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Optical technique identifies vulnerable
plaques in cardiac patients
Imaging technology may someday guide
therapy designed to prevent heart attacks
BOSTON - March 25, 2005 - A catheter-based imaging technology
called optical coherence tomography (OCT) can successfully identify
the characteristics of coronary plaques in patients with various
cardiac symptoms. The report from researchers at Massachusetts General
Hospital (MGH) will appear in the journal Circulation and
has received early online release at http://www.circulationaha.org/.
"More than 1.2 million people die from coronary artery disease
every year, a quarter of them before or soon after arriving at the
hospital," says Ik-Kyung Jang, MD, PhD, director of cardiovascular
clinical research in the MGH
Cardiology Division and lead author of the current study. "The
ability to identify dangerous plaques before they rupture and produce
a heart attack or sudden cardiac death will be crucial to innovative
preventive therapies."
Plaques are deposits of fats, cholesterol and other materials that
collect in major arteries, restricting or sometimes blocking blood
flow. While some plaques are relatively stable, others are vulnerable
to rupture and release their contents into the bloodstream, causing
a blood clot to form. Heart attacks and other acute coronary events
usually result from the rupture of high-risk, vulnerable plaques
in coronary arteries, and the characteristics of those plaques have
been determined primarily by autopsy studies.
OCT uses infrared light delivered via fiberoptic catheter to produce
high-resolution, cross-sectional images of blood vessels. Study
co-authors Guillermo Tearney, MD, PhD, of the MGH Pathology Department
and the Wellman
Center for Photomedicine at MGH, and Brett Bouma, PhD, also
of the Wellman Center, developed the use of OCT to visualize coronary
arteries, including vulnerable plaques. The technology developed
in their laboratory was used for this first study to examine the
structure of plaques in patients with cardiac disease.
The study enrolled patients scheduled to undergo cardiac catheterization
for whom angiograms or other imaging techniques had identified the
arterial lesion responsible for their symptoms. Participants either
had experienced a recent heart attack or had acute coronary syndrome
(ACS), a set of symptoms associated with reduced blood supply to
the heart muscle. A third group had stable angina, chest pain that
occurs with physical or mental stress, which is not usually related
to plaque rupture. Clear OCT images of the suspicious lesions were
obtained for 20 heart attack patients, 20 with ACS and 17 with stable
angina.
Vulnerable plaques are believed to have three major characteristics
- a deposit of lipids (fats), a thin cap of fibrous material covering
the lipid pool, and infiltration of the immune cells called macrophages.
The OCT images showed that the heart attack and ACS patients had
more lipid in their plaques and significantly thinner fibrous caps
than did the stable angina patients. Overall, vulnerable plaques
were identified in 72 percent of the heart attack patients, 50 percent
of those with ACS and only 20 percent of stable angina patients.
"This is the first technique that allows us to study the structural
changes underlying vulnerable plaques in living patients, and it
supports the conclusions of previously reported postmortem studies,"
says Jang. "We still need to gather more data to confirm these
characteristics, and our group will carry out further studies of
how plaques develop and rupture. Someday OCT may provide information
that will guide treatments to prevent plaque rupture and its disastrous
consequences." Jang is an associate professor of Medicine at
Harvard Medical School.
Along with the study's senior author Bouma and Tearney, additional
co-authors are Briain MacNeill, MD, Masamichi Takano, MD, and Fabian
Moselewski, of the MGH Cardiology Division; Nicusor Iftima, PhD,
and Milen Shishkov, PhD, of the Wellman Center; Stuart Houser, MD,
and Thomas Aretz, MD, MGH Department of Pathology; and Elkan Halpern,
MGH Department of Radiology. The study was supported by grants from
the Center for Integration
of Medicine and Innovative Technology, for development of the
imaging system platform; the National Institutes of Health and Guidant
Corporation.
Massachusetts General Hospital, established in 1811, is the original
and largest teaching hospital of Harvard Medical School. The MGH
conducts the largest hospital-based research program in the United
States, with an annual research budget of more than $450 million
and major research centers in AIDS, cardiovascular research, cancer,
cutaneous biology, medical imaging, neurodegenerative disorders,
transplantation biology and photomedicine. In 1994, MGH and Brigham
and Women's Hospital joined to form Partners HealthCare System,
an integrated health care delivery system comprising the two academic
medical centers, specialty and community hospitals, a network of
physician groups, and nonacute and home health services.
Media Contact: Sue
McGreevey, MGH Public Affairs
Physician Referral Service: 1-800-388-4644
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