Independent ablation of retrograde and anterograde accessory connection conduction at the atrial and ventricular insertion sites: evidence supporting the impedance mismatch hypothesis for unidirectional block.

INTRODUCTION: The impedance mismatch hypothesis has been proposed as one of the mechanisms responsible for accessory connection conduction block. METHODS AND
RESULTS: We describe a case in which retrograde conduction across a posteroseptal accessory connection was ablated at the atrial insertion site in the coronary sinus os, whereas anterograde conduction was ablated at the ventricular insertion site in the left ventricle.
CONCLUSION: The evidence supports the impedance mismatch concept as the cause of unidirectional conduction block and shows that the distal junction between the accessory connection and the myocardium is more vulnerable to ablation.