Wolff–Parkinson–White syndrome (WPW) is one of several disorders of the conduction system of the heart that are commonly referred to as pre-excitation syndromes. WPW is caused by the presence of an abnormal accessory electrical conduction pathway between the atria and the ventricles. Electrical signals travelling down this abnormal pathway (known as the bundle of Kent) may stimulate the ventricles to contract prematurely, resulting in a unique type of supraventricular tachycardia referred to as an atrioventricular reciprocating tachycardia.The incidence of WPW is between 0.1% and 0.3% in the general population.Sudden cardiac death in people with WPW is rare (incidence of less than 0.6%), and is usually caused by the propagation of an atrial tachydysrhythmia (rapid and abnormal heart rate) to the ventricles by the abnormal accessory pathway.

1. WPW SYNDROMEWPW SYNDROME
Ravi Kumar,DM(Cardiology)
NIMS,Hyderbad-50082
India

2. Historical perspectiveHistorical perspective
The earliest description of an accessory
pathway was reported by Stanley Kent in
1893 who suggested that impulses can
travel from the atrium to the ventricle
over a node-like structure other than the
atrioventricular (AV) node.
Cohn and Fraser reported the first case
of pre-excitation syndrome in 1913

3. In 1930, Louis Wolff,
Sir John Parkinson, and
Paul Dudley White
published a seminal
article describing 11
young patients who
suffered from attacks
of tachycardia
associated with an
electrocardiographic
pattern of bundle
branch block with a
short PR interval

4. Ohnell was the first to use the term
“pre-excitation,” whereas Seters
described the slurred initial component
of the QRS complex as a “delta” wave.

5. Curative therapy of WPW syndrome was
demonstrated in 1967 when Cobb et al
successfully ablated an accessory pathway
during open-hear surgery
The first successful catheter ablation of
an accessory pathway by delivering direct
current energy was reported by Morady
and Scheinman in 1984.

6. In 1987, Borggrefe et al. successfully
ablated a right-sided pathway by
delivering RF current. Radiofrequency
ablation of accessory pathways has
become a first line therapy and is
favoured over the medical treatment in
most of the patients.

7. INTRODUCTIONINTRODUCTION
Patients with pre-excitation syndromes
have an additional or accessory pathway,
which directly connects the atria and
ventricles.
In the Wolff-Parkinson-White pattern,
AV conduction through the bypass tract
results in earlier activation (preexcitation)
of the ventricles than if the impulse had
travelled through the AV node

8. Classic accessory pathway is the AV
bypass tract or bundle of kent in WPW
James fibres, AN tracts connect atrium to
distal AV node
Brechenmacher fibres(atrio- hisian tracts)
connect atrium to HIS bundle
Hisian -fascicular tracts(Mahaim fibres)

12. CONDUCTIONCONDUCTION

13. FrequencyFrequency
Delta waves detectable on an ECG have been
reported to be present in 0.15% to 0.25% of the
general population.
 A higher prevalence of 0.55% has been reported in
first-degree relatives of patients with accessory
pathways. Wolff–Parkinson–White syndrome is more
commonly diagnosed in men than in women, although
this sex difference is not observed in children.
Among those with the Wolff–Parkinson–White
syndrome, 3.4 percent have first-degree relatives
with preexcitation.
 The familial form is usually inherited as a mendelian
autosomal dominant trait

14. Inherited form of WPW syndrome
associated with familial hypertrophic
cardiomyopathy has been recently
described with the locus mapped to
chromosome 7q33.

15. The term Wolff-Parkinson-White
syndrome is used to describe individuals
with ventricular pre-excitation and
symptomatic tachycardias as originally
described by Wolff, Parkinson and White.
The term Wolff-Parkinson-White pattern
refers to the electrocardiographical
finding of ventricular preexcitation.

