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Thursday, September 20, 2007

Starr-Edwards Heart valve and MRI safety


Lasker Awards Announcement


America's highest medical prizes, the Lasker Awards, have been announced, and some of the winners are developers of prosthetic heart valves.
From the official announcement by the Lasker Foundation:
The Lasker Award for Basic Medical Research honors Ralph M. Steinman, 64, of the Rockefeller University, New York City, who discovered dendritic cells. These immune cells trigger other components of the immune system to thwart microbial invaders. Steinman's work has opened up novel therapeutic avenues for combating cancer and pathogens.
The Lasker Award for Clinical Medical Research honors Alain Carpentier, 74, of Hôpital Europeen Georges Pompidou, Paris, and Albert Starr, 81, of the Providence Health System, Portland (OR), who developed prosthetic mitral and aortic valves. These devices have prolonged and enhanced the lives of millions of people with heart disease, providing treatment where none existed before.
The Mary Woodard Lasker Award for Public Service, awarded bi-annually, honors Anthony S. Fauci, 66, Director of the National Institute of Allergy and Infectious Diseases, a component of the National Institutes of Health, for engineering two major U.S. governmental programs, one aimed at AIDS and the other at biodefense.
The fun part for us, of course, is about the development of artificial heart valves:

The 2007 Albert Lasker Award for Clinical Medical Research honors two surgeon-scientists who revolutionized the treatment of heart disease. Albert Starr and his engineer partner, the late Lowell Edwards, invented the world's first successful artificial heart valve. This device has transformed life for people with serious valve disease, providing a remedy where none previously existed. Alain Carpentier then circumvented the predominant limitation of mechanical valves--a propensity to clot within blood vessels and the associated need to take blood thinners--by adapting animal valves for use in humans. In the embryonic days of open-heart surgery, Starr and Carpentier opened up the entire field of valve replacement. Their work has restored health and longevity to millions of individuals with heart disease.
Starr's and Carpentier's contributions extend beyond these landmark innovations. In an era before the Food and Drug Administration (FDA) regulated medical devices, Starr set up the infrastructure for conducting clinical trials on his valves, including an informed-consent procedure and long-term patient tracking. This practice allowed him to evaluate valve replacement outcomes and seek solutions to clinical problems. Furthermore, his surgical patients required a new type of postoperative care. To deliver it, he assembled a multidisciplinary healthcare team, creating what corresponds to today's cardiac intensive care unit. Carpentier, in turn, augmented his own initial discovery by formulating techniques to repair rather than replace valves--a venture that was aided by the availability of prosthetic valves as a backup. He continues to probe the suboptimal areas of heart-valve surgery,relentlessly pursuing superior strategies.
Prior to the introduction of the Starr-Edwards valve, no human with a valve replacement had survived longer than three months. As of 2004, four live patients had replacement valves that had been implanted at least 40 years earlier. Currently, more than 90,000 people in the United States and approximately 300,000 people worldwide receive new valves annually; the procedure is the second most common heart surgery in the United States, exceeded only by coronary bypass operations.
MRI Safety of Heart Valves:

Heart valve prostheses and annuloplasty rings.—Numerous heart valve prostheses and annuloplasty rings have undergone testing for MR safety. Of these, the majority showed measurable but relatively minor translational attraction and/or torque in association with exposure to the MR systems used for testing. Since the magnetic field–related forces exerted on heart valves and annuloplasty rings are deemed minimal compared with the force exerted by the beating heart (ie, approximately 7.2 N) , an MR procedure is considered to be safe for a patient with any of the heart valve prostheses or annuloplasty rings that have undergone testing to date . This includes the Starr-Edwards model Pre-6000 heart valve prosthesis, which had previously been suggested to be potentially hazardous for a patient in the MR environment. Heart valve prostheses and annuloplasty rings tested at 3 T.—Many heart valve prostheses and annuloplasty rings have now been evaluated for MR safety by using 3-T units . Findings indicate that one annuloplasty ring (Carpentier-Edwards Physio Annuloplasty Ring, Mitral model 4450; Edwards Lifesciences, Irvine, Calif) showed relatively minor magnetic field interactions. Therefore, similar to heart valve prostheses and annuloplasty rings tested at 1.5 T, because the actual attractive forces exerted on these implants are deemed minimal compared to the force exerted by the beating heart, MR procedures at 3 T are not considered to be hazardous for individuals with these implants (5,128). Additional heart valves and annuloplasty rings from the Medtronic Heart Valve Division (Minneapolis, Minn) have undergone MR safety testing at 3 T. These implants were tested for magnetic field interactions and artifacts by using a shielded 3-T MR system. According to information provided by Medtronic (Bayer KM, personal communication, 2002), these specific implants are safe for patients undergoing procedures with MR systems operating up to 3 T.

(Frank G. Shellock, PhD
John V. Crues, MD)
Here's all 16 pages of the press release: SOURCE


Find more at the Lasker Awards' multimedia presentation...
Article at the New York Times...
The Lasker Foundation press release (.pdf)...

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