4,199
edits
Basics: Difference between revisions
Jump to navigation
Jump to search
m
no edit summary
Googletrans (talk | contribs) No edit summary |
mNo edit summary |
||
| (One intermediate revision by one other user not shown) | |||
| Line 39: | Line 39: | ||
==What does the ECG register?== | ==What does the ECG register?== | ||
;The electrocardiogram: An electrocardiogram (ECG or EKG) is a register of the heart's electrical activity. | ;The electrocardiogram: An electrocardiogram (ECG or EKG) is a register of the heart's electrical activity. | ||
Just like skeletal muscles, heart muscles are electrically stimulated to contract. This stimulation is also called ''activation'' or ''excitation''. Cardiac muscles are electrically charged at rest. The inside | Just like skeletal muscles, heart muscles are electrically stimulated to contract. This stimulation is also called ''activation'' or ''excitation''. Cardiac muscles are electrically charged at rest. The inside of the cell is negatively charged relative to the outside (resting potential). If the cardiac muscle cells are electrically stimulated, they depolarize (the resting potential changes from negative to positive) and contract. The electrical activity of a single cell can be registered as the [[action potential]]. | ||
As the electrical impulse spreads through the heart, the electrical field changes continually in size and direction. The ECG is a graph of these electrical cardiac signals. | As the electrical impulse spreads through the heart, the electrical field changes continually in size and direction. The ECG is a graph of these electrical cardiac signals. | ||
| Line 288: | Line 288: | ||
| image1 = E000559.jpg | | image1 = E000559.jpg | ||
| caption1 = A patient with atrial fibrillation with a 'Lewis Lead' | | 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. | ||
}} | }} | ||
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. | ||