Platinum at the heart of metals used in medicine

From time to time, I have written with enthusiasm about the wide applications of platinum group metals, including specific applications in medicine, which embraces chemotherapeutic agents and dramatic uses in metal form. It never occurred to me I would ever become involved with such uses. My references were about those unfortunate “other guys.”

A doctor mentioned that some hardware might help me. Dialogue slowly developed about implanting an artificial, battery-operated electronic heart pacemaker inside of me, so as to supplement the heart’s own heartbeat pacemaker when it has irregular or absent impulses.

The first phrase you start to hear is, “Surgery: it’s not really that bad.” A professional confided to me: “It’s a piece of cake!” Hmm! I wondered.

I knew that the first battery- powered heart pacemaker was tried on a man in 1958 and devices of the early ’60s were extremely simple by today’s standards.

The batteries then were mercury- zinc units with a few electronic parts, all encapsulated in epoxy. Companies did not have the technology to hermetically seal it all in metal cans.

The batteries developed small amounts of gas which regrettably permeated the epoxy into the body. If hermetically sealed in metal, gas would build up — a not too desirable result for the human victim.

With experience, it became clear that the stimulating electrodes delivering the electrical impulses to the heart would have to be made of noble metal. So, platinum came into use as the supremely implantable material.

I am afraid I winced when I learned the platinum tips of the electrodes have barbs like a fish-hook or an arrow in order to make a firm contact in two inner chambers of the heart.

The two wires that bring the electrical impulses to the heart are made of a nickel alloy and each electrode tip is made of expensive platinized platinum alloy (platinizing increases the surface area, thereby using smaller voltage and energy). The electrode ring near the tip is made of platinum-iridium alloy.

I instantly noted that platinum, iridium, gold (in the pacemaker circuits) and nickel are the metals that made the Sudbury mines famous.

From the 1970s, longer-lasting and more complex devices became necessary and this challenge was met by using miniaturized circuitry and later fully integrated circuits.

The circuit, at least, had to be sealed and this was done with gold- plated containers. Inside were the gold wires and pathways. The mercury batteries still caused problems, but help was coming: new batteries with lithium as an anode reacting with iodine, to form lithium iodide.

These devices were perfect, forming no gases and they could last up to 12 years. Over time, nickel or stainless steel current collectors embedded in the two reactive primary metals proved to be the best.

I began to recall my previous surgical experiences with general anesthetic but one day heard the chilling remark, “Oh! They only give you a local anesthetic,” and later, “It’s only a minor procedure — takes an hour or less.” The person wheeling my stretcher told several people, “This one’s only a pacemaker.”

The advantage of “local” is that you can occasionally talk to the surgeon, while he is a-cutting and a-thrusting, about the various metals used and how he sees, on a fluoroscope, into the heart while he positions the leads inside of it.

Fortunately, these devices implanted inside the chest can now be programmed from outside of the body by the physician, when changes become desirable. In Western Europe, porous tip leads made of sintered titanium and covered economically with sputter-coated platinum have been used.

My model is all right for exposure to microwave ovens, auto magnetos, etc., but I have a card to show airport metal-detector security personnel.

Why is it, I wonder, am I now worrying about how long the battery will last?005 0000,0606 T.P. (Tom) Mohide, a former president of the Winnipeg Commodity Exchange, served as a director of mining resources with the Ontario Ministry of Natural Resources prior to his retirement in 1986.