What happens when you give adenosine to a patient with this rhythm?

A 40-something presented with palpitations and had a regular pulse at 170.Here is his 12-lead ECG:The computer reads supraventricular tachycardia.What is it?It is atrial flutter with 2:1 conduction. It is not PSVT and not sinus.There are clear flutter waves in lead II across the bottom. In V1, there are upright waves that appear to be P-waves but are not: they are atrial waves and it is typical for atrial flutter waves to be upright in V1, whereas sinus P-waves are biphasic in V1.The flutter rate is relatively fast at 334, such that the ventricular rate is 167 (one half the atrial rate).As easy as it may seem to make this diagnosis, it is often misdiagnosed as PSVT. Thus, adenosine is often given.Such was the case here.Adenosine was given, during which this rhythm strip was recorded:The AV node is blocked by adenosine and QRSs disappear.This " reveals " the flutter waves, which of course continue.There are some ventricular escape beats.Adenosine simply blocks the AV node so that there is no QRS to hide the flutter waves, and they become obvious. So adenosine can help to diagnose atrial flutter, butit will nottreat atrial flutter. Atrial flutter does not use the AV node for part of its re-entrant loop, as does PSVT [whether AVNRT (a micro-reentrant intranodal loop) or AVRT (a macro re-entrant loop using bypass tract for one leg of the loop)]. Therefore adenosine will not interrupt the loop.  The half-life of adenosine is about 10 se...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs