Presentation is loading. Please wait.

Presentation is loading. Please wait.

Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Fast & Easy ECGs, 2E 1 © 2013 The McGraw-Hill Companies, Inc. All rights.

Similar presentations


Presentation on theme: "Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Fast & Easy ECGs, 2E 1 © 2013 The McGraw-Hill Companies, Inc. All rights."— Presentation transcript:

1 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Fast & Easy ECGs, 2E 1 © 2013 The McGraw-Hill Companies, Inc. All rights reserved. 1 Fast & Easy ECGs, 2E 12-Lead ECGs and Electrical Axis Fast & Easy ECGs, 2nd E – A Self- Paced Learning Program

2 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Heart’s Electrical Activity Depolarization and repolarization of the atria and ventricles are electrical events The ECG detects this electrical activity and displays it on the oscilloscope or prints it 2

3 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Planes of the Heart With the 12-lead ECG, electrodes are placed at specific spots on the patient’s extremities and/or torso and chest wall to view the heart’s electrical activity from two distinct planes: – frontal – horizontal These planes provide a cross-sectional view of the heart 3

4 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Frontal Plane Leads I, II, III and aV R, aV L, and aV F view the heart along this plane – Referred to as limb leads Four electrodes are positioned either on the extremities or on the torso – Can be placed far down on limbs or close to hips and shoulders, but they must be even (right vs. left) 4

5 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Limb Leads - Standard Leads I, II, and III form what is known as Einthoven’s triangle, which is an electrically equilateral triangle based on these three limb leads’ positions relative to one another – leads intersect at angles of 60 degrees 5 I I

6 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Limb Leads - Lead I Positive electrode - left arm (or left side of chest below the clavicle in the midclavicular line) Negative electrode - right arm (or right side of chest below the clavicle in the midclavicular line) Ground electrodes – left leg (or left side of chest in midclavicular line just beneath last rib) – Right leg (or right side of chest in midclavicular line just beneath last rib Waveforms are positive 6

7 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Limb Leads - Lead II Positive electrode - left leg (or on left side of chest in midclavicular line just beneath last rib) Negative electrode - right arm (or right side of chest below the right clavicle in the midclavicular line) Ground electrode – Left arm (or left side of chest in midclavicular line just below the left clavicle) – Right leg (or right side of chest in midclavicular line just beneath last rib) Waveforms are positive 7

8 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Limb Leads - Lead III Positive electrode - left leg (or left side of the chest in midclavicular line just beneath last rib) Negative electrode - left arm (or left side of chest below the clavicle in the midclavicular line) Ground electrode – Right arm (or right side of chest in midclavicular line just below the clavicle) – Right leg (or right side of chest in midclavicular line just beneath last rib) Waveforms are positive or biphasic 8

9 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Limb Leads - Augmented Leads Includes aVR, aVL and aVF Are unipolar Enhanced by ECG machine because waveforms produced by these leads are normally small I I 9

10 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Limb Leads - Lead aVR Positive electrode placed on the right arm (or right side of chest below the clavicle in the midclavicular line) Waveforms have negative deflection 10

11 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Limb Leads - Lead aVL Positive electrode placed on left arm (or left side of chest below the clavicle in the midclavicular line) Waveforms have positive deflection 11

12 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Limb Leads - Lead aVF Positive electrode located on left leg (or left side of chest below the last rib in the midclavicular line) Waveforms have a positive deflection 12

13 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Precordial Leads Includes leads V 1, V 2, V 3, V 4, V 5 and V 6 Positioned in order across the chest Unipolar – Opposing pole is center of heart as calculated by ECG I I 13

14 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 1 Electrode positioned in fourth intercostal space just to the right of the sternum Faces and is close to the right ventricle Also has a view of ventricular septum 14

15 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 1 Steps for positioning the V 1 electrode 15

16 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 2 Positioned in 4th intercostal space just to the left of the sternum Horizontally, it is at the same level as lead V 1 but on the opposite side the sternum Just like lead V 1, V 2 faces and is close to the right ventricle Although it has a view of the right ventricle and anterior wall of the heart, it is more recognized for its view of the ventricular septum 16

17 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 2 Steps for positioning the V 2 electrode 17

18 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 3 Located midway between leads V 2 and V 4 Views anterior wall of the left ventricle Depolarization of the left ventricle moves perpendicular to the positive electrode, resulting in a biphasic waveform 18 I I

