STEPUP Cardiovascular System: Tachyarrhythmias - Wolff-Parkinson-White Syndrome Flashcards
What is Wolff-Parkinson-White (WPW) syndrome?
An accessory conduction pathway from atria to ventricles through the bundle of Kent causes premature ventricular excitation because it lacks the delay seen in AV node
What may WPW lead to? What are the two mechanisms that cause this?
May lead to a paroxysmal tachycardia, which can be produced by two possible mechanisms:
1) Orthodromic reciprocating tachycardia
2) Supraventricular tachycardias (AFib or atrial flutter)
How does orthodromic reciprocating tachycardia occur in the setting of WPW?
1) The impulse travels through the AV node (anterograde limb) and depolarizes the ventricles. Then it travels back through the accessory pathway (the retrograde limb) and redepolarizes the atria, creating a reentry loop
2) No delta waves because conduction occurs retrograde over the accessory pathway
How does supraventricular tachycardia (AFib or atrial flutter) occur in the setting of WPW?
Usually, AV node only allows certain impulses to get to ventricles. With an accessory pathway, all or most of the impulses may pass to the ventricles. A fast ventricular rate may occur and cause hemodynamic compromise.
How do you diagnose WPW?
ECG: Narrow complex tachycardia, a short PR interval, and a delta wave (upward deflection seen before the QRS complex)
What is the treatment of WPW? What drugs should be avoided in the treatment of WPW? What class of anti-arrhythmic drugs are better choices for treatment?
1) Radiofrequency catheter ablation of one arm of the reentrant loop (i.e., of the accessory pathway) is an effective treatment. Medical options include procainamide or quinidine
2) Avoid drugs active on the AV node (e.g., digoxin, verapamil, beta-blockers) because they may accelerate conduction through the accessory pathway
3) Type IA or IC antiarrhythmics are better choices