Heart block

NEW YORK -- Exposure to maternal lupus autoantibodies confers a risk of congenital heart block and neonatal lupus on the fetus, but the risk is small, and no medical treatment is currently recommended, Jill P. Buyon, M.D., said at a meeting sponsored by the Lupus Foundation of America.

Women who are positive for anti-SSA/Ro and anti-SSB/La autoantibodies have a baseline 2% chance that fibrosis of the atrioventricular node and heart block will develop in the fetus, but that risk increases 10-fold if they have had a previous child with either heart block or a facial rash, she said.

These statistics have emerged from the ongoing Research Registry for Neonatal Lupus, which now includes more than 300 women. The registry is sponsored by the National Institute of Arthritis and Musculoskeletal and Skin Diseases and is directed by Dr. Buyon, professor of medicine and vice chairman of the department of rheumatology, New York University, New York City.

Thus far, 94 women in the registry have become pregnant and given birth after having had a child with heart block, and 67 of these babies have been healthy. Among the infants with manifestations of neonatal lupus, 15 had congenital heart block only, three had heart blocks plus a rash, and seven had the rash alone. There was one fetal demise and one neonatal death.

Clearly, women who have had a child with heart block or a neonatal rash should be followed carefully. "Our recommendation is to begin serial echocardiographic monitoring at 16 weeks, doing it weekly until week 28 if feasible and then every other week until [week] 32," she said. The timing and frequency are important because the fibrosis of congenital heart block develops very quickly, and almost always occurs between weeks 18 and 23, she said.

The fetal and neonatal injuries are thought to result in part from passage of the anti-SSA/Ro and anti-SSB/La anti-bodies across the placenta and into the fetal circulation. The antibodies certainly play some role in the congenital heart fibrotic process, but because the number of affected fetuses is so small, other factors--possibly environmental or fetal--must be involved as well, Dr. Buyon explained.

Efforts to find a way of treating fetal heart block have so far shown little success. Despite some reports in the literature on the use of steroids, there are no data suggesting that prophylactic therapy with these drugs has any beneficial effect, she stated.

"Especially if you're looking at a 98% chance that the woman will not have a baby with heart block, why would you expose her to steroids?" she asked. "And even if she's had a prior child with heart block, there are no data that support the a priori use of dexamethasone," she said.

There also is no reason to use the non-fluorinated steroids prednisone or methyl-prednisolone. Unlike for anti-DNA anti-bodies and possibly antiphospholipid antibodies, the levels of anti-SSA/Ro and anti-SSB/La antibodies do not decrease when glucocorticoids are given.

"And to use them to prevent heart block when they don't pass into the fetus makes no sense," she said. "So at this point, we suggest the serial echocardiographic approach and not a medical approach until we come up with better therapies."

One experimental treatment involving the use of intravenous immune globulin shows promise, according to Dr. Buyon. This therapy is expensive but is likely to have fewer adverse effects than steroids on either the mother or the fetus.

BY NANCY WALSH

New York Bureau

COPYRIGHT 2004 International Medical News Group
COPYRIGHT 2004 Gale Group