Friday, January 16, 2009

Cardiac Bioelectric Therapy

In the 4th Edition of Intermediate Physics for Medicine and Biology, Russ Hobbie and I introduce some fundamental concepts about the electrical properties of the heart (see, for example, Chapters 7 and 10). A new multi-author book, Cardiac Bioelectric Therapy: Mechanisms and Practical Implications, provides an in depth examination of this topic. In a forward to the book, Ray Ideker writes

"Since pacemakers and defibrillators were developed a little more than 50 years ago, their usage has grown rapidly, so that over 900,000 pacemakers and 200,000 defibrillators are implanted every year throughout the world. During this half century there have been astonishing advances in the efficacy and sophistication of these devices. Yet the devices still have major limitations...

Although there are many books that deal with the practical aspects of pacing and defibrillation, there is a pressing need for a single source that presents current knowledge about the basic mechanisms of cardiac bioelectric theory. This book, edited by Efimov, Kroll, and Tchou [admirably] fulfills this need. The chapters thoroughly and masterfully cover all aspects of this subject and are written by experts in the field.... I predict this book will be the standard source that will be consulted both by experienced workers in this area as well as by students and others who wish to learn more about this subject."
I have two chapters in this book: "The Bidomain Theory of Pacing" written with my former graduate student Debbie Janks, now at the University of Vermont College of Medicine, and "Virtual Electrode Theory of Pacing" coauthored with John Wikswo of Vanderbilt University, a long-time collaborator and my PhD dissertation advisor. Other chapters that I find particularly useful are "Bidomain Model of Defibrillation" by Natalia Trayanova and Gernot Plank, "The Generalized Activating Function" by Leslie Tung (who invented the bidomain model of cardiac tissue in his PhD dissertation), "Critical Points and the Upper Limit of Vulnerability for Defibrillation" by Raymond Ideker and Derek Dosdall, and "The Virtual Electrode Hypothesis of Defibrillation" by Crystal Ripplinger and Igor Efimov. This is only a partial list; other excellent chapters are written by a Who's Who of leaders in the field, such as Craig Henriquez, Steve Knisley, Vladimir Fast, Hrayr Karagueuzian, Niels Otani, Alain Karma, Shiien-Fong Lin, and Wanda Krassowska, among others.

The book covers two topics in detail: the bidomain, a mathematical model of the heart's electrical properties that I have worked on much in my career, and optical mapping of transmembrane potential. This second topic is an experimental technique that involves a fluorescent dye that is bound to the cell membrane. This amount the dye fluoresces depends on the transmembrane potential, which allows researchers to record an electrical quantity using optical methods.

I can think of only one problem with the book: at $199 it is expensive (you could get two copies of the 4th Edition of Intermediate Physics for Medicine and Biology for that price and still have money left over). But for students and researchers serious about understanding pacemakers and defibrillators, this book is worth the money. For students interested in browsing the book to expand their knowledge, all I can say is try your library, and there is always interlibrary loan.

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