The Only EKG Book You’ll Ever Need

The effects of repolarization on the EKG are similar to those of depolarization, except that the charges are reversed. A wave of repolarization moving toward a positive electrode inscribes a negative deflection on the EKG. A wave of repolarization moving away from a positive electrode produces a positive deflection on the EKG. A perpendicular wave produces a biphasic wave; however, the negative deflection of the biphasic wave now precedes the positive deflection.

The EKG finally returns to baseline once again when depolarization is complete.We can easily apply these concepts to the entire heart. Electrodes placed on the surface of the body will record waves of depolarization and repolarization as they sweep through the heart.

If a wave of depolarization passing through the heart is moving toward a surface electrode, that electrode will record a positive deflection (electrode A). If the wave of depolarization is moving away from the electrode, the electrode will record a negative deflection (electrode B). If the wave of depolarization is moving perpendicularly to the electrode, the electrode will record a biphasic wave (electrode C). The effects of repolarization are precisely the opposite of those of depolarization, as you would expect.

 

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Ophthalmology at a Glance Second Edition

Ophthalmology at a Glance is aimed at the medical student, special- ist trainee or general practitioner. It is a great pleasure to write the second edition of Ophthalmology at a Glance and introduce the reader to the many advances that have occurred in ophthalmology since 2004, not least with the training syllabus, corneal refractive surgery and cataract surgery, and in the treatment of medical retinal disorders. We hope that you find all of these advances reflected in this new edition.

We aim to provide the fundamentals of ophthalmology, starting with the basics of how to take a history, how to correct refractive errors, do the eye examination, the management of acute eye problems, and causes of gradual loss of vision in Parts 1 to 5. We will then discuss the areas of the eye and visual disturbance in more detail in the latter parts 6–13. The largest subspecialty part is vitreo-retinal, which in this

We have also introduced a new chapter dedicated to ocular oncology by Mandeep Sagoo and Karim Hammamji, an area that medical stu- dents, newly-trained doctors and GPs should be aware of. It is exciting in this second edition to have two new co-authors: Gurjeet Jutley, Specialist Trainee, and Laura Crawley, Glaucoma Fellow, who have both worked extremely hard to update many of the chapters, provide new images and write the case studies for the website.

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