EKG of the Week – Week 12 Answers

This week’s EKG is a tricky one.  In my opinion, it really shows how difficult it can be to tell the difference between SVT vs Aflutter.  I know we already did a long aflutter write up, but remember, if you see a rate of approx 150 (140-160) make sure to, at least briefly, consider aflutter.  Make sure to check leads II and V1 for flutter waves.  (ON THE IN SERVICE: if you see a rate of 150, you MUST consider Aflutter) Initially, we thought that this EKG was SVT (See style point below) and gave the patient adenosine, leading to EKG_Treatment.  This patient was tricky, he had a history of SVT and was treatment resistant to adenosine in the past.  He had needed to be cardioverted out of SVT.  Once the patient was given adenosine, we noticed what we thought were flutter waves.  The patient was given dilt and was immediately rate controlled and then admitted for further work up.
Even Life in the Fast Lane makes a point of how difficult it is to tell the difference between SVT and Aflutter:

Vagal Manoeuvres +/- Adenosine

• Atrial flutter will not usually cardiovert with these techniques (unlike AVNRT), although typically there will be a transient period of increased AV block during which flutter waves may be unmasked.

 Dr. Smith’s EKG Blog also does a nice write up of misdiagnosing Aflutter as SVT and unmasking it with adenosine (http://hqmeded-ecg.blogspot.com/2017/08/what-happens-when-you-give-adenosine-to.html)
EM Docs does a pretty cool write up on how to treat Aflutter once you diagnose it (http://www.emdocs.net/8635-2/)
Interesting style points, SVT is often commonly used interchangeably with AVNRT (AV Nodal Reentrant Tachycardia), but SVT refers to any tachydysrhythmia with an origin above the ventricles.  The list below, taken from life in the fast lane (https://lifeinthefastlane.com/ecg-library/svt/) are all technically types of SVT.
Site of origin: AtrialRegular Rhythm: Sinus Tachycardia, Atrial Tachycardia,  Atrial Flutter, Sinus Nodal Reentrant TachycardiaIrregular Rhythm: Afib, A flutter with variable block, MAT

site of origin: Atrio-ventricular: ALL OF THESE HAVE A REGULAR RHYTHM: AVRT, AVNRT, Automatic junctional tachycardia
Interrestingly, some of the more seasoned veterans on this distro list have pointed out that this ekg is likely atrial tachycardia, not atrial flutter.  Taken from life in the fast lane:

ECG Features of Atrial Tachycardia

• Atrial rate > 100 bpm.
• P wave morphology is abnormal when compared with sinus P wave due to ectopic origin.
• There is usually an abnormal P-wave axis (e.g. inverted in the inferior leads II, III and aVF)
• At least three consecutive identical ectopic p waves.
• QRS complexes usually normal morphology unless pre-existing bundle branch block, accessory pathway, or rate related aberrant conduction.
• Isoelectric baseline (unlike atrial flutter).
• AV block may be present — this is generally a physiological response to the rapid atrial rate, except in the case of digoxin toxicity where there is actually AV node suppression due to the vagotonic effects of digoxin, resulting in a slow ventricular rate (“PAT with block”).

What are we seeing here that makes atrial tachycardia more likely than flutter?  The isoelectric baseline.  Conveniently, from the ER’s perspective, the management of aflutter and atach is usually the same.