Basics of ECG

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Basics of Electrocardiography : 

1 Basics of Electrocardiography Dr. Annapoorna Kalia Associate Consultant Dept. of Cardiology

Cardiac Impulse : 

2 2 Cardiac Impulse

Cardiac Impulse : 

3 Cardiac Impulse Cardiac impulse originates in the SA node Traverses the atria simultaneously – no special conduction wires in atria – so the delay Reaches AV node – the check post – so delay Enters bundle of His and branches – through specialized conducting wires called Purkinje network - activates both ventricles – quick QRS First the septum from L to R, then right ventricle and then the left ventricle and finally the apex Then the ventricles recover for next impulse

Cardiac Conduction : 

4 4 Cardiac Conduction

Important Precautions : 

5 Important Precautions Correct Lead placement and good contact Proper earth connection, avoid other gadgets Deep inspiration record of L3, aVF Compare serial ECGs if available Relate the changes to Age, Sex, Clinical history Consider the co-morbidities that may effect ECG Make a xerox copy of the record for future use Interpret systematically to avoid errors

ECG Complex : 

6 ECG Complex P wave PR Interval QRS complex ST segment T Wave QT Interval RR Interval

ECG Complex : 

7 ECG Complex P Wave is Atrial contraction – Normal 0.12 sec PR interval is from the beginning of P wave to the beginning of QRS – Normal up to 0.2 sec QRS is Ventricular contraction –Normal 0.08 sec ST segment – Normal Isoelectic (electric silence) QT Interval – From the beginning of QRS to the end of T wave – Normal – 0.40 sec RR Interval – One Cardiac cycle 0.80 sec

Slide 8: 

8 + + + - - - ECG Bipolar Limb Leads R L F R F L

Slide 9: 

9 Standard ECG is recorded in 12 leads Six Limb leads – L1, L2, L3, aVR, aVL, aVF Six Chest Leads – V1 V2 V3 V4 V5 and V6 L1, L2 and L3 are called bipolar leads L1 between LA and RA L2 between LF and RA L3 between LF and LA ECG Bipolar Limb Leads

Slide 10: 

10 ECG Unipolar Limb Leads + + + Lead aVR Lead aVL Lead aVF R L F

Slide 11: 

11 Standard ECG is recorded in 12 leads Six Limb leads – L1, L2, L3, aVR, aVL, aVF Six Chest Leads – V1 V2 V3 V4 V5 and V6 aVR, aVL, aVF are called unipolar leads aVR – from Right Arm Positive aVL – from Left Arm Positive aVF – from Left Foot Positive ECG Unipolar Limb Leads

ECG Chest Leads : 

12 12 ECG Chest Leads

ECG Chest Leads : 

13 Precardial (chest) Lead Position V1 Fourth ICS, right sternal border V2 Fourth ICS, left sternal border V3 Equidistant between V2 and V4 V4 Fifth ICS, left Mid clavicular Line V5 Fifth ICS Left anterior axillary line V6 Fifth ICS Left mid axillary line ECG Chest Leads

The Six Chest Leads : 

14 The Six Chest Leads TRANSVERSE PLANE

ECG Graph Paper : 

15 ECG Graph Paper X- Axis time in seconds Y- Axis Amplitude in mill volts

Slide 16: 

16 16 X-Axis represents time - Scale X-Axis – 1 mm = 0.04 sec Y-Axis represents voltage - Scale Y-Axis – 1 mm = 0.1 mV One big square on X-Axis = 0.2 sec (big box) Two big squares on Y-Axis = 1 milli volt (mV) Each small square is 0.04 sec (1 mm in size) Each big square on the ECG represents 5 small squares = 0.04 x 5 = 0.2 seconds 5 such big squares = 0.2 x 5 = 1sec = 25 mm One second is 25 mm or 5 big squares One minute is 5 x 60 = 300 big squares ECG Graph Paper

Rate Determination : 

17 17 Next QRS Rate Determination QRS

Rate Determination : 

18 BRADY T ACHY NORMA L Rate Determination

What is the Heart Rate ? : 

19 19 What is the Heart Rate ? Answer on next slide

What is the Heart Rate ? : 

20 To find out the heart rate we need to know The R-R interval in terms of # of big squares If the R-R intervals are constant In this ECG the R-R intervals are constant R-R are approximately 3 big squares apart So the heart rate is 300 ÷ 3 = 100 What is the Heart Rate ?

