February 1997
DALLAS — Endocardial fibroelastosis (EFE) was a more common form of heart disease in children until about 1980, but has since declined dramatically. The reason may be linked to immunization with mumps vaccine, according to a study conducted by Jeffrey A. Towbin, MD, associate professor of pediatric cardiology, Baylor College of Medicine and Texas Children's Hospital, Houston.
Until about 17 years ago, this disease of the heart muscle often resulted in heart failure and death, and had an incidence rate of about one per 5,000 live births, according to a study recently published in the American Heart Association (AHA) journal Circulation.
"We found that mumps appears to have caused this disease [EFE] and that both the [mumps] virus and EFE were eradicated by the mumps vaccination," said Towbin, senior author of the study, in a release from the AHA.
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The study demonstrated that a significant proportion of patients with EFE have mumps virus genome in the middle and thickest layer of the heart wall, the myocardium. The data support that EFE is a sequela of a mumps virus-induced myocarditis rather than an enterovirus-induced episode.
Towbin said medical literature is full of contradictions about whether mumps infections during pregnancy could cause EFE in unborn and newborn infants.
With heart tissue samples obtained during autopsies of 29 infants who died of EFE between 1955 and 1992, Towbin and his colleagues used polymerase chain reaction (PCR) to search for several viruses including enterovirus, adenovirus, mumps, cytomegalovirus, parvovirus, influenza and herpes simplex virus.
PCR testing uncovered at least one virus type in all but three of the infants; 21 (72%) tested positive for the mumps virus, the report stated.
"EFE was previously considered a significant cause of infant mortality. In recent years, however, the incidence of this disease has declined dramatically, probably because of the availability of the mumps vaccine," the release stated. "Almost all the heart samples we looked at that were collected before 1980 had mumps, while none of them had it after 1980."
EFE is defined as a diffuse thickening of the left ventricular endocardium resulting from proliferation of fibrous and elastic tissue leading to decreased compliance and impaired diastolic function. EFE usually occurs in infants and young children with signs of congestive heart failure, and although genetic forms of the disease have been described, most cases are of unknown etiology, according to the study.
In an earlier study, Towbin and his colleagues found that adenoviruses are now the most common cause of acute heart-muscle inflammation in children; Coxsackie is the second most commonly found virus in children.
The mumps vaccine was first introduced in 1968.
For more information:
- Towbin, JA. Viral infection of the myocardium in endocardial fibroelastosis. Circulation. 1997;95:133-139.
Editor's Note: Epidemiologic studies failed to find a relationship between mumps in pregnant women and EFE in their offspring. If mumps virus prefers to grow in myocardium, one should not be surprised to not find sequences by PCR after the introduction of mumps vaccine. An interesting finding which should be pursued. — P. Brunell
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