Heart Pacemaker Danger Removed

Press, Volume CIII, Issue 30578, 22 October 1964, Page 8

Heart Pacemaker Danger Removed

(New Zealand Preu Aeeociatlon)

DUNEDIN, Oct 21. A safe pacemaker—a device for providing electrical stimuli to the heart—has been developed by the physics department at the University of Otago after the discovery that there were risks attached to the original machine. The thoracic surgery department at Dunedin Hospital had been experimenting with a pacemaker on animals, usually sheep, with a pacemaker available commercially for use by patients suffering from certain heart defects. The stimuli given regularly, and at the correct rate, can keep the heart beating. It was discovered at the hospital that .when certain types of electrical interference were present the pacemaker gave its stimulating pulses far too rapidly. Violet ray machines, diathermy machines, high frequency generators in the range of i to 30 megacycles a second, even very close proximity to a broadcasting aerial, all caused the pacemaker to emit its stimuli at an excessive rate.

“The result is serious. The heart no longer beats and the animal dies,” said Professor R. R. Nimmo, head of the physics department. “A patient depending on a pacemaker could hardly have a more favourable experience than any other animal, and the surgeons who discovered the consequences of electrical interference realised that they imposed a serious limitation on the usefulness of the pacemaker. “They discussed with th® physics department the possibility of avoiding these fatal effects of electrical interference.” Alternative Circuit The department radio technician, Mr Keith Mickle, examined the circuit of the machine and devised an alternative electronic circuit which was negligibly affected, even by quite intense electrical interference, said Professor Nimmo. “This circuit, which is a little more complicated than the commercial pacemaker, is expected to be just as effective and much safer because it is not affected by electrical interference.”