The 360 Degree Heart – Part I

The hexaxial reference system. If I asked you to imagine how the limb leads “look” at the heart, you would probably picture something like the image below. Heart drawing courtesy of Dawn Altman from the ECG Guru website: http://ecgguru.com/ Notice those gaps in the limb leads? They don’t really exist. They’re an illusion. This isn’t something that is commonly emphasized when the cardiac axis is being taught, but it’s absolutely vital to realize that in addition to each “positive” lead seen above, there is a corresponding “negative” lead in the opposite direction. These “negative” leads, which I denote with a (-) symbol, are literally nothing more than the original lead from the standard 12-lead ECG flipped upside down. Mapped on the above hexaxial reference system we now have the coverage shown below:   Now, in theory,  we have a full 360-degree view of the heart in the frontal plane. But how does this work in real life? Consider the 12-lead ECG showing infero-posterior STEMI below: Infero-posterior STEMI   All we really about for this discussion is the limb leads, so let’s focus on them and ignore the rest of the tracing:   This is what it would look like if we imagined the limb leads as displayed in the first diagram:   Notice how there’s a gap between leads I and II? Also, aVR seems way out in right field, not connected to any of the other leads. Now we’re goin...
Source: EMS 12-Lead - Category: Cardiology Authors: Tags: Uncategorized 12-Lead ECG axis axis determination cardiac axis Vince DiGiulio why learn axis determination? why learn axis? Source Type: research