Failure of adenosine to terminate focal atrial tachycardia.

Adenosine has proven effectiveness in the diagnosis and treatment of a variety of tachycardias with both normal and widened QRS complexes in children and adults. Its effectiveness is due to its depressant effects on atrioventricular node conduction. Adenosine might also be effective against automatic tachycardia due to spontaneous activation in partially depolarized cells. This report describes a patient presenting with tachycardia with normal QRS complexes. While the adenosine did not restore sinus rhythm, it did disclose the mechanism of the arrhythmia. Since other investigators have reported successful interruption of automatic atrial tachycardia, this case suggests that automatic atrial tachyarrhythmia may be due to more than one mechanism.