Ebook ECG workbook (3rd edition): Part 2
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Ebook ECG workbook (3rd edition): Part 2
Chapter 8Axis deviationWe have already learned about (he normal pathway of (he impulse as it (ravels through (he conducting system. We have also seen Ebook ECG workbook (3rd edition): Part 2 how (he direction of (his impulse and (he position of electrodes around (he hear( affeci (he polarity of the limb leads.However, there may be times when (he normal pathway of (he impulse is disrupted, e g. by a piece of damaged tissue as (he result of a heart attack. Such a disruption may cause (he Ebook ECG workbook (3rd edition): Part 2 pathway of (he impulse (0 deviate to (he left or (he right or in extreme cases back up (0 the direction from which it came. This IS known as axis devEbook ECG workbook (3rd edition): Part 2
iationThis disruption will affect the polarity of the limb leads. If something is causing the impulse to travel back from where it came, the aVR may bChapter 8Axis deviationWe have already learned about (he normal pathway of (he impulse as it (ravels through (he conducting system. We have also seen Ebook ECG workbook (3rd edition): Part 2is now travelling away from the lead.One way of working out axis deviation is therefore by looking at the polarity of two of the limb leads. This can be most easily done by assessing Lead I and the aVF.In a normal ECG. as we know, all the limb leads should be positive except aVR. Therefore, if the E Ebook ECG workbook (3rd edition): Part 2CG shows a normal axis deviation (meaning that there is no disruption of the normal pathway of electrical activity) both Lead I and the aVF should looEbook ECG workbook (3rd edition): Part 2
k positive (see fig 8.1).Figure 8.1: Normal cardiac axis demonstrated by both Lead I and the aVF being positive.47The ECG workbookIf there is an extreChapter 8Axis deviationWe have already learned about (he normal pathway of (he impulse as it (ravels through (he conducting system. We have also seen Ebook ECG workbook (3rd edition): Part 21 1aVt yvWyYtVkAAXA111aVFFigure 8.2: Extreme axis deviation. Lead I and rhe aVF lead are negative. Note that the aVR is positive; rhe electrical impulses are therefore moving in the opposite direction from normal.If the impulse deviates to the left, there is left axis deviation. Lead 1 is positive a Ebook ECG workbook (3rd edition): Part 2nd the aVF is negative. This can be easily remembered by thinking about the tips of the QRS complexes of these two leads as leaving each other or leavEbook ECG workbook (3rd edition): Part 2
ing the page: LEFT and LEAVING (start with the same letter!) (see fig 8.3).Figure 8.3:Ijeft axis deviation. Lead I is positive and the aVF is negativeChapter 8Axis deviationWe have already learned about (he normal pathway of (he impulse as it (ravels through (he conducting system. We have also seen Ebook ECG workbook (3rd edition): Part 2GHT and REACHING (see fig 8.4).Extreme axis deviation is the most worrying for a patient, then right axis deviation, and then left.In practice, axis deviation does not necessarily require any treatment in itself. However, if raises rhe question of what has caused the axis deviation in the First plac Ebook ECG workbook (3rd edition): Part 2e. Tor rhe clinician, the axis deviation will indicate how the patient's condition may be affecting the pathway of rhe impulse through rhe conductingEbook ECG workbook (3rd edition): Part 2
system, and thus how likely the patient is to become unstable and have arrhythmias. Using the above method, axis deviation can be assessed at a glanceChapter 8Axis deviationWe have already learned about (he normal pathway of (he impulse as it (ravels through (he conducting system. We have also seen Ebook ECG workbook (3rd edition): Part 2treme-ve-veOccasionally, in more advanced cardiology, it may be necessary to talk about axis deviation in terms of degrees of deviation, rather than just in terms of normal, left, right or extreme. This can be done by plotting the axis on a graph called the Hexaxial Reference System (see ng 8.5). If Ebook ECG workbook (3rd edition): Part 2 an ECG shows a right axis deviation of + 95 degrees, for example, it IS not as senous as a right axis deviation of + 170 degrees The first method (haEbook ECG workbook (3rd edition): Part 2
t we learned will be adequate for the majority of ECGs that you will encounter. However, calculating axis deviation using the Hexaxial Reference SysteChapter 8Axis deviationWe have already learned about (he normal pathway of (he impulse as it (ravels through (he conducting system. We have also seen Ebook ECG workbook (3rd edition): Part 2guished from one another by the degree of axis deviation that is present.The Hexaxiai Reference System.The purpose of including the Hexaxial Reference System within this text is simply to help make sense of what looks like a complex diagram in many ECG books. Such diagrams can make learners think (h Ebook ECG workbook (3rd edition): Part 2ey have reached (heir limit with ECG interpretation’The Hexaxial Reference System is divided into 30-degree segments. The numbers at (he bottom of theEbook ECG workbook (3rd edition): Part 2
Hexaxial Reference System are positive and those at (he (Op half, negative.If you look at Figure 8.5 you will see which portion of the diagram represChapter 8Axis deviationWe have already learned about (he normal pathway of (he impulse as it (ravels through (he conducting system. We have also seen Ebook ECG workbook (3rd edition): Part 2lse would flow through the conducting system directly towards Lead II. This falls within the normal axis deviation quadrant of the Hexaxial Reference System. Anything deviating between +90 degrees and -30 degrees is considered normal axis deviation. If the pathway of the impulse deviates to the pati Ebook ECG workbook (3rd edition): Part 2ent's left it would fall in the upper rightChapter 8Axis deviationWe have already learned about (he normal pathway of (he impulse as it (ravels through (he conducting system. We have also seen Chapter 8Axis deviationWe have already learned about (he normal pathway of (he impulse as it (ravels through (he conducting system. We have also seenGọi ngay
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