Localization of culprit artery in STEMI

Dr Bijilesh uSenior Resident,

Dept. of Cardiology,Medical College, Calicut

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

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)

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

Circumflex branch

– Posterior wall and variably inferior and lateral segments

– Posterior wall involvement usually underestimated and under treated.

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

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

RIGHT DOMINANT

LEFT DOMINANT

Dominance

RCA - 70% LCX - 10% Co - dominant – 20%

Identifies patients at risk for extensive myocardial damage with complications

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 - iso-electrical ST segment

AWMI

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)

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%)

Proximal LAD occlusion (Dominance of Basal area)

Direction of ST Vector and ECG Changes inProximal LAD Occlusion

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

Distal LAD occlusion(dominance of inferoapical area)

Distal LAD occlusion(dominance of inferoapical area)

ECG…

Absence of ST depression in inferior leads

STE in inferior leads in addition to V3-V6

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

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)

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

ECG…

ST depression in Lead III > Lead II

ST elevation lead AVL & lead 1

First septal branch not included(dominance of Lateral area)

ECG criteria to identify site of occlusion in the LAD

Engelen et al J Am Coll Cardiol. 1999;34:389-395

Inferoposterior wall MI

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

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

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

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.

RV infarction

STE >1mm V3R and V4R

STE V1 > V2

High degree AV block

RV infarction

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.

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

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

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

True PWMI

ST depression in V1, R/S >1, and upright T wave

V1 V9

AV conduction disturbances

AV nodal delay and block occurs with proximal RCA invt, frequently with RVMI

Higher in-hospital morbidity & mortality

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

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

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

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

RCA vs LCX

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

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)