16. VariantsVariants
Concealed Accessory Pathways
 Defined as pathways that are capable of conduction only in
the retrograde (VA) direction at rates similar or greater than
the sinus rate.
 The concealed accessory pathways are noted in between
15% to 42% of patients with accessory pathway.
 Approximately one third of AVRTs are due to concealed
accessory pathways.
 The clinical presentation of patients who have a concealed
accessory pathway is similar to the classic presentation of
WPW syndrome with the exception that no preexcitation,
rapid preexcited responses are not observed during AF.
 Concealed pathways are more frequently localized to the left
free wall (64%), and less frequently in Septal (31%) and right
free wall locations.

18. Decremental AccessoryDecremental Accessory
pathwayspathways
The electrophysiologic properties of
accessory pathways are similar to
working myocardium.
Few accessory pathways may exhibit
progressive delay in conduction in
response to increased rate of pacing.
Decremental conduction can be seen in
approximately 7% of the patients with
WPW syndrome

19. Multiple accessory pathways are present
in as many as 13 percent of patients
 Most patients with accessory pathways
do not have any structural cardiac
abnormalities but as many as 10 percent
of patients with Ebstein’s anomaly have
one or more accessory pathways.

20. PathophysiologyPathophysiology
Accessory AV muscle bridges are normally
presented in human fetal hearts but these
connections are interrupted during growth
of the fibrous annulus
Most accessory pathways consist of small
fibers resembling ordinary myocardium
crossing the AV groove.
The pathways insert directly into the atrial
and basal ventricular myocardium but they
may course through the AV groove at
variable depth ranging from subepicardial to
subendocardial locations.

21. Accessory pathways may have an oblique
course rather than perpendicular to the
transverse plane of the AV groove,
resulting in an atrial insertion that may be
transverse some distance from the
ventricular insertion site.

22. The presence of very short AV nodal
conduction times may cause the ventricular
preexcitation to be invisible on the surface
ECG.
Preexcitation can also be minimal when the
accessory pathway is located on the lateral
mitral ring relatively far from the origin of
the sinus impulse.
It was postulated that preexcitation pattern
with a PR interval >120ms typically indicates
a left free wall accessory pathway.

23. AV reentrant tachycardias (AVRT) occur
when two functionally different
conduction pathways are present.
The effective refractory period of the
accessory tract is usually longer than that
of the normal AV nodal His-Purkinje
tract.

24. orthodromic atrioventricularorthodromic atrioventricular
reciprocating tachycardia (AVRT)reciprocating tachycardia (AVRT)

25. Preexcitation pathwaysPreexcitation pathways

27. Antidromic AVRTAntidromic AVRT

29. Patients with antidromic tachycardias have
usually shorter refractoriness in the normal
retrograde VA conduction system and the
maintenance of tachycardia is favored by the
greater distance from the normal AV node.
AVRT using two accessory pathways is a
rare form of tachycardia with broad QRS
complexes in which anterograde conduction
is down one accessory pathway and
retrograde conduction is up another.

30. The rate of the AVRT depends on the
conduction times of all tissues involved in
the reentrant circuit and on the
autonomic tone modulation.
QRS complex alternans during
supraventricular tachycardia is relatively
specific for AVRT.

31. AFAF
Ventricular rates up to 350 bpm are
possible and the QRS morphology
reflects varying degree of preexcitation
due to conduction over the normal AV
node as well as the accessory pathway.
A causal relationship between ventricular
fibrillation and atrial fibrillation with rapid
ventricular response has been
documented

34. SymptomsSymptoms
The usual complaint of patients with WPW
syndrome and recurrent tachycardia is
usually rapid palpitations associated with
chest discomfort, shortness of breath,
lightheadedness or syncope.
The onset and offset are typically sudden.
Some patients may report precipitating
factors such as coffee, stress, menstrual
periods or pregnancy but most usually the
symptoms are sporadic and unpredictable.

35. Sudden death is rare but may sporadically
be the initial presentation in previously
asymptomatic individuals.
A history of syncope raises concerns
regarding a very rapid arrhythmia with
haemodynamic compromise.

36. The WPW pattern in symptomatic or
asymptomatic infants usually disappears,
especially in the first year of life.
However, once symptomatic recurrent
tachycardias appear in adolescence or
adulthood, the course is usually one of
recurring episodes.

