What is the definition and treatment of atrial fibrillation with a fast ventricular rate?

Atrial Fibrillation with Rapid Ventricular Response: Definition and Treatment

Atrial fibrillation with rapid ventricular response (AFib with RVR) is defined as AFib with an irregular ventricular rate typically exceeding 100 beats per minute, characterized on ECG by absent P waves, irregular R-R intervals, and fibrillatory waves, with the ventricular rate determined by AV nodal conduction properties and autonomic tone. 1

Definition and ECG Characteristics

AFib with RVR is a supraventricular tachyarrhythmia with specific features 1:

• Replacement of consistent P waves by rapid oscillations or fibrillatory waves that vary in size, shape, and timing 1
• Irregular R-R intervals when AV conduction is intact 1
• Absence of distinct repeating P waves 1
• Ventricular rate typically >100 bpm, often 120-160 bpm in untreated states 1

The ventricular rate depends on AV nodal electrophysiological properties, vagal and sympathetic tone, and drug effects 1. Extremely rapid rates exceeding 200 bpm suggest the presence of an accessory pathway (Wolff-Parkinson-White syndrome), which requires different management 1.

Treatment Algorithm

Step 1: Assess Hemodynamic Stability

Hemodynamically unstable patients require immediate synchronized electrical cardioversion 2. Instability includes 2:

• Symptomatic hypotension
• Acute heart failure or pulmonary edema
• Ongoing chest pain/acute coronary syndrome
• Altered mental status

Step 2: Hemodynamically Stable Patients - Rate Control

For stable patients, initiate rate control medications promptly rather than waiting for spontaneous conversion 2, 3.

First-Line Rate Control Agents

Beta-blockers or non-dihydropyridine calcium channel blockers are first-line therapy 2, 3, 4:

• Beta-blockers (metoprolol, esmolol): Recommended as Class I therapy, especially in patients with preserved left ventricular function (LVEF >40%) 3, 4
• Diltiazem: Achieves rate control faster than metoprolol and is highly effective 2, 5
• Verapamil: Alternative non-dihydropyridine calcium channel blocker 2

Target heart rate: <110 bpm at rest is the initial lenient goal for most patients 2, 3. A stricter target of 60-80 bpm is reserved only for patients with persistent symptoms or suspected tachycardia-induced cardiomyopathy 3.

Second-Line and Combination Therapy

• Digoxin: May be added to beta-blockers in heart failure patients with reduced ejection fraction, but should not be used as monotherapy in active patients (Class III recommendation) 3, 4
• Amiodarone: Preferred in patients with heart failure and reduced LVEF <35% 2, 4

Step 3: Special Populations

Wolff-Parkinson-White Syndrome with Pre-excited AFib

IV procainamide or ibutilide is recommended rather than AV nodal blocking agents 2, 6. Beta-blockers and calcium channel blockers are contraindicated as they can accelerate conduction through the accessory pathway 2, 6.

Heart Failure with Reduced Ejection Fraction

• Beta-blockers remain first-line due to prognostic benefits in LVEF ≤40% 3
• Amiodarone is preferred when beta-blockers are contraindicated or ineffective 2, 4
• IV non-dihydropyridine calcium channel blockers are contraindicated in decompensated heart failure (Class III) 3

Step 4: Consider Rhythm Control

Elective cardioversion or rhythm control strategies should be considered in 2, 7, 8:

• Patients who remain symptomatic despite adequate rate control
• First episode of AFib in younger patients with minimal heart disease
• Patients with tachycardia-induced cardiomyopathy
• Patient preference after shared decision-making

Step 5: Anticoagulation Assessment

Assess stroke risk using CHA2DS2-VASc score in all patients 9, 7, 8:

• Score ≥2 in men or ≥3 in women: Oral anticoagulation recommended with target INR 2.0-3.0 for warfarin 9
• Direct oral anticoagulants are first-line over warfarin when appropriate 7, 8
• High-risk features requiring anticoagulation include: prior stroke/TIA, age >75 years, heart failure, hypertension, diabetes, or vascular disease 9

Common Pitfalls to Avoid

• Do not use digoxin as monotherapy for rate control in active patients—it cannot control heart rate during exercise 3, 4
• Do not use AV nodal blockers in patients with accessory pathways (WPW)—use procainamide instead 2, 6
• Do not give IV calcium channel blockers to patients with decompensated heart failure 3
• Do not wait for spontaneous conversion in most patients—initiate rate control promptly 2
• Do not target overly strict rate control initially—lenient control (<110 bpm) is appropriate for most patients 2, 3

Monitoring and Follow-up

Obligatory evaluation includes 3:

• Resting heart rate measurement
• 24-hour Holter monitoring
• Exercise testing in symptomatic patients to assess rate control adequacy

Uncontrolled tachycardia ≥130 bpm can lead to tachycardia-induced cardiomyopathy, and adequate rate control can improve ejection fraction in approximately 25% of patients with LVEF <45% 3.