12 Lead ECG Interpretation: Quick review for Assessing for MI’s :12 Lead ECG Interpretation: Quick review for Assessing for MI’s Julio Diaz NREMT-P TEMS Training Officer Gwinnett Fire Academy 1


Objectives :review the ECG waveform and intervals Define myocardial ischemia, injury and infarction Identify the 5 major infarct areas on the 12 lead Name occluded arteries common to the area Differentiate ECG changes reflecting ischemia, injury and infarction Identify cardiac enzymes associated with ACS 2 Objectives


MI Definition :A result of occlusion of arterial flow to the myocardium. Ischemia, injury and necrosis is result Occlusion occurs via spasm, blood clot or stenosis 3 MI Definition


Slide 4:4 The Three I’s Ischemia lack of oxygenation ST segment depression or T wave inversion Injury prolonged ischemia ST segment elevation Infarct death of tissue may or may not show a Q wave


Slide 5:5 Injury/Infarct Recognition Epicardial Coronary Artery Lateral Wall of LV Positive Electrode Septum Interior Wall of LV Well Perfused Myocardium


Slide 6:Injury/Infarct Recognition Normal ECG


Injury/Infarct Recognition :Injury/Infarct Recognition Epicardial Coronary Artery Lateral Wall of LV Septum Interior Wall of LV Ischemia Positive Electrode Left Ventricular Cavity


Injury/Infarct Recognition :Injury/Infarct Recognition Ischemia Inadequate oxygen to tissue Represented by ST depression or T inversion May or may not result in infarct or Q waves


Injury/Infarct Recognition :Injury/Infarct Recognition ST Segment Depression


Injury/Infarct Recognition :Injury/Infarct Recognition Thrombus Ischemia Injury


Injury/Infarct Recognition :Injury/Infarct Recognition ST Segment Elevation


Injury/Infarct Recognition :Injury/Infarct Recognition Infarcted Area Electrically Silent Depolarization Infarct


Injury/Infarct Recognition :Injury/Infarct Recognition Infarct Death of tissue Represented by Q wave Not all infarcts develop Q waves


Localization :Localization Inferior: II, III, AVF Septal: V1, V2 Anterior: V3, V4 Lateral: I, AVL, V5, V6


Localization :Localization I Lateral II Inferior III Inferior aVR aVL Lateral V1 Septal aVF Inferior V2 Septal V3 Anterior V4 Anterior V5 Lateral V6 Lateral Which coronary arteries are most likely associated with each group of contiguous leads?


Localization: Left Coronary Artery :Localization: Left Coronary Artery Left Main Left Circumflex Lateral Wall Anterior Wall of Left Ventricle Septal Wall Right Ventricle Right Coronary Artery Anterior Descending Artery


Slide 17:Localization: Left Coronary Artery (LCA) Left Main (proximal LCA) occlusion Extensive Anterior injury Left Circumflex (LCX) occlusion Lateral injury Left Anterior Descending (LAD) occlusion Anteroseptal injury


Localization: Extensive Anterior MI :Localization: Extensive Anterior MI Evidence in septal, anterior, and lateral leads Often from proximal LCA lesion “Widow Maker” Complications common Left ventricular failure CHF / Pulmonary Edema Cardiogenic Shock


Localization: Right Coronary Artery (RCA) :Localization: Right Coronary Artery (RCA) Proximal RCA occlusion Right Ventricle injured Posterior wall of left ventricle injured Inferior wall of left ventricle injured Posterior descending artery (PDA) occlusion Inferior wall of right ventricle injured


Localization Summary :Localization Summary Left Coronary Artery Septal Anterior Lateral Possibly Inferior Right Coronary Artery Inferior Right Ventricular Infarct Posterior


Evolution of AMI :Evolution of AMI Hyperacute Early change suggestive of AMI Tall & Peaked May precede clinical symptoms Only seen in leads looking at infarcting area Not used as a diagnostic finding


Slide 22:Evolution of AMI Acute ST segment elevation Implies myocardial injury occurring Elevated ST segment presumed acute rather than old


Evolution of AMI :Evolution of AMI Age Undetermined Wide (pathologic) Q wave No ST segment elevation Old or “age undetermined” MI


AMI Recognition :AMI Recognition A normal 12-lead ECG DOES NOT mean the patient is not having acute ischemia, injury or infarction!!!


Reciprocal Changes :Reciprocal Changes


Reciprocal Changes :Reciprocal Changes II, III, aVF I, aVL, V leads


Slide 27:ST segment elevation is presumptive evidence for AMI


Precordial Leads :28 Precordial Leads


Slide 29:29 12-Lead ECG AMI recognition Two things to know What to look for Where you are looking


Slide 30:30 Where the positive electrode is positioned, determines what part of the heart is seen!


