Management of New Onset Atrial Fibrillation in the Hospital
For hemodynamically stable patients with new onset atrial fibrillation in the hospital, initiate rate control with IV beta-blockers (metoprolol 2.5-5 mg IV over 2 minutes) or non-dihydropyridine calcium channel blockers (diltiazem 0.25 mg/kg IV bolus), begin therapeutic anticoagulation immediately with IV heparin or subcutaneous enoxaparin, and assess stroke risk using CHA₂DS₂-VASc score to guide long-term anticoagulation decisions. 1, 2, 3
Immediate Assessment
Determine hemodynamic stability first by evaluating for symptomatic hypotension, ongoing chest pain, acute pulmonary edema, altered mental status, or heart failure not responding to initial measures. 4, 3 If any of these are present, proceed directly to immediate synchronized electrical cardioversion at 120-200 joules biphasic without waiting for anticoagulation. 1, 4
Obtain a 12-lead ECG to confirm the diagnosis and assess for pre-excitation (Wolff-Parkinson-White syndrome), which requires different management. 2, 3
Rate Control Strategy (Hemodynamically Stable Patients)
Administer IV beta-blockers as first-line therapy in patients with preserved left ventricular function (LVEF >40%). 1, 2, 3 Metoprolol 2.5-5 mg IV over 2 minutes, repeated every 5-10 minutes up to 15 mg total, is the preferred agent. 3
Alternatively, use diltiazem (non-dihydropyridine calcium channel blocker) at 0.25 mg/kg IV bolus over 2 minutes, followed by 0.35 mg/kg if needed, then continuous infusion at 5-15 mg/hour. 1, 3
Target heart rate <110 bpm at rest initially (lenient control), with stricter control (<80 bpm) only if symptoms persist. 3
For patients with reduced ejection fraction (LVEF ≤40%) or heart failure, use IV beta-blockers or digoxin, but avoid calcium channel blockers as they can worsen heart failure. 1, 2, 3 Amiodarone may be considered in this population for both rate control and potential rhythm conversion. 1
Critical pitfall: Digoxin alone is ineffective for rate control in paroxysmal atrial fibrillation and should not be used as monotherapy. 2, 3
Anticoagulation Management
Initiate therapeutic anticoagulation immediately with IV unfractionated heparin (80 units/kg bolus, then 18 units/kg/hour infusion targeting aPTT 1.5-2 times control) or subcutaneous enoxaparin (1 mg/kg twice daily) unless contraindicated. 3
For atrial fibrillation lasting >48 hours or unknown duration, anticoagulation must continue for at least 3-4 weeks before any elective cardioversion attempt and for at least 4 weeks after cardioversion. 1, 2, 4 This is because cardioversion can cause atrial stunning with delayed thrombus formation and embolization, with most thromboembolic events occurring within the first 10 days post-cardioversion. 1
Assess stroke risk using CHA₂DS₂-VASc score to determine need for long-term anticoagulation. 2, 3 Initiate oral anticoagulation for scores ≥2, preferring direct oral anticoagulants (DOACs) over warfarin unless the patient has mechanical heart valves or mitral stenosis. 2, 4
Rhythm Control Considerations
Immediate electrical cardioversion is indicated for hemodynamically unstable patients regardless of atrial fibrillation duration. 1, 4 Administer IV heparin first if possible, but do not delay cardioversion. 1
For stable patients with atrial fibrillation <48 hours duration, elective cardioversion (electrical or pharmacological) may be performed without prolonged anticoagulation, though immediate therapeutic anticoagulation should still be initiated. 1, 3
For atrial fibrillation >48 hours or unknown duration in stable patients, two options exist: 1, 3
- Anticoagulate therapeutically for 3 weeks, then perform cardioversion, followed by 4 weeks of continued anticoagulation
- Perform transesophageal echocardiography to exclude left atrial thrombus, then proceed with cardioversion if no thrombus is present, with continued anticoagulation
Pharmacological cardioversion agents include IV ibutilide or procainamide, though electrical cardioversion is generally more effective. 1 Amiodarone 150 mg IV over 10 minutes may facilitate conversion while also providing rate control. 1
Special Situations
Pre-excited atrial fibrillation (Wolff-Parkinson-White syndrome) requires immediate recognition. 1, 3 Never use AV nodal blocking agents (beta-blockers, calcium channel blockers, digoxin, adenosine) as these can paradoxically accelerate ventricular rate and precipitate ventricular fibrillation. 1, 3 Use IV procainamide (15 mg/kg over 30-60 minutes) or ibutilide instead, or proceed directly to electrical cardioversion if hemodynamically unstable. 1, 3
Acute coronary syndrome with atrial fibrillation requires urgent cardioversion if hemodynamic compromise, ongoing ischemia, or inadequate rate control is present. 1 IV beta-blockers are first-line for rate control unless contraindicated by heart failure or hemodynamic instability. 1
Postoperative atrial fibrillation should be managed with AV nodal blocking agents for rate control. 2 Prophylactic oral beta-blockers reduce the incidence of postoperative atrial fibrillation in cardiac surgery patients. 2
Duration of Therapy and Follow-up
Continue anticoagulation long-term based on CHA₂DS₂-VASc score, regardless of whether the patient remains in atrial fibrillation or converts to sinus rhythm. 2, 3 Patients who develop atrial fibrillation during acute illness have high long-term risks for recurrence and complications including stroke, heart failure, and death. 5
Antiarrhythmic medications may be initiated before cardioversion in patients with atrial fibrillation >3 months duration to reduce early recurrence, with brief duration of therapy (e.g., 1 month). 1 However, not all patients require long-term antiarrhythmic therapy after successful cardioversion. 1
Reassess patients after hospital discharge as new-onset atrial fibrillation during critical illness carries significant long-term risks that require ongoing management and monitoring. 5