Wide QRS-complex tachycardia following administration of adenosine

Velilla Moliner J, Salazar González JJ, Asso Abadía A, Giménez Valverde A, Marquina Lacueva MI, Placer Peralta LV

Regular tachycardia with a narrow QRS complex is a common presenting complaint in

emergency departments. The differential diagnosis includes atrioventricular reentrant

tachycardia (intranodal or accessory pathway-mediated) and atrial tachycardia (atrial

flutter). These types of tachycardia are commonly treated using vagal manoenvures and

adenosine. We describe a patient with a history of paroxysmal atrial fibrillation receiving

regular treatment with flecainide who presented with a regular narrow QRS-complex

tachycardia (205 beats/min). After administration of adenosine the heart rate slowed

briefly, followed by regular wide QRS-complex tachycardia at the same rate as before

and apparently ventricular in origin. The patient was in class 1C atrial flutter with 1:1

atrioventricular conduction. Severe conduction disturbance due to flecainide treatment

was intermittently exacerbated by the adenosine-induced atrioventricular block.

Asso Abadía A, Giménez Valverde A, Marquina Lacueva MI, Placer Peralta LV, Salazar González JJ, Velilla Moliner J