What is the Heart Rate ? : 

21 21 What is the Heart Rate ? Answer on next slide

What is the Heart Rate ? : 

22 To find out the heart rate we need to know The R-R interval in terms of # of big squares If the R-R intervals are constant In this ECG the R-R intervals are constant R-R are approximately 4.5 big squares apart So the heart rate is 300 ÷ 4.5 = 67 What is the Heart Rate ?

What is the Heart Rate ? : 

23 23 What is the Heart Rate ? Answer on next slide

What is the Heart Rate ? : 

24 To find out the heart rate we need to know The R-R interval in terms of # of Big Squares If the R-R intervals are constant In this ECG the R-R intervals are not constant R-R are varying from 2 boxes to 3 boxes It is an irregular rhythm – Sinus arrhythmia Heart rate is 300 ÷ 2 to 3 = 150 to 100 approx What is the Heart Rate ?

QRS Axis : 

25 25 QRS Axis SE NE NW SW

QRS Axis : 

26 QRS Axis The QRS electrical (vector) axis can have 4 directions Normal Axis - when it is downward and to the left – southeast quadrant – from -30 to +90 degrees Right Axis – when it is downward and to the right – southwest quadrant – from +90 to 180 degrees Left Axis – when it is upward and to the left – Northeast quadrant –from -30 to -90 degrees Indeterminate Axis – when it is upward & to the right – Northwest quadrant – from -90 to +180

Axis Determination : 

27 27 Axis Determination NORMAL RIGHT LEFT MEET LEAVE ALL UPRIGHT

Axis Determination : 

28 Axis Determination

Slide 29: 

29 29 What is the Axis ?

ECG With Normal Axis : 

30 ECG With Normal Axis Note the QRS voltages are positive and upright in the leads - L1, L2, L3 and aVF L2, L3 and aVF tell that it is downward L1, aVL tell that it is to the left Downward and leftward is Normal Axis Normal QRS axis

Slide 31: 

31 31 LEAD 1 LEAD 2 LEAD 3 What is the Axis ?

ECG With Right Axis : 

32 ECG With Right Axis Note the QRS voltages are positive and upright in leads L2, L3 Negative in Lead 1 L2, L3 tell that it is downward L1 tells that it is not to the left but to right Downward and rightward is Right Axis See the Right –Meet criterion QRS in L1 and L3 meet Right Axis Deviation - RAD

Slide 33: 

33 33 LEAD 1 LEAD 2 LEAD 3 aVR aVL aVF What is the Axis ?

ECG With Left Axis : 

34 ECG With Left Axis Note the QRS voltages are positive and upright in leads L1and aVL Negative in L2, L3 and aVF L1, aVL tell that it is leftward L2, L3, and aVF tell that it is not down ward - instead it is upward Upward and Leftward is Left Axis See the Left - Leave criterion QRS in L1 and L3 leave each other Left Axis Deviation - LAD

Normal ECG : 

35 35 Normal ECG

Normal ECG : 

36 Normal ECG Standardization – 10 mm (2 boxes) = 1 mV Double and half standardization if required Sinus Rhythm – Each P followed by QRS, R-R constant P waves – always examine for in L2, V1, L1 QRS positive in L1, L2, L3, aVF and aVL. – Neg in aVR QRS is < 0.08 narrow, Q in V5, V6 < 0.04, < 3 mm R wave progression from V1 to V6, QT interval < 0.4 Axis normal – L1, L3, and aVF all will be positive ST Isoelectric, T waves ↑, Normal T↓ in aVR,V1, V2

Pediatric ECG : 

37 37 Pediatric ECG

Pediatric ECG : 

38 This is the ECG of a 6 year old child Heart rate is 100 – Normal for the age See V1 + V5 R >> 35 – Not LVH – Normal T↓ in V1, V2, V3 – Normal in child Base line disturbances in V5, V6 – due to movement by child Pediatric ECG

Juvenile ECG : 

39 Juvenile ECG

Be aware of normal ECG : 

