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...