Harder Roads to Trek? Paradoxical Slowing of an Atrioventricular Reentrant Tachycardia With Contralateral Bundle Branch Block.

Slowing of the tachycardia with increase in cycle length and increase in VA time with ipsilateral bundle branch block is a characteristic feature of accessory pathway mediated AVRT. Contralateral bundle branch block has no effect on the tachycardia as it is not a part of the tachycardia circuit. We present an interesting phenomenon in which contralateral bundle branch block resulted in tachycardia slowing in a case of WPW syndrome.