ELECTROCARDIOGRAPHY(ECG)_Autosaved.pptx.

ELECTROCARDIOGRAPHY

1. ELECTROCARDIOGRAPHY(ECG) PRESENTERS SAEED MAZIMBA ESAU HARRIET MUGALA

2. PRESENTATION CONTENT Definition of ECG Indications of ECG Basic of ECG ECG interpretations

3. definition An ECG is a series of waves and deflections recording the heart electrical activity on the body surface from a certain view.

4. ECG INDICATIONS

5. CONTRAINDICATIONS 1. No absolute contraindication unless if patient refuses 2. some patients may have allergies or commonly sensitivities to the adhesive used to fix the leads, hypoallergenic alternative are available.

6. ANATOMY BACKGROUND The heart consist of two types of muscles; c onducting and contracting muscles. 1. conducting muscles ; these generate and transport electrical impulse(action potential)through the heart and these include sinoatrial node(SA NODE), AV node, common bundle branch, left bundle branch(anterior and posterior) and right bundle branch and the purkinje fibers. 2. contracting muscles ; these generate the force of contraction. C ontraction of any muscles is associated with electrical changes ( i.e depolarization)

7. PATHWAY OF THE IMPULSE Electrical discharge for each cardiac cycle normally starts in the right atrium (sinoatrial node-SA node) Depolarization then spreads through the atrial muscle fibers. • There is a delay while the depolarization spreads through the atrioventricular node (AV node) • The electrical discharge then travels rapidly down the bundle of His in the septum between the left and right ventricles • The left bundle branch itself divides into two. • In the ventricular muscles, conduction spreads somewhat slowly through the ‘Purkinje fibers’.

8. IMAGE

9. RHYTHM OF THE HEART N ormally electrical activation of the heart begins in the SA node . The normal heart rhythm, with electrical activation beginning in the SA node, is called ‘ Sinus rhythm

10. RECORDING AN ECG Think of a lead as pieces of wires that connect the patient to the ECG recorder but in essence a lead is an electrical picture of the heart The electrical activity of the heart is detected at the surface of the body through 5 electrodes which are joined to the ECG recorder by wires. One electrode is attached to each limb and one is held by suction to the front of the chest and moved to different position. (good contact is necessary with chest-shave the chest)

11. LEADS • A lead can either be bipolar or unipolar. • A lead composed of 2 electrodes of opposite polarity (one positive and one negative or reference point) is called a bipolar lead. • A lead composed of a single positive electrode and a reference point is a unipolar lead An ECG tracing looks different in each lead because the recorded angle of electrical activity changes with each lead . • Several different angles allow a more accurate perspective than a single one would. • In most hospital a 12 lead ECG (12 views) is used with

12. LEADS • Standard Limb leads (bipolar): I, II, III • Augmented Limb leads: IV ( aVR ), V ( aVL ), VI ( aVF ) • Unipolar Chest leads: V1-V6

13. AXISES ON THE ECG • In order to interpret the 12-lead EKG you must have an understanding of the electrical activity of the heart • The direction in which the impulses flow in the heart is important. • The 12 different leads pick up those impulses as they travel in many different directions through the heart.

14. ECG WAVE DERIVATION • Every lead represents a different electrical potential measured in 2 points in space. • Some leads use 2 electrodes: an exploring (positive ) and the other as reference (negative) • In some leads the references is a combination of 2 or 3 electrodes. If the depolarizing current heads towards the exploring lead it yields a positive wave/deflection and vice versa

15. NORMAL FRONTAL PLANE AXIS • The limb leads, of which there are 6 (I, II, III, aVF , aVR , and aVL ) have the exploring electrode and the reference point placed in the frontal plane. • These leads are therefore excellent for detecting vectors traveling in the frontal plane. • The chest (precordial) leads (V1, V2, V3, V4, V5 and V6) have the exploring electrodes located anteriorly on the chest wall and the references point located inside the chest . • The chest leads are excellent for detecting vectors traveling in the horizontal plane.

16. NOTE • The limb leads, of which there are 6 (I, II, III, aVF , aVR , and aVL ) have the exploring electrode and the reference point placed in the frontal plane. • These leads are therefore excellent for detecting vectors traveling in the frontal plane. • The chest (precordial) leads (V1, V2, V3, V4, V5 and V6) have the exploring electrodes located anteriorly on the chest wall and the references point located inside the chest. • The chest leads are excellent for detecting vectors traveling in the horizontal plane.