40 40 Be aware of normal ECG Normal Resting ECG – cannot exclude disease Ischemia may be covert – supply / demand equation Changes of MI take some time to develop in ECG Mild Ventricular hypertrophy - not detectable in ECG Some of the ECG abnormalities are non specific Single ECG cannot give progress – Need serial ECGs ECG changes not always correlate with Angio results Paroxysmal events will be missed in single ECG

Normal Variations in ECG : 

41 Normal Variations in ECG May have slight left axis due to rotation of heart May have high voltage QRS – simulating LVH Mild slurring of QRS but duration < 0.09 J point depression, early repolarization T inversions in V2, V3 and V4 – Juvenile T ↓ Similarly in women also T↓ Low voltages in obese women and men Non cardiac causes of ECG changes may occur

Early Repolarization : 

42 Early Repolarization This ECG has all normal features The ST-T (J) Junction point is elevated. T waves are tall, May be inverted in LIII, The ST segment initial portion is concave. This does not signify Ischemia

Pseudo Normalization : 

43 43 Pseudo Normalization Before Chest pain During Chest pain Chest pain Relieved T↓ T↓ T↑

Atrial Waves : 

44 44 Atrial Waves

Left Atrial Enlargement : 

45 45 Left Atrial Enlargement

Left Atrial Enlargement : 

46 46 Left Atrial Enlargement P wave duration is 4 boxes-0.04 x 4 = 0.16

Left Atrial Enlargement : 

47 Always examine V 1 and Lead 1 for LAE Biphasic P Waves, Prolonged P waves P wave 0.16 sec, ↑ Downward component Systemic Hypertension, MS and or MR Aortic Stenosis and Regurgitation Left ventricular hypertrophy with dysfunction Atrial Septal Defect with R to L shunt Left Atrial Enlargement

Right Atrial Enlargement : 

48 48 Right Atrial Enlargement

Right Atrial Enlargement : 

49 49 Right Atrial Enlargement P wave voltage is 4 boxes or 4 mm

Right Atrial Enlargement : 

50 Always examine Lead 2 for RAE Tall Peaked P Waves, Arrow head P waves Amplitude is 4 mm ( 0.4 mV) - abnormal Pulmonary Hypertension, Mitral Stenosis Tricuspid Stenosis, Regurgitation Pulmonary Valvular Stenosis Pulmonary Embolism Atrial Septal Defect with L to R shunt Right Atrial Enlargement

Ventricular Hypertrophy : 

51 51 Ventricular Hypertrophy Ventricular Muscle Hypertrophy QRS voltages in V1 and V6, L 1 and aVL We may have to record to ½ standardization T wave changes opposite to QRS direction Associated Axis shifts Associated Atrial hypertrophy

Right Ventricular Hypertrophy : 

52 52 Right Ventricular Hypertrophy

Right Ventricular Hypertrophy : 

53 Tall R in V1 with R >> S, or R/S ratio > 1 Deep S waves in V4, V5 and V6 The DD is RVH, Posterior MI, Anti-clock wise rotation of Heart Associated Right Axis Deviation, RAE Deep T inversions in V1, V2 and V3 Absence of Inferior MI Right Ventricular Hypertrophy

Slide 54: 

54 54 Is there any hypertrophy ?

Slide 55: 

55 Criteria and Causes of RVH Criteria of RVH Tall R in V1 with R >> S, or R/S ratio > 1 Deep S waves in V4, V5 and V6 The DD is RVH, Posterior MI, Rotation Associated Right Axis Deviation, RAE Deep T inversion in V1, V2 and V3 Cause of RVH Long standing Mitral Stenosis Pulmonary Hypertension of any cause VSD or ASD with initial L to R shunt Congenital heart with RV over load Tricuspid regurgitation, Pulmonary stenosis

Slide 56: 

56 56 What is in this ECG ?

