This document discusses localization of accessory pathways using electrocardiography. It describes that accessory pathways can be located in eight anatomical positions along the tricuspid and mitral valve annuli. Several algorithms are proposed to determine the location based on delta wave polarity and amplitude in various leads. The most accurate is the Arruda approach, which uses step-wise analysis of delta wave characteristics in leads I, II, aVL, aVF and V1 to identify the specific accessory pathway location with 90% sensitivity and 99% specificity. Characteristic ECG patterns are presented that help localize right anteroseptal, right posteroseptal, left lateral and right free wall accessory pathways.

1. LOCALIZATION OF ACCESSARY
PATHWAY BY ECG

2. INTRODUCTION
 First fully described by Wolf-Parkinson & White in 1930.
 It is the commonest variety of Pre-excitation Syndrome associated
with an accessory AV connection, called Kent Bundle or Paladino
tracts.
 The surface ECG is characterized by
1) Shortened PR interval for age (<120 milliseconds in adults),
2) Prolonged QRS duration for age (>120 milliseconds), with a
slurred slow rising onset of the R wave upstroke (Delta Wave).
3) Secondary ST and T wave changes which are directed opposite to
the major Delta wave and QRS vector.

3.  On the basis of large study of RF ablation of accessory
pathways in WPW syndrome, AP Fitzpatrick described eight
anatomical locations of pathways using fluoroscopic
landmarks
 Five of these accessory pathways are located on the right
side along the tricuspid valve annulus and three left sided
are located along the mitral valve annulus.

4. 1. Right anteroseptal (RAS)
2. Right midseptal (RMS)
3. Right posteroseptal (RPS)
4. Right anterolateral (RAL)
5. Right posterolateral (RPL)
6. Left anterolateral (LAL)
7. Left posterolateral (LPL)
8. Left posteroseptal (LPS)

5. LEFT SIDED
PATHWAYS
POSTERIOR
POSTEROLATERAL POSTEROSEPTAL
ANTERIOR
ANTEROLATERAL

6. RIGHT SIDED
PATHWAYS
SEPTAL
POSTERO
SEPTAL
MIDSEPTAL
ANTERO
SEPTAL
FREE WALL
ANTERO
LATERAL
POSTERO
LATERAL

8. 1. Left lateral (50 percent)
2. Posteroseptal (30 percent)
3. Right anteroseptal (10 percent)
4. Right lateral (10 percent).

9.  The most pre-excited 12 lead ECG is used to analyze the location of
accessory pathways and certain ECG variables are used for step
wise discriminate analysis.
 Following important ECG variables should be used to localize the
pathways.
-Delta wave frontal plane vector
-Delta wave polarity in V1.
-Delta wave height in leads I, II and Ill.
-Sum of the Delta wave polarities in leads II, Ill and aVF.

10.  The height or the polarity of the delta wave is measured on
the surface ECG in the first 40 msec of QRS complex from the
end of P wave.
 On the basis of this it is ISOELECTRIC, if it is on the baseline
or deflected above or below the baseline but comes back
before the onset of QRS complex.
 POSITIVE, if it is above the baseline and NEGATIVE, if it is
below the baseline

13. • QRS duration is significantly increased in right sided than the
left sided accessory pathways (145±17, range 100-180 msec;
versus 131±15, range 110-164 msec).

14. Localization of the accessory pathway
• Localization of the accessory pathway is generally of value only
when considering catheter ablation.
• The pathway localization or the degree of preexcitation otherwise
does not predict the clinical course.
• Various algorithms (Chern – En Chiang’s, Ftizpatrick’s and Xie’s
algorithms) have been used for predicting accessory pathway
location using different electrographic criteria.
• An algorithm developed by Arruda et.al utilizing the surface ECG
has an overall sensitivity of 90% and specificity of 99 %

15. Localization of the accessory pathway
 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)

17. Right Sided Vs Left Sided
 If QRS transition is at or before V1 or dominant R wave in V1, then it is Left
sided pathway.
 If transition is after V2, it is right sided pathway.
 If the transition is at V2 or between V1 and V2, then measure the amplitude
of R-wave and S wave in lead I.
 If R>S wave in lead I by 1 mV it is right sided otherwise it will be left sided
accessory pathway.

22. Left Anterolateral Vs Left Posterior
 The most significant variable is delta wave polarities in the inferior
leads and the ratio of the R wave to the S wave in lead avL.
 Two or more than two positive delta wave in inferior leads or S
wave larger than R wave in aVL indicates anterolateral location of
the accessory pathway.

