The 12 Leads of Christmas: Lead II

This article is the second in our latest series, The 12 Leads of Christmas, where each day we examine a new finding particular to an individual electrocardiographic lead. The Lead II Sign Yesterday we covered the lead I sign, so it’s only fitting that today we discuss the lead II sign. There’s a “lead I sign” in lead II.   It’s a commonly described finding but I’ve never seen that term used anywhere else; however, it seems fitting considering our last post. What we see here is looks a lot like the lead I sign except it’s in the wrong spot. Could this be a trick of the vectors again, where lead II just happens to be perpendicular to the three major vectors we see on the ECG (P, QRS, and T)? What kind of pathology could be responsible for that? Well there is something pathological going on here but it’s not in the patient, it’s on her: the EKG electrodes! This is an example of a right-arm/right-leg (RA/RL) cable swap. We see this pattern on the EKG because, electrocardiographically speaking, the right leg and left leg act as essentially the same limb. Imagine  what we are doing when we perform an ECG: We examine the change in voltage between two points as the heart depolarizes. If we’re monitoring lead II, we are looking at the change in voltage between the right arm (RA) and the left leg (LL) as the heart beats. Move the RA electrode to the right leg (a RA/RL swap), and now we’re examining the voltage dif...
Source: EMS 12-Lead - Category: Cardiology Authors: Tags: 12-Leads of Christmas Original Articles Vince DiGiulio Source Type: research