EKG of the Week 18 – ANSWERS
Solution to this week’s EKG of the week! Here was my read:
Rate: 170 (I cheated and looked off of the read)
Rhythm: Well, regular or irregular? I’d call it regular. Definitely tachycardic and I don’t see a P wave before each QRS…
Axis: Up in 1, down in aVF, looks Left axisIntervals: the big question here is: is the QRS wide or narrow. QRS is 102 ms, so narrow
Morphology: seems ok to me
So we have a regular, narrow complex tachycardia. I’m gonna borrow from our tachydysrhythmia chart:
Narrow and Regular: Sinus Tachycardia, Atrial Tachycardia, Atrial Flutter with a fixed block (remember if you see a rate of 150 on the exam LOOK FOR FLUTTER WAVES), and AVNRT (colloquially called SVT)
Narrow and IRREGULAR: Sinus tach with PACs (remember that non compensatory pause?), Afib, MAT, Atrial flutter with variable block
Wide and Regular: Regular SVT with BBB, Regular SVT with preexcitation, Vtach, V Paced (Check every EKG for pacer spikes)
Wide and IRREGULAR: Irregular SVT with BBB, Irreg SVT with preexcitation, VFib, Torsade de pointes
So if we look at the narrow and regular choices: Sinus Tachycardia: No p waves, right? So not Sinus Tach. Atrial Tachycardia: We haven’t covered atrial tachycardia expressly, but MAT and Aflutter and two types of atrial tachycardia. But, I cannot confidently pick out atrial activity, so I’m going to lean away from ATach. For more, see (https://lifeinthefastlane.com/ecg-library/atrial-tachycardia/) AFlutter: I don’t see flutter waves. The rate is 170, which is close to 150, but doesn’t appear to be flutter. But bonus points for thinking about it with a rate near 150.AVNRT (SVT): This looks like SVT to me.
So I read this as SVT. Lets take a quick side trip and refresh on what is going on with a patient in SVT:
Technically, we should be calling this AVNRT (that’s Atrioventricular Nodal Reentrant Tachycardia). This is the most common cause of SVT. Life in the fast lane has some excellent drawings of what is going on:
In this picture, the reentry circuit on the left is within the AV node (what is likely going on with our patient) as opposed to outside the AV node on the right which is more consistent with a process like WPW.
So what happens within the AV node??
If a PAC activates the slow pathway while the fast pathway is still refractory, BAM! you get SVT and an EKG that looks like this patient. For more, see : https://lifeinthefastlane.com/ecg-library/svt/
Cool! But I didn’t become an EM physician to talk about pathophys….
Very true, so with the first patient scenario, I’d give adenosine (6mg – 12mg – 12 mg). Remember, Adenosine is an AV node blocker and allows the heart a pause to reset and have the heart’s electrical activity go down the right pathway.
For the second patient, get out the paddles. This patient needs electricity. Remember to synchronized cardiovert this patient. Do not fibrillate someone with a pulse. Please.
For me, she was resistant to the first dose of adenosine but the 12 mg put her right back into NSR. She was admitted to the hospital for further work up as she had never been in SVT before.