What is Atrial Fibrillation (AFib) with Rapid Ventricular Response (RVR)?

Definition of Atrial Fibrillation with Rapid Ventricular Response (AFib with RVR)

Atrial fibrillation with rapid ventricular response (AFib with RVR) is a supraventricular tachyarrhythmia characterized by uncoordinated atrial activation with consequent deterioration of atrial mechanical function, associated with an irregular, frequently rapid ventricular rate typically exceeding 100-120 beats per minute due to intact atrioventricular conduction.

Diagnostic Characteristics

• On electrocardiogram (ECG), AFib is characterized by the replacement of consistent P waves with rapid oscillations or fibrillatory waves that vary in amplitude, shape, and timing 1
• The ventricular response is typically irregular with RR intervals that do not follow a repetitive pattern 1
• The ventricular rate in AFib with RVR is frequently rapid, often exceeding 100-120 beats per minute, which distinguishes it from controlled AFib 1, 2
• The atrial cycle length (when visible) is usually variable and less than 200 ms (≥300 bpm) 1

Pathophysiology

• The ventricular response to AFib depends on:

  • Electrophysiological properties of the AV node 1
  • Level of vagal and sympathetic tone 1
  • Presence or absence of accessory conduction pathways 1
  • Action of drugs affecting AV nodal conduction 1

• Extremely rapid rates (over 200 beats per minute) strongly suggest the presence of an accessory pathway or ventricular tachycardia 1

Hemodynamic Effects

• Acute loss of coordinated atrial mechanical function reduces cardiac output by 5-15% 1
• High ventricular rates limit ventricular filling due to shortened diastolic interval 1
• Irregularity of ventricular response can further reduce cardiac output due to force-interval relationships, causing variability in the strength of subsequent heartbeats and often resulting in pulse deficit 1
• Persistent elevation of ventricular rates above 120-130 bpm may produce ventricular tachycardiomyopathy 1

Clinical Significance

• AFib with RVR can lead to serious complications including:
  • Hypoperfusion and cardiac ischemia 2
  • Heart failure exacerbation 1
  • Tachycardia-induced cardiomyopathy with prolonged rapid rates 1, 2
  • Increased risk of stroke and thromboembolism 1, 2

Differential Diagnosis

• Other supraventricular arrhythmias may mimic AFib with RVR, including:

  • Atrial flutter with variable conduction 1
  • Atrial tachycardias 1
  • Rare forms of frequent atrial ectopy 1
  • Dual antegrade atrioventricular nodal conduction 1

• A 12-lead ECG of sufficient duration and quality is essential to evaluate atrial activity and confirm the diagnosis 1

Management Considerations

• Rate control using beta-blockers (e.g., metoprolol) or calcium channel blockers (e.g., diltiazem) is the primary approach for hemodynamically stable patients 2, 3
• Emergent cardioversion is indicated for hemodynamically unstable patients 2
• Anticoagulation assessment using tools like CHA₂DS₂-VASc is important for stroke prevention 2
• Direct oral anticoagulants are first-line for anticoagulation in eligible patients 2

Common Pitfalls and Caveats

• AFib with RVR may be misdiagnosed as atrial flutter when atrial activity is prominent on ECG in more than one lead 1
• Regular RR intervals are possible in AFib in the presence of AV block or interference by ventricular or junctional tachycardia, which may confuse the diagnosis 1
• In patients with implanted pacemakers, diagnosis of AFib may require temporary inhibition of the pacemaker to expose atrial fibrillatory activity 1
• Secondary causes of AFib with RVR (such as sepsis, hyperthyroidism, or pulmonary embolism) should always be considered and addressed 2