Biologic Pacemaker Reprograms Heart

Genetic Alternative May Replace Electronic Pacemakers

From the WebMD Archives

Sept. 12, 2002 -- Imagine a pacemaker that uses your own genes, rather than electricity, to recharge your ailing heart. Researchers say they've created the first "biologic" pacemaker that can do just that.

Their study, published in the Sept. 12 issue of Nature, shows the biologic pacemaker works in animal tests by using gene therapy to convert heart muscle cells into specialized "pacing" cells that can restore the heart's natural rhythm.

"We can now envision a day when it will be possible to recreate an individual's pacemaker cells or develop hybrid pacemakers -- part electronic and part biologic," says researcher Eduardo Marban, MD, PhD, of the Johns Hopkins Institute of Molecular Cardiology, in a news release.

The researchers say that in early embryonic development, every heart cell has pacemaker-like activity within it. As the cells mature, they become specialized to perform different functions.

A small number of these heart cells eventually become pacemaker cells responsible for "firing" the other cells into action and maintaining the heart's electrical and pumping action.

Most other heart cells contain a potassium channel that makes it harder for them to "fire" and generate electricity on their own. This makes them dependent on the pacemaker cells. When these pacemaker cells become damaged, a man-made electronic pacemaker must be implanted to restore the heart's rhythm.

According to the researchers, about 250,000 of these electronic pacemakers are implanted each year in the U.S.

But in initial tests in guinea pigs, researchers found that genetically blocking the potassium channel in the non-pacemaker heart cells allowed these cells to reconnect with their pacemaker past.

"When this [potassium] channel is blocked, heart muscle cells that normally have to wait for stimulation begin to beat on their own," says Marban.

Researchers say they believe the same principles should also apply to humans, and "biopacemakers" may eventually provide an important new option for people who are not good candidates for traditional, electronic pacemakers.