The key teaching point from AFFIRM is that in minimally symptomatic older adults, rate control is sufficient, and chasing sinus rhythm often harms the patient more than the disease itself.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

The AFFIRM trial allowed cross-over between arms, with many rhythm control patients ultimately receiving rate control due to drug failure. How does this cross-over affect the intention-to-treat analysis, and what alternative statistical frameworks could better estimate the true physiological effect of maintaining sinus rhythm?

Key Response

An ITT analysis preserves randomization but dilutes the treatment effect if cross-over is high, biasing results toward the null. A PhD researcher should consider per-protocol analyses, instrumental variable approaches, or inverse probability of censoring weighting to disentangle the physiological benefit of sinus rhythm from the specific clinical strategy of attempting to maintain it.

Journal Editor

The AFFIRM protocol allowed physicians to stop warfarin if they believed sinus rhythm was successfully maintained, leading to disproportionate strokes in the rhythm control arm. As an editor, how would you require the authors to address this major iatrogenic confounding factor in their safety and mortality conclusions?

Key Response

The protocol's allowance for stopping anticoagulation introduced a critical flaw. The editor would flag that the increased stroke and mortality rate in the rhythm arm was largely iatrogenic due to the false reassurance of sinus rhythm, rather than a direct physiological failure of rhythm control itself, severely confounding the primary and secondary endpoints.

Guideline Committee

Current AHA/ACC/HRS guidelines strongly recommend continuing anticoagulation based on CHA2DS2-VASc score regardless of whether a rate or rhythm control strategy is chosen. How did the specific stroke outcomes and protocol allowances in the AFFIRM trial directly inform the strength of this guideline recommendation?

Key Response

AFFIRM showed that rhythm control patients who stopped warfarin suffered the highest rates of stroke, primarily due to asymptomatic AFib recurrences. This provided the foundational Level A evidence for current guidelines stipulating that successful rhythm control does not sufficiently reduce stroke risk to justify discontinuing anticoagulation in patients with elevated CHA2DS2-VASc scores.

Clinical Landscape

Noteworthy Related Trials

2002

RACE Trial

n = 522 · NEJM

Tested

Rhythm control

Population

Patients with persistent atrial fibrillation

Comparator

Rate control

Endpoint

Composite of CV death, heart failure, thromboembolism, bleeding, pacemaker, or severe drug adverse effects

Key result: Rate control was not inferior to rhythm control for the prevention of cardiovascular morbidity and mortality.

2008

AF-CHF Trial

n = 1,376 · NEJM

Tested

Rhythm control

Population

Patients with atrial fibrillation and heart failure (LVEF <= 35%)

Comparator

Rate control

Endpoint

Cardiovascular death

Key result: There was no significant difference in cardiovascular mortality between the rate-control and rhythm-control strategies.

2020

EAST-AFNET 4 Trial

n = 2,789 · NEJM

Tested

Early rhythm control (drugs or ablation)

Population

Patients with recently diagnosed atrial fibrillation and cardiovascular conditions

Comparator

Usual care (primarily rate control)

Endpoint

Composite of CV death, stroke, or hospitalization for heart failure or ACS

Key result: Early rhythm-control therapy resulted in a significantly lower risk of adverse cardiovascular outcomes compared to usual care.

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