17. STANDARD LIMB LEADS- BIPOLAR • They consist of 2 electrodes of opposite polarity (negative and positive) and 1 ground electrode that minimizes electrical activity from other sources. • Leads include: • Lead I • Lead II • Lead III STANDARD LIMB LEADS • Electrodes are placed on the right arm (RA ), left arm (LA) and left leg . • Augmented limb leads are also connected in these same positions

18. STANDARD LIMB LEADS- BIPOLAR LEAD I Lead I: RA-negative, LA- positive • Lead I records electrical differences between the left and right arm electrodes . • This represents the left lateral view. LEAD II • The positive electrode is connected to the left leg and the negative electrode to the right arm. • Lead II records electrical differences between the left leg and the right arm electrodes. • This represents the inferior left lateral view of the heart.

19. STANDARD LIMB LEADS- BIPOLAR LEAD III • The positive electrode is connected to the left leg and the negative electrode is connected to the left arm. • This lead records the electrical difference between the left leg and left arm electrodes • This represents the inferior right lateral view of the heart.

20. When we combine the 3 limb leads I, II, and III

21. AUGMENTED LIMB LEADS • Have a single positive electrode and a reference point (with zero electrical potential) that lies in the center of the heart’s electrical field • Consists of: • aVF • aVL • aVR

22. AUGMENTED VECTOR RIGHT (AVR) • The positive electrode is connected to the right shoulder • Remember the “R” for right. • This looks at the right lateral side of the heart (150 degrees )

23. AUGMENTED VECTOR LEFT-AVL • The positive electrode is connected to the left shoulder • Remember the “L” for left. • This looks at the lateral side of the heart

24. AUGMENTED VECTOR FOOT-AVF • The positive electrode is connected to the left foot • Remember the “F” for foot. • This looks at the inferior view of the heart

25. AUGMENTED LIMB LEADS • When we combine the augmented limb leads

26. CHEST LEADS

27. HEXAXIAL REFERENCE SYSTEM • This represents the frontal plan. • The frontal plane only means that the patient is in anatomical position and facing you. Therefore, the patient’s left side is on your right • The 6 limb leads look at the heart from a 360 degrees point of view. Because of this you can pinpoint the location of any conduction defect in the heart.

28. THE ECG PAPER The ECG presents one diagram for each lead. • Voltage is on the vertical (Y-axis) and time is on the horizontal (X-axis). • Voltage is in millivolts (mV) and time is usually in seconds

29. COMPONENTS OF AN ECG • The P, Q, R, S and T deflections are called waves. • Sometimes there may be a U wave. • The Q, R, and S waves together make up a complex. • The interval between the S wave and the T wave is called the ST segment • Waves: • P wave • T wave • U wave Intervals: • PR interval • QRS complex/Interval • QT interval Segments: ST segment

30. COMPONENTS OF AN ECG

31. 12-LEAD ECG • Leads I, aVR and a VL are lateral limb leads , they look at the lateral surface of the left ventricle . • Leads II, III and aVF look at the inferior surface of the heart (left ventricle). They are inferior limb leads • Leads V1 and V2 look at the right ventricles and ventricular septum • Leads V3 and V4 look at the anterior wall of the left ventricle • Leads V5 and V6 look at the anterior and lateral walls of the left ventricle .

32. PACEMAKERS OF THE HEART • SA Node- dominant pacemaker with an intrinsic rate 60-100b/min • AV node- back-up pacemaker with an intrinsic rate of 40-60b/min • Ventricular cells- Back-up pacemaker with an intrinsic rate of 20-45 b/min . NORMAL SINUS RHYTHM • SA Node=> Internodal tracts=>Atrium=> AV node => Bundle of His=> Left and right bundle branches => Purkinje fibers • Normal timings and delays

33. P WAVE • This is the first wave seen. It is a small rounded wave. • It is directed inferiorly and therefore The P wave is upright in leads I, II, and aVF but is inverted in lead aVR . • The P wave is typically biphasic in lead V1 ( positivenegative ) but when the negative terminal component of the P wave exceeds 0.04s in duration (1 small box) it is abnormal . • Normal duration <120ms (3mm or 3 small boxes) • Normal amplitude <2.5 mm (2 and a half small boxes) • P waves can be bifid, inverted, absent or peaked

