Left ventricle

1. Localization of culprit artery in
STEMI
Dr Bijilesh u
Senior Resident,
Dept. of Cardiology,
Medical College, Calicut

2.  Careful analysis of the Surface ECG is
highly useful in localizing the culprit vessel
and immediate prognostication
 Helps in deciding the need for an aggressive
reperfusion strategy

3. Coronary circulation
 Left Main or left coronary artery (LCA)
– Left anterior descending (LAD)
• diagonal branches (D1, D2)
• septal branches
– Circumflex (Cx)
• Marginal branches (M1,M2)
 Right coronary artery
– Conus , sinoatrial branch
– RV branch
– Acute marginal branch (AM)
– AV node branch
– Posterior descending artery (PDA)

4.  LAD large MIs
– Supplies the anterior, lateral, anterior two-thirds
of septum, and frequently the inferoapical
segments of the left ventricle, proximal part of
bundle branches
 RCA
– Perfuses sinus node (55%), AV node,
posteromedial papillary muscle, inferior part of
LV, RV, and variably also the posterior and
lateral segments

5.  Circumflex branch
– Posterior wall and variably inferior and lateral
segments
– Posterior wall involvement  usually
underestimated and under treated.

6.  SA node – RCA in 55%
 AV node – RCA in 90%
 Bundle of His – mainly RCA
 RBB – LAD
 LBB – L Ant branch – LAD
L Post branch – LAD & Postr Desend A

7. Dominance
 Supplies circulation to the inferior wall &
inferior portion of the interventricular
septum
 Passes crux and interventricular septum,
giving rise to posterolateral branches & PDA
 Dominant artery also gives rise to the AV
nodal branch

8. RIGHT DOMINANT

9. LEFT DOMINANT

10. Dominance
 RCA - 70%
 LCX - 10%
 Co - dominant – 20%
 Identifies patients at risk for extensive
myocardial damage with complications

11. ST VECTOR
 Direction and displacement of the ST
segment - sum of direction and magnitude
of all ST vectors
 Resulting main vector point in the direction
of the most pronounced ischemia - ST
elevation in that area
 Opposite area record (reciprocal) ST
depression
 Lead perpendicular to dominant vector will
record an iso-electrical ST segment

12. AWMI

13. ECG in AWMI
 STE in V2, V3, V4
 Behaviour of ST in other leads depends on the
presence of ischemia in three vectorally
opposite areas
– Basoseptal area (1st septal branch)
– Basolateral area (1st diagonal branch)
– Inferoapical area ( when LAD wraps around apex)

14. Types of LAD occlusion
 Proximal to 1st septal and 1st diagonal branch (40%)
 Distal to S and D (40%)
 Proximal to D1 but distal to S1 (10%)
 Proximal to S1 but distal to D1 (10%)

15. Proximal LAD occlusion
(Dominance of Basal area)

16. Direction of ST Vector and ECG Changes in
Proximal LAD Occlusion

17. Proximal LAD occlusion
(Dominance of Basal area)
 ECG…
 RBBB
 STE aVR and STE in V1 > 2.5 mm
 ST depression in inferior leads and in V5

19. Distal LAD occlusion
(dominance of inferoapical area)

20. Distal LAD occlusion
(dominance of inferoapical area)
ECG…
 Absence of ST depression in inferior leads
 STE in inferior leads in addition to V3-V6

22. 1st Diagonal not involved
(Dominance of septal area)--Proximal to S1

23. ECG…
 STE in aVr and > 2.5 mm STE in V1
 ST depression in V5
 STE in V3R
 ST depression in aVL (Highly specific)
1st Diagonal not involved
(Dominance of septal area)

25. First septal branch not included
(dominance of Lateral area) – Proximal to D1

26. ECG…
 ST depression in Lead III > Lead II
 ST elevation lead AVL & lead 1
First septal branch not included
(dominance of Lateral area)

28. ECG criteria to identify site of occlusion
in the LAD
 Engelen et al
 J Am Coll Cardiol. 1999;34:389-395

29. Inferoposterior wall MI

31. Occlusion of the RCA
 ST-segment elevation in III > II
 ST-segment depression in I and aVL - aVL > I
Herz I, Assali AR et al Am J Cardiol 1997;80:1343-1345
 ST depression in the precordial leads is
smaller than ST elevation in inferior leads
 When occlusion is proximal to RV branches
ST elevation in V1 > V3 V4
 LAD occlusion ST elevation in V3V4 > V1

