It's Not What You Think it Is: Difference between revisions

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 treatment be?'''
-[[Answer]]
+[[Puzzle 2005_6_244 - Answer|Answer]]
-Figure 2 shows a narrow complex rhythm, with an RR
-interval of 560 msec, i.e. a rate exactly half of that
-before adenosine. P waves are now clearly discernable
-with an axis compatible with sinus rhythm. This suggests
-either sinus rhythm, or a supraventricular
-tachycardia with 2:1 block in the AV node caused by
-adenosine and comparable P wave morphology. AVRT
-can be excluded as a 1:1 relation between atrium and
-ventricle is required. AVNRT with 2:1 block to the
-ventricle is also highly unlikely because of the
-morphology of the P waves, which in that case would
-be negative in the inferior leads due to retrograde
-activation of the atrium. The only remaining alternative
-is atrial tachycardia from an area in the vicinity of the
-sinus node. Indeed, on closer examination there is
-evidence of a second P wave partly hidden in the
-terminal part of the T wave in lead V1.
-Shortly after this ECG was obtained the tachycardia
-(figure 1) resumed. A higher dose of adenosine
-terminated the tachycardia and sinus rhythm (60
-beats/min) appeared. Atrial tachycardias occasionally
-respond to adenosine. In those cases the underlying
-electrophysiological mechanism is triggered activity
-based on delayed afterdepolarisations.<cite>Markowitz</cite><cite>Lerman</cite> These tachycardias
-usually respond well to β-blockade or
-verapamil, and are generally amenable to catheter
-ablation.
-==References==
-<biblio>
-#Markowitz pmid=10355690
-#Lerman pmid=8743762
-</biblio>