Percutaneous Microwave Ablation with a Long Side‐Firing Antenna Array Can Successfully Treat a Nonsurgical Chronic Ovine Atrial Flutter Model

INTRODUCTION: Long side-firing microwave (MW) arrays can deliver energy uniformly over its length without the need for intimate endocardial contact. We hypothesize that a novel 6 Fr 20 mm long percutaneous high-efficiency MW antenna array ablation catheter can rapidly create long, continuous, and transmural linear ablation lesions. METHODS AND RESULTS: Cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) was created in 11 sheep by a line of radiofrequency ablation lesions in the posterior right atrium (RA) linking the venae cavae. After 4-6 weeks recovery, CTI-dependent AFL was still inducible in all 11 sheep (cycle length 178 +/- 13 ms). MW ablation of the CTI at 100 W for 30 seconds was then performed with an endpoint of AFL noninducibility. AFL was not inducible in all 11 sheep after 4.3 +/- 3.3 MW applications (129 +/- 99 seconds). The last 6 animals needed fewer ablations (2.2 +/- 1.5) and 3 of these sheep required only a single ablation. Although conduction times from proximal coronary sinus to lateral RA and vice versa increased postablation (51 +/- 14 ms to 118 +/- 31 ms [P = 0.0002] and 60 +/- 13 ms to 119 +/- 28 ms [P = 0.0001], respectively), AFL was still inducible in 2 sheep and further ablation was needed to reach the endpoint. CONCLUSIONS: High-efficiency side-firing MW array ablation can rapidly create long linear and electrically intact lesions in an ovine AFL model. AFL noninducibility may be a more reliable indicator than CTI conduction times of an intact line of ablation in this animal model.