Rosen & Barkin's 5-Minute Emergency Medicine Consult (86 page)

FOLLOW-UP

• Unstable AF:
  
  • Inability to control rate
    
• High risk for stroke:
  
  • Prior cardiovascular accident
    
  • CHF
    
• Associated medical problems contributing to the AF that require inpatient management
  

• Conversion to sinus rhythm if symptoms <48 hr
  
• Chronic AF with appropriate ventricular rate control and anticoagulation
  
• New-onset AF with rate control and anticoagulation
  

• Cardiology or an electrophysiologist
  
• Evaluation for outpatient cardioversion
  

• INR check if placed on warfarin
  
• The patient should return to the ED if feeling faint, dizzy, numbness or weakness of the face or limbs, or trouble seeing or speaking
  

• If hemodynamically unstable and life threatening, synchronized cardioversion is warranted
  
• Rate or rhythm control is an individualized option for stable atrial fibrillation using β-blockers, calcium channel blockers, or antiarrhythmics
  
• Do not mistake F-waves or U-waves as P-waves. Can misdiagnose AF as a sinus rhythm.
  
• Do not use channel blockers, β-blockers, or digoxin in AF with a wide complex AF in a patient with an underlying bypass tract
  

• Chinitz JS, Halperin JL, Reddy VY, et al. Rate or rhythm control for atrial fibrillation: Update and controversies.
  Am J Med.
  2012;125(11):1049–1056.
  
• Crandall MA, Bradley DJ, Packer DL, et al. Contemporary management of atrial fibrillation: Update on anticoagulation and invasive management strategies.
  Mayo Clin Proc
  . 2009;84:643–662.
  
• Fuster V, Ryden LE, Asinger RW, et al. ACC/AHA/ESC Guidelines for the Management of Patients with Atrial Fibrillation: Executive Summary a Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology.
  Circulation
  . 2006;148(4):e149–e246.
  
• Khoo CW, Lip GY. Acute management of atrial fibrillation.
  Chest
  . 2009;135(3):849–859.
  
• Stiell IG, Clement CM, Perry JJ, et al. Association of the Ottawa aggressive protocol with rapid discharge of emergency department patients with recent-onset atrial fibrillation or flutter.
  CJEM.
  2010;12(3):181–191.
  
• Wann LS, Curtis AB, January CT, et al. 2011 ACCF/AHA/HRS focused update on the management of patients with atrial fibrillation (updating the 2006 guideline): A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines.
  J Am Coll Cardiol
  . 2011;57(2):223–242.
  

CODES

427.31 Atrial fibrillation

BASICS

• Atrial dysrhythmia
  
• 200,000 new cases each year
  
• A macroreentrant circuit in the right atrium is thought to be the underlying mechanism.
  
• Most sensitive rhythm to cardioversion
  
• Seldom occurs in the absence of organic heart disease
  
• Less common than supraventricular tachycardia (SVT) or atrial fibrillation
  
• Typically paroxysmal, lasting seconds to hours
  
• Occurs in ∼25–35% of patients with atrial fibrillation
  
• Untreated, may promote cardiomyopathy
  

• Alcoholism
  
• Cardiomyopathies and myocarditis
  
• CHF
  
• Electrolyte abnormalities
  
• Ischemic heart disease
  
• Pulmonary embolus and other pulm diseases
  
• Valvular heart diseases
  
• Post op following cardiac surgery (often in 1st postoperative week)
  
• Thyrotoxicosis
  

• Occurs in children but is often asymptomatic
  
• Associated mortality is highest in the neonatal period.
  
• Associated with:
  
  • Congenital heart disease
    
  • Infectious etiologies, such as rheumatic fever or myocarditis
    
• Be sure to consider potential toxic ingestions in pediatric patients with new AV block
  

DIAGNOSIS

• Palpitations
  
• Syncope/presyncope
  
• Chest pain
  
• Fatigue
  
• Dyspnea
  
• Poor exercise capacity
  
• Tachycardia—HR >150 bpm:
  
• Hypotension
  
• Heart failure
  

• Infants do not tolerate atrial flutter well.
  
• The aortic valve (AV) node is capable of very rapid conduction.
  
• Extremely rapid ventricular rates can lead to shock or CHF.
  
