A few new tools for better detection and understanding of STEMIs in the field.

Transcription

1 A few new tools for better detection and understanding of STEMIs in the field.

2 Let s talk, prep and placement. Try to shoot for quality, consistency and no artifact! (looking sometimes for 1 or 2 mm changes) Prep skin!!!!!!!!! Pick good spots for limb leads. Rub in all electrodes. Know and use the anatomic locators for chest leads. Don t let your electrodes dry out.

3 Getting your electrical eyes We are only seeing electrical activity in the heart. The electricity moves from Neg (-) to Positive (+) The line from origin to our detector (+) we call a vector.

4 Get the Vector, Victor Direction of electrical movement. Moving toward a Positive electrode makes an upright deflection. Moving away from a positive electrode, makes a downward deflection.

5 UNDERSTANDING THE POINT OF VIEW Coming at you.

6 Force Going away from you

7 Force passing By Not directly toward or away

8 Proper powers of description are still important. (because your transmission equipment always works flawlessly doesn t it?)

9 Q First downward deflection after the P Q waves Physiologic Q waves <.04 sec (40ms) Pathologic Q >.04 sec (40 ms)

10 The result of infarction Myocardial tissue has died, it does not regenerate. As it turns to mush and rots away, it is replaced by scar tissue. Scar tissue does not pump and it does not conduct electricity. It is a patch, that is all.

11 Thrombus Infarcted Area Electrically Silent Ischemia Depolarization

12 Since we are mentioning infarcts Some make Q waves and some don t. Some make ST segment elevation and some don t. What s the difference? Transmural (full thickness) Make ST elevation and usually make Q waves eventually. Describe the Subendocardial AMI. Often marked only by ST segment depression or T wave inversion.

13 QRS, Wave definitions Q wave

14 QS Complex

15 R Wave

16 S Wave

17 Various Ventricular waves

18 ST Segment Compare to TP segment ST TP

19 J-Point

20 ST Segment changes T wave inversion ST depression Hyperacute T waves ST Segment elevation

21 Evolution of AMI Hyperacute T Wave Big is bad

22 Evolution of AMI Acute

23 ST segment Criteria Changes must be in at least 2 contiguous leads. Must be at least 1 mm.

24 AND NOW THE IMPORTANT STUFF!! Recognition of acute injury patterns: ST segment elevation Measuring degree of elevation - begins at the J point (junction of the end of the QRS complex with the ST segment) and ends at the beginning of the T wave Count the boxes of elevation from the isoelectric line - #mm of elevation

25 Practice Find J-points and ST segments

26 ST elevation

27 Find the elevation

28 3 parts to the class Part one Strengthening component recognition and basics. Part 2 A. Concave vs. convex ST segments. Other things that may cause ST elevation. B. Using reciprocal leads to aid suspicion for STEMI and hidden STEMI. C. Sgarbossa criteria. Seeing STEMIs through BBBs and paced rhythms. Part 3. A few tidbits and using axis.

29 Things that cause ST elevation STEMIs of course. Must be at least 1 mm of elevation in 2 contiguious leads. Are there other things that could cause ST elevation? 2 things that we have all seen immediately come to mind. Pericarditis-Elevation in multiple leads usually. Pain that gets better if the Pt leans forward.

30 Non-STEMI ST elevation Continued Early repolarization. Usually seen in tall slender athletic males. More often in blacks than whites.

31 Looking at the ST segment, a few clues. The J point (Define) healthy J points usually show a clearly defined S to T wave transition. Sharp turns. Sick J points usually are slurred. This is a reason we count out 80 ms before we measure elevation. Identify the segment as concave vs. convex. Convex usually injury concave may be other cause. Straight line in elevation after J point also more likely to be STEMI.

32 J POINT Measure the J Point beginning two small boxes from the end of the QRS complex; then count the number of boxes either above or below the isoelectric line this is the number of millimeters of ST elevation (acute injury) or ST depression (ischemia) Baseline Quantity or depth of ST-segment depression J-point.08 seconds

33

34

35

36

37

38

39

40

41

42

43

44 Reciprocal changes As we have learned in the past, an additional confirmation for ST elevation can be ST depression in another lead that borders the injury zone. Not all leads have a reciprocal mate. Anterior for instance, does not have a direct reciprocal in the standard 12 lead. (it does with a 15 lead though) Some recriprocal changes can be as subtle as flattening of an ST segment in the recriprocal lead.

45 Reciprocal changes continued.. One simple way many of us have used this is to be suspicious of a posterior AMI if you see ST depression in V1-2 which may be elevation on the other side of the heart, V8-9. The inferior AMI, represents over 50% of all AMIs and it fortunately has recriprocal depression in the High lateral leads I and AVL showing depression and T wave inversion there.

46

47 Why it s hard to detect posterior and RV AMIs with the standard 12 lead. where are the electrodes that watch these sites?

48 Where is the elevation and where is the recriprocal depression?

49 Same question

50 Is there recriprocal confirmation here?

51 Using a recriprocal principle, what might you be suspicious ids happening here? What could you do to rule it in or out?

