Basics of ECG
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The document provides information about electrocardiograms (ECGs): 1) It defines an ECG as the physical translation of the electrical phenomena created in the heart muscles and produced as a graph by an ECG machine. 2) It describes how ECGs can be used to identify arrhythmias, ischemia, chamber hypertrophy, and other cardiac conditions. 3) It explains the basics of heart anatomy including the four chambers and valves, and how the electrical conduction system generates and transmits electrical impulses to trigger contractions.
Basics of ECG
- 1. Basics of ECG Dr. Sreedhar Rao MD(Rog Nidan), (Ph.D), MBA (Hospital Management) Asst. Professor, Dept. of Rog Nidan
- 2. Module 1 - Objectives • Define ECG • Describe heart anatomy and circulation • Describe the fundamentals of heart electrophysiology
- 3. What is ECG? • Electrocardiogram is the physical translation of the electrical phenomena created in the heart muscles.
- 4. The graph paper recording produced by the machine is termed an electrocardiogram, It is usually called ECG or EKG STANDARD CALLIBRATION Speed = 25mm/s Amplitude = 0.1mV/mm 1mV à10mm high 1 large square à 0.2s(200ms) 1 small squareà 0.04s (40ms) or 1 mV amplitude
- 5. With ECGs we can identify •Arrhythmias •Myocardial ischemia and infarction •Pericarditis •Chamber hypertrophy •Electrolyte disturbances (i.e. hyperkalemia, hypokalemia) •Drug toxicity (i.e. digoxin and drugs which prolong the QT interval)
- 6. THE HISTORY OF ECG MACHINE 1903 NOW Willem Einthoven Modern ECG machine A Dutch has evolved into compact doctor and physiologist. electronic systems that often He invented the first include computerized practical electrocardiogram and interpretation of the received the Nobel Prize in electrocardiogram. Medicine in 1924 for it
- 7. Basic Regions of the heart This is where the blood from the body enters
- 8. Basic Regions of the heart The Triscuspid valve is a three- flap valve that lies between the right atrium and right ventricle
- 9. Basic Regions of the heart This chamber empties its content into the pulmonary artery going to the lungs.
- 10. Basic Regions of the heart This chamber empties its content into the pulmonary artery going to the lungs.
- 11. Basic Structures inside the heart Pulmonary artery carries blood to the lungs
- 12. Basic Regions of the heart Thicker heart muscles of the left than the right ventricle due to greater force needed to circulate blood.
- 13. Basic Regions of the heart Pulmonary veins carries blood back to the heart.
- 14. Basic Structures inside the heart Mitral Valve prevents the reflux of its content back to the left atria.
- 15. Basic Structures inside the heart The Aortic Valve is a 3-flap, semilunar valve that keeps the blood from coming back to the ventricles at diastole.
- 16. Basic Regions of the heart The blood from the lungs return to the body after receiving oxygen through here.
- 17. Basic Structures inside the heart The chordae tendinae is a fibrous cartilage like tissue that controls the mechanical movement of the valve.
- 18. Basic Structures inside the heart The papillary muscles suspends the chordae tendinae.
- 19. Basic Structures inside the heart The septum divides the heart into two. The right side receives the unoxygenated blood and the left side send the oxygenated blood to the periphery.
- 20. The Basics of Electrophysiology In response to the stimulation to the Vagus nerve, the SA node genertes its own electrical conduction, normally, 60 -100 impulses per minute.
- 21. The Basics of Electrophysiology From the SA node the electrical conduction will travel through a nodal pathway. That is Anterior, Middle, and Posterior Internodal pathway
- 22. The Basics of Electrophysiology Bachmann bundle is the SA node pathway that stimulates the left atrium.
- 23. The Basics of Electrophysiology The AV Node generates about 40-60 stimulations per minutes, if the SA node fails to function.
- 24. The Basics of Electrophysiology The AV Bundle (also known as Bungle of His) branches into two main bundle.
- 25. The Basics of Electrophysiology The Left and Right Bundle Branches then attach to the myocardial muscles through Purkinje fibers.
- 26. Module 2 - Objectives Topic: ECG Calibration, Representation, • Describe how the electrophysiological property of the heart influences its mechanical activity. • Describe how ECG is calibrated. • Describe the ECG waveforms.
