US scientists use gene therapy to create biological heart pacemaker

No batteries required: scientists are creating a biological pacemaker by injecting a gene into the hearts of sick pigs that changes ordinary cardiac cells into a special kind that induces a steady heartbeat.

Their new study represents a big step towards developing an alternative to implanted electronic pacemakers.

"There are people who desperately need a pacemaker but can't get one safely," said Dr Eduardo Marban, director of the Cedars-Sinai Heart Institute in Los Angeles in the US state of California, who led the work. "This development heralds a new era of gene therapy" that one day might offer them an option.

A human heartbeat depends on a natural pacemaker, a small cluster of cells - about the size of a peppercorn, Marban says - that generates electrical activity.

Called the sinoatrial node, it acts like a metronome to keep the heart pulsing at 60 to 100 beats a minute or so - more in an active person. If that node quits working correctly, hooking the heart to an electronic pacemaker works very well for most people.

But about 2 per cent of recipients developed an infection that required the pacemaker to be removed for weeks until antibiotics wiped out the germs, Marban said. And some fetuses were at risk of stillbirth when their heartbeat faltered, a condition called congenital heart block.

For over a decade, teams of researchers have worked to create a biological alternative that might help those kinds of patients, trying such approaches as using stem cells to spur the growth of a new sinoatrial node.