The results of the study were published in the Feb. 6, 2003 issue of the journal Nature.
Basing their research on a French family with a form (Type 4) of inherited Long QT Syndrome (LQTS) and experiments in mice, the researchers found the mutation in a specific gene encoding ankyrin-B, a protein within heart muscle cells. Their discovery identifies what appears to be a novel mechanism for cardiac arrhythmia.
Normally, ankyrin-B acts as a biochemical symphony conductor, ensuring that microscopic pores in heart muscle cells known as ion channels open and close in a coordinated fashion. These channels allow such chemicals as calcium, potassium, sodium and chloride to pass in and out of the cell with each heartbeat, thereby regulating the electrical activity of the heart.
"We have found a brand new mechanism for cardiac arrhythmias based on the coordination of these different ion channels," said HHMI investigator and Duke cell biologist Vann Bennett, M.D., senior member of the research team. "It appears now that the arrhythmia arises, not due to some malfunction of the ion channels themselves, but a failure to ensure that multiple ion channels open at the right place and at the right time. Scientists have been looking for ion channel mutations, but they have not been able to find them."
The QT interval is a measurement taken by electrocardiogram that represents the period of time from electrical stimulation of the heart's pumping chambers to their recharging for the next heartbeat. In normal people, this interval ranges from 0.38 to 0.44 seconds. However, for people with LQTS, this period of recharging can be delayed up to 0.5 seconds, which put these patient
Contact: Richard Merritt
Duke University Medical Center