37. Sudden death in WPWSudden death in WPW
syndromesyndrome
The incidence of sudden cardiac death in patients
with the WPW syndrome has been estimated to
range from 0.15% to 0.39%.
 It is unusual for cardiac arrest to be the first
symptomatic manifestation of WPW syndrome.
Risk factors identified for sudden death include,a
shortest pre-excited R-R interval less than 250ms
during spontaneous or induced AF, history of
symptomatic tachycardia, multiple accessory
pathways, Ebstein’s anomaly and familial WPW
syndrome.

38. Findings suggestive of a low likelihood of
sudden death include
preexcitation that is intermittent,
the ability to produce anterograde
conduction block with drugs such as
procainamide, and
the disappearance of preexcitation during
exercise

39. In patients without manifest pre-excitation
the initial activation of the septum is usually
from the left to the right side producing a Q
wave in lateral leads and R wave in lead aVR.
It was claimed that in the presence of a
manifest accessory pathway the usual septal
activation is masked and therefore the
finding of a septal Q wave in lead excludes
ventricular pre-excitation.
 However, several other studies have
reported the presence of the septal Q wave
in lead V6 despite manifest pre-excitation.

42.  46 to 60 percent of
accessory pathways are
found within the left free
wall space
 25 percent are within
the posteroseptal space
 13 to 21 percent of
pathways are within the
right free wall space
 2 percent are within the
anteroseptal space
AV ACCESSORY PATHWAYSAV ACCESSORY PATHWAYS

43. Localization of the accessoryLocalization of the accessory
pathwaypathway
Several algorithms have been proposed
for anatomical localization of the
accessory pathway.
Rosebaum in 1945 divided WPW into
type A, left sided pathways (tall R wave in
lead V1, i.e. a positive delta wave), and
type B, right sided pathways (QS
complex in lead V1, i.e. a negative delta
wave)

46. Polarity of QRS QRS
AXIS
DELT
A
AXIS
V1 V2 V3
Antero septal
- - - NORMAL NORMAL
Rt lat
- - - LEFT
[ -60]
LEFT
[ -60]
Rt postseptal
- + + LEFT [ -30] LEFT[ -60]
Lt postseptal
+ + + LEFT[ -30] LEFT[ -60]

47. DELTA IN
V1
QRS IN V1 QRS IN V2
RT POST
SEPTAL
ISO or NEGATIVE DOMINANTLY
NEGATIVE
POSITIVE
LT POST
SEPTAL
POSITVE
[ALWAYS]
DOMINANTLY
POSITIVE or
equiphasic
positive

49. The predictive accuracy of all these
algorithms is significantly reduced in the
presence of multiple pathways.
Coexistent anomalies such as Acute MI
or LVH may alter the QRS morphology

50. ElectrophysiologicalElectrophysiological
assessmentassessment
The main indication for electrophysiological
testing is a decision to undergo catheter ablation
or less frequently, diagnostic study for risk
stratification.
Electrophysiological studies utilize the placement
of a decapolar catheter to the coronary sinus and
three quadripolar catheters to the high right
atrium, right ventricular apex and His bundle
region.
The presence of an accessory AV connection is
confirmed by the presence of a delta wave on the
surface ECG and increased preexcitation and
shortening of HV interval during incremental and
programmed atrial pacing.

51. Indications ofIndications of ElectrophysiologicalElectrophysiological
Studies in WPWStudies in WPW
 1) Sudden deaths have the peculiarity to occur during
exercise, hence all competitive athletes with WPW
syndrome should be studied.
 2) Patient with high responsibility profession such as
professional pilot (plane, truck, bus, train)
 3) The indications in children are more controversial, the
conductionin accessory pathway and normal AV conduction
system are more rapid, probably without a clinical
significance.
 The indications should be liberal in children who are
competitive athletes and in all children above the age of 10
years.
 4) In elderly, the propensity for atrial fibrillation increases
hence the risk of occurrence of a potentially severe
arrhythmia in an asymptomatic WPW patient should not be
underestimated.