• Atrial flutter can occur in the fetus and young infants without associated cardiac defects:
  
  • Often does not recur beyond neonatal period
    
• Most older children have an underlying cardiac abnormality
  
  • More likely to recur and difficult to control
    

• EKG
  
• Labs
  
• CXR
  

• Electrolytes and mineral panel
  
• Cardiac enzymes
  
• Digoxin level
  
• PT/PTT
  

• CXR:
  
  • May identify cardiomyopathy or CHF
    
• Echo:
  
  • May identify regional wall motion abnormalities or valvular dysfunction
    

• SVT
  
• Sinus tachycardia
  
• Atrial fibrillation
  
• Multifocal atrial tachycardia
  
• Ventricular tachycardia (VT)
  

TREATMENT

• Oxygen, monitor, IV access
  
• Unstable patients should be cardioverted in the field:
  
  • Immediate synchronized cardioversion
    
  • Start with 100 J
    

• Oxygen, monitor, IV access
  
• Immediate synchronized cardioversion if unstable
  
  • Current guidelines recommend starting at 150–200 J min to improve initial success and to limit cumulative energy doses.
    

• Rate control:
  
  • Rate control should be instituted prior to giving an antidysrhythmic to avoid risk of a 1:1 AV conduction ratio and hemodynamic collapse.
    
  • May be difficult to achieve
    
• Anticoagulation:
  
  • Same guidelines as for atrial fibrillation:
    
    • INR 2–3 for 3 wk prior to cardioversion if >48 hr or unknown duration
      
    • Recommended even if negative transesophageal echo
      
    • Risk of thromboembolism ranges from 1.7–7%.
      
  • CHADS
    ₂
    score: Used for decision regarding anticoagulation
    
    • CHF history (1 point)
      
    • Hypertension history (1 point)
      
    • Age ≥75 (1 point)
      
    • DM history (1 point)
      
    • Stroke symptoms or TIA history (2 points):
      
      • Score 0: Aspirin is sufficient prophylaxis
        
      • Score 1: Oral anticoagulants preferred
        
      • Score 2 or more: Oral anticoagulants strongly recommended
        
  • Patients at higher thromboembolism risk:
    
    • Valvular heart disease
      
    • Fluctuating a fib/flutter rhythms
      
    • Left ventricular (LV) dysfunction
      
    • Prior stroke or thromboembolism
      
    • Longer symptom duration (>48 hr)
      
• Antiarrhythmic drugs:
  
  • Adenosine:
    
    • Unlikely to break atrial flutter
      
    • May aid in the diagnosis of atrial flutter by unmasking the flutter waves
      
  • Amiodarone:
    
    • Rate control in patients with pre-excited atrial arrhythmias (i.e., WPW)
      
    • Preferable antiarrhythmic agent for patients with severely impaired heart function
      
    • Major adverse effects are hypotension and bradycardia, slower infusions can prevent this.
      
  • Calcium channel blockers:
    
    • Rate control
      
    • Verapamil has higher incidence of symptomatic hypotension than diltiazem.
      
    • Verapamil should only be used in narrow-complex arrhythmias
      
  • β-blockers:
    
    • Rate control
      
    • Added benefit of cardioprotective effects for patients with ACS
      
  • Magnesium sulfate:
    
    • Rate control
      
    • Low-level evidence
      
  • Digoxin:
    
    • Rate control
      
    • 3rd-line drug
      
    • Has inotropic properties so may be useful in patients with ventricular dysfunction
      
    • Longer onset to therapeutic effect
      
  • Procainamide:
    
    • Rhythm control
      
    • Drug of choice for patients with known pre-excitation syndromes (i.e., WPW) and preserved ventricular function
      
    • Caution if patient has QT prolongation
      
  • Sotalol:
    
    • Rhythm control
      
    • Not a 1st-line drug
      
    • For use in WPW and preserved ventricular function if duration of arrhythmia is ≤48 hr
      
  • Ibutilide:
    
    • Rhythm control
      
    • For acute pharmacologic rhythm conversion in patients with preserved ventricular function (EF >30%) if duration of arrhythmia is ≤48 hr
      
    • Correct potassium and magnesium before use
      
    • Contraindicated if QTc >440 msec or in patients with severe structural heart disease
      
    • Efficacy rate of 38–76%
      
    • Mean time to conversion is 30 min.
      
    • Incidence of sustained polymorphic VT 1.2–1.7%
      
    • Observe for 4–6 hr after administration for QT prolongation or VT.
      
• Cardioversion:
  
  • 100–360 J
    
  • Sedation when possible
    
  • Safest and most effective means of restoring sinus rhythm
    
• Maintenance of sinus rhythm after cardioversion:
  
  • High recurrence rate: ∼50% at 1 yr; however, difficult to determine rate because data combines atrial fibrillation with atrial flutter
    
  • Amiodarone most effective
    
• Percutaneous catheter ablation:
  
  • Acute success rates exceed 95%.
    
  • 5–10% recurrence in 1–2 yr of follow-up
    
  • Low complication rate
    
  • Candidates include:
    
    • Recurrent episodes of drug-resistant atrial flutter
      
    • Patients who are drug intolerant
      
    • Patients who do not desire long-term drug therapy