Temperature-Controlled Cooled-Tip Radiofrequency Linear Ablation of the Atria Guided by a Realtime Position Management System

Abstract

SummaryDue to the difficulty in producing a transmural linear lesion and the possibility of complications such as thrombus formation leading to thromboembolism, the catheter-based maze procedure remains problematic.We tested, in pigs, the possibility of using a temperature-controlled cooled-tip radiofrequency (RF) ablation system together with a realtime position management (RPM) system to create a transmural linear lesion uncomplicated by thrombus formation.Nine pigs underwent insertion of two electrode catheters (each with two ultrasound electrodes), one into the coronary sinus (CS) and one into the right ventricular apex (references for ultrasound-based non-fluoroscopic three-dimensional mapping). A cooled-tip catheter (with two ultrasound electrodes) was introduced into the right atrium. Linear right atrial ablation was performed with a custom radiofrequency (RF) generator. The catheter was perfused with 0.66 mL/ second of saline. RF was delivered for 60 seconds at a target temperature of 40°C. A linear ablation line was created between the superior vena cava and inferior vena cava. Three-dimensional isochronal maps were created during CS pacing before and after ablation.In 4 of the 9 pigs, a transmural linear ablation line was confirmed by three-dimensional mapping and postmortem macroscopic examination. No endocardial thrombus formation was noted.Temperature-controlled cooled-tip RF linear ablation guided by an RPM system appears to have potential for creating linear lesions in the atria. Further studies are needed to determine whether such an ablation technique and the parameters used will facilitate successful completion of the catheter-based maze procedure. (Int Heart J 2011; 52: 50-55) Key words: Cooled-tip ablation, Atrium, Three-dimensional mapping, Linear ablation P ulmonary vein (PV) isolation is an established treatment for paroxysmal atrial fibrillation (AF), and the success rate is relatively high.1,2) However, persistent AF often requires atrial linear ablation.3,4) Irrigated-tip catheter ablation has been shown to facilitate bidirectional conduction block in the atria.5,6) However, there is greater discrepancy between measured electrode tip temperature and actual tissue temperature than with a standard ablation catheter; thus, there is greater potential for excessive but unrecognized heating within the myocardium. 7,8) This overheating results in the boiling of any water in the tissues and the creation of steam, which erupts through the tissue surface and is heard as a pop. We have shown the feasibility of temperature-controlled cooled-tip radiofrequency (RF) ablation in in vivo experiments. 9) However, precise positioning of the ablation catheter by fluoroscopy only is difficult and time consuming, resulting in long fluoroscopy times. RF catheter ablation procedures may be facilitated using additional endocardial mapping techniques; however, current available techniques are limited. Single electrode mapping or the use of multiple catheters is time consuming, and geometric reconstruction is di...

Are The Virtual Lines Created with the Ensite Electroanatomical Mapping System Really Continuous?

“…It is worth noting that the methodology used to access the left atrium, as well as the creation of lines by RF application was similar to that used clinically and findings were consistent for over 90% of the animals. Moreover, the swine model is used in studies to assess atrial lesions generated by radiofrequency 10,11 .…”

“…i) magnetic navigation systems to guide the catheter, either a platinum 10 or golden tip 16 , which increase its stability; ii) pressure sensors on the tip of the catheter 17 , allowing to measure its contact with the atrial surface, hypothetically improving the creation of transmural lesions; iii) integrating an ultrasound to the catheter tip to visualize in real time the lesion formation is capable to distinguish necrosis from hemorrhage in real time 11 ; iv) endoscopic ablation system with balloon that visualizes directly the vein to be isolated and performs laser ablation. However, until the validation and daily use of these technologies, creating lines with electroanatomic mapping guidance remains as gold-standard for linear ablation for AF treatment.…”

Current Status and Future of Cardiac Mapping in Atrial Fibrillation

“…Ultrasound ranging technique is used to (i) construct a 3D representation of catheters including electrodes and transducers, anatomic structures, and ablation sites and (ii) display real-time movement of the tip and shaft of the catheters. As a non-fluoroscopic map-guide system, RPM, cooled RF ablation was tested in animal experience [26]. RPM system has advantages over CARTO or NavX system regarding stable catheter position that is minimally influenced by body, cardiac, respiratory movement, and sweating, and also no need for skin electrodes or patches.…”