Friday, August 4, 2017

Machines In Our Hearts

In Chapter 7 of Intermediate Physics for Medicine and Biology, Russ Hobbie and I discuss pacemakers and defibrillators. When introducing this topic, we cite Kirk Jeffrey’s book Machines In Our Hearts: The Cardiac Pacemaker, the Implantable Defibrillator, and American Health Care. The book not only gives a great introduction to these medical devices, but also examines the medical device industry. In his introduction, Jeffrey writes
“This book gives an account of the invention of the cardiac pacemaker and the subsequent development and transformation of this machine….The pacemaker was born in 1952 as an appliance the size of a breadbox that stood on a hospital cart and plugged into a wall socket. As it grew, it shrank. Within a few years, medical researchers and engineers had transformed it into a little device that was completely implanted within the patient’s body with one component actually threaded down a vein into the heart’s interior. Today we have a number of implanted machines, such as defibrillators and nerve stimulators, that manage some physiological function, but the pacemaker was the very first of these. Surgeons carried out the earliest implants in human beings between 1958 and 1960.

Pacemakers (or pacers) in the 1990s are no larger than wristwatches with one or two leads instead of a wristband. In the early days of implantable pacers, the devices were thicker and heavier than an old pocket watch; people in fact sometimes called them “heart tickers.” But a pacemaker today can do far more than send little ticks of electricity to the heart. Most pacers implanted in the 1990s coordinate the pumping action of the upper and lower chambers (the atria and ventricles) and change their rate depending on the patient’s activity level. Some can intervene to slow down a dangerously fast heartbeat. We live in ‘the age of the smart machine’; this phrase certainly applies to the newer pacers, for they include microprocessors and have become, in effect, computers…Once implanted, a pacemaker can be reprogrammed, its behavior completely reconfigured. In the near future, these tiny machines may be smart enough to diagnose the patient’s heart-rhythm problems and choose how to respond by themselves, without the doctor’s needing to intervene at all….

This book shifts its focus midway from the physicians and engineers who invented cardiac pacing and created a technological community to the manufacturing firms that have the greatest degree of control over the technology today. The manufacturers supplemented research physicians as the prime directors of technological change during the 1970s. The upshot is that when it comes to cardiac pacing and defibrillation, doctors are in effect working in alliance with large corporations in determining how best to treat patients.”
Anyone interested in working in the medical device industry in general, and in designing new pacemakers and defibrillators in particular, should read Machines In Our Hearts. It is a case study of how physics can be applied to medicine and biology.

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