- 27. Electrophysiology Property of the heart Electrical Cells – make up the cardiac conduction system. Properties: ü Automaticity – the ability to spontaneously generate and discharge an electric impulse. ü Excitability – the ability of the cell to respond to an electrical impulse ü Conductivity – the ability to transmit an electrical impulse from one cell to the next.
- 28. Electrophysiology Property of the heart Myocardial cells – make up the muscular walls of the atrium and ventricles of the heart. ü Contractility – the ability of the cell to shorten and lengthen its fibers. ü Extensibility – the ability of the cell stretch
- 29. HOW TO DO ELECTROCARDIOGRAPHY 1. Place the patient in a supine or semi-Fowler's position. If the patient cannot tolerate being flat, you can do the ECG in a more upright position. 2. Instruct the patient to place their arms down by their side and to relax their shoulders. 3. Make sure the patient's legs are uncrossed. 4. Remove any electrical devices, such as cell phones, away from Patient, supine position the patient as they may interfere with the machine. 5. If you're getting artifact in the limb leads, try having the patient sit on top of their hands. 6. Causes of artifact: patient movement, loose/defective electrodes/apparatus, improper grounding. An ECG with artifacts.
- 30. Electrodes Usually consist of a conducting gel, embedded in the middle of a self-adhesive pad onto which cables clip. Ten electrodes are used for a 12-lead ECG. Placement of electrodes The limb electrodes RA - On the right arm, avoiding thick muscle LA – On the left arm this time. RL - On the right leg, lateral calf muscle LL - On the left leg this time.- The 6 chest electrodes V1 - Fourth intercostal space, right sternal border. V2 - Fourth intercostal space, left sternal border. V3 - Midway between V2 and V4. V4 - Fifth intercostal space, left midclavicular line. V5 - Level with V4, left anterior axillary line. V6 - Level with V4, left mid axillary line.
- 32. PEOPLE USUALLY REFER THE ELECTRODES CABLES AS LEADS LEADS should be correctly defined as the tracing of the voltage DUDE, THAT’S difference between the electrodes and is CONFUSING! what is actually produced by the ECG recorder.
- 33. SO, WHERE ARE THE LEADS?
- 34. LEADS I, II, III THEY ARE FORMED BY VOLTAGE TRACINGS BETWEEN THE LIMB ELECTRODES (RA, LA, RL AND LL). THESE ARE THE ONLY BIPOLAR LEADS. ALL TOGETHER THEY ARE CALLED THE LIMB LEADS OR THE EINTHOVEN’S TRIANGLE RA I LA II III RL LL
- 35. LEADS aVR, aVL, aVF THEY ARE ALSO DERIVED FROM THE LIMB ELECTRODES, THEY MEASURE THE ELECTRIC POTENTIAL AT ONE POINT WITH RESPECT TO A NULL POINT. THEY ARE THE AUGMENTED LIMB LEADS RA LA aVR aVL aVF RL LL
- 36. LEADS V1,V2,V3,V4,V5,V6 THEY ARE PLACED DIRECTLY ON THE CHEST. BECAUSE OF THEIR CLOSE PROXIMITY OF THE HEART, THEY DO NOT REQUIRE AUGMENTATION. THEY ARE CALLED THE PRECORDIAL LEADS RA LA V1 V2 V3 V4 V6 V5 RL LL
- 37. These leads help to determine heart’s electrical axis. The limb leads and the augmented limb leads form the frontal plane. The precordial leads form the horizontal plane.
