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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