34. PR/PQ INTERVAL • This is the time from depolarization of the SA node to the onset of ventricular depolarization. • Recall there is a delay in conduction of the impulse to the AV node . • It measures the time during which a depolarization wave travels from the atria to the ventricles • It is from the beginning of the P wave to the first part of the QRS complex • Normal duration is 0.12 to 0.20 s (3 to 5 small boxes) • It can shorten (2 possibilities-ectopic or accessory bundle) or lengthen (heart block)

35. QRS COMPLEX • The QRS duration represents the time for ventricular depolarization. • The first deflection is downward and is called the Q wave. An upward deflection is called an R wave (Whether it is preceded by a Q wave or not) • Any deflection below the baseline following an R wave is called an S wave (whether there has been a preceding Q wave or not) • The duration is normally 0.06 to 0.12 seconds (< 3 small squares). An abnormality of conduction takes longer and causes a widened QRS complex. • Amplitude varies with age, race, and cardiac pathology and it should increase across the precordium from leads V1-V5.

36. QRS COMPLEX IN CHEST LEADS • Shape is determined by: • Septum between the ventricles is depolarized before the walls of the ventricle and the depolarization wave spreads across the septum from left to right • In normal heart there is more muscle in the walls of the left ventricle than in the right ventricle and so the left ventricle exerts more influence on the ECG pattern than the right

37. QRS COMPLEXES IN THE CHEST LEADS • Recall leads V1 and V2 look at the right ventricle, Lead V3 and V4 look at the septum and leads V5 and V6 at the left ventricle. • In the right ventricular lead the deflection is first upwards (R wave) as the septum is depolarized (there is no Q wave). • In a left ventricular lead the opposite pattern is seen. There is a small downward deflection (Septal Q wave). • In a right ventricular lead (V1 and V2) there is then a downward deflection (S wave) as the main muscle mass is depolarized. • The electrical effects in the bigger left ventricle (in which depolarization is spreading away from a right ventricular lead) outweighing those in the smaller right ventricle (in which depolarization is moving towards a right ventricular lead)

38. QRS COMPLEXES IN THE CHEST LEADS • In a left ventricular lead, there is an upward deflection (R wave) as the ventricular muscles is depolarized . • When the whole of the myocardium is depolarized the ECG returns to baseline • The QRS complex in the chest leads shows a progression from V1 where it is predominantly downwards to V6 where it is predominantly upwards

39. ST SEGMENT • The ST segment is the interval between ventricular depolarization and ventricular repolarization. • It is identified at the end of the QRS complex to the beginning of the T wave. • The end of the T wave to the beginning of the P wave is called the TP segment. • The ST segment is at the isoelectric point. • The J point is located at the junction between the end of the QRS complex and the beginning of the ST segment. J-point elevation is known as an Osborne wave it represents distortion of the earliest phase of membrane repolarization and is associated with hypothermia

40. T WAVES • It is rounded (upright) positive wave following the QRS in most leads. • T wave is positive in all leads except aVR , aVL , III and V1 • It represents ventricular repolarization. • T wave inversions from V1 to V4 in children are normal. • In adults T wave inversions are less commonly found but can be normal from V1 to V3. The depth of the T wave also becomes progressively shallow from one to the next lead. • The height of the T wave should not exceed 5mm (5 small boxes) in limb leads and more than 10mm in precordial leads (10 small boxes)

41. U WAVES • The is a small rounded, upright wave following the T wave. • Most easily seen with a slow heart rate • Represents repolarization of purkinje fibers

42. QT INTERVAL • Measured from the beginning of the QRS to the end of the T wave • It represents total ventricular activity. • QT prolongation is associated with development of ventricular arrhythmias and sudden death. Commonly caused by many medications • The QT interval depends on the heart rate. • Fast heart rate= short QT interval, Slow heart rate= Longer QT interval • A corrected QT interval ( QTc ) corrects for the variations in heart rate. • QTcb is the QT interval divided by the square root of the RR interval when using the Bazett formula. The normal value of the QTcb in men is 0.44 s or less and 0.46 or less in women

43. INTERPRETATION OF THE ECG Rate Rhythm Wave, segments and intervals Axis Hypertrophy Ischemia and infarction

44. RATE • Normal= 60-100b/min • Tachycardia >100b/min • Bradycardia <60 b/min OR Shortcut • If R-R 3-5 big boxes (15-25 small boxes): normal • If R-R <3 big boxes (15 small boxes): tachycardia • If R-R >5 big boxes (25 small boxes): bradycardia