- 38. The Different Views Reflect The Angles At Which LEADS "LOOK" At The Heart And The Direction Of The Heart's Electrical Depolarization. Leads Anatomical representation of the heart V1, V2, V3, V4 Anterior I, aVL, V5, V6 left lateral II, III, aVF inferior aVR, V1 Right atrium
- 39. ECG Calibration • Horizontally • One small box - 0.04 s • One large box - 0.20 s • Vertically • One large box - 0.5 mV
- 40. ECG Calibration
- 41. A NORMAL ECG WAVE REMEMBER
- 42. THE NORMAL SIZE <3 small square < 2 small square <3-5 small square < 2 large square
- 43. ECG Representation P wave represents Atrial depolarization Vector is from SA node to AV node
- 44. ECG Representation QRS Complex represents Ventricular depolarization Normal 0.06 to 0.10 seconds
- 45. ECG Representation T wave represents Ventricular repolarization Vector is from SA node to AV node
- 46. ECG Representation PR Interval 0.12 – 0.20 seconds Time for electrical impulse takes to travel from sinus node through the AV node and entering the ventricles
- 47. ECG Representation QT Interval 0.32 – 0.40 seconds A prolonged QT interval is a risk factor for ventrial tachyarrhythmias and sudden death
- 48. ECG Representation ST segment represents the early phase of ventricular repolarization It is Isoelectric
- 50. Understanding ECG Waveform If a wavefront of depolarization travels towards the positive electrode, a positive-going deflection will result. If the waveform travels away from the positive electrode, a negative going deflection will be seen.
- 51. ECG RULES • Professor Chamberlains 10 rules of normal:-
- 52. RULE 1 PR interval should be 120 to 200 milliseconds or 3 to 5 little squares
- 53. RULE 2 The width of the QRS complex should not exceed 110 ms, less than 3 little squares
- 54. RULE 3 The QRS complex should be dominantly upright in leads I and II
- 55. RULE 4 QRS and T waves tend to have the same general direction in the limb leads
- 56. RULE 5 All waves are negative in lead aVR
- 57. RULE 6 The R wave must grow from V1 to at least V4 The S wave must grow from V1 to at least V3 and disappear in V6
- 58. RULE 7 The ST segment should start isoelectric except in V1 and V2 where it may be elevated
- 59. RULE 8 The P waves should be upright in I, II, and V2 to V6
- 60. RULE 9 There should be no Q wave or only a small q less than 0.04 seconds in width in I, II, V2 to V6
- 61. RULE 10 The T wave must be upright in I, II, V2 to V6
- 62. INTERPRETATION The More You See, The More You Know
- 63. The best way to interpret an ECG is to do it step-by-step Rate Rhythm Cardiac Axis P – wave PR - interval QRS Complex ST Segment QT interval (Include T and U wave) Other ECG signs
- 64. RATE
- 65. CALCULATING RATE As a general interpretation, look at lead II at the bottom part of the ECG strip. This lead is the rhythm strip which shows the rhythm for the whole time the ECG is recorded. Look at the number of square between one R-R interval. To calculate rate, use any of the following formulas: 300 Rate = the number of BIG SQUARE between R-R interval OR 1500 Rate = the number of SMALL SQUARE between R-R interval
- 66. CALCULATING RATE For example: 300 1500 Rate = or Rate = 3 15 Rate = 100 beats per minute
- 67. CALCULATING RATE If you think that the rhythm is not regular, count the number of electrical beats in a 6-second strip and multiply that number by 10.(Note that some ECG strips have 3 seconds and 6 seconds marks) Example below: 1 2 3 4 5 6 7 8 There are 8 waves in this 6-seconds strip. Rate = (Number of waves in 6-second strips) x 10 = 8 x 10 = 80 bpm
- 68. CALCULATING RATE You can also count the number of beats on any one row over the ten-second strip (the whole lenght) and multiply by 6. Example: Rate = (Number of waves in 10-second strips) x 6 = 13 x 6 = 78 bpm
- 69. CALCULATING RATE Interpretation bpm Causes Normal 60-99 - Bradycardia <60 hypothermia, increased vagal tone (due to vagal stimulation or e.g. drugs), atheletes (fit people) hypothyroidism, beta blockade, marked intracranial hypertension, obstructive jaundice, and even in uraemia, structural SA node disease, or ischaemia. Tachycardia >100 Any cause of adrenergic stimulation (including pain); thyrotoxicosis; hypovolaemia; vagolytic drugs (e.g. atropine) anaemia, pregnancy; vasodilator drugs, including many hypotensive agents; FEVER, myocarditis
- 70. RHYTHM
- 71. RHYTHM Look at p waves and their relationship to QRS complexes. Lead II is commonly used Regular or irregular? If in doubt, use a paper strip to map out consecutive beats and see whether the rate is the same further along the ECG. Measure ventricular rhythm by measuring the R-R interval and atrial rhythm by measuring P-P interval.
