In 1958, the first ever fully implantable pacemaker was inserted into the heart of 43-year-old Arne Larson, who was close to dying due to his heart beating at a rate of only 28 beats per minute — a normal rate is closer to between 60 and 100 beats per minute. Since his secret operation at the Karolinska Institute, millions of people have had the device implanted in their hearts (nearly 200,000 in 2009 alone). But what if there was a way to treat heart rhythm disorders without such invasive surgery? A new gene transplantation procedure may be the way to go.
“We have been able, for the first time, to create a biological pacemaker using minimally invasive methods, and to show that the biological pacemaker supports the demands of daily life,” said Dr. Eduardo Marbán, director of Cedars-Sinai Heart Institute, where the procedure was developed, in a press release. “We are also the first to reprogram a heart cell in a living animal in order to effectively cure a disease.”
Everyone has a set of cells in their hearts called pacemaker cells. These are the true “biological pacemakers,” as they are able to generate the electrical pulses that contract the heart, which ultimately keeps us alive. These cells may not function properly among people with slow heart rates, which is called bradycardia, or heart blocks, among other heart rhythm disorders. The Cedars-Sinai team, however, developed a gene therapy that can regrow unspecialized heart cells into these cells, thus normalizing heart rate naturally.
For the study, lab pigs with complete heart block were injected with the gene TBX18 through a catheter. Previous studies have showed that the gene, which is crucial for embryonic development, may also help with forming new pacemaker cells. It took only two days for the pigs that were injected with the gene to experience an increase in heart rate. Fourteen days later, when the study period ended, the heart rates remained normal.
“Originally, we thought that biological pacemaker cells could be a temporary bridge therapy for patients who had an infection in the implanted pacemaker area,” Marbán said. “These results show us that with more research, we might be able to develop a long-lasting biological treatment for patients.”
If the therapy can be developed for use among humans — the researchers suggested this could happen in three years — then it would be especially useful for babies, who are sometimes born with heart block. Because they’re unable to receive a pacemaker while still in the womb, the researchers said that a catheter-based treatment, such as this one, may help save them.