45. How to calculate rate on ECG Paper speed 25 mm/sec Each large square(5mm) =0.20 sec ( small square 1 mm = 0.04 sec)

46. RATE Heart can be fast, slow or normal Two methods are used box method and R-wave Box method • Count the number of large/small squares present within one R-R interval • Rate= 300 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑏𝑖𝑔 𝑏𝑜𝑥𝑒𝑠 or 1500 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑠𝑚𝑎𝑙𝑙 𝑏𝑜𝑥𝑒𝑠 • Example: if 4 large boxes are present in the R-R interval the rate= 300/4= 75 beats per minute • Using 1500 is a more accurate way

47. RATE R- WAVE METHOD Count the number of R-wave in a lead the multiply by 6 E.G

48. RHYTHM Rhythm can either be regular or irregular • Irregular rhythms can either be: • Regular irregular (i.e. a recurrent pattern of irregularity) • Irregular irregular (i.e. completely disorganized-chaos) • To determine this, mark out several consecutive R-R or PP intervals on a piece of paper, then move them along the rhythm strip to check if the subsequent intervals are the same (check on lead II)

49. HEART Rhythm • Absent P waves with “irregularly irregular” QRS complexes=> Atrial fibrillation

50. INCREASED HEART RATE • Absent P waves with Wide QRS complex and fast heart rate=> Ventricular tachycardia

51. INCREASED HEART RATE • A “Saw tooth” pattern with QRS complexes => Atrial flutter

52. INCREASED HEART RATE • A “Sine wave pattern”=> Ventricular flutter

53. CONDUCTION PROBLEMS • Interference with the conduction process causes the ECG phenomenon called ‘ heart block’ • Heart block • Bundle branch block- Left and right • Fascicular block

54. FIRST DEGREE HEART BLOCK • Each wave of depolarization that originates in the SA node is conducted to the ventricle but there is a delay somewhere along the conduction pathway. • The PR interval is prolonged. • First degree heart block is not in itself important , but it may be a sign of coronary artery disease, acute rheumatic carditis , digoxin toxicity or electrolyte disturbances.

55. FIRST DEGREE HEART BLOCK-LEADII • Rhythm: regular (there is 1 P wave per QRS complex ) • P waves: normal (upright and uniform) • PR interval: Prolonged (>0.20s/ 5 squares) • QRS: normal (1-3 squares)

56. SECOND DEGREE HEART BLOCK • Some excitation completely fails to pass through the AV node or the bundle of HIS. • When this occurs intermittently this is called 2nd degree heart block. • There are 3 variations • Morbitz Type 1 (WENCKBACH PHENOMENON) • Morbitz Type 2 • Alternate conducted and non-conducted atrial beats The causes are the same as first degree block. • It usually indicates heart disease often acute myocardial infarction

57. MORBITZ TYPE 1 (WENCKEBACH PHENOMENON) • There is a progressive lengthening of the PR interval and then failure of conduction of an atrial beat, followed by a conducted beat with a shorter PR interval and then a repetition of this cycle .

58. MORBITZ TYPE 2 • Most beats are conducted with a constant PR interval but occasionally there is an atrial contraction without a subsequent ventricular contraction . • PR interval is fixed but there are dropped beats (QRS complex)

59. SECOND DEGREE

60. • Rate atrial rate (usually 60-100b/min) and is faster than ventricular rate • Rhythm: atrial is regular and ventricular irregular • P waves: normal (upright and uniform), more P waves than QRS complexes • PR interval: Normal or prolonged but constant • QRS: usually wide (>0.10 sec)

61. THIRD DEGREE HEART BLOCK • This is also known as complete heart block. • Atrial contraction is normal but no beats are conducted to the ventricles. • When this occurs the ventricles are excited by a slow ‘Escape mechanism’ from a depolarizing focus within the ventricular muscle • Complete block is not always immediately obvious on a 12 lead ECG, where there may be only a few QRS complexes per lead. YOU HAVE TO LOOK AT THE PR INTERVAL IN ALL THE LEADS • Complete heart block occurs as an acute phenomenon in patients with myocardial infarction (when it is usually transient) or it may be a chronic state usually due to fibrosis around the bundle of HIS • It may also be caused by the blockage of both bundle branches

