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Electrode Placement and Lead Configuration

Electrodes may be placed distally or proximally on the limb without affecting the recording. The negative electrode is placed on the right shoulder, the positive electrode on the left shoulder, and another positive electrode on either leg as a grounding lead. The right or left leg can be used as a grounding lead without an effect on the ECG results. The axis between the right and left shoulder forms lead I, the axis between the left shoulder and left leg forms lead II, and the axis between the leg and right arm forms lead III. Each lead measures the potential difference between the positive and negative electrodes. The axes of these leads form an imaginary inverted equilateral triangle with the heart in the center. Using the axial reference system, lead I has a zero degree angle of orientation, lead II has a 60 degree angle, and lead III has a 120 degree angle.

Each lead measures the electric field created by the heart during the depolarization and depolarization of myocytes. The electric field can be represented as a vector that changes continuously and can be measured by recording the voltage difference between electrodes.

Using Einthoven's Triangle to Identify Lead Misplacements

Though Einthoven's triangle is no longer used in contemporary ECGs, Einthoven's triangle can be helpful in the identification in incorrect placement of leads. Incorrect placement of leads can lead to error in the recording, which can ultimately lead to misdiagnosis. If the arm electrodes are reversed, lead I changes polarity, causing lead II and lead II to switch. If the right arm electrode is reversed with the leg's electrode, lead II also changes polarity, causing lead I to become lead III, and vice versa. Reversal of the left arm and leg causes a change in polarity of lead III and switching of leads I and II.

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Einthoven's triangle is a three bipolar limb lead technique used in electrocardiography. Leads I and II are placed on the arms and lead III is placed on the leg. With the leads as vertices, the axes create an inverted equilateral triangle with the heart at the center. The leads can be placed proximally or distally. When the voltages of all three leads are summed, they equal zero potential. The technique was developed by Willem Einthoven through the use of Clement Ader's string galvanometer.

Improvements on the current article would be to go into more detail on each lead and the physics behind how each lead works. I also think it could go into more detail on the history of the triangle.

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I plan on going into detail on the basis of Einthoven's Triangle and why leads are placed where. I believe this information is lacking in the article's current form. I would also like to discuss what would happen if the leads were placed incorrectly.

Here is a list of sources that I believe could be helpful in improving this article.

Pages 99-101 of Cardiopulmonary System Structure and Function by Daniel R Richardson, David Clark Randall, and Dexter F Speck

Pages 34-35 of Cardiovascular Physiology Concepts by Richard E Klabunde

Pages 258-259 of Handbook of Cardiac Anatomy, Physiology, and Devices by Paul A Iaizzo

Page 4 in Understanding Electrocardiography by Mary Boudreau Conover

"William Einthoven - The Father of Electrocardiography" by Mark E Silverman MD

"Einthoven's Triangle Transparency: A Practical Method to Explain Limb Lead Configuration Following Single Lead Misplacements"

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Week 2: Evaluation of Physiology Page

In reading the page on physiology, I noticed a few things that could be changed. In the "women in physiology" section, sources are needed. Also, I believe this section can be done away with and the information placed in it can be moved into the history of physiology section. Its own section implies some framed bias.

From what I could see, the sources seemed to be reputable and of unbiased origins. However, the page is riddled with "citation needed" markings. I could not find any indication of closed paraphrasing or plagiarism. No bias from sources was noted.

There were some grammatical errors that should also be corrected.

The article mostly aligns with the topics we discussed in class and our class's definition of physiology and pathophysiology, as well as our discussion of the history of the word. More information is needed in the human physiology section, and inclusion of other physiologies are also needed on the page. More information could also be included in the history section.

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Growth factors that inhibit neovascularization include those that affect endothelial cell division and differentiation. These growth factors often act in a paracrine or autocrine fashion, and include fibroblast growth factor, placental growth factor, insulin-like growth factor, hepatocyte growth factor, and platelet-derived endothelial growth factor.