- 72. RHYTHM Normal Sinus Rhythm ECG rhythm characterized by a usual rate of anywhere between 60-99 bpm, every P wave must be followed by a QRS and every QRS is preceded by P wave. Normal duration of PR interval is 3-5 small squares. The P wave is upright in leads I and II
- 73. RHYTHM Sinus Bradycardia Rate < 60bpm, otherwise normal
- 74. RHYTHM Sinus Tachycardia Rate >100bpm, otherwise, normal
- 75. RHYTHM Sinus pause In disease (e.g. sick sinus syndrome) the SA node can fail in its pacing function. If failure is brief and recovery is prompt, the result is only a missed beat (sinus pause). If recovery is delayed and no other focus assumes pacing function, cardiac arrest follows.
- 76. RHYTHM Atrial Fibrillation A-fib is the most common cardiac arrhythmia involving atria. Rate= ~150bpm, irregularly irregular, baseline irregularity, no visible p waves, QRS occur irregularly with its length usually < 0.12s
- 77. RHYTHM Atrial Flutter Atrial Rate=~300bpm, similar to A-fib, but have flutter waves, ECG baseline adapts ‘saw-toothed’ appearance’. Occurs with atrioventricular block (fixed degree), eg: 3 flutters to 1 QRS complex:
- 78. RHYTHM Ventricular Fibrillation A severely abnormal heart rhythm (arrhythmia) that can be life-threatening. Emergency- requires Basic Life Support Rate cannot be discerned, rhythm unorganized
- 79. RHYTHM Ventricular tachycardia fast heart rhythm, that originates in one of the ventricles- potentially life- threatening arrhythmia because it may lead to ventricular fibrillation, asystole, and sudden death. Rate=100-250bpm
- 80. RHYTHM Torsades de Pointes literally meaning twisting of points, is a distinctive form of polymorphic ventricular tachycardia characterized by a gradual change in the amplitude and twisting of the QRS complexes around the isoelectric line. Rate cannot be determined.
- 81. RHYTHM Supraventricular Tachycardia SVT is any tachycardiac rhythm originating above the ventricular tissue. Atrial and ventricular rate= 150-250bpm Regular rhythm, p is usually not discernable. *Types: •Sinoatrial node reentrant tachycardia (SANRT) •Ectopic (unifocal) atrial tachycardia (EAT) •Multifocal atrial tachycardia (MAT) •A-fib or A flutter with rapid ventricular response. Without rapid ventricular response both usually not classified as SVT •AV nodal reentrant tachycardia (AVNRT) •Permanent (or persistent) junctional reciprocating tachycardia (PJRT) •AV reentrant tachycardia (AVRT)
- 82. RHYTHM Atrial Escape a cardiac dysrhythmia occurring when sustained suppression of sinus impulse formation causes other atrial foci to act as cardiac pacemakers. Rate= 60-80bpm, p wave of atrial escape has abnormal axis and different from the p wave in the sinus beat. However QRS complexes look exactly the same.
- 83. RHYTHM Junctional Escape Depolarization initiated in the atrioventricular junction when one or more impulses from the sinus node are ineffective or nonexistent. Rate: 40-60 bpm, Rhythm: Irregular in single junctional escape complex; regular in junctional escape rhythm, P waves: Depends on the site of the ectopic focus. They will be inverted, and may appear before or after the QRS complex, or they may be absent, hidden by the QRS. QRS is usually normal
- 84. RHYTHM Ventricular escape The depolarization wave spreads slowly via abnormal pathway in the ventricular myocardium and not via the His bundle and bundle branches.
- 85. RHYTHM Atrial premature beat (APB) Arises from an irritable focus in one of the atria. APB produces different looking P wave, because depolarization vector is abnormal. QRS complex has normal duration and same morphology .
- 86. RHYTHM Junctional Premature Beat Arises from an irritable focus at the AV junction. The P wave associated with atrial depolarization in this instance is usually buried inside the QRS complex and not visible. If p is visible, it is -ve in lead II and +ve in lead aVR and it it may occur before or after QRS.
