Rosen & Barkin's 5-Minute Emergency Medicine Consult (788 page)

• Tachycardia:
  
  • Rapid and regular:
    
    • Supraventricular tachycardia
      
    • Atrial flutter
      
  • Irregular:
    
    • Atrial fibrillation
      
• Signs of instability:
  
  • Chest pain
    
  • Hypotension
    
  • Change in mental status
    
  • Rales
    
  • Cyanosis
    

• WPW syndrome should be considered the underlying etiology in all cases of tachydysrhythmia.
  
• The diagnosis should be based on the characteristic ECG findings.
  

• Cardiac enzymes only if signs of ischemia
  
• Consider electrolytes and thyroid disease
  

• EKG
  
• Pre-excitation:
  
  • Short PR interval, <0.12 sec
    
  • Δ-wave: Small slurred upstroke at the beginning of the QRS
    
  • Prolonged QRS, >0.10 sec with variable morphology linked to specific accessory pathway
    
• Left lateral pathway:
  
  • Positive Δ-waves
    
  • Q-waves with negative to isoelectric deflections in V1 and in the inferior leads:
    
    • May suggest a former high lateral MI and right axis deviation
      
• Posteroseptal accessory pathway:
  
  • Negative deflecting Δ-waves
    
  • QRS complexes in the inferior leads:
    
    • Often mistaken for prior inferior MI
      
• Tachydysrhythmias:
  
  • Orthodromic atrioventricular re-entrant tachycardia (OAVRT):
    
    • The pathway that conducts the impulse to the ventricle is the AV node/His–Purkinje system
      
    • Narrow QRS complex tachycardia
      
    • However, this may be associated with a wide QRS complex in the presence of a pre-existing or rate-related functional bundle branch block.
      
    • P-wave following the QRS
      
    • Rate between 150–250 bpm
      
    • The Δ-wave seen during sinus rhythm is lost since antegrade conduction is not via the accessory pathway
      
  • Antidromic AVRT:
    
    • Regular
      
    • Wide QRS complex
      
    • The antegrade limb is usually the accessory pathway.
      
  • Atrial fibrillation:
    
    • Irregular
      
    • Wide complex with variable QRS morphologies
      

• Pre-excitation:
  
  • Inferior MI
    
• Narrow complex supraventricular tachycardias without an accessory pathway:
  
  • AV nodal re-entry tachycardia (AVNRT)
    
• Wide complex tachycardia:
  
  • Atrial fibrillation with intraventricular conduction delay
    
  • Ventricular tachycardia
    

TREATMENT

• Supplemental oxygen and monitor
  
• Vagal maneuvers (Valsalva), carotid massage, and ice water on the face
  
• Synchronized cardioversion for:
  
  • Signs of instability (hypotension, AMS, etc.)
    
  • Atrial fibrillation with WPW; wide complex tachycardia
    
• Pre-hospital use of adenosine:
  
  • Stable patients: No emergent conversion.
    
  • Unstable patients: Need cardioversion, not adenosine.
    

• Unstable patients:
  
  • Synchronized cardioversion (start with 100 J)
    
  • Increase incrementally until sinus rhythm is restored (200 J then 360 J).
    
• Stable patients with wide complex tachycardia:
  
  • Amiodarone
    
  • Procainamide
    
  • DO NOT USE:
    Lidocaine, calcium channel blockers, β-blockers, and Digoxin in patients with wide complex tachycardia and suspected WPW.
    

• Stable patients:
  
  • Vagal maneuvers: Valsalva and carotid massage:
    
    • Right carotid artery massage for no more than 10 sec
      
    • Auscultate the artery 1st for a bruit that would contraindicate this procedure.
      
  • Fluid replacement and Trendelenburg if the patient has mild hypotension
    
  • Pharmacologic conversion if carotid massage fails
    
• Orthodromic (usually narrow complex) AVRT:
  
  • Adenosine or verapamil
    
• Antidromic (usually wide complex) AVRT:
  
  • Procainamide is the drug of choice
    
  • Although verapamil and β-blockers can be used when the diagnosis is certain, their administration can be dangerous in ventricular tachycardia and WPW with atrial fibrillation, which can be hard to distinguish from this dysrhythmia.
    
• Irregular wide complex tachycardia:
  
  • WPW syndrome with atrial fibrillation
    
  • Amiodarone or procainamide.
    

• Children may develop ventricular rates up to 320 bpm that are poorly tolerated.
  
• Cardiovert unstable children with 0.5–2 J/kg.
  
• Vagal maneuvers and adenosine are safe in stable children.
  

• Adenosine: 6 mg rapid IV bolus over 1–2 sec; if ineffective, repeat with 12 mg (peds: 0.1 mg/kg rapid IV push, repeat with 0.2 mg/kg)
  
• Amiodarone: 150 mg IV over 10 min, 360 mg over the next 6 hr
  
• Magnesium: 2 g IV bolus
  
• Procainamide: 6–13 mg/kg IV at 0.2–0.5 mg/kg/min until either arrhythmia controlled, QRS widens 50%, or hypotension, then 2–6 mg/min, max. of 1,000 mg
  

• Amiodarone for wide complex tachycardias
  
• Adenosine for narrow complex tachycardias
  

• Procainamide for wide complex tachycardias
  
• IV Procainamide, IV Verapamil 5–10 mg, IV Diltiazem 10–20 mg, or Esmolol can be considered as 2nd-line agents for patients with WPW presenting with regular narrow complex tachycardias.
  

FOLLOW-UP

• Signs of instability and/or history of syncope
  
• Failure of outpatient therapy for continuous pharmacologic control or ablation
  

• Most patients will be stable and can be discharged once converted to sinus rhythm
  
• Follow-up should be arranged with a cardiologist
  

Electrophysiology studies to assess for radiofrequency ablation or surgery may be performed on outpatient basis.

The patient should be instructed to return to the ED with any symptoms suggestive of a tachydysrhythmia:

• Palpitations
  
• Dizziness
  
• Chest pain
  
• Feeling faint or actual syncope
  

Never use calcium channel blockers, β-blockers, or digoxin in patients with pre-excitation with atrial fibrillation or wide complex tachycardia:

• These medications prolong the refractory period of the AV node, increasing the rate of transmission through the accessory pathway, and may result in fatal ventricular dysrhythmias.
  
• If symptoms >48 hr, anticoagulation must be addressed prior to cardioversion as 1–3% of patients will have embolic event. Transesophogeal echo should be considered to rule out left atrial thrombus.
  

• Keating L, Morris FP, Brady WJ. Electrocardiographic features of Wolff-Parkinson-White syndrome.
  Emerg Med J
  . 2003;20(5):491–493.
  
• Mark DG, Brady WJ, Pines JM. Preexcitation syndrome: Diagnostic considerations in the ED.
  Am J Emerg Med
  . 2009;27:878–888.
  
• Schwieler JH, Zlochiver S, Pandit SV, et al. Reentry in an accessory atrioventricular pathway as a trigger for atrial fibrillation initiation in manifest Woff-Parkinson-White syndrome: A matter of reflection?
  Heart Rhythm
  . 2008;5(9):1238–1247.
  
• Simonian SM, Lotfipour S, Wall C, et al. Challenging the superiority of amiodarone for rate control in Wolff-Parkinson-White and atrial fibrillation.
  Intern Emerg Med.
  2010;5(5):421–426.
  

See Also (Topic, Algorithm, Electronic Media Element)

CODES

426.7 Anomalous atrioventricular excitation

BASICS