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| image1    = E000559.jpg

| image1    = E000559.jpg

| caption1  = A patient with atrial fibrillation with a 'Lewis Lead' poling of the leads. Compared with the normal lead configuration, the atrial signal is enlarged.

| caption1  = A patient with atrial fibrillation with a 'Lewis Lead' positioning of the leads. Compared with the normal lead configuration, the atrial signal is enlarged. Although some parts have a 'sawtooth' appearance consistent with atrial flutter, the rhythm is atrial fibrillation as there is a changing pattern in the atrial activity.

| image2    = E000557.jpg

| image2    = E000557.jpg

| caption2  = The same patient with a normal lead configuration

| caption2  = The same patient with a normal lead configuration. The rhythm is atrial fibrillation. The atrial activity in lead V1 is organized probably due to a organisation of electrical activity after it enters the right atrial appendage, close to lead V1.

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Throughout history extra lead positions have been tried. Most are rarely used in practice, but they can deliver very valuable diagnostic clues in specific cases.

Throughout history extra lead positions have been tried. Most are rarely used in practice, but they can deliver very valuable diagnostic clues in specific cases.