- 87. RHYTHM Premature Ventricular Complexes (PVCs) is a relatively common event where the heartbeat is initiated by the heart ventricles(arrow) rather than by the sinoatrial node, Rate depends on underlying rhythm and number of PVCs. Occasionally irregular rhythm, no p-wave associated with PVCs. May produce bizarre looking T wave.
- 88. RHYTHM Asystole a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow. Rate, rhythm, p and QRS are absent
- 89. RHYTHM Pulseless Electrical Activity (PEA) Not an actual rhythm. The absence of a palpable pulse and myocardial muscle activity with the presence of organized muscle activity (excluding VT and VF) on cardiac monitor. Pt is clinically dead.
- 90. RHYTHM Artificial pacemaker Sharp, thin spike. Rate depends on pacemaker, p wave maybe absent or present Ventricular paced rhythm shows wide ventricular pacemaker spikes
- 92. CARDIAC AXIS
- 93. CARDIAC AXIS The cardiac axis refers to the general direction of the heart's depolarization wavefront (or mean electrical vector) in the frontal plane. With a healthy conducting system the cardiac axis is related to where the major muscle bulk of the heart lies. Electrical impulse that travels towards the electrode produces an upright (positive) deflection (of the QRS complex) relative to the isoelectric baseline. One that travels away produces negative deflection. And one that travels at a right angle to the lead, produces a biphasic wave.
- 94. CARDIAC AXIS To determine cardiac axis look at QRS complexes of lead , II, III. Axis Lead I Lead II Lead III Normal Positive Positive Positive/Negative Right axis Negative Positive Positive deviation Left axis Positive Negative Negative deviation Remember, positive(upgoing) QRS omplex means the impulse travels towards the lead. Negative means moving away.
- 95. CARDIAC AXIS Positive Positive Positive Normal Axis Deviation
- 96. CARDIAC AXIS Positive Negative Negative Left Axis Deviation
- 97. CARDIAC AXIS Negative Positive Positive Right Axis Deviation
- 98. CARDIAC AXIS Cardiac Axis Causes Left axis deviation Normal variation in pregnancy, obesity; Ascites, abdominal distention, tumour; left anterior hemiblock, left ventricular hypertrophy, Q Wolff- Parkinson-White syndrome, Inferior MI Right axis deviation normal finding in children and tall thin adults, chronic lung disease(COPD), left posterior hemiblock, Wolff-Parkinson-White syndrome, anterolateral MI. North West emphysema, hyperkalaemia. lead transposition, artificial cardiac pacing, ventricular tachycardia
- 99. P- WAVE
- 100. P -WAVE Normal P- wave 3 small square wide, and 2.5 small square high. Always positive in lead I and II in NSR Always negative in lead aVR in NSR Commonly biphasic in lead V1
- 101. P -WAVE P pulmonale Tall peaked P wave. Generally due to enlarged right atrium- commonly associated with congenital heart disease, tricuspid valve disease, pulmonary hypertension and diffuse lung disease. Biphasic P wave Its terminal negative deflection more than 40 ms wide and more than 1 mm deep is an ECG sign of left atrial enlargement. P mitrale Wide P wave, often bifid, may be due to mitral stenosis or left atrial enlargement.
- 102. PR- INTERVAL
- 103. PR INTERVAL NORMAL PR INTERVAL Long PR interval may indicate heart block Short PR interval may disease like Wolf-Parkinson- PR-Interval 3-5 small square (120-200ms) White
- 104. PR-INTERVAL First degree heart block P wave precedes QRS complex but P-R intervals prolong (>5 small squares) and remain constant from beat to beat
- 105. PR-INTERVAL Second degree heart block 1. Mobitz Type I or Wenckenbach Runs in cycle, first P-R interval is often normal. With successive beat, P-R interval lengthens until there will be a P wave with no following QRS complex. The block is at AV node, often transient, maybe asymptomatic
- 106. PR-INTERVAL Second degree heart block 2. Mobitz Type 2 P-R interval is constant, duration is normal/prolonged. Periodically, no conduction between atria and ventricles- producing a p wave with no associated QRS complex. (blocked p wave). The block is most often below AV node, at bundle of His or BB, May progress to third degree heart block
- 107. PR-INTERVAL Third degree heart block (Complete heart block) No relationship between P waves and QRS complexes An accessory pacemaker in the lower chambers will typically activate the ventricles- escape rhythm. Atrial rate= 60-100bpm. Ventricular rate based on site of escape pacemaker. Atrial and ventricular rhythm both are regular.
