Localization of culprit artery in STEMI Dr Bijilesh u Senior 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.

Bundle of His – mainly RCA RBB – LAD 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 Obstruction 0f bld sply 2 cond system can esult in cond syts abnormalities

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 Cor circ can b r or l dominant sy

RIGHT DOMINANT Along the inferior (diaphragmatic) aspect of the heart, the atrioventricular, interventricular, and interatrial grooves form a cross-shaped intersection called the crux cordis (crux of the heart).

LEFT DOMINANT

Dominance RCA - 70% LCX - 10% Co - dominant – 20% Identifies patients at risk for extensive myocardial damage with complications It is very important to recognize which vessel is dominant because this

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 in Proximal 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) St vector points inf due to ischemic dom of inferoapical area. Iferiorly directed vector leads to st d in avr n ste in inf leads

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 Direction of st vec in medial direction result ste avr 3 std in avl

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

First septal branch not included (dominance of Lateral area) – Proximal to D1 Dominance of isch inlat area result in st vector pointing in that direction.. Leads to ST negativity in 3 and avr .2 isoelectric. 1 n avl ste

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

ECG criteria to identify site of occlusion in the LAD Engelen et al J Am Coll Cardiol. 1999;34:389-395 Right bundle branch block remains, as described in chapter 3, a very specific marker of an occlusion before the first septal branch. ST elevation in has to be more than 2mm to be sufficiently specific for that location. ST elevation in AVR is apart from being specific the most sensitive marker for proximal LAD occlusion. ST depression in is not a very frequent, but specific marker. Lead AVL is the most useful lead to identify an occlusion site proximal (starting with a Q wave) or distal (showing a negative ST segment) to the first diagonal branch

Inferoposterior wall MI

Both arteries supply inf part of lv Both arteries supply inf part of lv.. Rca more medially including the inf septum cx postero basal and lateral area. So st vec inf n r in rca and inf n left in cx

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

STE in these leads implies a larger area at risk Right coronary Circumflex coronary Inferoseptal ischemia Inferoposterolateral isch. Vector directed to III Directed to II STE III > II STE II > III ST depression in aVL>I ST depression in I>aVL RV can be involved True PWMI can occur V5 and V6 are of little value in differentiating between RCA or Cx occlusion. STE in these leads implies a larger area at risk

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

RV infarction

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

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 diagnosed by finding reciprocal ST segment depression in the precordial leads. When present in RCA occlusion, it indicates dominance of this vesselIn case of CX occlusion posterior wall involvement is almost obligatory 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)