- Ion Adventure in the Heartland, vol 1
Dale Dubin has written a remarkable book for "the scientifically curious with a compelling passion for new enlightenment." A 17-year labor of love, Ion Adventure in the Heartland deals with the complex issues of what Dubin calls the "heart's ionic-molecular microcosm." Dubin is probably best known as the author of the most widely used book on learning electrocardiography, Rapid Interpretation of EKGs, which is now in its sixth edition.
Dubin uses three-dimensionally rendered color illustrations, with little text, to program instruction. Our guide is Dale, Dr. Dubin as a child, which reinforces the manner in which children progress from conceptualization to knowledge. Historical figures, such as Waller's bulldog Jimmy, help to illustrate the points. In the opening figure, a couple of illustrations make clear Galvani's experiment of 1792, in which electrical stimulation caused contraction in the legs, and Kolliker and Mueller's observation in the mid-1800s that a frog's heart could cause rhythmic stimulation of the motor nerve to a frog's leg.
For those of us who could never keep cation and anion straight and who therefore never use these terms and refer only to positive and negative charges, Dale shows a picture of his pet cat with three toy balls labeled Ca++, Na+, and K+—hard to forget once you have the image in mind.
The concepts become quite complex, but the approach works. As an example, for the spatially challenged Dale presents an ion channel with its four domains sticking through a membrane, then a close-up of the continuous peptide chain of six coiled segments that forms a domain, and finally the ion channel [End Page 461] pore viewed from the extracellular side, showing how the segment ends of the coiled segments are packed. As the story progresses, it becomes clear that the segments S1, S2, and S3 are positioned towards the periphery, the positively charged S4 is positioned to act as the voltage sensor, and the S5 and S6 segments of each domain form the lumen of the channel. Once the positions of these segments are clear, the p loop between S5 and S6 is shown to line the pore, and since each p loop has a negative charge positioned near the external pore, positive ions are attracted that line up in the pore of the closed, resting channel. And the story continues, reinforced in a later chapter by looking at the segments and the p loop in more detail and at their role in controlling the flow of ionic currents through the channel.
The 12 chapters of volume 1 touch upon the electrocardiogram, the autonomic nervous system, the relationship between ions and molecules, events in the myocytes that lead to contraction and other functions, ion channels and their microanatomy, as well as the electrical consequences of the molecular and ionic events, specialized structures in the heart such as the atrioventricular node, and practical issues underlying conduction and arrhythmias including those caused by abnormal channels as in the long QT-syndrome. Volume 2 promises to be on automaticity.
The strategy of transforming the abstract (concepts, equations, ideas) into the concrete (pictures) is not new, but rarely has it been so ambitiously pursued using a very skilled illustrator, Paul Heinrich, and a number of talented people, scientific and not, who helped in the project. The book is comprehensive and profusely illustrated in color. I do not know how they brought the publication price in at $85. A challenge will be updating this book and keeping it current.
Thanks are due to the late George C. Griffith, to whom the book is dedicated, who seems to have triggered Dubin's lifelong interest in electrocardiography. I would also like to thank the child Dale and the adult who gave him voice. This is a remarkable publication. Dubin certainly had fun writing it, and I enjoyed reading it. I recommend it most highly.
University of Chicago