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It's Not What You Think it Is: Difference between revisions
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m (New page: {{NHJ| |mainauthor= '''A.A.M. Wilde, R.B.A. van den Brink''' |edition= 2005:6,244 }} Figure 1|thumb Figure 2|thumb...) |
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is normal and no P wave can be identified. The | is normal and no P wave can be identified. The | ||
differential diagnosis is: | differential diagnosis is: | ||
# atrioventricular nodal reentry | # atrioventricular nodal reentry tachycardia (AVNRT), | ||
tachycardia (AVNRT), | # orthodromic tachycardia with a concealed bypass (AVRT) and | ||
# orthodromic tachycardia | # atrial tachy-cardia. Adenosine was administered and the ECG presented in figure 2 was recorded. | ||
with a concealed bypass (AVRT) and | |||
# atrial tachy-cardia. Adenosine was administered and the ECG | |||
presented in figure 2 was recorded. | |||
'''What is your diagnosis and what would your further | '''What is your diagnosis and what would your further | ||
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[[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> | |||