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ECG DIAGNOSIS OF ISCHEMIC VT

ECG DIAGNOSIS OF ISCHEMIC VT . BY SAID FAWZY ASSISSTENT LECTURER OF CARDIOLOGY BENHA UNIVERSITY. Disclosures. None. Do you think that it is important to have a 12 lead ECG recording of VT before starting VT ablation procedure ?. YES NO IT DEPENDS.

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ECG DIAGNOSIS OF ISCHEMIC VT

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  1. ECG DIAGNOSIS OF ISCHEMIC VT BY SAID FAWZY ASSISSTENT LECTURER OF CARDIOLOGY BENHA UNIVERSITY

  2. Disclosures None

  3. Do you think that it is important to have a 12 lead ECG recording of VT before starting VT ablation procedure ? • YES • NO • IT DEPENDS

  4. ECG is very specific tool for localizing VT foci or reentry circuit exit sites ? • AGREE • DO NOT AGREE • IT DEPENDS

  5. Clinical or inducible non clinical VT ?!

  6. Possible VT mechanisms in ischemic patients • Scar related reentrant VTs (most common). • Focal VTs (including those originating from the papillary muscles). • Fascicular VTs (inter-fascicular) • BBR VT

  7. What do we expect from the ECG ? • Localize or at least Regionalize the focus or the exit site. • The possible mechanism of the tachycardia. • Is it endocardial or Epicardial

  8. Limitations of the ECG as a mapping tool • The presence and the extent of infarction. • The degree of intra-myocardial fibrosis. • The shape of the heart and its position in the chest . • Influence of non-uniform anisotropy in affecting propagation from tachy site.

  9. Continue…Limitations • Effect of acute ischemia,drugs,and metabolic abnormalities on conduction. • Integrity of the His-Purkinje system. • Presence of increased myocardial mass

  10. What we are searching for ? • QRS initial forces • QRS amplitude • QRS width • QRS frontal plane axis • BBB pattern • Concordance • The presnece of QR complexes.

  11. QRS initial forces • Rapid initial forces>>> More likely arising from normal myocardium • Slurred initial forces (pseudodelta wave )>>> More likely from a scar or from epicardium

  12. QRS amplitude • Usually VTs arising from diseased myocardium have lower QRS amplitudes from those arising from normal myocardium

  13. QRS width • Free wall VTs > Septal VTs ( assuming conduction in all directions is equal ) • Epicardial VTs > Endocardial VTs

  14. QRS frontal plane axis • Superior axis >>> apical site (septal or lateral ) or inferior wall VTs • Inferior axis>>> basal , outflow tract,high septal or latral wall of LV.

  15. Concordance • Positive concordance>>> Basal sites • Negative concordance>>> Apical ( mainly apical septum and most commonly seen with anteroseptal infarctions )

  16. BBB pattern • RBBBR pattern>>> VT certainly from LV • LBBB pattern>>> VT from LV septum or the right side of the septum

  17. Presence of QS complexes • QS complexes in the inferior leads>>> Activation start at the inferior wall ! • QS complexes in precordial leads>>> Activation is going away from the anterior wall.

  18. Just to rememeber

  19. Basic roles in post MI VTs • Almost all VTs arise in the LV or IVS • ECG looses a lot of its ability to precisely localize VT origin or exit sites • Accuracy of the ECG in anterior MI (greater myocardial damage)patients is much less than in inferior MI.

  20. Continue…Basic roles • It is extremely rare for an inferior MI dependent VT to have an exit site at the higher septum close to the aortic valve • QS complexes in the lateral leads (V4-V6) reflect origin near the apex ( septal or lateral ) • Almost impossible to distinguish VTs coming from apical septum and apical free wall based on ECG alone

  21. Inferior infarction VT • Activation goes from back to front>> large R wave in the precordial leads starting from V2 • LBBB VT in inferior MI >> mainly basal septum (inferobasal septum with left axis and higher septal with normal axis).

  22. Anterior infarction VT • The situation becomes more complicated with less accuracy of the ECG (more myocardial damage). • LBBB VT or RBBB VT can occur • LBBB VT and LAD is associated usually with inferoapical septal region.It can present with negative concordance and always associated with Q wave in I and aVL

  23. R wave in V1 and Q in aVL indicates more posterior position on the septum • RBBB VT usually shows superior axis. V1 can show monophasic R or qR pattern with QS from V2-V4 or up to V6

  24. Endocadial or Epicardial VT ? Can the ECG alone answer this Q ?

  25. The answer is simply NO

  26. What is epicardial VT ? • VTs in which the origin or the critical sites of the reentrant circuit are located in the subepicardial tissue as suggested by entrainment maneuvers and/or termination withen 10 seconds of standard RF pulses. • Critical epicardial sites may be entained or interrupted from both the epicardial and endocardial surfaces making it difficult to demonstrate the presence of a truly epicardial circuit in a given case

  27. Limitations • Most of the adopted ECG criteria to predict Epicardial foci or exit sites have been described in patients with NICM and idiopathic VTs . • Even VTs with presumed epicardial exit sites can be still ablated from the endocardial approach (The entrance or the central isthmus). • No ECG features distinguished outflow tract epicardial exit sites. • Poor sensitivity and specificty.

  28. Suggested ECG criteria

  29. 1-Total QRS duration • QRS more than 198 ms has 86% specificity and 69% sensitivity for epicardial origin of VT.

  30. 2-Pseudo delta wave • Earliest ventricular actiavation to the fastest delection an any precordial lead • Pdw >34 ms has 80% sensitivity and specificty

  31. 3-Intrinscoid deflection time • ID from the earlist ventricular activation to the nadir of the first S wave in any precordial lead . • ID more than 97 ms has 80% specificity and 50% sensitivity for epicardial VT origin.

  32. 4-RS duration • RS from the earliest ventricular activation to the peak of R wave in lead V2 • RS >121 ms is 82% specific and 57% sensitive for epicardial VT

  33. 5-Maximum Deflection Index( MDI) • It is defined as the shortest time to maximum positive or negative deflection in any precordial lead divided by the QRS duration. • A cut-off value of 0.55 has high sensitivity (100%) and specificity (98%) for epicardial VT. • This was mainly adopted for epicardial VTs arising from sinuses of Valsalva.

  34. 6-Precordial pattern break (R wave regression progression) • This was mainly described by Marchilinski group in Pheladelphia and was in the context of idiopathic VTs (but may still work). • There is a brupt loss of R wave in V2 followed by a resumption in R waves from V3 to V6. • Unkown predictive value.

  35. 7-Regional Q waves

  36. Again….Remember • Even with the presence of all of the above mentioned criteria, the ECG is not predictive for epicardial access and mapping . • Endocardial mapping should be commenced at first for all cases • The role of the above mentioned criteria in post MI patients has no strong evidence.

  37. Post MI VTs from papillary muscles When to suspect ?

  38. ECG…nothing specific

  39. Gadolinium enhanced MRI

  40. BBR VT • More common in patients with NIDCM. • Its incidence is propably underestimated. • Should be considered in DD specially if there is ECG evidence of His Purkinje disease

  41. Typical and Atypical BBR VT.

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