- 108. PR-INTERVAL Wolff–Parkinson–White syndrome Wolf Parkinson White Syndrome One beat from a rhythm strip in V2 demonstrating characteristic findings in WPW syndrome. Note the characteristic delta wave (above the blue bar), the short PR interval (red bar) of 0.08 seconds, and the long QRS complex (green) at 0.12 seconds Accessory pathway (Bundle of Kent) allows early activation of the ventricle (delta wave and short PR interval)
- 109. QRS-COMPLEX
- 110. QRS COMPLEX NORMAL QRS COMPLEX S amplitude in V1 + R amplitude in V5 < 3.5 Q wave amplitude less than Increased amplitude 1/3 QRS amplitude(R+S) or indicated cardiac hypertrophy < 1 small square QRS complex< 3 small square (0.06 - 0.10 sec) Prolonged indicates hyperkalemia or bundle branch block
- 111. QRS COMPLEX Left Bundle Branch Block (LBBB) Right bundle branch block (RBBB) indirect activation causes left ventricle contracts indirect activation causes right ventricle later than the right ventricle. contracts later than the left ventricle QS or rS complex in V1 - W-shaped Terminal R wave (rSR’) in V1 - M-shaped RsR' wave in V6- M-shaped Slurred S wave in V6 - W-shaped Mnemonic: WILLIAM Mnemonic: MARROW
- 112. ST- SEGMENT
- 113. ST SEGMENT NORMAL ST SEGMENT ST segment is isoelectric and at the same level as subsequent PR-interval ST segment < 2-3 small square (80 to 120 ms)
- 114. ST SEGMENT OK, WE GONNA TALK ABOUT MYOCARDIAL INFARCTION (MI) THERE ARE 2 TYPES OF MI ST-ELEVATION MI (STEMI) AND NON ST-ELEVATION MI (NSTEMI) WE DECIDE THIS BY LOOKING AT THE ST SEGMENT IN ALL LEADS Flat (isoelectric) ± Same level with subsequent PR segment NORMAL ST SEGMENT Elevation or depression of ST segment by 1 mm or more, measured at J point is abnormal. J point is the point between QRS and ST segment
- 115. Ischaemic change can be attributed to ST-SEGMENT different coronary arteries supplying the area. Localizing MI Location of Lead with Affected Look at ST changes, Q wave in all leads. Grouping MI ST changes coronary the leads into anatomical location, we have this: artery I aVR V1 V4 Anterior V1, V2, V3, LAD V4 II aVL V2 V5 Septum V1, V2 LAD III aVF V3 V6 left lateral I, aVL, V5, Left V6 circumflex inferior II, III, aVF RCA Right atrium aVR, V1 RCA *Posterior Posterior RCA chest leads (RCA) *Right Right sided RCA ventricle leads (LAD) *To help identify MI, right sided and posterior leads can be applied
- 116. DIAGNOSING MYOCARDIAL INFARCTION (STEMI) Criteria: ST elevation in > 2 chest leads > 2mm elevation ST elevation in > 2 limb leads > 1mm elevation Q wave > 0.04s (1 small square). *Be careful of LBBB The diagnosis of acute myocardial infarction should be made circumspectively in the presence of pre-existing LBBB. On the other hand, the appearance of new LBBB should be regarded as sign of acute MI until proven otherwise Pathologic Q waves are a sign of previous myocardial infarction. Definition of a pathologic Q wave Any Q-wave in leads V2–V3 ≥ 0.02 s or QS complex in leads V2 and V3 Q-wave ≥ 0.03 s and > 0.1 mV deep or QS complex in leads I, II, aVL, aVF, or V4–V6 in any two leads of a contiguous lead grouping (I, aVL,V6; V4–V6; II, III, and aVF) R-wave ≥ 0.04 s in V1–V2 and R/S ≥ 1 with a concordant positive T-wave in the absence of a conduction defect. A little bit troublesome to remember? I usually take pathological Q wave as >1 small square deep
