ECG Lead placement. The diagram below shows a heart and the direction of the resultant electrical vector. Below it, the 12 leads are shown as typically appear on an ECG tracing. The three limp leads, the three augmented limp leads, and the six precordial chest leads. The plus or negative sign with a circle around it shows you which direction the QRS wave will be deflected. Positive is up and negative is down. I forgot to add the plus signs to both lead II and III.
