Pacemakers From Living Cells?

Interesting post on the potential for a pacemaker from living cells instead of a permanent electronic pacemaker. Great stuff. But before you rush out to cash in your old pacemaker, read the fine print:

When the engineered tissue was implanted into rats, between the right atrium and right ventricle, the implanted cells integrated with the surrounding heart tissue and electrically coupled to neighboring heart cells. Optical mapping of the heart showed that in nearly a third of the hearts, the engineered tissue had established an electrical conduction pathway, which disappeared when the implants were destroyed. The implants remained functional through the animals' lifespan (about 3 years).

"The advantage of using myoblasts is that they can be taken from skeletal muscle rather than the heart itself--which will be important for newborns whose hearts are so tiny they cannot spare any tissue for the biopsy--and that they're resistant to ischemia, meaning they can go without a good blood supply for a relatively long period of time," (investigator) Cowan says.

This is interesting because it is basically creating a biologic accessory pathway. We "heart electrical types" like to speculate about issues that might occur when skeletal muscle is used for the conduction system:

• There might not be decremental conduction properties (like the normal AV node), so atrial fibrillation might be a dangerous because it might conduct too rapidly and induce dangerous lower chamber (ventricular) arrhythmias.
• Since only one in three mice "took" with the biologic implant, this won't be reliable enough to implement this in humans (especially children) yet.
• Some heart block occurs in an anterograde-only direction (from atrium to ventricle) but conduction through the normal AV node can be maintained in a retrograde (ventricle to atrium) direction. If a tachycardia were created in patients with such a biologic accessory pathway implant anterograde down the implant and conduction circulated back to the atrium by the person's normal AV node, which should be ablated?
• How will drugs effect skeletal muscle implants in the heart?
• The human immune system might recognize these cells as foreign from biologic manipulation, and late failure due to late scarring and failure of conduction might occur.

(Isn't is amazing how many new questions can be generated from new research like this!)

But the work is cool, nonetheless, and worthwhile since issues raised with this work might effect other areas in biologic research. Many teams are working on this... But its great to see the developments so far. I wish ALL researchers in this area the best of luck!

--Wes (via Instapundit and Slashdot)