- 117. ST SEGMENT ST-ELEVATION MI (STEMI) 0 HOUR Pronounced T Wave initially ST elevation (convex type) Depressed R Wave, and Pronounced T Wave. Pathological Q waves 1-24H may appear within hours or may take greater than 24 hr.- indicating full- thickness MI. Q wave is pathological if it is wider than 40 ms or deeper than a third of the height of the entire QRS complex Day 1-2 Exaggeration of T Wave continues for 24h. Days later T Wave inverts as the ST elevation begins to resolve. Persistent ST elevation is rare except in the presence of a ventricular aneurysm. Weeks later ECG returns to normal T wave, but retains pronounced Q wave. An old infarct may look like this
- 118. ST SEGMENT Let’s see this >2mm Pathological Q wave Check again! I aVR V1 ST elevation in > 2 chest leads > 2mm V4 Q wave > 0.04s (1 small square). II aVL V2 V5 Yup, It’s acute anterolateral MI! III aVF V3 V6
- 119. ST SEGMENT How about this one? Check again! I aVR V1 V4 Inferior MI! II aVL V2 V5 III aVF V3 V6
- 120. ST SEGMENT NON ST-ELEVATION MI (NSTEMI) NSTEMI is also known as subendocardial or non Q-wave MI. In a pt with Acute Coronary Syndrome (ACS) in which the ECG does not show ST elevation, NSTEMI (subendocardial MI) is suspected if •ST Depression (A) •T wave inversion with or without ST depression (B) •Q wave and ST elevation will never happen To confirm a NSTEMI, do Troponin test: •If positive - NSTEMI •If negative – unstable angina pectoris
- 121. ST SEGMENT NON ST-ELEVATION MI (NSTEMI) N-STEMI: acute coronary syndrome (with troponin increase). Arrows indicate ischemic ST segment changes. Without appropriate treatment in many cases STEMI infarction will occur.
- 122. ST SEGMENT MYOCARDIAL ISCHEMIA 1mm ST-segment depression Symmetrical, tall T wave Long QT- interval A ST depression is more suggestive of myocardial ischaemia than infarction
- 123. ST SEGMENT PERICARDITIS ST elevation with concave shape, mostly seen in all leads
- 124. ST SEGMENT DIGOXIN Down sloping ST segment depression also known as the "reverse tick" or "reverse check" sign in supratherapeutic digoxin level.
- 125. ST SEGMENT Now, moving to LEFT VENTRICULAR AND RIGHT VENTRICULAR HYPERTROPHY HYPERTROPHY So, we have to start looking at the S waves and R waves
- 126. ST SEGMENT Left ventricular hypertrophy (LVH) To determine LVH, use one of the following Criteria: Sokolow & Lyon Criteria: S (V1) + R(V5 or V6) > 35mm Cornell Criteria: S (V3) + R (aVL) > 28 mm (men) or > 20 mm (women) Others: R (aVL) > 13mm Example: S (V1) + R(V5) = 15 + 25 = 40mm S(V3) + R (aVL)= 15 + 14 =29mm R(aVL) =14 mm LVH!
- 127. ST SEGMENT Let’s see another example of LVH LVH strain pattern Tall R waves in V4 and V5 with down sloping ST segment depression and T wave inversion are suggestive of left ventricular hypertrophy (LVH) with strain pattern. LVH with strain pattern usually occurs in pressure overload of the left ventricle as in systemic hypertension or aortic stenosis.
- 128. ST SEGMENT Right ventricular hypertrophy (RVH) Right axis deviation (QRS axis >100o) V1(R>S), V6 (S>R) Right ventricular strain T wave inversion Example: So, it’s RVH!
