Other Universityaffiliated Medical Devices

Many of the major breakthroughs in cardiac device development at the university of Minnesota occurred in associated collaborations with the Surgery Department. In more recent times, several more cardiovascular medical devices have been invented in departments other than the Department of Surgery, specifically the Departments of Medicine and Radiology. Several areas of cardiovascular devices are described in the following sections.

6.1. Active Compression/Decompression Cardiopulmonary Resuscitation Devices: The CardioPump®

The CardioPump® is an active compression/decompression device for cardiopulmonary resuscitation (CPR). Weighing a mere pound and half, it looks like a modified toilet plunger with a pliable cup that fits onto the patient's chest (Fig. 14). It employs a combination handgrip/pressure gauge instead of a wooden handle. Manual CPR exerts downward pressure on the chest, but the chest has to reexpand naturally; importantly, the CardioPump can apply pressure in both directions. With this action, the heart behaves somewhat like a bellows and allows blood to be pulled back into the heart and air into the lungs.

Fig. 12. The Lillehei-Kalke rigid bileaflet prosthesis (1968).

Fig. 13. St. Jude bileaflet prosthesis developed in 1976. Courtesy of St. Jude Medical.

Fig. 13. St. Jude bileaflet prosthesis developed in 1976. Courtesy of St. Jude Medical.

Fig. 14. CardioPump, an active compression/decompression device for cardiopulmonary resuscitation.

Fig. 15. Self-centering transcatheter device called Angel Wings®. Reprinted from Heart 1998;80:517-521. With permission from the BMJ Publishing Group.
Fig. 16. One of the numerous Amplatzer occlusion devices.

Dr. Keith Lurie, from the Department of Medicine (Division of Cardiovascular Medicine), and his colleagues outside the university designed this device and licensed it through a Danish company, Ambu Inc. (Linthicum, MD). It is now considered the first line of therapy for standard CPR and could improve a person's chance of survival and minimize neurological impairment; it has been shown to extend the 1-year survival rate by 10-40%, as indicated in a comparative study of standard CPR and active compression/decompression resuscitation for out-of-hospital cardiac arrest (8).

6.2. Transcatheter Closure Devices for Congenital Heart Defects

Transcatheter closure devices are permanent cardiac implants designed to close defects between chambers of the heart. Such devices are self-expanding, self-centering, umbrella-like devices with a design and shape that varies, as does the exact mode of their deployment. These are implanted in the heart, in a cardiac catheterization laboratory, through catheters inserted into either the artery or vein. Transcatheter closure devices are intended to provide a less-invasive alternative to open heart surgery, which has been the standard of care.

The first reported use of a transcatheter closure device for an atrial septal defect was in 1976 by T.D. King and N.L. Mills (Tulane University Medical School, New Orleans, LA). Despite two decades of research, early models of the device were not approved for clinical use because of persistent residual leakage, high failure rates, wire fractures, or embolization of the device. Nevertheless, several University of Minnesota faculty members used their previous experience with these early devices to devise novel closure models in the early 1990s.

One such enhancement was Angel Wings® (Microvena Corp., White Bear Lake, MN), a transcatheter atrial septal defect closure device designed in 1993 by Gladwin Das MD, an interventional cardiologist in the Department of Medicine (Cardiovascular Division) (9). This device is a self-centering, nitrinol-polyester prosthesis with two square-shape disks and a customized delivery catheter (Fig. 15). The implantation success rate for such closures was 97% for patients with patent foramen ovale and 100% for patients with atrial septal defects in phase II trials, 86% of these patients had zero or 1-mm shunts, and 14% had 1-2-mm shunts. The device was subsequently modified to have two circular disks and to make it retrievable into the delivery catheter and repositionable. The Angel Wings II device is anticipated to enter clinical trials in the near future.

6.3. Amplatzer® Family of Occlusion Devices

Radiologist Kurt Amplatz MD, from the Department of Radiology at the University of Minnesota, has designed a family of occlusion devices. All Amplatzer® occlusion devices (AGA Medical Corp., Golden Valley, MN) are preformed "baskets" of wire that resume their preformed mushroomlike shapes when extruded from the catheter sheaths (Fig. 16). The currently used wire is made from a special alloy of nickel and titanium (Nitinol) that does not break, accepts growth of cardiac endothelial tissue lining, and is absorbed into the heart's septal wall. More recent versions include specialized Dacron fibers, which are contained within the basket component of the device and immediately stop flow. The position of the device is checked by echocardiography and fluoroscopy prior to patient release (see Chapter 29).

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