MNS, first developed in 1998 for use in neurosurgery, involve two large magnets positioned at either side of the patient to create magnetic fields capable of generating sufficient force to steer magnetically tipped interventional devices through the vasculature body. Real-time fluoroscopy displays a “live road map” on the control panel, allowing the operator to drive the device from a remote room. A computer calculates the appropriate position for each of the permanent magnets to achieve the desired movement. Addition of the cardiodrive device allows for truly remote controlled catheter ablation, since manual operators are no longer required to push or pull the catheter.
In comparison with manual ablation, says Professor Luc Jordaens from Rotterdam, the Netherlands, who discusses the technique in a Symposium later today, MNS allows for extremely precise catheter movements, decreased procedure time and the opportunity to couple catheters with 3-D imaging. The approach also decreases the number of catheters needed in the heart, results in fewer complications at puncture sites, and reduces fluoroscopic exposure for both patients and physicians. “One of the real advantages is that MNS catheters are like floppy spaghetti, so there's virtually no risk of perforation,” explains Jordaens, adding that this risk occurs in 2-3% of manual ablations.
Challenge of atrial fibrillation
Already electrophysiologists are using MNS to successfully treat supraventricular tachycardia, atrial flutter, Wolff-Parkinson White syndrome an
d some ventricular arrhythmias. Atrial fibrillation (AF) however, has proved altogether more challenging. The difficulty is that AF requires more extensive ablations which can result in “charring”, and an added risk of blood clots and stroke. The way forward here, says Sabine Ernst from the Royal Brompton and Harefield Hospital in the UK is the use of irrigated catheters which flush saline, thereby reducing the temperature at the tip of the catheter, making clots less likely to form. There have, however, been delays, with magnetic irrigation devices to become available as a commercial product.
PCI data suggest that MNS could be used in tortuous vessels, or for complex lesions such as bifurcations, thereby reducing the number of patients requiring CABG procedures. Another possibility is that MNS catheters could be used to accurately deliver stem cells to infarcted areas that can not be accessed by normal catheters.
There are also initiatives to use MNS to position pacing wires, and replace valves.
“Ultimately the remoteness of the technique is likely to increase," says Ernst. "If you can do the procedure from the next room, there's absolutely no reason why you couldn't perform it from another city, or even another planet." She notes, however, that “remoteness” creates challenging ethical issues over who takes clinical responsibility – the clinician standing next to the patient or the one performing the remote-controlled procedure.