Genetics Trump Digital Health In New Biological Pacemaker Study

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Researchers with Cedars-Sinai Heart Institute have announced promising results from a study testing the theory that an abnormal heart beat could be corrected by introducing a small genetic mutation designed to repair the heart, rather than by implanting a traditional electronic pacemaker.

Researchers tested the “biological pacemaker” theory first by isolating a gene called TBX18 which, when injected into heart tissue, will convert the local cells into sinoatrial node cells, the primary cells responsible for regulating heart rhythm. Next, TBX18 was injected directly into the hearts of a group of pigs that had a defect called complete heart block, which results in a slow heart rhythm. The TBX18 genes then went to work converting a small area of the pig’s heart into sinoatrial node cells. This resulted in near-immediate cardiovascular improvements. The pigs that were treated with TBX18 had faster heartbeats than a control group and their hearts were able to speed up or slow down their heart rhythm as needed based on physical activity. These pigs were also more physically active overall than the control group. In essence, the injection of genes yielded the same results that an implanted pacemaker would, but without the need for surgery.

Researchers had already substantiated this approach in earlier studies on rodents, but moved on to pigs because their hearts are so similar to human hearts. With encouraging results demonstrated in pigs, researchers will focus on the few outstanding concerns left before pushing forward with human testing. One concern noted is that if the TBX18 gene splits upon injection, it may inadvertently create two biological pacemakers that could compete for heart rhythm control, and ultimately do more harm than good. Another concern is that the agent used to introduce the genes is a virus that after delivering the genes could spread to other areas of the patient’s body, potentially complicating their recovery.

The treatment tested in the study was designed for short-term therapy, meaning that by the end of two weeks the heart had returned to its original state. Researchers are also interested in studying whether an injection could be created that would provide more lasting treatment.

While many patients suffering from abnormal heart rhythms are good candidates for a traditional pacemaker, some patients are not candidates, such as patients who experience serious infections from their pacemakers and need to have the devices removed, or fetuses in utero with heart problems. "Babies still in the womb cannot have a pacemaker. It is possible that one day, we might be able to save lives by replacing hardware with an injection of genes," explains Dr. Eugenio Cingolani, director of the Cardiogenetics-Familial Arrhythmia Clinic at Cedars-Sinai Heart Institute.

The new findings were published in the July issue of Science Translational Medicine.


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