Magnetic navigation can help facilitate guidewire placement in complex lesion sets

February 07, 2006

Houston, TX - The use of powerful electromagnets to advance and position the guidewire across difficult-to-treat lesions appears to help operators facilitate PCI in patients with tortuous and severely angulated coronary arteries, according to newly published data[1]. First reports on the use of magnetic navigation in the percutaneous treatment of complex lesion sets suggest that the technology has the potential to become a useful adjunct for wire placement in complex PCI cases, investigators say.

Describing their initial experiences with the magnetic navigation system (Stereotaxis, St Louis, MO) in the February 7, 2006 issue of the Journal of the American College of Cardiology, lead investigator Dr Satya Reddy Atmakuri (Baylor College of Medicine, Houston, TX) and colleagues write that the navigation system enabled PCI to be extended to patients with tortuous and angulated vessels. "Although the current report represents a consecutive series of individual cases without a control group, it demonstrates that this novel near-robotic technique is feasible in human PCI and has the potential to expand the utility of the procedure," write the authors.

As previously reported by heart wire , the magnetic navigation system has been shown to be useful in various cardiac electrophysiology procedures, including mapping, pacing, and ablation. With the system, two magnets, external to the patient, create a magnetic field and generate sufficient force to steer magnetically tipped catheters and guidewires. Navigation is achieved by changes in the magnetic field to deflect the interventional device, allowing a guidewire to interrogate angles up to 120º.

In this first peer-reviewed report on the use of magnetic navigation in PCI, patients were selected for inclusion, in addition to the usual criteria, if the operator believed access to the target vessel with the guidewire would be difficult or impossible using conventional means. Patients who previously underwent an attempted but unsuccessful conventional PCI were also included if the operator felt a second attempt at approaching the lesion might be possible with the magnetic navigation system. Overall, 14 operators performed PCI in 69 patients using the magnetic navigation system. Most lesions attempted were ACC/AHA type B2 (53%), followed by type C lesions (43%).

The target lesion was crossed with the magnetically tipped guidewire in 85% of cases. In four of these cases, a balloon could not be passed across the lesion following guidewire placement, leading to a procedural success rate of 79%.

Procedure variables

Variable Magnetic-navigation-assisted intervention, primary attempt Magnetic-navigation-assisted intervention, secondary attempt Total
Total lesions attempted, n 55 13 68
Successful placement of guidewire, n (%) 49 (89) 9 (69) 58 (85)
Unsuccessful PCI after guidewire placement, n (%) 3 (5) 1 (8) 4 (6)
Procedural success, n (%) 46 (84) 8 (62) 54 (79)
Guidewire placement time, min (range) 10 (5-15.5) 14 (8-38) 10.5 (6-18)
Total procedure time, min (range) 62 (38-74) 70 (59-89) 64 (41-76)
Fluoroscopy time, min (range) 23.2 (13.7-41.8) 59 (41.4-75) 30 (15.2-60.1)
Contrast, mL (range) 173 (125-271) 230 (210-260) 190 (140-270)

In the report, Atmakuri and colleagues point out that it is not clear how wide the applicability of magnetic-assisted navigation is likely to be, given that few clinical trials or registries report the severity of angulation or tortuosity. One report, however, found that 24% of patients in the National Heart, Lung, and Blood Institute-sponsored Dynamic registry had a moderately or severely tortuous vessel.

Like most early reports, the authors note, the study has limitations, and further trials will be needed. In the current study, a control group was not used, as the inclusion criteria were largely "intuitive and operator dependent." Further comparisons with conventional techniques in a randomized trial are still needed, they write.

"Although this report describes an acceptably high success rate in a particularly complex lesion subset, the available interventional equipment (for example, magnetic-assisted intervention guidewires and catheters) represents early and perhaps 'primitive technology,' " conclude the authors. As advancements materialize, higher success rates in more complex lesions might be possible, they write. In addition, fluoroscopic and total procedural times, considerably longer than generally reported, would be expected to decrease as operators learn how to use the system efficiently, write the authors.

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