62. THIRD DEGREE P wave rate 90/min • QRS complex rate 36/min • No relationship between P wave and QRS complexes • Abnormally-shaped QRS complexes because of abnormal spread of depolarization from a ventricular focus

63. THIRD DEGREE 3RD degree heart block always indicates conducting tissue disease- more often fibrosis.

64. BUNDLE BRANCH BLOCK • The depolarization wave reaches the interventericular septum normally therefore, the PR interval is normal. • If there is abnormal conduction through either right or left bundle branches (‘Bundle branch block ’) there will be a delay in the depolarization of pat of the ventricular muscle. • The extra time taken for depolarization of the whole of the ventricular muscle causes widening of the QRS complex.

65. • In a normal heart, the time taken for the depolarization wave to spread from the interventricular septum to the furthest part of the ventricles is less than 120 ms (3 squares). • If the QRS complex duration >120ms then conduction within the ventricles must have occurred by an abnormal and therefore slow pathway . • Block of both bundle branches has the same effect as block of the His bundle, and causes complete (3rd degree heart block ) • Bundle branch can either be • Right bundle branch block (RBBB) • Left bundle branch block (LBBB)

66. RIGHT BUNDLE BRANCH BLOCK (RBBB) • Often indicates problems in the right side of the heart but RBBB patterns with a QRS complex of normal duration are quite common in health people (recall the left ventricle contributes to the majority of the QRS complex) • In RBBB there is conduction down the right bundle branch but the septum is depolarized from the left side as usual causing an R wave in the right ventricular lead (V1) and a small Q wave in a left ventricular lead (V6) • It takes longer than in a normal heart for excitation to reach the right ventricle because of the failure of the normal conducting pathway. • The right ventricle therefore depolarizes after the left . This causes a second R wave (R’) in lead V1 and a wide and deep S wave in lead V6. • An RSR’ pattern but with a normal wideth QRS complex is sometimes called partial right bundle branch block. It is of rare clinical significance as itis considered a normal variant.

67. RBBB-2ND STAGE AND 3RD STAGE

68. SINUS RHYTHM WITH RBBB • Sinus rhythm, rate 75b/min • Normal PR interval • Normal cardiac axis • Wide QRS complex (160ms ) • RSR’ pattern in lead V1 and deep, wide S waves in lead V6 • Normal ST segments and T waves

69. LEFT BUNDLE BRANCH BLOCK-LBBB • The conduction of the impulse down the left bundle branch fails. • LBBB is always an indication of heart disease, usually of the left side. • The septum becomes depolarized from right to the left causing a small Q wave in lead V1 and an R wave in lead V6 • Subsequent depolarization of the left ventricle cause an S wave in lead V1 and another R wave in lead V6 LBBB is associated with T wave inversion in the lateral leads (I, V2 and V5-V6 ) • Causes could aortic stenosis and ischemic disease. • A patient has recently had severe chest pain , LBBB may indicate an acute myocardial infarction and thrombolysis should be considered

70. LBBB

71. SUMMARY • RBBB • Best seen in lead V1 where there is an RSR’ pattern • LBBB • Best seen in lead V6 where there is a broad complex with a notched top, which resembles the letter ‘M’ and thus known as an ‘M pattern’ • The complete picture with a ‘W’ pattern in lead V1 is often not fully developed.

72. RHYTHM ABNORMALITIES when the depolarization begins in the SA node the heart is said to be in sinus rhythm . Rhythm occurring from these other places is referred to as an “arrhythmia”. • Abnormalities in P waves and the width of the QRS complexes rhythm probloms • Atrial contraction is associated with the P wave of the ECG • Ventricular contraction is associated with the QRS complex • Atrial contraction normally precedes ventricular contraction and there is normally 1 atrial contraction per ventricular contraction (equal P waves and QRS complexes )

73. Abnormal cardiac rhythms can begin in 3 places • Atrial muscle • Region around the AV node (nodal or junctional ) • Ventricular muscle • These can be divided into Supraventricular rhythms (sinus rhythm, Atrial rhythm and junctional rhythm) and Ventricular rhythms

74. SUPRAVENTRICULAR RHYTHMS • Sinus rhythm, atrial rhythm and junctional rhythm together constitute ‘Supraventricular’ rhythms. • The depolarization wave spreads to the ventricles in the normal way via the His bundle and its branches . • The QRS complex is therefore normal and is the same whether depolarization was initiated by the SA node, atrial muscle or the junctional region

75. IMAGE

76. VENTRICULAR RHYTHMS • Depolarization wave spreads through the ventricles by an abnormal, and therefore slower, pathway through the purkinje fibers. • The QRS complex is wide and abnormal. • Repolarization is also abnormal so the T wave is of abnormal shape.