19 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 4 Is placed at the 5th intercostal space n the midclavicular line Views the anterior wall of left ventricle and is close to the heart’s apex Depolarization of the left ventricle moves perpendicular to the positive electrode resulting in a biphasic waveform 19 I I

20 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 4 Steps for positioning the V 4 electrode 20

21 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 5 Placed in 5th intercostal space at the anterior axillary line Horizontally, it is even with V 4 but in the anterior axillary line Views lateral wall of the left ventricle Depolarization of left ventricle moves toward the positive electrode, producing a tall R wave 21 I I

22 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 5 22 Steps for positioning the V 5 electrode

23 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 6 Located horizontally level with V 4 and V 5 at the midaxillary line Views lateral wall of left ventricle Depolarization of left ventricle moves toward the positive electrode producing a tall R wave 23 I I

24 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Lead V 6 24 Steps for positioning the V 6 electrode

25 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. 12 Lead ECG Waveforms Each view provides different information When assessing the 12 lead ECG look for characteristic normalcy and changes in all leads 25

26 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Contiguous Leads Two leads that look at neighboring anatomical areas of the heart are said to be contiguous 26

27 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Right Ventricular Leads View the right ventricle Are in addition to the 12 lead ECG and require relocating the precordial ECG electrodes 27

28 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Posterior Leads View the posterior surface of the heart Are in addition to the 12 lead ECG and require relocating the precordial electrodes 28

29 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Conditions Identified by 12-Lead ECG 29

30 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Conditions Identified by 12-Lead ECG 30

31 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Conditions Identified by 12-Lead ECG 31

32 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Electrical Axis The 12-lead ECG can measure the axis of the electrical flow of energy during the cardiac cycle 32

33 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Instantaneous Vectors Cardiac cell depolarization and repolarization produces many small electrical currents – Sum of these currents called instantaneous vectors – Average of instantaneous vectors called the mean vector I I 33

34 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Mean Electrical Axis Direction of the mean vector called the mean electrical axis Axis is defined in the frontal plane only 34

35 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. ECG Deflection Wave of depolarization and its affect on the ECG 35

36 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. QRS Axis Most important and frequently determined axis 36

37 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Ventricular Depolarization and Mean QRS Axis Interventricular septum depolarization represents the first cardiac vector associated with ventricular depolarization A sequence of vectors is produced as the Purkinje fibers carry the impulse from the endocardial lining of the RV and LV through the ventricular wall toward the epicardium 37

38 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Ventricular Depolarization and Mean QRS Axis Completion of right ventricular activation occurs first The thinner wall of the RV transmits impulse quicker than the thicker wall of LV 38

39 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Mean QRS Axis The small depolarization vectors of the thicker LV are larger Therefore, the mean QRS axis points more to the left I I 39

40 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Position of Mean QRS Axis Limb leads provide information about the frontal plane and are used to determine the position of the mean QRS axis Described in degrees within an imaginary circle drawn over the patient’s chest I I 40

41 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Position of Mean QRS Axis AV node is center of circle Intersection of all lines divides circle into equal, 30-degree segments Lead I starts at +0 degrees and is located at the three o’clock position Lead aVF starts at +90 degrees and is located at the six o’clock position 41

42 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Position of Mean QRS Axis Mean QRS axis normally points downward and to patient’s left (between 0 and +90 degrees) 42

43 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Determining Electrical Axis Use leads I and aVF – These two leads can best detect variations in the heart’s electrical axis I I 43

44 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Determining Electrical Axis If the mean QRS vector directed anywhere between - 90º and +90º, positive QRS complex in lead I I I 44

45 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Determining Electrical Axis If mean QRS vector directed between 0º and +180º, positive QRS complex in lead aVF I I 45

46 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Right Axis Deviation An axis between +90 and ±180 degrees indicates right axis deviation 46

47 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Left Axis Deviation An axis between 0 and −90 degrees indicates left axis deviation 47

48 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. I I Determining Electrical Axis The deflection of the QRS complexes in leads I and aV F help identify electrical axis 48

49 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Determining Electrical Axis Location of axis influenced by: – Heart’s position in the chest – Heart size – Patient’s body size – Conduction pathways – Force of electrical impulses being generated 49

50 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect Determine if the mean QRS is normal or if there is axis deviation 50 I I

51 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect Determine if the mean QRS is normal or if there is axis deviation 51 I I

