14th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 2000

Jan. 29 - Feb. 5, 2000
Marilleva, Trento, Italy

RT-206

Double potential unipolar recording during RF ablation of typical atrial flutter:theoretical and practical implications

Domenico Catanzariti, Fulvio Cozzi, Walter Spagnolli, Roberto Accardi, Ferdinando Imperadore, Giovanni Morani, Giuseppe Bonadies, Giuseppe Vergara.
Division of Cardiology, S.Maria del Carmine Hospital, Rovereto, Italy

Introduction

Typical atrial flutter (TAF) is a macroreentrant arrhythmia. Its circuit is located within the right atrium, encircling the tricuspid valve annulus (TA)¹. The wave front propagates around the TA with posterior lines of conduction block along the crista terminalis (CT) and along an isthmus between the coronary sinus (CS) os and the posteroseptal region of TA and between the eustachian valve ridge (EVR)/inferior vena cava (IVC) and the posterior region of TA².

Electrophysiologically guided focal radiofrequency ablation (RFA) of the isthmus was not very effective and resulted in long-lasting procedure³. Anatomical RF ablation of the IVC/ER-TA isthmus is a simplified procedure based on the interruption and noninducibility of the arrhythmia but with a significantly high number of recurrence during the follow-up (20% at 1 year)⁴.

The bidirectional complete conduction block (CCB) across the isthmus is a more recent and reliable marker of success^5,6. By making linear RF applications between the TA and IVC/ER (and/or CS), TAF recurrences can be prevented. Following ablation, a line of conduction block could be demonstrated while pacing from either side of the lesion. Then a bidirectional line of block rather than simply absence of inducibility appears to be the most dependable marker of ablation success.

Currently available tecniques in assessing the CCB are based on the mapping of activation sequence around the TA during low-rate atrial pacing from either side of the lesion line^1-7. Although the abrupt transition from early to late activation as the mapping catheter was moved further away (and across the ablation line) from the pacing catheter is highly suggestive of true block, it is not possible to exclude profound slowing (as opposed to block) through the isthmus only.

A point-to-point local analysis could allow to establish that the conduction block across the line is complete or a limited gap is active through the isthmus⁸. Furthermore it is well-known that relatively unfiltered unipolar recordings can identify the specific findings of the collision of a wave front on conductive barriers⁹.

Aim of our study was to assess the role of unipolar recording in the evaluation of CCB and of a gap in the isthmus linear lesion.