In a new study in the September issue of the journal Pediatrics, Drs. Jeffrey Towbin, BCM professor of pediatrics at BCM, and John Belmont, BCM professor of molecular and human genetics, found that these first degree relatives of children with severe defects of the left side of the heart had a fivefold increased risk of having an abnormality called bicuspid aortic valve.

The finding solidifies the currently held belief that such disorders are related to several genes - as few as two and as many as six, said Belmont.

"What this tells us, is that multiple other relatives including parents and siblings are at risk for progressive heart disease and that they should be screened by a cardiologist," said Towbin, also chief of cardiology at Texas Children's Hospital. At present, specialists do not recommend screening of close relatives of these children with severe heart defects.

A normal aortic valve has three cusps or "flaps" that open and close to regulate the flow of blood. A bicuspid valve has only two. Individuals with this disorder are predisposed to heart valve infections and a narrowing of the valve later in life.

Approximately 0.9 percent of people in the general population have bicuspid aortic valve, but the rate among brothers, sisters and parents of these infants is five times greater, said Belmont.

"This is an impressive statistic, as a significant number of these individuals will develop symptomatic disease later in life, and could require catheter or surgical procedures on the heart," Towbin said.

The infants' severe heart defects included congenital aortic valve stenosis, coarctation of the aorta and hypoplastic left heart syndrome.

Congenital aortic valve stenosis involves a narrowing of the valve that impedes the pumping of blood from the heart. Coarctation of the aorta is a narrowing of the aorta, the largest artery in the body. Hypoplastic left heart syndrome means that the left side of the heart did not develop properly and cannot adequately pump blood to the rest of the body. In their study, Belmont and Towbin evaluated ultrasound-generated images of the hearts of 278 relatives of 113 children. Thirteen had bicuspid aortic valve and 32 had a variety of abnormalities involving the left side of the heart.

Belmont said it is difficult to determine whether the 32 other abnormalities found represent an increase because data do not exist that show how common they are in the general population.

"For many of those individuals, the problems are medically significant and need to be followed up by a cardiologist," he said. "Before, we would have completely ignored these people. Now we know they need medical follow-up."

Others who participated in the research include Drs. Mark B. Lewin, Kim L. McBride, Ricardo Pignatelli, Ana Combes, Andres Menesses, Wilbur Lam and Louis I. Bezold and Susan Fernbach, all of BCM and Dr. Norman Kaplan of Research Triangle Park, NC.