A patient with no known history is found today to have atrial fibrillation with a ventricular rate of approximately 135 beats per minute on ECG; what is the appropriate acute management?

Acute Management of Atrial Fibrillation with Rapid Ventricular Response (Heart Rate ~135 bpm)

Immediately assess hemodynamic stability and initiate rate control with intravenous beta-blockers as first-line therapy, while simultaneously evaluating stroke risk and need for anticoagulation. 1

Immediate Assessment

Evaluate for hemodynamic instability by checking for:

• Hypotension, chest pain, dyspnea, altered mental status, or signs of acute heart failure 1
• Symptoms suggesting hypoperfusion, acute stroke, or rate-related cardiac ischemia 1
• Document rhythm with 12-lead ECG to confirm atrial fibrillation and assess for ischemic changes 2, 1

The ventricular rate of approximately 135 bpm (9 QRS complexes in 20 large boxes at 25 mm/s) indicates rapid ventricular response requiring urgent rate control. 2

Rate Control Strategy (Hemodynamically Stable Patients)

Administer IV metoprolol 2.5-5 mg over 2 minutes as first-line therapy for immediate rate control, targeting a heart rate of 80-110 bpm at rest. 1

• Beta-blockers are Class I (Level A) recommendation for rate control in atrial fibrillation 2, 1
• If beta-blockers are contraindicated, consider IV diltiazem as an alternative calcium channel blocker 3
• Digoxin may be added as a second agent for synergistic AV nodal blockade if monotherapy is insufficient 1

Common pitfall: Atrial fibrillation complicates 15-20% of myocardial infarctions and is frequently associated with severe left ventricular damage. 2 Always assess for underlying acute coronary syndrome or heart failure as precipitating causes. 2, 4

Anticoagulation and Stroke Risk Assessment

Calculate CHA₂DS₂-VASc score immediately to determine stroke risk:

• Age ≥75 years (2 points), age 65-74 (1 point)
• Female sex (1 point)
• Hypertension, diabetes, heart failure, vascular disease (1 point each)
• Prior stroke/TIA (2 points) 1

Initiate oral anticoagulation with a direct oral anticoagulant (apixaban, rivaroxaban, or edoxaban) for CHA₂DS₂-VASc score ≥2 in men or ≥3 in women, as this reduces stroke risk by 60-80% compared to placebo. 5, 1

• Direct oral anticoagulants are preferred over warfarin due to lower bleeding risks 5
• Aspirin is NOT recommended for stroke prevention in atrial fibrillation due to poorer efficacy 5

Cardioversion Considerations

Do NOT attempt immediate cardioversion if atrial fibrillation duration is unknown or >48 hours due to thromboembolism risk. 1, 2

• If cardioversion is desired, require either:
  • 3 weeks of therapeutic anticoagulation prior to cardioversion, OR
  • Transesophageal echocardiography to exclude left atrial thrombus 1
• Continue anticoagulation indefinitely after cardioversion in patients with high stroke risk 1

Exception: Emergent electrical cardioversion is indicated only in hemodynamically unstable patients with hypotension, acute heart failure, or ongoing myocardial ischemia. 2, 4

Disposition and Follow-up

Discharge is appropriate only if:

• Rate control achieved (heart rate <110 bpm at rest) 1
• Hemodynamically stable without ongoing symptoms 1
• Appropriate anticoagulation initiated based on stroke risk 1
• Close cardiology follow-up arranged within 1-2 weeks 1

Consider admission if:

• First episode of atrial fibrillation requiring workup for underlying etiology 6, 4
• Inadequate rate control despite therapy 4
• Concern for acute coronary syndrome, heart failure, or other precipitating conditions 2, 4
• High-risk features requiring inpatient monitoring 4

Key Clinical Pearls

• The irregular ventricular rhythm in atrial fibrillation creates beat-to-beat variations in stroke volume, potentially causing a pulse deficit where apical heart rate exceeds peripheral pulse rate 7
• Extremely rapid rates (>200 bpm) suggest presence of an accessory pathway (Wolff-Parkinson-White syndrome) and require urgent cardiology consultation 2, 7
• Atrial fibrillation may be the initial presentation of underlying conditions including hyperthyroidism, valvular disease, or acute coronary syndrome—evaluate for reversible causes 6, 8
• Loss of atrial contraction ("atrial kick") decreases cardiac output by 20-30% in normal individuals and more in those with heart disease 8