September 19th, 2013

A Novel Navigation System for CRT Device Implantation

CardioExchange’s editor-in-chief Harlan Krumholz interviews Sergio Richter, lead investigator of a new study of a non–fluoroscopy-based tracking system that can be used when implanting a cardiac resynchronization therapy (CRT) device. The study is published in Circulation: Arrhythmia and Electrophysiology.


Investigators used a novel, sensor-based electromagnetic tracking system (MediGuide) for implanting a CRT device in 15 consecutive patients who had an established indication for CRT. The system was successfully implanted with a lateral or posterolateral LV lead position in all patients. The mean total procedure time was 116 minutes, the median total fluoroscopy time was 5.2 minutes, and the median fluoroscopy time for LV lead deployment was 2.6 minutes. There were no severe complications that required an acute intervention or reoperation during the peri- or postoperative periods (patients were followed for 4 weeks after implantation). The system’s manufacturer funded the study.


Harlan Krumholz: Non–fluoroscopy-based technology has been used for catheter ablation and coronary interventions. Please explain how it works and whether it has features that are unique to the CRT system.

Richter: Conventional fluoroscopy is still needed for transvenous implantation of cardiac pacing devices, but the MediGuide system has the potential to substantially reduce the radiation time and exposure. Implantation of the right atrial and right ventricular leads requires conventional fluoroscopy. Thereafter, recording of cineloops in different angulations is necessary. Intubation of the coronary sinus is possible with a sensor-equipped outer sheath and EP catheter without use of radiation (in the vast majority of patients). The occlusive venography of the coronary sinus again requires radiation, but from then on it’s possible to work on these ECG-gated cineloops. The tip of different LV-lead delivery tools (outer sheath, inner sheath for subselection of side branches, and guidewires) is non-fluoroscopically displayed within the system. The CRT device is a conventional one, and the final positioning of the LV lead again requires fluoroscopy, as the lead itself is not equipped with a sensor.

Harlan Krumholz: The mean fluoroscopy time for CRT procedures is 22 minutes, compared with a median fluoroscopy time of 5 minutes in your study. What should a health system be willing to pay to avoid 17 minutes of fluoroscopy?

Richter: The biggest benefit of reducing fluoroscopy time and exposure is on the implanting physician’s (not the patient’s) side, as the patient receives the radiation exposure only once, not daily. The cost ought to be absorbed by the physician’s employer, which should seek maximum safety for its employees who conduct these procedures routinely.

Harlan Krumholz: How difficult is it to learn this system?

Richter: The system is very easy to learn. Different tools for delivery of the LV lead are equipped with an electromagnetic sensor at the tip. They have to be cable-connected to the patient’s interface unit of the MediGuide system. The handling differs nonessentially from the original tools, and the operation time is only slightly prolonged. During the very first implantations using the new system, we had to adjust to the fact that only the tip is displaced on the screen and one cannot “see” the behavior of the shaft of the used tools. But after a steep learning curve, it became easy to work with the system.

Harlan Krumholz: What are the next steps in evaluating the system?

Richter: Our institution is preparing a case-control study with nearly 60 patients implanted with the new electromagnetic tracking system. A prospective randomized trial comparing CRT device implantation with the MediGuide system versus conventional fluoroscopy is underway.

Harlan Krumholz: What do you predict about the use of these systems in the future?

Richter: Electromagnetic navigation has the potential to gain a better spatial anatomical orientation and reduce radiation exposure during invasive cardiovascular interventions.

Moreover, the capability of real-time sensor tracking offers the possibility to record or map actual wall-motion data from the endocardium and epicardium of the left ventricle. Such information may become relevant for tailored LV lead positioning, to optimize CRT response and clinical outcome in patients with congestive heart failure. It’s also possible to envision an extended use of this technology during complex coronary interventions, implantation of transfemoral valves, or interventions at the great arteries.

Harlan Krumholz: What is your response to people who express concern that the authors have received honoraria from the manufacturer of this product?

Richter: All authors received lecture honoraria and conference sponsorship from different companies. This has nothing to do with the design and development of the system or the integration into our clinical workflow. St. Jude Medical, the manufacturer of the system, funded the study, but none of the authors received honoraria directly associated with this particular study.


How much promise do you think the MediGuide system holds for the future of CRT device implantation?

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