52. Atrial pacing from the sites closer to the
accessory pathway will preferentially
conduct over this pathway with enhanced
preexcitation.
Therefore, in a patient with a left-sided
accessory pathway, the stimulus to delta
wave will be shorter during pacing from the
coronary sinus than during right atrial
pacing. This is especially useful in exposing
left-sided pathways with minimal
preexcitation on the surface ECG.

53. Multipolar catheters located in the coronary
sinus are useful for accurate localization of
the left sided accessory pathways as the
coronary sinus runs in the epicardial fat in
the posterior groove around the posterior
and lateral aspects of the mitral valve.
The coronary sinus ostium empties into the
junction of the inferior and medial walls of
the right atrium and approximates the
inferoposterior corner of the interatrial
septum.

54. Mapping on the tricuspid ring is more
difficult and preformed sheaths to facilitate
contact, multipolar “halo” catheters to
record signals along the tricuspid ring or
catheters for mapping within the right
coronary artery are available.
The distal portion of the catheter recording
the His bundle electrogram approximates
the superior limit of the atrial septum where
it joins the tricuspid valve.

55. Exact localization of an accessory pathway
may be limited by the possible occurrence of
multiple pathways.
It may also be difficult to distinguish
between retrograde atrial activation due to
a midseptal pathway and atypical AV node
reentry.
The use of pharmacologic agent that
selectively slows conduction over the AV
node, such as adenosine, may be useful to
accentuate accessory pathway conduction
during atrial pacing.

58. Left lat APLeft lat AP

60. Diag criteriaDiag criteria

61. Antidromic tachycardiaAntidromic tachycardia
Obligatory 1:1 AV relationship.
QRS morphology in tachycardia consistent
with max preexitation.
Tachycardia QRS morphology reproduced
by atrial pacing near pathway insertion.
Advanced ventricular activation by atrial
extrastimuli near insertion with
advancement of subsequent His activation.
Changes in V –His interval precede changes
in cycle length.

62. The presence of an accessory pathway
participating in the tachycardia circuit can
be confirmed by prolongation of the cycle
length with ipsilateral bundle branch
block and termination of tachycardia
after a premature ventricular
extrastimulus that does not conduct to
the atria and occurs when the His bundle
is refractory.

64. Differentiation between atrial tachycardia
and AVRT is best accomplished by
dissociating the ventricles from the
tachycardia.
The demonstration of a VA-AV response
after termination of ventricular pacing
that entrains the atrium excludes an
AVRT and confirms atrial tachycardia

65. For left free wall accessory pathways, the
diagnosis of AVRT can be mimicked by
antrioventricular nodal reentry with
eccentric atrial activation or by atrial
tachycardias arising from the CS
musculature or the ligament of Marshall.

66. The differential diagnosis of an antidromic
tachycardia includes ventricular tachycardia that
should be diagnosed by the dissociation of the
atrium from the ventricle or a variable His-to-
atrium timing relationship without alteration of
the tachycardia cycle length.
Antidromic tachycardia is diagnosed by
demonstrating the reproduction of tachycardia
QRS morphology by atrial pacing at the
presumed accessory pathway insertion site and
advancement of the ventricular and subsequent
His activation by a premature atrial stimulus near
the accessory pathway site.

67. VA conduction indices : Using
ventricular-induced atrial pre-excitation,
Miles et al devised pre-excitation index
Progressively premature right ventricular
extrastimuli were introduced during
tachycardia and the difference between
the TCL and the longest stimulation
interval at which atrial pre-excitation
occurred
pre-excitation indexpre-excitation index

69. Atrial preexcitation at >90% TCL means
the presence of a septal or right sided BT
If PEI is <25 then Anteroseptal or Right
Free Wall
If PEI is > 75 then Left Lateral or AVNRT

70. More than 75 ms – left free wall
Less than 45 ms- septal tracts

71. The new index was computed
(AV conduction time during SVT) +
(ventriculoatrial conduction time during
ventricular pacing at the SVT cycle length)
-(SVT cycle length).

72.  new index could differentiate AV
reentrant tachycardia (index 60 ms,)
from AV nodal reentrant tachycardia
( 100 ms ).