November 19, 2015 by dailybolusoflr
By: Erin Kane, MD
WPW– Quick review
- Accessory pathway directly connects the atria and ventricles, allowing electrical activity to bypass the AV node
- WPW pattern occurs in 0.13 to 0.25 percent of general population; only 1-2% of those with WPW pattern will have WPW syndrome (i.e., will have a tachydysrhythmia)
WPW pattern on EKG (triad)
- Short PR
- Delta wave / slurred upstroke
- Prolonged QRS
- May not always be present on baseline EKG despite presence of accessory pathway (“concealed” accessory pathway) – pathways that are only capable of retrograde conduction will not have short PR or delta wave
- SVT (AVRT – atrioventricular reciprocating tachycardia) with orthodromic or antidromic conduction – 80%, majority of those orthodromic
- Atrial fibrillation – 15-20%
- Palpitations, lightheadedness, syncope or presyncope, chest pain, sudden cardiac death
Atrial fibrillation in WPW – why it matters
- Intrinsic rate of atrial fibrillation is 450-600, but in most patients, the rate is limited by the refractory period of the His-Purkinje system, so not all of these beats are conducted
- In WPW, the accessory pathway can conduct faster and will conduct more of these beats
- Ventricular rates can exceed 300 bpm and may degenerate into VF
- Incidence of sudden death in WPW is low, but when it occurs is due to afib
Atrial fibrillation in WPW – how to identify
- Consider in a young patient with no hx cardiac disease presenting with a wide complex tachycardia or in patient with known history of WPW
- Rhythm is irregular; there is significant beat-to-beat variation between QRS complexes; may have occasional narrow QRS
- DDx: SVT with aberrancy, monomorphic VT, polymorphic VT (which is especially difficult to differentiate)
- If unstable (altered, hypotensive), electrical cardioversion (synchronized so long as R waves can be distinguished)
- If pharmacologic management, procainamide 30 mg/min
- Any pharmacologic agent that blocks AV node may cause degeneration into VF and death – DO NOT give calcium channel blockers, beta blockers, adenosine, or digoxin in wide complex tachycardia in known WPW
- Amiodarone should NOT be used in patients with AF and an accessory pathway does not slow the accessory pathway and has some beta blocking properties
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- Di Biase, L and EP Walsh. Epidemiology, clinical manifestations, and diagnosis of the Wolff-Parkinson-White syndrome. Up to Date.
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