ECG analysis

[biology_06er]

Hi there

Just wondeirng in a lab we, using different leads we saw the heart beats. we had a normal subject but our aVL lead produced a negative deflection--now this isn't suppose to happen-i constructed my einthoven's triangle and it shows a positive deflection---just wondering what are some possible reasons why it could be inverted---i talked to someone else in a diff. group and her aVL was also inverted??

any suggestions?
cheers,
biology_06er

[Bman83]

Maybe potassium imbalance??