16.01.06 | Siemens is making it easier for physicians to perform interventional cardiac procedures, thanks to angiography systems that use magnetic navigation to steer a catheter. With these new systems, the cardiologist uses a joystick to precisely steer the catheter. This makes it possible to navigate through even narrow, twisting arteries and easily reach the smallest coronary vessels. For cardiologists who want to determine if their patients’ arteries are narrowed or blocked, angiography systems allow minimally invasive interventional procedures, without the need for surgery. The patient is X-rayed, and the physician inserts a catheter through the arteries. That makes it possible to expand the narrowed cardiac blood vessel. The patient is injected with a contrast medium which then circulates in the bloodstream and makes the veins and arteries visible with the help of X-rays. That shows the physician where to insert the catheter and how to guide it toward the heart.

With the new magnetic guided systems, which Siemens developed together with the American company Stereotaxis, two refrigerator-sized magnets generate a magnetic field in the area to be investigated. The doctor can use the joystick to control the magnetic field, which in turn guides the catheter by means of a magnet attached to its tip. At the same time, the position of the catheter is fine-tuned by a small motor that pushes it back and forth. The new angiography systems thus make it possible to precisely guide cardiac interventions to the point where they are needed. They enable the cardiologist to reach parts of the anatomy that are difficult to access without magnets.

In a process known as catheter ablation, a therapy used to treat cardiac irregularity, cells within the heart muscle must be obliterated. While the magnetic navigation system precisely guides the catheter toward its target, the catheter's metal tip is heated to a temperature of approximately 60° C and obliterates the cells in question with millimeter precision. The advantage for the cardiologist is that he or she can position the catheter from a control room by means of a joystick, and is thus not repeatedly exposed to the X-rays.

It's even possible to navigate the catheter automatically. First, computer tomography is carried out. Special software uses the tomograms to generate a three-dimensional image of the heart. All the physician now needs to do is mouse-click on the target location, and the catheter automatically advances to the selected spot.

Another innovation that can also be used for conventional, manually guided angiography systems is voice-controlled navigation by means of a headset. In order to choose a previously marked position, the physician must carry out several hand motions, but with the new system only a single voice command is needed. The voice control option saves time and allows the physician to focus more closely on conducting the intervention itself and monitoring the patient. No special training is necessary, as the system understands the physician's spoken commands in either English or German. (IN 2006.01.1)