Delta waves detected on ECG ~0.15-0.25% general population
Higher prevalence in 0.55% in 1st degree relatives
Conduction: antegrade (manifest WPW), retrograde only (“concealed”), both
“WPW Syndrome” – both pre-excitation and tachyarrhythmias

AV re-entrant tachycardia:
- orthodromic (most common)
- antidromic
Atrial arrhythmias:
- atrial tachycardia
- atrial flutter
- atrial fibrillation
AVNRT (bystander AP)
Incidence of sudden death 0.15-0.39% over 3-10 year follow-up
Cardiac arrest unusual to be 1st manifestation
In ~ ½ of cardiac arrest cases in WPW pts, it is the 1st manifestation
Etiology: Rapid conduction during AF down AP, with degeneration to VF

Risk factors for SCD
Shortest pre-excited R-R <250 ms during spontaneous or induced AF
History of symptomatic tachycardia
Multiple accessory pathways
Ebstein’s anomaly
Family history sudden death

Non Invasive Risk Stratification
Abrupt loss of delta wave (correlates with long antegrade refractory period AP) – spontaneous or     
during stress testing
Loss of antegrade pre-excitation following procainamide

Evaluate properties of AP
- antegrade ERP <270
- shortest R-R in AF <250
Induce arrhythmia
- Success rate ≥ 95% most series
- Low risk with experience (& risks
depends on location)

Evaluation of asymptomatic WPW
1/3 of asymptomatic individuals <40 years old eventually developed symptoms
~20% of asymptomatic pts demonstrate RVR during AF at EPS
Clinical decision to evaluate individuals with high-risk occupations (e.g., school bus drivers, pilots, scuba
divers, competitive athletes)

Pappone JACC 2003;41:239
BLEPS in 212 pts with asymptomatic pre-excitation underwent EPS
FU 38 ± 16 mos
33 pts became symptomatic
- 3 pts VF
- 1 death
Most important risk factor for predicting outcome = inducibility of AVRT or AF
62% of the 47 inducible pts developed symptomatic arrhythmia during FU

Prophylactic RF Ablation in Asymptomatic WPW Syndrome
Pappone N Engl J Med 2003;349:1803
224 eligible asymptomatic pts
76 pts at high risk for arrhythmias: randomly assigned to RFA (37 pts) vs. no treatment (35 pts)
Endpoint: Occurrence of arrhythmias over 5 year follow-up
2/37 (5%) RFA and 21/35 (60%) control had arrhythmic events
1 control pt: VF as presenting arrhythmia
Arrhythmia Event-Free Survival Among
Asymptomatic Patients
Arrhythmia Event-Free Survival Among
Asymptomatic Patients According to
Type of Arrhythmia Induced at EPS
Delta wave algorithm is accurate 70% of the time, the algorithms that report more accuracy is in
maximal preexcitation, pacing on top of the AP or blocking AVN
LL: + V1, starting on Left  conducting to Right, RBBB pattern to it, + in AVF and key lead is aVL -
going away from the left side of the left shoulder
LP/S: still on L side + in V1, - in aVF (anything on the back space of the heart posteroseptal is
negative in aVF), + aVL
RP/S: Starting on R to L -V1, LB pattern, back of heart so - aVF, and + in aVL conducting to L
side of heart, + aVL
RL/A: -V1, LB pattern, + aVF cause anterior, + aVL R to L
V1+ ->L, V1- => R ; aVF + lateral/A, aVF - posterior/septal; aVL + => left lateral
V1+ Left / aVF- Post-septal / aVL+ LL
RV pacing – short VA interval vs SVT long VA consistent with AP
AS                                     + III,aVF
LFW        - I,aVL                - III,aVF                Transition at V1 or earlier

-If His ES does not cancel preexcitation then AP is located below His (fasciculo-ventricular or Mahaim)
-By frequency: LFW > PS > RFW > AS
-Only annular area with no AP is Left posteroseptal (aorto-mitral continuity)
-V2 overlies the IVS: + delta in V2 (abrupt transition): RPS or RMS
-Terminal r in V1 in the absence of RBBB is a sign of late activation of the RV => L septal
-Epicardial: epicardial PS in CS or its branches
                      -Negative Delta in II
                      -Positive Steep > 45 Delta in aVR
                      -R<S deep S in V6
-R sided AP: late transition at V3 or later
-AS AP: LBBB pattern transition before V4

ORT P Axis
L => + aVR, -aVL
R => -aVR, + aVL
PS => equal aVR/aVL
AS => + P inferior leads