77. IMAGE

78. SUMMARY • Supraventricular rhythms have narrow QRS complexes . • Ventricular rhythms have wide QRS complexes • The only exception to this rule occurs when there is a supraventricular rhythm with right or left bundle branch block.

79. ABNORMALITIES OF P-QRS-T WAVES • When interpreting an ECG, first identify the rhythm • Are there any abnormalities of the P wave? • What is the cardiac axis (look at the QRS complex in leads I, II, III and aVF ) • Is the QRS complex of normal duration? • Are there any abnormalities in the QRS complex particularly , are there any abnormal Q waves? • Is the ST segment raised or depressed? • Is the T wave normal?

80. • The P wave can be normal, unusually tall or unusually broad. • The QRS complex can only have 3 abnormalities- too broad, too tall and it may contain an abnormal Q wave • The ST segment can be normal, elevated or depressed • The T wave can be upright, peaked or inverted

81. ABNORMALITIES OF THE P WAVE • Apart from alterations of the shape of the P wave associated with rhythm changes there are 2 important abnormalities: • Anything that causes the right atrium to become hypertrophied (e.g. tricuspid valve stenosis or pulmonary hypertension) causes the P wave to become peaked • Left atrial hypertrophy (usually due to mitral stenosis ) causes a broad and bifid P wave

82. ATRIAL HYPERTROPHY Atrial hypertrophy can be diagnosed from the contour of the P waves seen best in lead II. RIGHT ATRIAL HYPERTROPHY • In right atrial hypertrophy the initial component is prominent. The P wave is tall and peaked in lead II (>2 and a half small squares). It is common with pulmonary hypertension (P- pulmonale )

83. IMAGE

84. LEFT ATRIAL HYPERTROPHY • In left atrial hypertrophy the second component is delayed and prominent producing a wide (>2 and a half squares) and notched P wave ( Pmitrale -common in mitral valve disease)

85. BIATRIAL HYPERTROPHY Tall and broad P waves (>2 and a half small squares )

86. BIATRIAL HYPERTROPHY

87. SUMMARY

88. ABNORMALITIES OF THE QRS COMPLEX ABNORMALITIES OF THE WIDTH OF THE QRS COMPLEX • QRS complexes are abnormally wide in the presence of bundle branch block or when depolarization is initiated by a focus in the ventricular muscle causing ventricular escape beats . • In either case, the increased width indicates that depolarization has spread through the ventricles by an abnormal and therefore slow pathway .

89. INCREASED HEIGHT OF THE QRS COMPLEX • An increase of muscle mass in either ventricle will leads to increased electrical activity and to an increase in the height of the QRS complex. • Ventricular hypertrophy is diagnosed from the pattern and amplitude of the QRS complexes in the chest leads V1 to V6 • S wave in right sided chest leads disappears as you progress from V1 to V6 • R-S wave are roughly equal in V4 • R wave progressively increases from V1-V6

90. IMAGE

91. LEFT VENTRICULAR HYPERTROPHY • Pattern from V1 to V 6 (normal R-S wave progression) remains the same but amplitude increases. • In LVH there are deep S waves in V1 and V2, R-S waves equal in V3, very tall R waves in V5 and V6. • Measure amplitude of S wave in V1 or V2 (whichever is larger) and amplitude of V5 and V6 whichever is larger ➢ SV1> 25mm or RV6 > 25mm or SV1 + RV6 >35 then there is LVH • It is usually associated with LAD and P mitrale of left atrial hypertrophy in lead II • In significant hypertrophy there are also inverted T waves in leads I, aVL , V5 and V6 and sometimes V4

92. IMAGE Tall R- wave in leads v5,v6 & deep s waves in v1, v2 inverted t wave in lead i , ii, v5 v6

93. RIGHT VENTRICULAR HYPERTROPHY • Patterns of the QRS complexes in chest leads is changed. • V1 and V2 shows a prominent R wave. Leads V3 and V4 are similar with equal R and S waves . Lead V5 shows a deep S wave and leads V6 shows a prominent S wave. Deep s waves & dominant R-waves in lead I Deep s waves in lead v6(clockwise rotation) Inverted T-waves in I-III, avF , v1-v4

