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Essentials of 12 Lead ECG Interpretation Terry White, RN, EMT-P.

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Presentation on theme: "Essentials of 12 Lead ECG Interpretation Terry White, RN, EMT-P."— Presentation transcript:

1 Essentials of 12 Lead ECG Interpretation Terry White, RN, EMT-P

2 Topics l Anatomy Revisited l The 12 Lead ECG Device l The 12 Lead ECG Format l Waveform Components l Lead Views

3 Anatomy Revisited l RCA –right ventricle –inferior wall of LV –posterior wall of LV (75%) –SA Node (60%) –AV Node (>80%) l LCA –septal wall of LV –anterior wall of LV –lateral wall of LV –posterior wall of LV (10%)

4 Anatomy Revisited l SA node l Intra-atrial pathways l AV node l Bundle of His l Left and Right bundle branches –left anterior fascicle –left posterior fascicle l Purkinje fibers

5 The 12 Lead ECG Device l Device serves as a voltmeter –measures the flow of electricity l Unipolar vs Bipolar Leads

6 Bipolar Leads l 1 positive and 1 negative electrode –RA always negative –LL always positive l Traditional limb leads are examples of these –Lead I –Lead II –Lead III l View from a vertical plane

7 Unipolar Leads l 1 positive electrode & 1 negative “reference point” –calculated by using summation of 2 negative leads l Augmented Limb Leads –aVR, aVF, aVL –view from a vertical plane l Precordial or Chest Leads –V1-V6 –view from a horizontal plane

8 The 12-Lead ECG Format Leads typically produced by devices used prehospital

9 The 12-Lead ECG Format Fields not typically produced by devices used prehospital

10 The 12-Lead ECG Format Device prints out 2.5 sec each of Leads I, II, III then switches to aVR, aVL, aVF then switches to V1, V2, V3 and then to V4, V5, V6 (varies by device) Device computer analyzes all 10 sec of all 12 leads but only prints 2.5 sec of each group

11 The 12-Lead ECG Format The computer diagnosis is not always accurate!!!

12 The 12-lead ECG Format The computer IS very accurate at measuring intervals & durations

13 Waveform Components: R Wave First positive deflection; R wave includes the downstroke returning to the baseline

14 Waveform Components: Q Wave First negative deflection before R wave; Q wave includes the negative downstroke & return to baseline

15 Waveform Components: S Wave Negative deflection following the R wave; S wave includes departure from & return to baseline

16 Waveform Components: QRS l Q waves –Can occur normally in several leads Normal Q waves called physiologic –Physiologic Q waves <.04 sec (40ms) –Pathologic Q >.04 sec (40 ms)

17 Waveform Components: QRS l Q wave –Measure width –Pathologic if greater than or equal to 0.04 seconds (1 small box)

18 Waveform Components: QS Complex Entire complex is negatively deflected; No R wave present

19 Waveform Components: J-Point Junction between end of QRS and beginning of ST segment; Where QRS stops & makes a sudden sharp change of direction

20 Waveform Components: ST Segment Segment between J-point and beginning of T wave

21 Waveform Components: ST Segment l Need reference point –Compare to TP segment –DO NOT use PR segment as reference! STTP

22 Waveform Components: Practice l Find J-points and ST segments

23 Waveform Components: Practice l Find J-points and ST segments

24 Lead “Views”

25 Limb LeadsChest Leads IaVR V1 V4 IIaVL V2 V5 IIIaVF V3 V6 Lead Groups

26 Inferior Wall l II, III, aVF –View from Left Leg  –inferior wall of left ventricle I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

27 Inferior Wall I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 l Posterior View –portion resting on diaphragm –ST elevation  suspect inferior injury

28 Lateral Wall l I and aVL –View from Left Arm  –lateral wall of left ventricle I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

29 Lateral Wall l V5 and V6 –Left lateral chest –lateral wall of left ventricle I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

30 Lateral Wall l I, aVL, V5, V6 –ST elevation  suspect lateral wall injury I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

31 Anterior Wall l V3, V4 –Left anterior chest –  electrode on anterior chest I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

32 Anterior Wall I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 l V3, V4 –ST segment elevation  suspect anterior wall injury

33 Septal Wall l V1, V2 –Along sternal borders –Look through right ventricle & see septal wall I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

34 Septal I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 l V1, V2 –septum is left ventricular tissue

35 ST Segment Analysis For each complex, determine whether the ST segment is elevated one millimeter or more above the TP segment

36 12-Lead ECG l AMI recognition –Two things to know What to look for Where you are looking

37 AMI Recognition l What to look for –ST segment elevation One millimeter or more (one small box) Present in two anatomically contiguous leads


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