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March 18, 2003 Volume 39 Issue 11

New device suggests blood flow could one day power pacemakers

New device suggests blood flow could one day power pacemakers

By Mike Martin

BANGALORE, INDIA – Using nanotubes, scientists here have invented what they see as the precursor to an arterial turbine—a device that would use flowing blood to generate enough electrical charge to power a pacemaker.

The research team, led by Dr. Ajay Sood (PhD), a physicist at the Indian Institute of Science, refers to the invention as the world's first "flow sensor." When downsized, it would be small enough to fit in a blood vessel and make possible a pacemaker without a cumbersome battery.

"Our experiments have demonstrated for the first time that flow induces electrical response in single-walled carbon nano- tubes," Dr. Sood said. "The response of the nanotubes is relatively large even for very small flow velocities, of the order of 1 mm per second."

The researchers packed bundles of nanotubes between two metal electrodes, producing a sensor 1 mm long, 0.2 mm thick and 2 mm wide.

Introducing water flowing at a speed of 5 mm/s induced a voltage of 0.65 mV in the device along the flow direction. As the liquid velocity increased, the voltage went up almost logarithmically.

Eliminating the surgery required to replace pacemaker batteries interests Dr. Nieca Goldberg, chief of the Cardiac Rehabilitation and Prevention Centre at Lenox Hill Hospital in New York City. "It would reduce the need for surgical procedures to change the pacemaker battery, which is usually required at an average time of five years."

The flow sensor could also be used to track blood flow inside arteries and veins in real time. "Real-time blood flow monitoring could give some idea how well the heart is functioning," said Dr. Judy Tharp, a Lansing, Kan.-based clinician and general practitioner.

A battery-less pacemaker may have many advantages, but there are concerns. Disadvantages related to the frail condition of elderly patients might adversely affect the pacemaker's operation.

Potential "dysrhythmias" could also disturb the blood flow sensor, Dr. Tharp said. "If a patient suddenly experiences a rhythm disturbance where blood is not flowing, the battery-less pacemaker won't work."

Until the unit is fully tested and all concerns laid to rest, "we need to take a wait-and-see approach until this technology is developed," Dr. Goldberg added.

Dr. Sood is confident the flow sensor will eventually become a routine cardiac implant.

"At present, we are in the process of patenting the device in both India and the United States," said Dr. Sood. Clinical trials in animals would then follow.

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