It's Not What You Think it Is

Author(s)	A.A.M. Wilde, R.B.A. van den Brink
NHJ edition:	2005:6,244
These Rhythm Puzzles have been published in the Netherlands Heart Journal and are reproduced here under the prevailing creative commons license with permission from the publisher, Bohn Stafleu Van Loghum.
The ECG can be enlarged twice by clicking on the image and it's first enlargement

Figure 1

Figure 2

A20-year-old male is having palpitations. They occur without a specific trigger, although episodes are sometimes related to emotion or exercise. Duration is between two minutes and one hour. He does not feel well during an attack, but has never fainted. Physical examination reveals no abnormalities nor does laboratory investigation or echocardiography. His baseline ECG is normal (not shown). He was asked to come to the emergency room if an episode lasted long enough, which he did (figure 1).

Upon presentation during an attack the ECG recorded a narrow-complex tachycardia with an RR interval of 280 msec (214 beats/min). There is a slight rightward deviation of the electrical axis. ST morphology is normal and no P wave can be identified. The differential diagnosis is:

1. atrioventricular nodal reentry

tachycardia (AVNRT),

1. orthodromic tachycardia

with a concealed bypass (AVRT) and

1. atrial tachy-cardia. Adenosine was administered and the ECG

presented in figure 2 was recorded.

What is your diagnosis and what would your further treatment be?

Answer