Arrhythmia management is one of the things I really love about emergency medicine.  There’s something satisfying about slapping the defibrillator pads on a patient and analyzing an ecg rhythm.   I thought I would share a recent lecture I gave on SVT during USF Conference and review some of the common ecg findings and pitfalls associated with this arrhythmia.  In the full lecture below, you’ll learn more about SVT and the management of this condition. 

Technically speaking, SVT includes any arrhythmia that originates above the Bundle of His - this would include etiologies such as afib and flutter.  However, from an ER perspective, when we use the term SVT, we are not talking about afib or flutter.  We are usually using this term synonymously with AVNRT (AV nodal reentrant tachycardia) though there are certainly other types of “SVT”.  For more on AVNRT and other forms of SVT, check out the lecture!

Let’s review 5 ecg findings you may see in SVT. 

And now, let’s review a few SVT pitfalls!

• Remember that at really fast rates, everything looks regular.  This is one of the key teaching points I took from Dr. Littmann and this knowledge bomb has helped me time and time again.  Look at this ECG which initially looks like SVT.  When examined closely, it is more likely afib given the slight irregularity that can be appreciated. 

• Be paranoid about atrial flutter because flutter waves like to hide!  Atrial flutter can mimic both sinus tachycardia and SVT.  The first ECG below was mistaken for SVT and it’s easy to see why.  There’s really nothing about that initial ecg that would make me think flutter other than the rate.  Once the patient was given Adenosine, flutter waves were revealed.  The second ECG is a patient who was initially thought to be in SVT.  On closer review of the rhythm, p waves can be identified in V2.  Thus, the patient was either having sinus tachycardia or atrial flutter.  Ultimately, the patient was found to have flutter.  The third ECG below is patient number 2 again.  I’ve simply circled the hidden p waves that I marched out with fancy $10 calipers.  One last final atrial flutter ecg is included.  In this ecg, flutter was actually mistaken for sinus tachycardia on initial review.  However, notice that the p waves in the inferior leads are inverted.  Sinus does not produce inverted p waves in the inferior leads.  This is a big clue that you are dealing with a rhythm that originates somewhere other than the sinus node. 

• Sinus tachycardia can easily be mistaken for SVT at rapid rates. The patient below was brought in via EMS with an identical rhythm strip.  Because of her fast rate, she was given adenosine.  The patient clearly has p waves and likely was in sinus rhythm the whole time. Remember that the max heart rate is 220 minus the patient’s age.  Many patients can have HRs as high as 200 even in sinus! 

• Lastly, the most important pitfall to avoid is don’t assume that a wide complex tachycardia is SVT.  You and your patient will be safest if you assume that wide complex tachycardias are ventricular tachycardia and treat it as such!

  I hope you’ve enjoyed the post!  Check out the lecture and email me with any questions!  Special thanks to all of my favorite educators in cardiology (Drs. Laszlo Littmann, James Bower, Troy Leo, Todd Haber, Amal Mattu, and the crew at Life in the Fast Lane)!

About the author

Dr. Okonkwo is the Assistant Program Director at USF.  She attended medical school at Indiana University and completed her emergency medicine residency training at Carolinas Medical Center in Charlotte, North Carolina.