94. RIGHT VENTRICULAR HYPERTROPHY

95. PULMONARY EMBOLISM • ECG may show features of RVH although in many cases there is nothing abnormal other than a sinus tachycardia • Peaked P waves • RAD (S waves in lead I) • Tall R waves in lead V1 • RBBB • Inverted T waves in lead V1 (normal), spreading across to lead V2 or V3 • A shift of transition point to the left so that the R wave equals the S wave in lead V5 or V6 rather than in lead V3 or V4 (clockwise rotation). A deep S wave persists in lead V6 • A Q wave in lead III resembling an inferior infarction is seen.

96. Q WAVES • Q waves >1 small square in width and at least 2mm deep therefore indicate a MI, and the leads in which the Q wave appears give some indication of the part of the heart that has been damaged. • Thus infarction of the anterior wall of the left ventricle causes a Q wave in the leads looking at the heart from the front V3-V4 or V5. • If the infarction involves both the anterior and lateral surfaces of the heart, a Q wave will be present in leads V3 and V4 and in the leads that look at the lateral surface- I, aVL , and V5-V6 • The presence of a Q wave does not give any indication of the age of an infarction because once a Q wave has developed it is usually permanent.

97. IMAGE

98. ABNORMALITIES OF THE ST SEGMENT • The ST segment lies between the QRS complex and the T wave • It should be ‘isoelectric’- that is, at the same level as the part between the T wave and the next P wave but it may be elevated or depressed . • Elevation of the ST segment is an indication of acute Myocardial injury usually due either to a recent infarction or to pericarditis. • The leads in which the elevation occurs indicate the part of the heart that is damaged- anterior damage shows in the V leads and inferior damage in leads III and aVF • Pericarditis is not usually a localized affair and so it causes ST elevation in most leads

99. IMAGE

100. • Horizontal depression of the ST segment, associated with an upright T wave, is usually a sign of ischemia as opposed to infarction. • When the ECG at rest is normal ST segment depression may appear during exercise, particularly when effort induces angina. • Down sloping as opposed to horizontally depressed ST segments are usually due to treatment with digoxin

101. IMAGE

102. ABNORMALITIES OF THE T WAVE • T wave inversion is seen in • Normality • Ischemia • Ventricular hypertrophy • RBBB • Digoxin treatment • Leads adjacent to those showing inverted T waves sometimes show ‘biphasic’ T waves-initially upright and then inverted.

103. NORMALITY • T wave is normally inverted in laeds aVR and V1 (and in lead V2 in young people and also in lead V3 in some black people).

104. ISCHEMIA • After a MI, the first abnormality seen on the ECG is elevation of the St segment. • Subsequent Q waves appears and T waves become inverted • The ST segment returns to the baseline, the whole process taking a variable time but usually within the range of 24-48 hours. • T wave inversion is often permanent • If an infarction is not full thickness and does not cause an electrical window there will be T wave inversion but no Q waves (Non-Q wave infarction pattern). Sometime called a subendocardial infarction (often not pathologically correct though).

105. IMAGE

106. VENTRICULAR HYPERTROPHY • LVH causes inverted T waves in leads looking at the left ventricle (V5, V6, II and aVL ) • RVH causes T wave inversion in the leads looking at the RV (T wave inversion is normal in lead V1 but in white adults is abnormal in leads V2 or V3)

107. BBB • The abnormal path of depolarization in bundle branch block is usually associated with an abnormal path of repolarization • Inverted T waves associated with QRS complexes which have a duration of 160ms or more have no significance in themselves.

108. DIGOXIN • Digoxin causes T wave inversion characteristically with slopping depression of the ST segment • It is helpful to record an ECG before giving digoxin to save later confusion about the significance of T wave changes

109. OTHER ST-T ABNORMALITIES • Electrolyte abnormalities • Hypokalemia: T wave flattening and the appearance of a hump on the end of the T wave (U wave) • Hyperkalemia: Peaked T waves with disappearance of the ST segment. Widened QRS complex (similar effects with magnesium) • Hypocalcemia: prolongation of QT interval • Hypercalcemia: shortened QT interval