Localization of WPW( accessory Pathway) by surface ECG

Localization of accessory pathway by ECG

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 lateral (50 percent) Posteroseptal (30 percent) Right anteroseptal (10 percent) Right lateral (10 percent).

6. 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.

7. 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

8. 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 ).

9. 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 %

10. 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)

11. 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.

12. 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.

13. 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.

14. 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).

15. 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%).

16. 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).

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

18. 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

19. 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.

20. 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.

21. 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.

22. 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.

23. Polarity of QRS QRS AXIS DELTA 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] Lt lateral + + + INFERIOR [+60 TO 90] INFERIOR [+ 90 TO 120]

24. 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

25. 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.

26. 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.

27. 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.

28. 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.

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