Effect of radiofrequency ablation on atrial myocardium

R. Becker et al., Effect of radiofrequency ablation on atrial myocardium, BAS R CARD, 96(5), 2001, pp. 478-486
Citations number
Categorie Soggetti
Cardiovascular & Hematology Research
Journal title
ISSN journal
0300-8428 → ACNP
Year of publication
478 - 486
SICI code
Objectives Successful RF ablation of atrial fibrillation supposedly require s the creation of continuous linear lesions. This study aimed to determine the potential role of functional modifications of atrial myocardium in the vicinity of anatomic RF lesions. Methods In 10 normal beagles (group A), a multiplexer mapping system and an epicardial multi-electrode were used to r econstruct atrial activation patterns during pacing at two cycle lengths be fore and after attempts to induce two linear right atrial lesions with a st andard ablation catheter, respectively. An intercaval "drawback" was repeat ed 3 times over 5 min at a set temperature of 70 degreesC, followed by a tr ansversal "point-by-point" ablation from the interatrial septum to the righ t-lateral tricuspid annulus at 70 degreesC/60 s each. Induction of atrial f lutter was attempted before and after each ablation. In another 6 beagles ( group B), a high-resolution multi-electrode was used to study epicardial fu nctional effects resulting from single endocardial RF lesions on the free r ight atrial wall. Using three energy settings (60 degreesC/30 s, 60 degrees C/60 s, 70 degreesC/60 s), activation patterns were analyzed at two cycle l engths and local effective refractory periods were measured across the lesi on. Results The lesions induced in group A only marginally affected atrial activation patterns and total activation times. However, as shown in dogs w ith atrial flutter, regional slow conduction was enhanced and functional co nduction blocks were facilitated at high atrial rates, resulting in a signi ficant prolongation in the revolution time of respective reentrant circuits . Apart from inducing anatomic lesions, single endocardial RF lesions (grou p B) were shown to delay epicardial conduction in adjacent myocardium in an energy- and rate-dependent way. Furthermore, an energy-dependent prolongat ion of effective refractory periods by far exceeding the size of anatomic l esions was observed. Conclusions Continuous linear atrial lesions are hard to achieve with conventional ablation techniques. However, RF lesions induc e changes in conduction and refractoriness around the anatomic lesion, whic h are likely to contribute to the overall effect of respective therapeutic interventions.