- DALLAS - A common respiratory virus can infect the hearts of adults
-- young and old -- and cause heart muscle damage that can shorten life
and cause sudden death, according to a study in today's Circulation: Journal
of the American Heart Association.
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- The discovery resolves an issue of nearly
a decade's standing: whether certain adenoviruses, which normally infect
the upper airway, can cause the condition left ventricular dysfunction
(LVD) in adults. Several adenoviruses have been known for almost a decade
to cause LVD in children.
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- Senior author of the study, Jeffrey A.
Towbin, M.D., at Baylor College of Medicine in Houston, says the finding
could lead to new strategies to prevent or treat LVD, which leads to disabling
and eventually fatal heart failure and can also cause sudden death.
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- Physicians can treat the fever and inflammation
commonly caused by adenoviruses, but not the virus itself, says Towbin.
When symptoms occur, drugs can be used to strengthen the heart's weakened
pumping ability, but in some cases, a heart transplant is required.
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- "Adenovirus, a common cause of upper
respiratory infection, must be considered as a potential cause of heart
muscle disease," he says. "For that reason, pediatricians, family
physicians and internists should take into account the potential late-onset
of cardiovascular complications that may occur after the typical flu-like
illness. Patients who feel poorly several weeks after a flu-like illness
should contact their physicians. Usually symptoms will be fatigue or shortness
of breath that continue after recovery from the respiratory illness. A
physical exam or chest X-ray can reveal heart enlargement."
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- A vaccine against specific adenovirus
types exists, but is not widely used and may not be effective against the
types that cause LVD, says Towbin, professor of pediatrics (cardiology),
molecular and human genetics, and cardiovascular sciences.
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- In the United States, two to eight new
cases of LVD occur per 100,000 persons each year. An estimated 40 out every
100,000 Americans suffer from the problem, which costs the U.S. economy
an estimated $12 billion a year.
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- "LVD is not a common disease, but
it has a major impact. When you see a high school student drop dead playing
sports, LVD is one of the common causes," Towbin says.
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- LVD can be caused by coronary heart disease,
a genetic defect, and even tissue damage from using cocaine. Viruses, primarily
members of a group known as the enteroviruses, have been known to cause
LVD in children and adults for about half a century. In the early 1990s,
Towbin, who specializes in studying heart muscle problems in children,
reported studies that demonstrated that several types of adenoviruses were
also a significant cause of LVD in children.
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- "Adenoviral infections are at least
10 to 15 percent more common in the heart muscle of children with LVD than
enteroviral infections," he says. "That's held up over the many
hundreds of pediatric cases that we've studied. Typically, a child gets
a cold, it lingers four or five days, and goes away. Three weeks later,
the child starts feeling bad, and that's when the heart enlarges and pumps
poorly."
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- Physicians often can not pinpoint the
cause of LVD in children or adults. And despite the findings linking adenoviruses
to pediatric LVD, many researchers rejected the idea that it caused some
of the adult cases for which a cause could not be determined, says Towbin.
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- At Towbin's invitation, leading supporters
of enteroviral -- not adenoviral causes -- of LVD, Heinz-Peter Schultheiss,
M.D. and Matthias Pauschinger, M.D., researchers at the Benjamin Franklin
Freie University and co-authors of the paper, brought heart biopsies obtained
in their studies to Houston to do a collaborative study with the Baylor
team.
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- They studied tissue samples from the
hearts of 94 adults, ages 17 to 76, whose LVD resulted from an unknown
cause. In carrying out their study, the researchers used a genetic test
known as polymerase chain reaction (PCR) to search for viruses in the heart
muscle. Not only can PCR detect a specific segment of genetic material,
but the technique can make many thousands of copies of it for researchers
to examine in detail. In this study, genetic evidence of adenoviruses was
detected in 12 LVD patients, and genetic material from enteroviruses was
found in another 12. "These findings are similar to data from pediatric
patients," the researchers note.
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- "Adenovirus is an important cause
of heart muscle infection and heart muscle dysfunction, and it is important
in both children and adults, says Towbin. "The diagnostic test PCR
will increase the likelihood of determining the underlying cause of heart
muscle dysfunction in individual patients."
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- No evidence of viral infections was found
in the hearts of any of the 14 members of the control group. All of the
adenoviruses detected were type 2, one of the more common types among the
more than 40 known adenoviruses. The researchers urged further study of
LVD patients "to accurately determine the frequency of virus infection."
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- Co-authors of the paper are Neil E. Bowles,
Ph.D.; F. Javier Fuentes-Garcia, B.S.; Vanlinh Pham; Uwe Kuhl, M.D.; and
Peter L. Schwimmbeck, M.D.
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