? about 12 lead ekg i've been wondering about

I think you're right that it's probably because the leads are right over the heart. The QRS is also quite large compared to the other leads (albeit negative) for this same reason. Then as the wave of repolarization comes back up toward V2 the T wave is large and positive. I don't know this for a fact but I think you're hypothesis seems reasonable.

thanks for your help! i did look in my EKG class and ACLS book and it gave me the answer that the chest leads which would be V1-V6 can seem unusually big up to 2 lg boxes on the ekg strip.

It has to do with the orientation of V1-V4 to the left side of the heart. Look at the pattern of the QRS complexes, V1-V3 are predominantly downward deflections because the sum of the depolarization wave is moving away from the positive lead (because the Left Ventricle has more mass, and thus more effect on the sum of depolarization). The heart repolarizes in the same way, the sum of the wave of negative charge returning is mostly going away from those leads, so to speak. Negative going away from a positive will look the same as a positive wave going towards a positive. This explains why the more negative QRS complexes are associated with more positive T waves. I hope that makes a little sense. Its a complex concept, you need to think of the "wave" as a sum of of all the electrical activity around the heart and then think of that sum as a vector. The vector's orientation to the poles of the leads and its the strength determine everything you see on that strip. Hopefully, thats not too confusing. If you really, really want to understand 12 leads, read Dale Dubin's Rapid Interpretation of EKG's. There are more complex EKG books but none that really hit on the basics well enough for you to really understand.

This link describes the vector thing way better. I'm a pretty bad teacher :)

http://www.cvphysiology.com/Arrhythmias/A015.htm

This is really good also. It explains pretty much everything else.

http://www.cvphysiology.com/Arrhythmias/A014.htm

The amplitude is dependent on a few things - the amount of muscle involved and the vector of the signal are the two biggest factors. Also, T wave size is very different from ST segment changes though they may be related.

-Mike