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ECG Evaluation in Patients with Acute Coronary Syndrome 359

should be repeated at least every 20 to 30 minutes.
St Segment Depression > 1Mm 3
In Leads V1,V2 Or V3 In addition to the evolution of the ECG changes in
ACS, clinicians should also remember an uncom-
St Segment Elevation > 5Mm 2 mon source of error which is pseudo normalisation
And Discordant With The QRS of baseline T wave inversion during the chest pain.
Complex So, one should always compare with the previous
A Score Of > 3 Had A Specificity available old ECG’s.
Of 98% For Acute MI With LBBB
PRESENCE (OR) ABSENCE OF NEW Q
The findings of ECG in STEMI depends on the WAVES:
1. Duration - Hyperacute, Acute,Evolving or Old MI Although STEMI is typically associated with the evo-

2. Size - Amount of myocardium affected lution of pathologic Q waves, some patients do not
develop new Q waves. The appearance of new Q
Location waves in the setting of STEMI predicts both a larger
infarct and increased mortality².
II ECG IN NSTEMI
New horizontal or down sloping ST depression ≥ IDENTIFICATON OF INFARCT RELATED
0.05mv (0.5mm) in two anatomically contiguous ARTERY:
leads with or without T wave inversion ≥ 0.1mv (1mm)
(See figure-2) 1. INFERIOR WALL STEMI:

Figure -2 Inferior wall STEMI may be due to Right Coronary Ar-
tery occlusion (RCA) or due to Left CircumflexArtery
occlusion (LCX) (See figure-3)
If it is RCA occlusion causing inferior MI-Lead III ST
elevation will be greater than lead II³

If it is Left Circumflex occlusion -Lead II ST elevation
will be greater than lead III Figure-3
4

LOCALISING THE AREA OF INFARCT / ISCHEMIA:-
1. Anterior Wall: Two or more of the precordial leads
(V1-V6)

2. Antero septal: Leads V1to V3
3. High lateral – Leads LI and AVL.
4. Lateral – V4 to V6, LI & AVL.
5. Inferior wall – Leads II,III, AVF IMPORTANCE OF V4R IN LOCALISING THE
6. Right ventricular – Right sided precordial leads ARTERY CAUSING INFERIOR STEMI (See
(Right sided leads V4R,V5R should be obtained in figure- 4)
patients with inferior wall infarct)
ST- elevation in V4R - Proximal RCA occlusion
7. Posterior wall- Septal precordial leads.Posterior
leads V7, V8 and V9 may be useful if there isan evi- No ST elevation in V4R – Distal RCA occlusion.
dence of posterior wall infarct as suggested by prom- ST depression in V4R – LCX occlusion.
inent R waves and ST depression in leads V1&V2.
(The above findings in V4R is in addition to the ST
elevation in inferior leads)
IMPORTANCE OF SERIAL ECG’s:
Clinicians must be aware that the initial ECG may
NOT be diagnostic in some patients with ACS.ECG

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