50 something yo F calls 911 for new onset palpitations

She has a history of DM II, HTN and depression and is compliant with all medications. She called 911 when she started having palpitations that started at rest. On my arrival, overall she looked well but worried. She denied chest pain and had a slight increase in respiratory effort. Radial pulses were bounding, I counted about 25 bpm in 10 secs (~150bpm) while my partner obtained the rest of her V/S. I captured a 12 lead – Fig. 1 

Fig. 1

The rhythm confirmed my pulse count as Tachycardic, overall it has a grossly regular R-R appearance and the QRS are narrow. The baseline of the Hexaxial Leads caught my eye and initially I thought this was artifact. I repeated the tracing and it was nearly identical. I then moved the limb leads to insure I hadn’t placed them over a pulsating artery which can cause this appearance – it also looked nearly identical.  
I still thought this was artifact, regardless…
♦ Looking at the T wave in V1 – it is not only upright but rather large in comparison to the QRS and it’s larger than the T wave in V6. 
♦ The T wave in V2 is also a bit large and symmetric.
♦ There are several leads with minimal but present ST depression –  Leads II, AVF, V2-V6 with AVR having the obligatory reciprocal ST Elevation, again minimal but present. 
♦ What appears to be P waves in Leads II and AVF are quite large and rather pointy. The ECG has poor specificity regarding atrial enlargement however these do appear to be suspicious of Right Atrial Enlargement (RAA).
♦ The QT is prolonged at greater that 1/2 the R-R.
         

                                       *Could this be an occlusion of the LAD? an isolated Posterior occlusion?
 I remembered back to an article Dr. Steve Smith wrote – {I’m paraphrasing here} Occlusion is unlikely to present with Tachycardia over ~140 bpm with a narrow QRS unless there is underlying A Fib or the patient is in shock. Clearly neither were the case here. 

So we have tachycardia and quite a bit of ST Depression = Subendocardial Ischemia I.E. Demand Ischemia. The hearts beating too fast to keep up with the oxygen demand. 

I handed the 12 lead off to my partner who is finishing up his Paramedic training and asked his opinion. He knows by now that when I ask him about a 12 lead – there’s a teaching point coming 🙂

He immediately picked up on the ST Depression in the Precordials – his response – Posterior MI? Nice! so many providers still don’t appreciate ST Depression in V1-V4.
Playing the devils advocate, I said probably not with that heart rate but what about the Flutter waves in Lead I? There’s also a positive Bix Rule in V2.
 
         Bix Rule: If the P wave / T wave falls exactly 1/2 way between the QRS’, then there is most likely a hidden P (actually F wave) inside the QRS indicating a 2:1 Atrial Flutter

Atrial Flutter is probably the most overlooked rhythm; you’ll only find it IF you are looking for it. Not all Atrial Flutter appears as the textbook examples of a clear “sawtooth” appearance. Any tachycardia over about 140 bpm should prompt you to at least consider Flutter. It’s also not well known that Flutter waves CAN be inverted. In addition, Atrial Flutter is a common STEMI mimic producing STE and STD. 
He asks me – so how do we know if it is Flutter? Great question! He’s going to make an awesome Medic.
I said we capture Lewis Leads of course…and he gives me that look of huh?

See the source imagePicture from Life in the Fast Lane – https://litfl.com/ecg-lead-positioning/ 
If you have the green Right Limb Lead – it stays in place, no need to move it. 
Litfl is a great resource especially for a quick “snapshot” on an ECG topic, I highly recommend it. 

Lewis Leads captured: 
 *Note – when this modification is used, we only inspect Lead I and only the P wave (We would now relabel Lead I to S5). Ideally you would want to change the calibration to 20 mm/mv. Unfortunately, we were not able to adjust that setting – but I think you’ll get the point in Fig. 2. 

Fig. 2

Let’s zoom in on Lead I in Fig. 3:

Fig. 3

As you can see – Atrial activity is greatly enlarged. This method is particularly useful with a regular Wide Complex Tachycardia suspected of VT. It can uncover hidden AV Dissociation which is near 100% diagnostic of VT. 
♦ It’s important to emphasize that this ONLY enhances atrial activity meaning the QRS and T wave should not be a consideration in your interpretation. 

By using this lead modification in our presenting case, we can now confirm this IS Sinus Tachycardia (not Atrial Flutter) and my original assumption of artifact was indeed correct. The heart rate is the most likely cause of the ST depression indicating Demand Ischemia. 

During our patient contact, she admitted to N/V/D for 2 days. I treated this as volume depletion and not true ACS. After a fluid bolus, the heart rate improved to ~100 bpm. 

My hope in this blog was to bring the lead modification to your attention, many providers have never heard of Lewis Leads. 

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