Robotic navigation systems in the spotlight


The use of robotic navigation in procedures to treat heart rhythm problems such as atrial flutters is gaining popularity as technology becomes more and more advanced.
The use of robotics can allow for greater precision than possible with equipment such manual catheters. Remote procedures also provide protection from radiation for surgeons and can be more precise than a close-up manual procedure.

REMOTE study
New studies and clinical experience are allowing for more confidence with these new guidance systems. At this years Transcatheter Cardiovascular Therapeutics (TCT) conference, held in Washington DC in October, Dr Marvin Slepian presented on the Remote Manipulation Of Intra-Cardiac Catheter (REMOTE study), which examined the Sensei robotic catheter system (Hansen Medical).

Slepian said that the system is safe and effective for diagnostic and therapeutic access and delivery to multiple intra-cardiac and vascular locations. The system was described in a paper by Dr Sabine Ernst, Royal Brompton Hospital, London, in the Journal of Interventional Cardiology (April 2008) as comprising a ” ‘master’ input that transmits the operator’s movement using a ‘joystick’ via an electromechanical ‘slave’ at the patient’s side”.

REMOTE enrolled 63 patients at five European sites were treated for atrial arrhythmias with ablation using the Sensei system and mapping. Clinical endpoints were: navigation to anatomical targets; targeting and delivery of radiofrequency (RF) therapy; and safety. Clinical success at the navigation to intracardiac targets stage was 332/338 patients. In terms of safety, there was one pericardial effusion from a manual transseptal puncture and one pericardial effusion during radiofrequency ablation. Thirty-three out of 34 cases of atrial fibrillation and 100% of flutters were treated.

Slepian detailed the advantages of the Sensei system over magnetic navigation, as used in the Stereotaxis Niobe system, discussing catheter tip motion, variable force, contact pressure measuring and control of multiple catheters. In Slepian’s opinion, the Sensei has the edge in all the categories, with instinctive motion at the catheter tip, variable force, quantification of contact between the catheter tip and the heart wall, and multiple catheter capability.

According to Slepian, the integration of the robotic technology with computational movement is the key to the system’s success, with multiple imaging modalities allowing a user-friendly, 3D workspace. Many catheter systems and devices can be used with the Sensei system. Consisting of a robotic guide and robotic catheter manipulator, a commercial catheter can be directed from a remote workstation with console displays, imaging modalities and haemodynamics. The physician operates the system using an instinctive motion controller, which records and digitises motion and uses proprietary control logic. The catheter manipulator uses servo-motors that continuously tension and re-tension pull wires for movement and employ a computer feedback loop.
Slepian noted that the system is approved in the US and Europe.

Stereotaxis Niobe in paediatric cases
The Niobe system from Stereotaxis, a magnetic remote navigation system, uses a computer-controlled magnetic field to remotely steer devices through vessels. Doctors discussed their clinical experiences with the Stereotaxis Niobe system at this year’s Heart Rhythm conference, held in May.

Dr Xu Chen, Copenhagen University Hospital, Denmark, reported using the Niobe in paediatric supraventricular tachycardia a 100% acute success rate and a rate of 92% in chronic cases, with no complications. He said that the use of the remote system reduced the X-ray exposure of his patients to five minutes, which he noted was important in child patients to minimise the long-term effects of radiation. He added that the flexible catheter reduced the risk of perforation.

Further favourable reports came from Professor Tamas Szili-Torok, Erasmus Medical Center, Rotterdam, The Netherlands, who said that remote magnetic navigation is the standard of care at his centre when treating paediatric cases due to its good safety and suitability for use in complex anatomy. He also reported 100% acute success in paediatric supraventricular tachycardia, with 81% chronic success. In challenging congenital heart disease cases, he reported 92% acute and 75% chronic success. All results were at one-year follow-up.

Remote ablation was also discussed at the 7th International Symposium on Catheter Ablation Techniques (ISCAT) meeting by Dr Giuseppe Augello, San Raffaele University Hospital, Milan, Italy, in his talk, ‘Evolution, safety and efficacy or remote magnetic AF ablation’. He believes the remote use of catheters has improved but that more developments are still needed.

Discussing his centre’s experience, Augello noted that he and his team have treated 2009 patients with paroxysmal or chronic atrial fibrillation since 1998. Their initial experience with the first-generation Thermocool RTM in 34 patients was a mean fall of 10Ω ***OMEGA SYMBOL*** across all lesions, using 15 seconds of power, limited to 30 watts. Using ten-11 seconds of power in the same place on the lesion achieved a steady state of lowered impedance.

The second-generation Thermocool has now been launched, with a new design combining magnet and electrode components to avoid catheter heating due to electromagnetic forces. It includes automatic functions for navigation, ablation and the assessment of lines. Augello acknowledged the limitations of the system, including the 2D fluoro-based autonavigation, which he says should be 3D and respiration-compensated. The system is closed and therefore not compatible with other products. Regarding autoablation, there is a low magnetic force at the mitral isthmus and the septum, and an algorithm is needed to fully automate ablation parameters.

Augello’s advice when it comes to assessing the efficacy of a system is that the success of ablation procedures or techniques depends on pulmonary vein isolation (PVI) and that doctors can use any tool they prefer, but PVI must be pursued. He said that “ablation stops when PVI is confirmed and not before or after”.