Thanks Itdood, I'll save your response for my reference.
estelle, did you have question about echocardiograms too? Your subject could be a typo, or you simply got me on something new, I don't know about (and that would be easy to do with me).
For the atria contracting (P wave, depolarization), the wave is moving toward the positive electrode, and causes a positive deflection (above the isoelectric).
For the Ventricles recovering, (T wave, repolarization) the wave is (supposed to be) moving away from the positive lead and that also causes a positive deflection.
P wave: As the *positive* impulse from the atria travels, it moves *toward* the positive lead(s), causing a positive deflection.
T wave: When the *negative* impulse from the ventricles travels, it moves *away* from the positive lead(s), causing a positive deflection.
Hopefully that makes sense. tough to explain. Also consider that if you look at negative leads, or bi polar leads, these rules all change. Ever look at an ECG and see a bunch of different looking traces for V1, V2, etc?.... that's what you're seeing.