Scientists have found a gene that predisposes some people to potentially fatal heart spasms. The discovery, reported in today's issue of Nature, could lead to a genetic test and perhaps eventually to drugs that prevent the spasms, called ventricular fibrillation.
A fibrillating heart beats irregularly, twitching and writhing like there are "a million snakes inside," says cardiologist Jeffrey Towbin of Baylor College of Medicine in Houston. Because the heart stops pumping blood, fibrillation kills within minutes unless the heart recovers on its own or is shocked back into its natural rhythm with a defibrillator.
Qing Wang, a molecular geneticist working with Towbin and an international team of cardiologists and geneticists, suspected that a gene called SCN5A was involved in ventricular fibrillation. SCN5A codes for a protein, embedded in the cell membrane, that plays a key role in the contraction of heart muscle cells. The team took blood samples from members of three families with a history of ventricular fibrillation, isolated the gene, and determined its nucleotide sequence. Each family, they discovered, had a different abnormal version of SCN5A--and all three versions code for a deformed protein that doesn't work.
Bagging the fibrillation gene is "a major advance that will help us with this rare disease," predicts Dan Roden, a cardiologist at Vanderbilt University in Nashville, Tennessee. The finding may also explain why some people with severe heart disease begin fibrillating, while others don't. The answer, Roden speculates, is that some people who fibrillate have a defective version of SCN5A.