Vaccine Against Heart Failure and Sudden Death?

Would a vaccine against ìadenovirusî prevent some cases of heart failure and sudden death?

New evidence that the mumps vaccine wiped out one specific type of heart failure raises a question: Would vaccines against other viruses known to infect heart muscle cells prevent other types of heart disease?

Relatively common among children until about 1980, the heart muscle disease called endocardial fibroelastosis, or EFE, often resulted in heart failure and death, a team of Houston researchers points out in todayís American Heart Association journal Circulation.

ìWe found that mumps appears to have caused this disease (EFE) and that both the (mumps) virus and EFE were eradicated by the mumps vaccination,î says Jeffrey A. Towbin, M.D., senior author of the new study and associate professor of cardiology at Baylor College of Medicine and Texas Childrenís Hospital in Houston.

The study is the first to provide hard evidence that mumps was the underlying cause of EFE, says Towbin, and the first to ìstrongly inferî that use of a vaccination has had an impact on any type of heart disease.

Scientists have speculated for decades that viruses are involved in some forms of heart disease. Towbin says the medical literature is full of arguments about whether mumps infections during pregnancy could cause EFE in unborn and newborn infants.

Until the development of a technique called polymerase chain reaction, or PCR, searching for viruses in the heart during an autopsy was like looking for a needle in a haystack. But now scientists need only a small piece of a virusí genetic material in order to ìamplifyî it with PCR and then identify it.

With heart tissue samples obtained during autopsies of 29 infants who died between 1955 and 1992, Towbin and his colleagues used PCR to search for several viruses -- enterovirus, adenovirus, mumps, cytomegalovirus, parvovirus, influenza and herpes simplex virus.

EFE had been documented in all 29 autopsies. PCR testing uncovered at least one virus type in all but three of the infants. Twenty-one of them (72 percent) were ìpositiveî for the mumps virus, reports Towbinís team. ìThe most striking result was the number of EFE patient samples that were PCR positive for mumps,î the researchers write in Circulation.

ìEFE was previously considered a significant cause of infant mortality,î they continue. ìIn recent years, however, the incidence of this disease has declined dramatically, probably because of the availability of the mumps vaccine.î

ìAlmost all the heart samples we looked at that were collected before 1980 had mumps,î says Towbin, ìwhile none of them had it after 1980.î

Their finding has more than just historical significance. The next step is to determine what viruses are causing heart muscle infections nowadays, he says. ìIt may be worthwhile investing in vaccinations against those viruses, too, if it saves young childrenís hearts.î

In an earlier paper published in Circulation, (V. 90, pp. 330-339, 1994), Towbinís team found adenoviruses now are the most common cause of acute heart-muscle inflammation in children. Adenoviruses are a group known to cause eye and upper respiratory infections, as well as viral pneumonia.

A vaccine against adenoviruses already is being produced, Towbin says, but currently itís available only to some U.S. military personnel.

Towbinís laboratory has performed PCR tests on hundreds of samples of heart muscle. These samples can be obtained from living individuals by using a long, thin tube (a catheter called a bioptome) that slides through the circulatory system until one end reaches the heart.

In heart muscle samples from cases after 1980, investigators usually find adenoviruses, he says. How do viruses that normally infect the eye, nose and throat end up in the heart?

At some point during a viral infection, ìyou have a brief period of so-called viremia, when the virus is in the bloodstream,î Towbin explains. Certain viruses, including adenoviruses, have affinity for heart muscle -- ìthey enjoy the heart,î he says.

As the virus-laden blood flows through the heart, some heart muscle cells become infected and eventually lose their ability to contract normally.

When echocardiography shows a childís heart is enlarged and dysfunctional, a viral infection often is the cause, says Towbin. ìWe believe adenovirus is the most common cause, at least in kids,î The second most commonly found virus is Coxsackie virus, he adds.

But children arenít the only ones who are susceptible. The death certificate for Reggie Lewis, the Boston Celtics basketball player who collapsed on the court, states that he died of inflammation of the heart caused by adenovirus, Towbin says.

ìNobody really knowsî the incidence or prevalence of heart muscle diseases caused by viral infections, the researcher says. Towbin is a principal investigator on a new federally funded registry of children with heart muscle disease, in collaboration with scientists at Bostonís Children Hospital. Pediatric centers such as Towbinís and the one in Boston see about 10 to 12 cases of this type each year, he says.

Towbinís co-authors are Jiyuan Ni, M.D.; Neil E. Bowles, Ph.D.; Young-Hwue Kim, M.D.; Gail Demmler, M.D.; Debra Kearney, M.D.; and J. Timothy Bricker, M.D.

Circulation is one of five scientific journals published by the Dallas-based AHA.