33. Dominance of RCA
 When RCA is dominant, ST-segment
elevation is seen in V5 and V6
 ST-segment elevation ≥ 2 mm - RCA very
dominant
 Involvement of posterior wall
 PR prolongation.. AV nodal artery arises
from dominant artery

34. Occlusion of the LCX
 ST- elevation in II ≥ III
 ST elevation in I and aVL.
 ST-segment elevation in II, III, and aVF is
usually smaller than the ST depression in
right precordial leads
 When LCX is quite dominant - ST
depression in aVL, but very rarely in I

36. OM vs D1 OCCLUSION
0M
 ST elevation I, aVL,
and V5−6
 Slight ST depression in
V1-3
D1
 ST elevation I, aVL,
and V5−6
 ST-elevation in
precordial leads
 ST-depression inferior
leads.

37. RV infarction

38.  STE >1mm V3R and V4R
 STE V1 > V2
 High degree AV block
RV infarction

39. Value of ST – T changes in V4R in
acute infero posterior MI
(RVMI)
Braat SH, Gorgels APM, Bar FWHM, Wellens HJJ
Am J Cardiol 1998;62:140-142.

41. Isolated RVMI
 Minor changes in inferior leads,
 STE prominent in leads V1 and
V2 , V3R and V4R
 Small or collaterally filled RCA
 Occlusion of an RV branch only

42. ST depression in anterior leads in
IWMI
 Implies posterior wall involvement
 May extend from V1 to V6 and indicate larger MI
 Maximal ST depression in V4 – V6 is seen more in
three vessel disease and lower LVEF
Birnbaum Y,
J Am Coll Cardiol 1996;28:313-318.
 Can occur both in RCA and Cx artery invt
 Absence indicates RCA

43. ST depression in anterior leads
 Isolated ST depression – Cx occlusion with a true
PWMI or nonocclusive myocardial ischemia
 Max ST depression in V2 and V3 is predictive of Cx
 V7 –V9 shows ST elevation

44. True PWMI
 ST depression in V1, R/S >1, and upright T
wave
V1 V9

45. AV conduction disturbances
 AV nodal delay and block occurs with proximal
RCA invt, frequently with RVMI
 Higher in-hospital morbidity & mortality

46. Sub AV conduction disturbances
 RBBB with or without hemiblock during acute
AWMI indicates proximal LAD
 BBB or CHB indicates poor prognosis
 LAHB in acute IWMI indicates additional LAD
disease

47. LEFT MAIN STEM OCCLUSION OR
TRIPLE VESSEL DISEASE
 Acute LMCA occlusion rare but causes serious
hemodynamic deterioration
 More commonly, subtotal occlusion occurs with
collaterals filling from RCA  presents as Unstable
angina
 ECG of subtotal occlusion similar to triple vessel
disease

48. LEFT MAIN STEM OCCLUSION OR
TRIPLE VESSEL DISEASE
 Marked downsloping ST depression in I, II, and V4 – V6 and
STE in aVR
 aVR STE occurred more in LMCA than in LAD
 V1 STE was less in LMCA than LAD
 High mortality rate in those with higher STE in Avr
Yamaji H et al
J Am Coll Cardiol 2001;38:1348-1354

50. Atrial infarction
 Signs of atrial MI are seen in PTa segment
 PTa segment elevation occurs in I, II, III, V5 or V6
or a depression in precordial leads
 Occurs in 10 % of inferoposterior MI
 Isolated occurrence is rare
 Proximal RCA or Cx

53. RCA vs LCX

54. Limitations
 Assessment of the site of occlusion of
coronary vessel by ECG is most reliable in
case of 1st MI
 Impaired
– Multivessel disease
– Collateral circulation
– When ventricular activation is prolonged as in
• LVH
• Preexistent LBBB
• Preexcitation
• Paced rhythm

55. REFERENCE
 Bayes de Luna, Antman - The 12 lead ECG in STEMI
 Hein J J Wellens, Anton P M Gorgels, Pieter A Doevendans:
The ECG in Acute Myocardial Infarction and Unstable angina –
diagnosis and risk stratification
 Y .Birnbaum Bj Drew – Ecg in STEMI - correlation with
coronary anatomy and prognosis
 YAMAJI H - Prediction of acute left main coronary artery
obstruction by 12-lead electrocardiography. ST segment
elevation in lead aVR with less ST segment elevation in lead
V(1)