<unk>  in a 2-month-old girl following cardiac surgery. In this case the right bundle branch block was present during<unk>  and during normal sinus rhythm.<unk>  is most commonly diagnosed using a 12-lead ECG. The appearance is usually of a<unk>  with rapid, regular ventricular rates of 170-260 beats per minute. The QRS complexes are usually narrow, but may be broad if a bundle branch block is present. There may a 1:1 relationship between atria and ventricular activity with a short RP interval, or atrioventricular dissociation with slower atrial than ventricular rates if the AV node is unable to conduct from the ventricles to the atria. The differential diagnosis of<unk>  includes other forms of supraventricular<unk> , most commonly atrioventricular nodal reentrant<unk>  (AVNRT). These can be distinguished using adenosine. The response to adenosine in<unk>  is a temporary loss of conduction to the atria leading to continuation of the<unk>  but with atrioventricular dissociation. In contrast, administration of adenosine in AVNRT will usually terminate the arrhythmia. The diagnosis can be conclusively proven by performing an invasive electrophysiological study.
Junctional ectopic tachycardia
AV nodal reentrant tachycardia
Wandering atrial pacemaker
Tachycardia
AV nodal reentrant tachycardia  AV-nodal reentrant tachycardia  1
Ventricular escape beat
Atrioventricular reentrant tachycardia
Accelerated idioventricular rhythm