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
transition V3-V4 + D II > 1 mV                I + or V1 R>S                        RAO 45: cephalad to bipole on His catheter
transition after V2-V3                             II+                                         with A=V
+D in > 2 inferior leads                          V1 +- or -                               LAO 40: 12-1 o'clock
                                                        aVF +
                                                        III R>S
transition V3-V4 and Delta II>1 mV       I+ or V1 R<S                          RAO 45: between His catheter and CS Os
transition V2-V3                                    II+
Delta = in > 2 inferior leads                  V1 +- or -
                                                      aVF +
                                                      III R<S

transition V3-V4 & D II > 1 mV              I+ or V1 R<S                          LAO 40: posterior to Cs OS or at its level
transition V2-V3                                   II +                                          RAO 45: behind CS Os
Delta negative in > 2inferior leads       V1 +- or -
                                                      aVF -

transition V4                                       I + or V1 R<S                         LAO 40: at 5 o'clock
transition V3-V4, D II< 1 mV               II +
D frontal axis < 0                                V1 +
R III< 0 mV                                         aVF -
                                                    II -

transition V4                                      I+ or V1 R<S
transition V3-V4, D II < 1 mV             II+
D front axis > 0                                 V1+
or R III > 0 mV                                  aVF+

transition V1 or <                             I+ or V1 R<S                LAO 40: MA 1-1.5 cm from Cs Os
D-> 2 inferior leads                         II+
SaVL < RaVL                                  V1 +- or -
I: R/S> 0.8                                      aVF +-
Sum inferior D -

transition V1 or <                           I +- or -                        LAO 40: 3 o'clock
D - in > 2 inferior leads                  V1 R>S
SaVL< RaVL                                 aVF +
I: R>S but R/S < 0.8 mV
Sum inferior Delta +

transition V1 or <                           I+- or -                       LAO: 2 o'clock
D+ in > 2 inferior leads                  V1 R>S
SaVL > R aVL                               aVF+
RV pacing – short VA interval vs SVT long VA consistent with AP