Wolff-Parkinson-White Syndrome Medical Slides

Emphasize that blocking the AV node (with adenosine, verapamil, diltiazem, or digoxin) removes the "brake" on conduction, forcing all impulses down the accessory pathway which has no decremental conduction properties. This can accelerate ventricular rates to 250-350 bpm, degenerating into ventricular fibrillation. Teach that procainamide (slows accessory pathway conduction) or electrical cardioversion are the correct treatments for pre-excited AF.

Present the intermittent pre-excitation concept: abrupt loss of the delta wave during exercise testing or Holter monitoring suggests the pathway has a long refractory period and lower risk. EP study with measurement of the shortest pre-excited RR interval (SPERRI) during induced AF is the gold standard — SPERRI ≤250 ms indicates high risk. The 2015 ACC/AHA/HRS guidelines give a Class IIa recommendation for catheter ablation in asymptomatic patients with high-risk features.

Present delta wave polarity analysis across all 12 leads to predict pathway location (left lateral, posteroseptal, right free wall, anteroseptal). Left-sided pathways show positive delta waves in V1 with left axis; right-sided pathways show negative delta waves in V1. This is educationally valuable for understanding the EP study and helps predict procedural complexity (left-sided pathways may require retrograde aortic or transseptal approach).