Researchers at the University of Michigan in Ann Arbor have successfully implanted in a U.S. patient the first left ventricular assist device that uses magnetic levitation.
The DuraHeart Left Ventricular Assist System (Terumo Heart Inc.) is an experimental device that uses a centrifugal pump combined with a magnetic-powered impeller. After blood enters the centrifugal pump, it is pushed through the outflow conduit by a rotating impeller suspended within a magnetic field. The impeller is not attached to the walls of the chamber as with traditional LV assist systems, thereby reducing damage to the blood cells as well as reducing internal friction and device wear, according to the University of Michigan.
The manufacturer has plans to conduct a nonrandomized, 140-
patient clinical trial for the DuraHeart pump. The device is approved in Europe, where it is currently implanted in more than 70 patients.
This trial will test the DuraHearts potential to overcome some of the issues that have been seen with other devices, including hemolysis caused by sheer stress on red blood cells, and clotting risk caused by blood that does not circulate rapidly enough from all areas of the chamber, said Francis Pagani, MD, PhD, an associate professor of surgery at the University of Michigan Cardiovascular Center who implanted the DuraHeart device in the U.S. patient, in a press release. It also remains to be seen if this device offers superior durability, which might make it useful as a destination therapy that could remove the need for a heart transplant. – by Eric Raible
This device and other centrifugal pumps offer an attractive theoretical advantage. The fewer friction points, the less the wear. In addition, the less friction there is, the less the heat, and so there is less formed element trauma and clotting. To date, however, anticoagulation is still the norm with these devices, and therefore they offer a theoretical advantage only over the new axial flow devices like HeartMate II.
The potential disadvantage is exposure to a magnetic field that could alter the balance of the device and cause problems. The other disadvantage to a free-spinning centrifugal pump is the stress placed by rotation, such as an acute change in angle; this is similar to a caster effect on a bicycle where the spinning wheel resists turning. This does not seem to be a big issue in these pumps, however.
We are anxiously awaiting studies with magnetically suspended centrifugal pumps to see how durable they are in the human environment where the rule seems to be: If it can be damaged, the patient will find a way to damage it. Thus, testing and implant days are essential to determine equivalence or superiority to available devices.
Frank Smart, MD
Cardiology Today Editorial Board member