24. Left Posterolateral vs. Left Posteroseptal
 The sum of the inferior delta wave polarities and the
amplitude of R wave to S wave in lead I are the best ECG
variables to differentiate the two sites.
 If the R wave is greater than S wave in lead 1 by 0.8 mV and
delta waves are negative in inferior leads, the pathway is
located at left posteroseptal site otherwise it will be left
posterolateral location of the accessory pathway.

27. Right Septal vs. Right Free Wall
 QRS transition is the most significant variable and delta wave amplitude
in lead II can assist to discriminate where the first variable is equivocal.
 QRS transition at or before V3 indicates a septal location, whereas
transition at or after V4 indicates free wall location (Anterolateral or
poserolateral) of the accessory pathways.
 If the transition is between V3 & V4 then look for the amplitude of delta
wave in lead II; if it is equal or more than 1 mV then septal location
otherwise lateral location (97% sensitivity & 95% specificity).

31. Right Anteroseptal vs. Right Posteroseptal vs. Right
Mid Septal
 Delta wave polarities in leads II, Ill and aVF is the most significant variable.
 If it is greater than +1, the pathway is located at anteroseptal region; if it is
less than 1 then it is posteroseptal and if it is 0 or +1 or -1 then it is located
at midseptal site (sensitivity and specificity is between 85-100%).

33. Right Anterolateral vs. Right Postero Lateral
 Delta wave frontal plane axis is the most significant variable and if this is
equivocal the R wave amplitude in lead III.
 If the delta wave frontal plane axis is equal or more than zero, then the
pathway location is at anterolateral site otherwise it is at posterolateral
location (92% sensitivity, 100% specificity).

37. Arruda aproach
An algorithm developed by Arruda et.al utilizing the surface
ECG has an overall sensitivity of 90% and specificity of 99%.

38.  Step 1: If the delta wave in lead 1 is negative or isoelectric or the R wave is
greater in amplitude than the S wave in V1 a left free wall accessory
pathway is present. If these criteria are fulfilled then lead aVF is
examined.
 If the delta wave in lead aVF is positive, a left lateral, anterolateral
accessory pathway is identified.
 If the the delta wave in lead aVF is isoelectric or negative then the
accessory pathway is located at the left posterior or posterolateral region

40. Step 2: lead II is examined.
• A negative delta wave in lead II identifies the subepicardial
coronary sinus or middle cardiac vein accessory pathway.
• If the delta wave in lead II is isoelectric or positive, proceed to
step 3.

42. Step 3:lead V1 is examined.
 A negative or isoelectric delta wave in lead Vi identifies a septal accessory
pathway.
If these criteria are fulfilled, lead aVf is examined.
 If the delta wave is negative, an accessory pathway is identified, which is
located at the posteroseptal tricuspid annulus .
 If the delta wave is isoelectric in lead aVF, the accessory pathway may be
located to either the posteroseptal tricuspid annulus or the posteroseptal
mitral annulus.

43.  A positive delta wave in aVF identifies a pathway located within the
anteroseptal/right anterior paraseptal or midseptal tricuspid annulus
regions .
 If the delta wave in V1 is positive after having excluded patients with a left
free-wall accessory pathway in Step 1, a right free wall accessory AV
pathway is identified.
Proceed to Step 4.

45. Step 4: In patients with a right free –wall accessory pathways, examine aVF.
 A positive delta wave in aVF identifies a right anterior/ anterolateral
accessory pathway.
 If the delta wave in aVF is isoelectric or negative, examine lead II.
 A positive delta wave in lead II identifies a right lateral accessory
pathway , and an isoelectric delta wave in lead II identifies a right
posterior/posterolateral pathway.

51. Right anteroseptal accessory pathway. The 12-lead ECG characteristically exhibits a
normal to inferior axis. The delta wave is upright in leads I, II, and aVF; isoelectric or
negative in aVL; and negative in aVR. There is an rS in V1 and V2.

52. Right posteroseptal accessory pathway. Negative delta waves in leads II, III, and
aVF, upright in I and aVL, localize this pathway to the posteroseptal region. The
negative delta wave in V1 with sharp transition to an upright delta wave in V2
pinpoints it to the right posteroseptal area. Atrial fibrillation is present.

53. Left lateral accessory pathway. A positive delta wave in the anterior precordial leads and in leads II, III, and
aVF, positive or isoelectric in leads I and aVL, and isoelectric or negative in leads V5 and V6 are typical of a
left lateral accessory pathway. Also notice the relatively small amount of preexcitation typical of left lateral
accessory pathways during sinus rhythm, which is caused by the sinus impulse taking longer to travel
through the entire right and left atria to the accessory pathway than it does from the sinus node to the AV
node.

54. Right free wall accessory pathway. The predominantly negative delta wave in V1
and the axis more leftward than in A indicate the presence of a right free wall
accessory pathway.

55. THANK YOU