- Any of three standard bipolar limb leads of an electrocardiograph, designated I, II and III. Lead I records potential difference between the right and left arms; lead II, the difference between right arm and left leg; lead III, the difference between left arm and left leg.
- A record obtained from such a lead.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.