- 129. ST SEGMENT Common Causes of LVH and RVH LVH RVH Hypertension (most common cause) Pulmonary hypertension Aortic stenosis Tetralogy of Fallot Aortic regurgitation Pulmonary valve stenosis Mitral regurgitation Ventricular septal defect (VSD) Coarctation of the aorta High altitude Hypertrophic cardiomyopathy Cardiac fibrosis COPD Athletic heart syndrome
- 130. QT- INTERVAL
- 131. QT- INTERVAL QT interval decreases when heart rate increases. A general guide to the upper limit of QT interval. For HR = 70 bpm, QT<0.40 sec. •For every 10 bpm increase above 70 subtract 0.02s. •For every 10 bpm decrease below 70 add 0.02 s As a general guide the QT interval should be 0.35- 0.45 s,(<2 large square) and should not be more than half of the interval between adjacent R waves (R-R interval) : < 2 large square
- 132. Calculation of QT interval 1.Use lead II. Use lead V5 alternatively if lead II cannot be read. 2.Draw a line through the baseline (preferably the PR segment) 3.Draw a tangent against the steepest part of the end of the T wave. If the T wave has two positive deflections, the taller deflection should be chosen. If the T wave is biphasic, the end of the taller deflection should be chosen. 4.The QT interval starts at the beginning of the QRS interval and ends where the tangent and baseline cross. 5.If the QRS duration exceeds 120ms the amount surpassing ,120ms should be deducted from the QT interval (i.e. QT=QT-(QRS width-120ms) ) To calculate the heart rate-corrected QT interval QTc. Bazett's formula is used
- 133. QT = 0.04 x 10 small square= 0.4s 18 small square RR = 0.04 x 18 small square= 0.72s 10 small square If abnormally prolonged or shortened, there is a risk of developing ventricular arrhythmias The QT interval is prolonged in congenital long QT syndrome, but QT prolongation can also occur as a consequence of •Medication (anti-arrhythmics, tricyclic antidepressants, phenothiazedes) •Electrolyte imbalances •Ischemia. QT prolongation is often treated with beta blockers.
- 134. LONG QT SYNDROME LQT is a rare inborn heart condition in which repolarization of the heart is delayed following a heartbeat. Example: Jervell and Lange-Nielsen Syndrome or Romano-Ward Syndrome T-WAVE Normal T wave Asymmetrical, the first half having more gradual slope than the second half >1/8 and < 2/3 of the amplitude of corresponding R wave Amplitude rarely exceeds 10mm Abnormal T waves are symmetrical, tall, peaked, biphasic, or inverted.
- 135. U-WAVE The U wave is a wave on an electrocardiogram that is not always seen. It is typically small, and, by definition, follows the T wave. U waves are thought to represent repolarization of the papillary muscles or Purkinje fibers Normal U waves are small, round and symmetrical and positive in lead II. It is the same direction as T wave in that lead. Prominent U waves are most often seen in hypokalemia, but may be present in hypercalcemia, thyrotoxicosis, or exposure to digitalis,epinephrine, and Class 1A and 3 antiarrhythmics, as well as in congenital long QT syndrome, and in the setting of intracranial hemorrhage. An inverted U wave may represent myocardial ischemia or left ventricular volume overload
- 136. OTHER ECG SIGNS
- 137. HYPERKALAEMIA Narrow and tall peaked T wave (A) is an early sign PR interval becomes longer P wave loses its amplitude and may disappear QRS complex widens (B) When hyperkalemia is very severe, the widened QRS complexes merge with their corresponding T waves and the resultant ECG looks like a series of sine waves (C). If untreated, the heart arrests in asystole HYPOKALAEMIA T wave becomes flattened together with appearance of a prominent U wave. The ST segment may become depressed and the T wave inverted. these additional changes are not related to the degree of hypokalemia.
- 138. HYPERCALCEMIA/HYPOCALCEMIA Usually, signs are not obvious Hypercalcemia is associated with short QT interval (A) and Hypocalcemia with long QT interval (B). Interval shortening or lengthening is mainly in the ST segment.
- 139. PULMONARY EMBOLISM Tachycardia and incomplete RBBB differentiated PE from no PE. SIQIIITIII = deep S wave in lead I, pathological Q wave in lead III, and inverted T wave in lead III. The ECG is often abnormal in PE, but findings are not sensitive, not specific Any cause of acute cor pulmonale can cause the S1Q3T3 finding on the ECG.
- 140. Thanks for your attention! Now, find some ECG practice!