Lewis lead

A Lewis Lead (also called the S5 lead) is a modified EKG lead used to detect atrial flutter waves when atrial flutter is suspected clinically but not definitely demonstrated on the standard 12 lead EKG. In order to create the Lewis Lead, the right arm electrode is moved to the right, second intercostal space adjacent to the sternum. Then the left arm electrode is moved to the right, fourth intercostal space adjacent to the sternum. The Lewis Lead is then read as Lead I on the EKG and, since in most patients it will be roughly perpendicular to the wave of atrial depolarization, flutter waves may be more apparent.