52 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect Determine if the mean QRS is normal or if there is axis deviation 52 I I

53 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Practice Makes Perfect Determine if the mean QRS is normal or if there is axis deviation 53 I I

54 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary Because the electrodes positioned on the patient’s skin detect the heart’s electrical activity, placing them in a different location changes the lead or view. The shape of the waveform is described from the perspective of the positive electrode of the selected lead. Bipolar leads include leads I, II, and III. Unipolar leads include leads aV R, aV L, and aV F and the precordial leads V 1, V 2, V 3, V 4, V 5, and V 6. 54

55 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary Limb leads are produced by placing electrodes on the right arm (RA), left arm (LA), left leg (LL), and right leg (RL). The limb leads include leads I, II, and III; augmented voltage right (aV R ); augmented voltage left (aV L ); and augmented voltage foot (aV F ). – They provide a view of the electrical activity along the heart’s frontal plane. The precordial leads include leads V 1, V 2, V 3, V 4, V 5, and V 6. – They provide information about the electrical activity along the horizontal plane of the heart. 55

56 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary The mean or average of all the instantaneous vectors which the ECG detects is called the mean vector. The direction of the mean vector is called the mean electrical axis. When the electrical current traveling through the heart is moving toward a positive ECG electrode on a person’s chest or extremity the ECG machine records it as a positive or upright waveform. 56

57 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary The mean of all vectors that result from ventricular depolarization is called the QRS axis. Completion of right ventricle activation occurs first as the thinner wall of the right ventricle transmits the impulse in a fraction of the time it takes the impulse to travel through the thick lateral wall of the left ventricle. Sum of all the small vectors of ventricular depolarization is called the mean QRS vector. 57

58 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary Because the small depolarization vectors of the thicker left ventricle are larger, the mean QRS axis points more to the left. The limb leads are used to determine the position (axis) of the mean QRS vector which is described in degrees within an imaginary circle drawn over the patient’s chest. Lead I starts at +0 degrees and is located at the three o’clock position. Lead aVF starts at +90 degrees and is located at the six o’clock position. 58

59 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary The mean QRS axis normally points downward and to the patient’s left, between 0 and +90 degrees. An axis between +90 and +180 degrees indicates right axis deviation, and one between 0 and -90 degrees indicates left axis deviation. An axis deviation between -180 and -90 degrees indicates extreme axis deviation and is called an indeterminate axis. 59

60 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary Leads I and aVF can be used to quickly determine whether the mean QRS axis on any ECG is normal. If the QRS complex is positive in leads I and aVF, the QRS axis must be normal. 60

61 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary If the QRS complex is upright in lead I and negative in lead aVF then left axis deviation exists. If the QRS complex is negative in lead I and positive in lead aVF then right axis deviation exists. If the QRS complex is negative in both leads extreme right axis deviation exists. 61

62 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary Electrodes placed on patient’s skin detect heart’s electrical activity. Graphic record or tracing is called an electrocardiogram. Abnormalities in cardiac rate and/or rhythm are called dysrhythmias. 62

63 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary ECG paper consists of horizontal and vertical lines that form a grid. Horizontal measurements used to determine heart rate and duration of various waveforms, segments and intervals. Vertically on ECG paper, distance between lines, or boxes, represents amplitude in millimeters (mm) or electrical voltage in millivolts (mV). 63

64 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary Conduction of electrical impulse through the heart can be seen on ECG as P wave, PR interval, QRS complex, ST segment and T wave. Artifact is markings on ECG tracing that have no relationship to electrical activity of the heart. 64

65 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary Each lead provides a different view of heart. Impulses traveling toward a positive electrode are recorded on ECG as upward deflections. Impulses traveling away from a positive electrode or toward a negative electrode are recorded as downward deflections. 65

66 Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Summary Limb leads are produced by placing electrodes on right arm (RA), left arm (LA) and left leg (LL). – Include leads I, II, III, augmented vector right (aVR), augmented vector left (aVL) and augmented vector foot (aVF). Precordial leads include leads V1, V2, V3, V4, V5, and V6. 66


Download ppt "Fast & Easy ECGs, 2E © 2013 The McGraw-Hill Companies, Inc. All rights reserved. Fast & Easy ECGs, 2E 1 © 2013 The McGraw-Hill Companies, Inc. All rights."

Similar presentations


Ads by Google