Thursday, April 17, 2008

The Challenges of Biologic Pacing

I worry when business journals report things better placed in medical journals, especially since medicine has become Big Business.

Witness today's article reported in the Wall Street Journal about biologic pacing and it's promise to supplant or supplement permanent pacemakers. Just replace the sick pacemaker cells with biologically engineered ones and the heart will beat, right?


I wish it were so simple.

The heart is a gloriously complex and amazing organ, full of a diverse set of specially designed cells which are carefully interconnected in an almost magical way to provide carefully-timed mechanical propulsion to blood. From the leaky sinus node cells, capable of generating the rhythmic automaticity that begins the cardiac cadence, to the nerves that supply those cells to assure they are bathed in the appropriate balance of neurotransmitters to increase that cadence with exercise or stress, to the gap junction interconnections that permit the spontaneous electrical impulse to be transmitted to neighboring cells in rapid succession, to the remarkable AV node that slows the electrical conduction ever so slightly to allow time for blood to travel from the top to bottom chambers of the heart, to the His-Purkinje system that rapidly speeds that electrical impulse symmetrically to the lower chambers of the heart and distributes the electrical impulse in a lightning-fast way to stimulate the cardiac myocytes to contract in unison, it's a complicated endeavor to get the heart to beat properly. Far be it from me to suggest that the wonder of cardiac electrophysiology and reliable cardiac pacing can be distilled simply to a petri dish of beating stem cells.

Only a tiny fraction of pacemaker patients have a sick sinus node (the pacemaker cells). Many others have interrupted AV nodes, others have cardiomyopathies that need pacemakers to restore mechanical synchrony to improve cardiac output, and many more are on medications that chemically slow the heart's normal cells to such a degree that a pacemaker is required to maintain an acceptable heart rhythm for activity.

Economically, we are left to wonder why we would use such cells as a supplement (rather than as a replacement) for a permanent pacemaker. Would they be used to reduce the amount of pacing required in a chamber just to conserve battery life of the permanent pacemaker? Realistically, there's little cost savings to our health care system in that approach. And if these cells are transfected into a ventricle (the lower pumping chambers), will people develop "pacemaker syndrome" from the loss of AV synchrony?

More likely, in this era of cut-backs for funding for innovative research, such articles in business journals help researchers cast a wide net for funding. The biotech, pharmaceutical and medical device industries have increasingly become vital resources for financial support that permits pioneering research work to continue because they seek one thing: the Pot of Gold at the end of the long research rainbow. So where better to turn to advertise describe your work and the need for more funding than a prominent business journal?

But business speculators should consider the hurdle they're approaching carefully. Although this is fascinating work, realize that the obstacles to overcome for the development of a true biologic pacemaker are considerable.


1 comment:

Anonymous said...

Dr. Wes,
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