52

53 What areas of the heart does the RCA generally feed?

54 Sgarbossa criteria.reading through the bundle branches Sgarbossa Criteria: LBBB and AMI Sgarbossa EB et al, for GUSTO-1 investigators. ECG diagnosis of evolving AMI in the presence of LBBB. New Engl J Med 1996; 334: In a Left Bundle Branch Block (LBBB), the major, terminal portion of the QRS complex will normally be appropriately discordant with the ST segment. Example: If the QRS is negative, the ST segment will be normally elevated. Sgarbossa criteria: For detecting an AMI in the setting of a LBBB Derived from the GUSTO-1 trial Be aware that Sgarbossa are not perfect in screening for AMI. Use as another data point in risk-stratiying these complex patients with LBBB. Sgarbossa criteria hold true for LBBB pattern seen in pacemaker patients

55 What it tells us. In LBBB, a concordant complex to ST elevation relationship that is greater than or equal to 1 mm will represent true elevation and is predictive of STEMI over 9 out of 10 times. >95% ST depression that is discordant in V1-3 is either true depression or posterior elevation. Just as if you saw it without the BBB. ST elevation that is discordant but greater or equal to 5 mm is predictive of AMI. Past 10mm, usually associated with LVH and is not reiable.

56 Definitions Concordant- to be in agreement In this case, the major direction of the ventricular depolarization wave points in the same direction as the T wave. In Sgarbossa world, this is a bad thing when a BBB is present and elevation is greater than 1 mm.

57 Discordant To have non-agreement or discord. In Sgarbossa world, this means that the T wave points in the opposite direction of the vetricular compex. In most cases, this is read as a negative result.

58

59 Of course, there are exceptions. Excessive discordance, where the ST elevation is at or exceeds 5mm. If this appears in lead groups, it is read as injury.

60

61 In a nutshell Discordant usually good. Concordant usually bad.

62

63

64

65

66

67

68

69 Brugada Syndrome A cause of sudden cardiac death from polymorphic VT or VF in an otherwise normal heart. First published in 1992, it is believed to be responsible for 50% 0f the sudden deaths in structurally normal hearts. It shows up on the 12 lead. It has a genetic component. Drugs don t help. When found an ICD is placed.

70

71

72

73 LAD Stenosis

74 A practical understanding that we can apply

75 Determining the QRS vector The vector is a summation of the generalized direction of the electrical line and direction of travel as the ventricles depolarize. The process uses 6 leads I,II,III,AVR, AVL, AVF. A the same complex is examined in each of these leads and a value either positive or negative is calculated by counting the mm above and below the isoelectric line and subtracting the negative mm from the positive. The lead with the largest number determines the vector plotted on the hexaxial reference diagram.

76 Fortunately, we aren t going to do it that way!

77 Recall that the axis can be considered in terms of four quadrants, with lead I oriented at 0, and avf oriented at +90. An ECG with the QRS axis oriented to the quadrant between 0 and 90 is said to be normal. An ECG with the QRS axis oriented to the quadrant between -1 and -90 is said to have left axis deviation. An ECG with the QRS oriented to the quadrant between +91 and 180 is said to have right axis deviation. An ECG with the QRS oriented to the quadrant between -91 and -180 is said to have an indeterminate axis because one cannot tell if it represents right or left axis deviation.

78 We need to know basically If the axis is normal. If there is RT or Left axis deviation. If there is extreme Rt axis deviation. If there is limb lead reversal.

79 Useful stuff If I and AVF are positive, The axis is normal. If The ECG is upside down in lead I including the P waves, the limb leads are reversed. This is further confirmed by upright complexes in AVR. Unless there is ERAD (ventricular rhythm or VT ), or lead reversal, AVR is always negative. You can use the calculated QRS axis in every `12 lead printout and compare it to a hexaxial diagram. You can master the 4 quadrant method and do it yourself. Or use a 4 quadrant cheat sheet.

80 Causes of Left axis deviation Left anterior hemiblock Pathologic left axis. Big Q waves from a Inferior wall infarct.

81 Right axis deviation Pulmonary disease. R. t ventricular hypertrophy. Left posterior hemiblock. Rt. Bundle branch (fooler) RBBB makes the axis appear rightward.

82 Extreme Right Axis deviation also called indeterminent axis. V Tach Ventricular rhythm Limb lead reversal

83

84

85 Please draw a circle on a piece of paper. Divide the circle into 4 equal quadrants. Recalling where AVF is, label it s location. Recalling where Lead I is label its location. Label the 4 quadrants Normal, RAD, LAD, ERAD. Draw a new circle, and we will construct a hexaxial diagram together. Set it aside for reference. Then we are going to use these tools on the next series of ECGs.

86 Draw and label the circle diagram with I and AVF

87 Color in the diagram

88 Color it in we are going to get help from lead II in this one

89

90

91

92

93 Ventricular tachycardias These don t always follow all of these rules. There are multiple sources of VT Like Rt. Ventricular outflow tract VT Or, left fascicular VT Lets use what we now know about leads and see what we can do with these following rhythms. Of Course, if the Pt is decompensating, cardiovert it!

94 What does AVR say? What about V6, vector toward or away?

95

96

97

98

99

100 VT from a RT Ventricular dysplasia

101 Sources EMS 12 lead. Critical care transport manual K.S. Chow School of medical sciences, Universiti Sains Malaysia Journal of Emergency Medicine. Goldberger, Clinical electrophysiology