Systematic way to look for cardiac ischemia on ECGs
Systematic way to look for cardiac ischemia on ECGs
Note- one normal ECG does not exclude cardiac ischemia.
Leads & relationship to heart
●Septum = V1-V2
●Anterior wall = V3-V4
●Lateral wall = V5, V6, I, aVL
●Inferior wall = II, III, aVF
1. Look for Q waves
Pathological Q waves indicates an AMI (new or old).
Any Q wave in V1-V3
0.03 seconds or wider (0.03 seconds is ¾ width of one little square)
Depth of the Q wave is equal to or greater than 25% of the height of the R wave.
[pic]
Above: Anterior (V1-V3) Q waves with associated ST segment elevation indicating an anterior STEMI
2. Check the ST segment
◙ The ST segment may elevate above the isoelectric baseline (T-P segment).
The overall “look” of the ST elevation is variable.
[pic]
◙ OR The ST segment may go below the isoelectric baseline (ST depression)
Note: Underlying left ventricular hypertrophy, LBBB & ventricular paced rhythms change baseline ST/T (so may see ST/T changes that are “normal” for the underlying rhythm).
3. Check the T waves
Normally: T waves should be upright in I, II, V3-V6.
T waves usually inverted only in aVR, III and V1.
Look for
◙ T wave flattening
◙ Inverted T waves (flipped/negative T wave)
Occurs in multiple leads based on the anatomical location of the area of ischaemia/infarction:
• Inferior = II, III, aVF
• Lateral = I, aVL, V5-6
• Anterior = V2-6
[pic]
Above: T wave inversion in the inferior leads (II, III, aVF). T wave upright in aVL indicating the high lateral leads (aVL) are not affected.
◙Hyperacute T waves (look “peaky”)
• Broad, asymmetrically peaked T-waves are seen in the early stages of ST-elevation MI (STEMI) and often precede the appearance of ST elevation and Q waves. Hence, repeat ECGs frequently if ongoing chest pain to look for dynamic changes.
[pic]
4. Look for reciprocal changes
The lead/s on the wall opposite an AMI is registering the reciprocal change of that AMI.
II, III, aVF (inferior) ↔ I, aVL (high lateral leads)
Ie if there is an inferior STEMI, you will likely see ST depression and T wave inversion in I & aVL.
V1, V2 (septal) ↔ V7, V8, V9 (need to do a posterior lead ECG)
Ie if ST depression seen in V1 & V2, this may indicate a posterior STEMI
Progression of non reperfused STEMI (if not lysed, nor stented in cath lab)
|Hyperacute T wave |Minutes |
|Upright, broad based, asymmetrical T | |
|May be 1st sign of coronary occlusion | |
|ST Elevation |STEMI- persistent STE in at least 2 contiguous leads: |
| |1mm or more in limb leads |
| |2mm or more in precordial leads |
| |Follow STEMI lysis pathway. |
|Reciprocal ST depression | |
|Improves specificity for STEMI in presence of normal conduction| |
|(but absence of reciprocal ST depress does not rule it out) | |
|Q wave |Seen within 1 hr, complete by 12 hrs |
| |[likely not to develop if reperfused eg lysis] |
|Shallow T wave inversion |Within 72 hrs |
| |Shallow TWI in presence of deep QS waves = AMI late in its |
| |course. |
|Resolution of ST segment |Most within 2 weeks |
| |If ongoing STE- ventricular aneurysm |
|Normalisation of T waves |Days-months |
Wellen’s syndrome
⌂Indicates a recent transient STEMI due to critical narrowing of proximal LAD (left anterior descending artery) →occlusion, that has spontaneously opened or received collateral flow.
⌂Look at leads V2-V4
⌂Pattern A: Terminal T wave inversion (looks biphasic)
(picture to the right)
⌂Pattern B: symmetrical deep TWI (picture below left)
High risk for re-occlusion with recurrent STEMI.
Treatment: Urgent retrieval to Brisbane for
angiography.
Differential of ST elevation
I find the trickiest cases are the 25-45yo cohort- they could be benign early repolarisation, pericarditis or a STEMI. Do frequent ECGs for dynamic changes and liaise with cardiology in Brisbane early! (We have had a 31yo and 34yo have a STEMI recently)
|STEMI |Arterial territory distribution |
| | |
| |Morphology- straight or convex (may be concave) |
| | |
| |Measured from J point (end of QRS, where ST segment begins) |
| | |
| |Diagnostic criteria: Persistent STE in at least 2 contiguous leads: |
| |1mm or more in limb leads |
| |2mm or more in precordial leads |
| | |
| |Associated features |
| |T wave inversion at same time. Reciprocal changes, Q waves. |
|BER |Normal variant. Age < 50 (rarely after 70yo) |
|= benign |J point elevation ................
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