A patient presented to the ER complaning that "Doc, My heart is zipping a way and I cant stop sweating". He adds that he was in the supermarket looking at the turnips when all of a sudden he got really sweaty and dizzy. He also states that he could feel his heart "racing away". He did not fall, did not lose conciousness, and denied any chest pain at the time. He looks pale and is very diaphoretic. He denies any previous episodes ever happening. His medical history is significant for Hypertension and no others. He denies alcohol, drug, smoking and has moderate caffiene intake. On physical exam pertinent positives were Pulse of 185, BP 100/60, patient looking very pale and diaphoretic. No other significant findings were present. A stat EKG is done and this is what was found.

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SVT was diagnosed and a cardizem drip was started. After the Drip was started and a bolus was given, the tachycardia broke and the following EKG was gotten. With the before and after cardizem EKG's can you tell what was the cause of this patients SVT and what would be the next appropriate step in management?

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With the first EKG showing a narrow complex tachycardia we can safely assume that the origin of the arrythmia is not from the ventricle system itself so we can say it is a Supra Ventricular Tachycardia or SVT. Now its not ok to stop there. We have to figure out what kind of SVT. The basic differential of an SVT is Sinus Tachycardia, Atrial Tachycardia, A-Flutt/AFib, AV Node Re-entry tachycardia, and Atrioventricular reentry tachycardia. With some SVT's you cant really pin point what the cause is until you take the patient to the EP lab and a study is done. However on these two EKG's there is enough information to pin point the cause.

First of all, it is regular so we can knock out A-Fib.

The next thing to do is to try and find some hint of P wave presence if there is any. There is no obvious p waves so with the rate being as fast as it is (192) the chances of it being sinus tach and atrial tachycardia are really low. Some times T waves can have notches in them where the p wave is burried but that is not the case here. What is present if you look very closeley at the v1 leads in the first EKG is what seems to be the beggining of a R' wave. Now with out the after EKG this does not help us. But looking at the after EKG closer we can see that after the tachycardia breaks that R' disappears. (notice the peaks of the R vs R's deflection and compare the two ekgs). So therefore, we can call the R' in the first EKG a "psuedo R' wave". The R' is really a retrograde P wave. So now we have a Narrow, Regular SVT with retrograde P waves visible at the tail end of the QRS with a very short R-P interval (time between the R deflection and next visible p wave) this must be AV nodal reentry tachycardia.

What adds to our confidence is the post cardizem EKG. After the rate slows down, we see a sinus rhythm. If aflutter was the case we would clearly see the saw tooth pattern which we dont. There is no preexcitation pattern or delta wave so Atrioventricular reentry is now also knocked off the list. So we can safely diagnose this patient as having AVNRT and treat them appropriately.

The next step would be to take this patient to the EP lab and ablate the "accessory pathway" they have in their AV node which is allowing this rhythm to take place and they are cured!