ECG continued

To complement Margot's stunning work, here's a little more on groupings.

ECG lead groupings

I assume we all know by now that ST elevation is grounds for diagnosis of acute myocardial infarction, Q waves are good reason to believe that there has been a past MI and that ST depression can mean ischaemia. What we may not know is that these changes are generally not present in all leads of an ECG. By looking at the basic principles of the ECG and where the electrodes are places, we are able to determine where an infarction has occurred, or which area of the heart is ischaemic. This is ultimately achieved through lead groupings.

Each lead of the ECG looks at a different part of the heart. Leads V1 through V6 measure conduction in a transverse plane, transecting the heart; the other leads focus on coronal plane, running along the anterior aspect of the heart.

The following pictures should help explain which leads do which!

Inferior (right coronary artery) – II, III, aVF
Right Ventricle

Anterior (left anterior descending) – V2, V3, V4
Septal and anterior parts of left ventricle

Septal – V1, V2
Intraventricular septum

Lateral – I, aVL, V5, V6
Lateral right ventricle

Any combinations of these can also happen.

Hence, ST elevation inV2, V3, I, aVL suggests an anterolateral MI.

Pix: http://medinfo.ufl.edu/~ekg/QRST%20changes.html
The rest taken lovingly, albeit sparingly, from ECG made easy.