How is a regularly irregular rhythm, such as atrial fibrillation, managed?

Management of Regularly Irregular Rhythm (Atrial Fibrillation)

For most patients with atrial fibrillation, rate control with chronic anticoagulation is the recommended primary strategy, as rhythm control has not demonstrated superiority in reducing morbidity and mortality and may be inferior in certain patient subgroups. 1

Initial Assessment and Diagnosis

When encountering an irregular rhythm, the diagnostic approach should focus on:

• An irregular narrow-complex or wide-complex tachycardia is most likely atrial fibrillation with uncontrolled ventricular response, though other possibilities include multifocal atrial tachycardia (MAT) or sinus rhythm with frequent premature beats 1
• Obtain a 12-lead ECG with expert consultation when there is doubt about the rhythm diagnosis in stable patients 1
• Wide-complex irregular rhythms should be considered pre-excited atrial fibrillation requiring expert consultation 1

Management Strategy: Rate Control vs Rhythm Control

Rate Control (Preferred for Most Patients)

Rate control with chronic anticoagulation is recommended for the majority of patients based on multiple large trials showing no mortality benefit and potentially increased harm with aggressive rhythm control 1. The evidence supporting this includes:

• The AFFIRM trial showed a trend toward increased mortality in rhythm-control patients older than 65 years, those without heart failure, and those with coronary disease 1
• The RACE trial demonstrated a trend for increased mortality in rhythm-control patients with hypertension and in women 1
• Only 39-40% of patients in rhythm-control groups maintained sinus rhythm at one year despite aggressive treatment 1
• Rhythm-control patients consistently experienced more hospitalizations and adverse drug events 1

When to Consider Rhythm Control

Rhythm control is appropriate in specific circumstances 1:

• Patients with severe symptoms despite adequate rate control
• Young patients with structurally normal hearts (not well-represented in major trials)
• Patients with paroxysmal AF (underrepresented in trials)
• Patient preference after informed discussion of risks and benefits
• Heart failure with reduced ejection fraction where catheter ablation may improve outcomes 2

Acute Rate Control Strategies

Hemodynamically Stable Patients

IV beta-blockers and nondihydropyridine calcium channel blockers (diltiazem) are the drugs of choice for acute rate control (Class IIa, LOE A) 1:

• Diltiazem IV 1
• Esmolol IV 1
• Verapamil IV or oral 1
• Other beta-blockers IV or oral 1

For patients with heart failure:

• Digoxin and amiodarone may be used for rate control in congestive heart failure patients 1
• Critical caveat: Consider the potential risk of conversion to sinus rhythm with amiodarone before using this agent 1

Hemodynamically Unstable Patients

Prompt electrical cardioversion is indicated for patients who are hemodynamically unstable 1

Critical Pitfall: Pre-Excited Atrial Fibrillation

Avoid AV nodal blocking agents (adenosine, calcium channel blockers, digoxin, and possibly beta-blockers) in patients with pre-excitation atrial fibrillation, as these drugs may cause paradoxical increase in ventricular response 1:

• These patients typically present with very rapid heart rates
• Emergent electrical cardioversion is required 1
• When cardioversion is not feasible, rhythm control agents may be useful 1

Cardioversion Considerations

Timing and Anticoagulation

Electric or pharmacologic cardioversion should not be attempted in patients with AF duration >48 hours unless the patient is unstable 1:

• Patients with AF >48 hours have increased risk for cardioembolic events 1
• Alternative strategy: cardioversion following anticoagulation with heparin and transesophageal echocardiography to exclude left atrial thrombus 1
• Maintain therapeutic anticoagulation even after cardioversion when no thrombus is identified by TEE 1

Rhythm Control Agents

For pharmacologic cardioversion, expert consultation is recommended as various agents show different efficacy 1. The 2024 ESC guidelines support early rhythm control in selected patients with symptomatic AF 1.

Long-Term Anticoagulation

Chronic anticoagulation is essential regardless of whether rate or rhythm control strategy is chosen 1:

• All primary endpoints in the STAF trial occurred in patients in atrial fibrillation, even in the rhythm-control group 1
• This suggests that anticoagulation should continue indefinitely even with rhythm control attempts 1
• Direct oral anticoagulants (apixaban, rivaroxaban, edoxaban) are preferred over warfarin due to lower bleeding risks 2

Combination Therapy

A combination of digoxin and beta-blockers appears more effective than digoxin and diltiazem for rate control 1

Emerging Evidence

Recent data increasingly supports early rhythm control in patients with AF that has not become long-standing to reduce irreversible atrial remodeling and prevent AF-related deaths, heart failure, and strokes 3. However, current practice still favors rate control for most patients based on the strongest guideline evidence 1.