Magnets help doctors navigate through blood vessels

As any 8-year-old knows, remote-controlled cars are far better than their hand-powered counterparts: They’re easier to control and better at zooming around twists and turns.

Bruce Lindsay

Similarly, heart and brain specialists now have a potentially easier, more efficient way to navigate through the body’s curving blood vessels.

Magnetically guided catheters have been designed to possibly provide better control and access to the heart and brain than their traditional, wire-threaded counterparts.

They also may make it easier to treat conditions such as heart rhythm abnormalities, according to University research.

“The difficulty with traditional devices is that it’s hard to get them to the target, and it’s hard to move them with exact precision,” said Bruce D. Lindsay, M.D., associate professor of medicine. “The goal of this research is to develop a system that will help us maneuver catheters with greater accuracy and less risk.”

To treat heart rhythm disturbances, cardiologists first must map the heart’s electrical system and pinpoint the source of the abnormality. To do so, they thread a tube called a catheter — which is about the size of a piece of spaghetti — through blood vessels in the groin that lead to the heart.

A wire inside the catheter allows physicians to physically twist and turn the catheter by using X-ray images for guidance.

But wire-threaded catheters have several shortcomings. In particular, they can bend in only one or two directions, so physicians have to physically rotate the entire catheter in order to reorient it.

Not only are these manual adjustments somewhat crude, but they’re also inefficient. Twists initiated outside the body near the groin yield much smaller movements at the wire tip several inches away. Moreover, after multiple manipulations, the wire becomes kinked and less malleable.

To alleviate these concerns, University cardiologists have been testing the Magnetic Navigation System (MNS) developed by Stereotaxis Inc.

Instead of a wire, MNS catheters contain a magnetic tip, which is directed by the computer-controlled magnet system positioned around the patient. An electrophysiologist “draws” commands for each desired direction or movement on a specially designed pen-tablet or by using a three-dimensional computer software interface, with the commands overlaid onto the patient’s constantly updated X-rays.

Thanks to research at several institutions, including the School of Medicine, the Food and Drug Administration (FDA) already has cleared one such magnetic device for mapping the right side of the heart.

By mapping the organ, specialists can localize problem areas so that treatment can then be applied directly to affected regions.

An endovascular guidewire (a device similar to the magnetic catheter but about the size of a piece of string) already is cleared by the FDA and allows surgeons to deliver and position therapeutic devices and treatment in the blood vessels in and around the heart.

School of Medicine researchers are now exploring the use of magnetically guided catheters for treating heart rhythm abnormalities. Destroying areas of diseased tissue to divert abnormal electrical activity can effectively cure many heart rhythm abnormalities.

In a recent publication in the journal Circulation, Lindsay and his team’s preclinical studies in non-human subjects showed that the magnetic system appeared capable of navigating a catheter to the heart, determining the origin of a heart rhythm singeing — and thereby attempting to treat — that area of tissue.

“Our research and experience using this system suggests that it will allow us to navigate to difficult sites with greater precision and to do procedures more efficiently and with potentially less complexity,” Lindsay said.

Lindsay’s team now is examining the use of this magnetic catheter system to treat heart rhythm abnormalities in human patients.

Neurosurgeons at the School of Medicine also are investigating the use of this system in delivering and positioning therapeutic devices to the brain to treat disorders such as aneurysms.