Our thanks to Tim Nowak for stopping in and talking to us. For those of you who don’t know Tim, he is a stellar individual that has quite a bit of experience in EMS. He hails from the Green Bay area, and is currently working as an EMS educator in Castle Rock, CO and is the CEO of Emergency Medical Solutions, LLC. Tim is also resurrecting his publication, the EMS Director, so check it out!
The Purpose of the 3-Lead
- There is a way to detect limb-lead displacement with a 3-lead; read this article from LITFL about looking into limb-lead reversal.
- Good for rate and rhythm detection, but not much else.
- Using a 3-lead only is lazy…
Common Pitfalls of the 12-Lead Acquisition
- Limb leads need to go on the limbs…
- Large muscle and adipose mass just adds to more artifact and lessens the view that is offered by the 12-lead.
- Lack of investigation into axis deviation, suspicious looking 12-leads without actually STEMI criteria.
15-Leads: Placement and Purpose
The 15-lead is designed to offset the left-focused views that a normal 12-lead gives. By focusing on the right side of the heart, we find RCA occlusion. The posterior placement is looking at the circumflex artery or the distal end of the LAD.
There is a significantly increased mortality rate found in this article associated with patients that have right ventricular involvement with a suspected inferior wall MI.
Roughly 24-50% of all inferior AMIs are masking RCA occlusion; you can read more about this phenomenon in this study here. If the occurrence of RVMI is that high with inferior MI, why is this not common practice? The use of nitroglycerine for an unrecognized right-sided MI, we risk dumping our patient’s preload. Check out this video for an awesome understanding of right ventricle involvement!
18-Lead: Placement and Purpose
18-leads are designed to look at the posterior aspects of the heart. The RCx and RCA can both feed into the posterior aspects of the heart. Remember that if you have reciprocal changes, then some area of the heart is being affected! Reciprocal typically refers to the opposite area; therefore, if you are seeing isolated anterior or septal depression, then there is a significant chance there could be some element of posterior MI.
About 15-20% of all MIs are actually posterior in nature; check out this paper here for further reading about this. On top of that, 3-11% of all AMIs are posterior in nature without any reciprocal changes on any limb leads or precordial leads. The next that you have that ACS patient with no ST abnormalities on their 12-lead, consider the 18-lead.
There is a significant amount of information that prehospital (and in-hospital providers) miss on the average 12-lead EKG:
- How do we train providers to investigate EKGs more in depth?
- How do we change the culture of lack of investigation?
- Why aren’t 15 or 18-lead EKGs part of the initial training process?
- How do we maintain proficiency on 15 or 18-lead EKG proficiency?