Slide 31:31 Lead “Views”


Slide 32:32 Limb Leads Chest Leads I aVR V1 V4 II aVL V2 V5 III aVF V3 V6 Lead Groups


The ECG Tracing :33 The ECG Tracing


ECG Changes : Ischemia :T-wave inversion ( flipped T) ST segment depression T wave flattening Biphasic T-waves 34 ECG Changes : Ischemia


ECG Changes: Injury :ST segment elevation of greater than 1mm in at least 2 contiguous leads Heightened or peaked T waves Directly related to portions of myocardium rendered electrically inactive 35 ECG Changes: Injury Baseline


Slide 36:36 Inferior Wall II, III, aVF View from Left Leg ? inferior wall of left ventricle I II III aVR aVL aVF V1 V2 V3 V4 V5 V6


Inferior MI :37 Inferior MI


Slide 38:38 Lateral Wall I and aVL View from Left Arm ? lateral wall of left ventricle I II III aVR aVL aVF V1 V2 V3 V4 V5 V6


Slide 39:Lateral Wall V5 and V6 Left lateral chest lateral wall of left ventricle I II III aVR aVL aVF V1 V2 V3 V4 V5 V6


Lateral Wall :Lateral Wall Lateral Wall I, aVL, V5, V6 ST elevation ? suspect lateral wall injury


Anterior Wall :Anterior Wall V3, V4 Left anterior chest ? electrode on anterior chest I II III aVR aVL aVF V1 V2 V3 V4 V5 V6


Lateral MI :42 Lateral MI


Anterior Wall :Anterior Wall I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 V3, V4 ST segment elevation ? suspect anterior wall injury


Slide 44:Septal Wall V1, V2 Along sternal borders Look through right ventricle & see septal wall I II III aVR aVL aVF V1 V2 V3 V4 V5 V6


Slide 45:Septal I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 V1, V2 septum is left ventricular tissue


Right Sided EKG???? :Right Sided EKG???? RVI occurs around 40% in inferior MI’s Significance Larger area of infarct Both ventricles Different treatment Right leads “look” directly at Right Ventricle and can show ST elevations in leads II. III. AVF, V4R , V5R and V6R Occlusion in RCA and proximal enough to involve the RV 46 The single most accurate tool used in measuring RVI. 90% sensitive and specific


Posterior Leads :Posterior Leads Posterior leads V1, V2 Posterior Infarct with ST Depressions and/ tall R wave RCA and/or LCX Artery Understand Reciprocal changes The posterior aspect of the heart is viewed as a mirror image and therefore depressions versus elevations indicate MI Rarely by itself usually in combo 47


Practice 1 :48 Practice 1 Anterior MI with lateral involvement ST elevations V2, V3, V4 ST elevations II, AVL, V5


Practice 2 :49 Practice 2 Anteroseptal MI ST elevations V1, V2, V3, V4


Practice 3 :50 Practice 3 Inferior MI ST elevation 2,3 AVF


Practice 4 :51 Practice 4 Inferior lateral MI ST elevations 2, 3, AVF ST elevations V5


Practice 5 :52 Practice 5 Acute inferior MI Lateral ischemia


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Cardiac Enzymes Indicating Infarct :Normals CPK- 10-155u/liter begin rise 3-6 hours and peaks 12-24 with return to norm 3-5 days CPK-MB < than 5% IU/liter LDH 85-200 IU/liter Begin rise 12 hours, peaks 36-72 and normal around 10 days LDH 1- 18.1% - 29% of total LDH 2- 27.4% to 37.5% of total 69 Cardiac Enzymes Indicating Infarct


Cardiac Enzymes Indicating Infarct :Cardiac Enzymes Indicating Infarct Troponins- Now the Gold Standard! Rises after 3-6 hours Negative Troponin within 6 hours of onset of S&S rules out the MI Peaks at about 20 hours May be raised for 14 days 70


Cardiac Enzymes Indicating Infarct :Troponin T 84% sensitivity for MI 8 hours after onset of symptoms 22% for unstable angina Advantages Highly sensitive for detecting myocardial ischemia Levels may help to stratify risks Disadvantages Less specific than Troponin I Increased in angina Increased in chronic renal failure 71 Cardiac Enzymes Indicating Infarct


Cardiac Enzymes Indicating Infarct :Troponin I 90% sensitivity for MI 8 hours after onset of S&S and 95% specificity Level greater than 1.2 suggest MI Negative rules out MI Obtain two negative troponin values 4 hours apart Normally exceedingly low Even a small elevation indicates myocardial damage 72 Cardiac Enzymes Indicating Infarct


References :Twelve Lead Electrocardiography for ACLS Providers, D. Bruce Foster, D.O.W.B. Saunders Company Rapid Interpretation of EKG’s , Dale Dubin, M.D., Cover Publishing Co. 1998 ECG’s Made Easy, Barbara Aehlert, RN, Mosby, 1995 The 12 Lead ECG in Acute Myocardial Infarction, Tim Phalen, Mosby, 1996 Color Coding EKG’s , Tim Carrick, RN, H &H Publishing, 1994 www.ecglibrary.com/ecghome.html www.urbanhealth.udmercy.edu/ekg/read.html www.ecglibrary.com/ecghome.html www.nyerrn.com/h/ekg.htm Drawings by Jill Gregory, Medical Illustrator, CGEY 73 References