What is the initial treatment for atrial fibrillation (AF) in a hemodynamically unstable patient in a casualty setting?

Treatment of Atrial Fibrillation in Casualty

If the patient is hemodynamically unstable (hypotension, shock, altered mental status, pulmonary edema, ongoing chest pain), perform immediate synchronized electrical cardioversion at 120-200 joules biphasic without waiting for anticoagulation. 1, 2, 3

Immediate Assessment

Upon arrival, rapidly assess for signs of hemodynamic instability:

• Hypotension or shock 2, 3
• Altered mental status or decreased consciousness 2
• Ongoing chest pain or acute myocardial infarction 2
• Pulmonary edema or acute heart failure 2
• Severe dyspnea 2

Document the arrhythmia with at least a single-lead ECG recording before initiating treatment, and assess ventricular rate, QRS duration, and QT interval. 3

Hemodynamically Unstable Patients

Proceed directly to synchronized electrical cardioversion without delay for anticoagulation. 1, 2, 3

• Deliver 120-200 joules biphasic (or 200 joules monophasic) under appropriate sedation 3
• Administer intravenous unfractionated heparin bolus followed by continuous infusion concurrently with cardioversion 2, 3
• Continue anticoagulation for at least 4 weeks after cardioversion regardless of CHA₂DS₂-VASc score 2

Critical Pitfall to Avoid

Do not delay cardioversion for anticoagulation in truly unstable patients—hemodynamic instability takes precedence over thromboembolic risk. 3

Hemodynamically Stable Patients

For stable patients, the initial strategy focuses on rate control as the first-line approach in the acute casualty setting. 1

Rate Control Strategy

Administer intravenous beta-blockers or non-dihydropyridine calcium channel blockers as first-line therapy for patients with preserved ejection fraction (LVEF >40%). 1, 4, 3

Medication Options for LVEF >40%:

• Metoprolol: 2.5-5 mg IV bolus over 2 minutes, repeat every 5-10 minutes up to 15 mg total 3
• Diltiazem: 0.25 mg/kg IV bolus over 2 minutes, followed by 0.35 mg/kg if needed, then continuous infusion 5-15 mg/hour 3
• Verapamil: Can be used as alternative to diltiazem 1

Target initial heart rate <110 beats per minute (lenient rate control). 3

For Patients with Reduced Ejection Fraction (LVEF ≤40%):

Use beta-blockers and/or digoxin—avoid calcium channel blockers due to negative inotropic effects. 1, 4, 3

• Digoxin: 0.0625-0.25 mg per day 4
• Beta-blockers are preferred due to favorable effects on morbidity and mortality in systolic heart failure 4

Special Populations

Patients with COPD or Active Bronchospasm:

Avoid beta-blockers and use diltiazem 60 mg PO three times daily as first-line rate control. 4

Patients with Pre-excited Atrial Fibrillation (Wolff-Parkinson-White):

Avoid AV nodal blocking agents (adenosine, calcium channel blockers, digoxin, beta-blockers) as they can accelerate ventricular rate and precipitate ventricular fibrillation. 1, 2, 3

• If hemodynamically unstable: immediate DC cardioversion 4
• If stable: consider IV procainamide or ibutilide 4, 2

Anticoagulation in the Casualty Setting

Begin anticoagulation as soon as possible after initial stabilization for all eligible patients. 2

Stroke Risk Assessment:

Calculate CHA₂DS₂-VASc score immediately:

• Congestive heart failure (1 point) 4, 3
• Hypertension (1 point) 4, 3
• Age ≥75 years (2 points) 3
• Diabetes mellitus (1 point) 3
• Stroke/TIA/thromboembolism (2 points) 3
• Vascular disease (1 point) 3
• Age 65-74 years (1 point) 3
• Sex category female (1 point) 4, 3

Initiate anticoagulation for all patients with CHA₂DS₂-VASc score ≥2. 1, 3

Prescribe direct oral anticoagulants (DOACs)—apixaban, dabigatran, edoxaban, or rivaroxaban—over warfarin except in patients with mechanical heart valves or mitral stenosis. 1, 3

Rhythm Control Considerations in Casualty

When to Consider Pharmacological Cardioversion:

Consider rhythm control for symptomatic patients who remain symptomatic despite adequate rate control, younger patients, or those with new-onset AF (<48 hours). 3

Cardioversion Timing Based on AF Duration:

AF Duration <48 Hours:

Cardioversion may proceed after initiating anticoagulation without waiting for therapeutic levels. 3

AF Duration >48 Hours or Unknown:

Provide therapeutic anticoagulation for 3 weeks before elective cardioversion, then continue anticoagulation for minimum 4 weeks after cardioversion. 1, 3

Alternative: Perform transesophageal echocardiography to exclude left atrial thrombus followed by prompt cardioversion. 1

Pharmacological Cardioversion Options:

For patients without structural heart disease, severe left ventricular hypertrophy, HFrEF, or coronary artery disease:

• Intravenous flecainide or propafenone 1
• Intravenous vernakalant (excluding patients with recent ACS, HFrEF, or severe aortic stenosis) 1

For patients with severe left ventricular hypertrophy, HFrEF, or coronary artery disease:

• Intravenous amiodarone: 150 mg IV over 10 minutes for supplemental doses, or 300 mg IV diluted in 250 ml of 5% glucose over 30-60 minutes 1, 4, 2, 5
• Maintenance infusion: 0.5 mg/min (720 mg per 24 hours) using concentrations of 1-6 mg/mL via central venous catheter 5

Critical Pitfall:

Do not use pharmacological cardioversion in patients with sinus node dysfunction, atrioventricular conduction disturbances, or prolonged QTc (>500 ms) unless risks for proarrhythmia and bradycardia have been carefully considered. 1

Initial Diagnostic Workup Before Discharge

Obtain transthoracic echocardiogram to assess left atrial size, left ventricular function, valvular disease, and exclude structural abnormalities. 3

Order blood tests for thyroid function (TSH), renal function (creatinine clearance), hepatic function, and electrolytes. 3

Common Pitfalls in Casualty Management

• Do not use digoxin as sole agent for rate control in paroxysmal AF—it is ineffective during exercise and sympathetic surge 3
• Do not combine anticoagulants with antiplatelet agents unless acute vascular event or specific procedural indication—increases bleeding risk without additional benefit 1, 3
• Do not use AV nodal blockers in pre-excited AF (wide-complex irregular rhythm)—can cause paradoxical increase in ventricular response 1, 4
• Do not exceed amiodarone concentrations of 2 mg/mL for infusions longer than 1 hour unless using central venous catheter—high incidence of peripheral vein phlebitis 5