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Lateral STEMI on a 12-lead ECG

ST elevation in I, aVL, V5 and V6, with reciprocal depression in III and aVF.

What to look for

Lateral wall injury, from the circumflex or a diagonal or obtuse marginal branch, gives ST elevation in I, aVL, V5 and V6. When I and aVL are elevated, you'll see reciprocal depression in III and aVF. A circumflex occlusion often brings posterior changes too, so look at V1-V2 for ST depression.

Examples

Each is a standard 12-lead: 2.5 seconds of each lead in four columns, with 10 seconds of lead II along the bottom, drawn to scale (25 mm a second, 10 mm a millivolt). The measurements are under each one.

Example 1 · 12-lead · 10 seconds
IaVRV1V4IIaVLV2V5IIIaVFV3V6II25 mm/s · 10 mm/mV
Rate
68/min
Rhythm
RegularSinus: upright in II, biphasic in V1, one before every QRS
PR
0.20 s
QRS
0.10 s, narrow
Axis
57°, normal
QTc
0.43 s
ST up
I, aVL, V4, V5, V6 (lateral)
ST down
III, aVR, aVF, V1, V2, V3 (reciprocal)
T inverted
V1
Example 2 · 12-lead · 10 seconds
IaVRV1V4IIaVLV2V5IIIaVFV3V6II25 mm/s · 10 mm/mV
Rate
75/min
Rhythm
RegularSinus: upright in II, biphasic in V1, one before every QRS
PR
0.14 s
QRS
0.08 s, narrow
Axis
21°, normal
QTc
0.42 s
ST up
I, aVL, V5, V6 (lateral)
ST down
III, aVR, aVF, V1, V2, V3 (reciprocal)
T inverted
III, V1
Also
Smaller ST elevation (under the STEMI cut-off) in V4 · Biphasic T waves in V2

Don't confuse it with

The ECG tool in the app gives you a new 12-lead every time and walks you through reading it: rate, QRS, axis, then where the ST is up and down. It's part of the Paramedic level, and you can try 5 ECGs a day free.

Try the 12-lead drill

Where the criteria come from

Others in the STEMI and occlusion MI group