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ECG Basics: Paroxysmal Supraventricular Tachycardia Converted With Adenosine

Dawn's picture
Mon, 10/28/2013 - 20:15 -- Dawn

Today, you get THREE strips for your basic classes!  The first shows a PSVT - paroxysmal supraventricular tachycardia at a rate of about 220/minute.  The QRS complexes are narrow, and the rhythm is regular.  In the second strip, we see the moment of conversion after a dose of 6 mg. of adenosine was administered by rapid I.V. infusion.  The re-entry cycle is broken, and the patient experiences many PVCs, including groups of two, three, and even four in a row.  Soon, however, the rhythm settles into sinus rhythm with PACs, and later, just sinus rhythm (not shown).  For your more advanced students, the second strip shows the PVCs interacting with the underlying sinus rhythm.  There are several fusion beats with varying degrees of fusion, and one can sometimes see a sinus P wave just before a PVC.  None of this is clinically significant in this patient, because the ventricular ectopy was a side effect of the treatment, and was self-limited.  It is a great strip for teaching, though! 

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ekgpress@mac.com's picture

     The "beauty" of Adenosine - it works quickly! The drug's onset of action is within seconds after rapid IV administration - with a half-life of less than 10 seconds (this being the reason Adenosine needs to be given IV push as fast as possible).

  • Adenosine is highly effective for reentry SVT rhythms (AVNRT/PSVT) - with a successful conversion rate of over 90%. Brief review regarding specifics about Adenosine dosing can be found by CLICKING HERE.
  • It is important to be aware that on the way from tachycardia-to-conversion-to-sinus-rhythm - there may be side effects (transient extreme bradycardia or frequent ectopics including short runs of VT as seen here). The advantage of Adenosine's short half-life is that adverse effects rarely last more than a minute or so. Some providers choose to look the other way for 30-40 seconds after Adenosine is given. While not advising you to do this - Awareness of the transient nature of Adenosine's effect is at least reassuring that arrhythmias arising as a result of treatment are likely to be short-lived.
  • After it is all over - We can admire the interesting array of fusion beats in the middle rhythm strip at the onset of runs of nonsustained VT.

 

Ken Grauer, MD  www.kg-ekgpress.com   [email protected] 

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