ECG OF MS with RVH, RAE : 

57 ECG OF MS with RVH, RAE Classical changes seen are Right ventricular hypertrophy Right axis deviation Right Bundle Branch Block P – Pulmonale - Right Atrial enlargement P – Mitrale – Left Atrial enlargement If Atrial Fibrillation develops – ‘P’ disappears

Left Ventricular Hypertrophy : 

58 58 Left Ventricular Hypertrophy

Left Ventricular Hypertrophy : 

59 High QRS voltages in limb leads R in Lead I + S in Lead III > 25 mm S in V1 + R in V5 > 35 mm R in aVL > 11 mm or S V3 + R aVL > 24 ♂, > 20 ♀ Deep symmetric T inversion in V4, V5 & V6 QRS duration > 0.09 sec Associated Left Axis Deviation, LAE Cornell Voltage criteria, Estes point scoring Left Ventricular Hypertrophy

Slide 60: 

60 60 What is in this ECG ?

Slide 61: 

61 Causes of LVH Pressure overload - Systemic Hypertension, Aortic Stenosis Volume overload - AR or MR - dilated cardiomyopathy VSD - cause both right & left ventricular volume overload Hypertrophic cardiomyopathy – No pressure or volume overload Criteria of LVH High QRS voltages in limb leads R in Lead I + S in Lead III > 25 mm or S in V1 + R in V5 > 35 mm R in aVL > 11 mm or S V3 + R aVL > 24 ♂, > 20 ♀ Deep symmetric T inversion in V4, V5 & V6 QRS duration > 0.09 sec, Associated Left Axis Deviation, LAE Causes and Criteria of LVH

Atrial Ectopics : 

62 62 Atrial Ectopics

Slide 63: 

63 Note the premature (ectopic) beats marked as APC (Atrial Premature Contractions) These occurred before the next expected QRS complex (premature) Each APC has a P wave preceding the QRS of that beat – So impulse has originated in the atria The QRS duration is normal < 0.08, not wide Atrial Ectopics

Ventricular Ectopics : 

64 64 Ventricular Ectopics

Slide 65: 

65 Note the premature (ectopic) beats marked as VPC (Ventricular Premature Contractions) These occurred before the next expected QRS complex (premature) Each VPC has no definite P wave preceding the QRS of that beat – So impulse has originated in the ventricles The QRS complexes are wide with abnormal duration of > 0.12 and their shapes are bizarre Ventricular Ectopics

Complete RBBB : 

66 66 Complete RBBB

Complete RBBB : 

67 Complete RBBB Complete RBBB has a QRS duration > 0.12 sec R' wave in lead V1 (usually see rSR' complex) S waves in leads I, aVL, V6, R wave in lead aVR QRS axis in RBBB is -30 to +90 (Normal) Incomplete RBBB has a QRS duration of 0.10 to 0.12 sec with the same QRS features as above The "normal" ST-T waves in RBBB should be oriented opposite to the direction of the QRS

Complete LBBB : 

68 68 Complete LBBB

Complete LBBB : 

69 Complete LBBB Complete LBBB has a QRS duration > 0.12 sec Prominent S waves in lead V1, R in L I, aVL, V6 Usually broad, Bizarre R waves are seen, M pattern Poor R progression from V1 to V3 is common. The "normal" ST-T waves in LBBB should be oriented opposite to the direction of the QRS Incomplete LBBB looks like LBBB but QRS duration is 0.10 to 0.12 sec, with less ST-T change. This is often a progression of LVH changes.

Blood Supply of Heart : 

70 70 Blood Supply of Heart LCA RCA LAD LCX RCA

Blood Supply of Heart : 

71 Heart has four surfaces Anterior surface – LAD, Left Circumflex (LCx) Left lateral surface – LCx, partly LAD Inferior surface – RCA, LAD terminal portion Posterior surface – RCA, LCx branches Rt. and Lt. coronary arteries arise from aorta They are 2.5 mm at origin, 0.5 mm at the end Coronary arteries fill during diastole Flow - epicardium to endocardium – poverty/plenty Blood Supply of Heart

Ischemia, Injury & Infarction : 

72 72 Ischemia, Injury & Infarction Ischemia produces ST segment depression with or without T inversion Injury causes ST segment elevation with or without loss of R wave voltage Infarction causes deep Q waves with loss of R wave voltage.

Ischemia and Infarction : 

73 73 Ischemia and Infarction TRANSMURAL Injury ST Elevation

Ischemic Heart Disease (IHD) : 

74 Ischemic Heart Disease (IHD)

Slide 75: 

75 75 Interpret this ECG

NSTEMI : 

76 NSTEMI Non ST ↑ MI or NSTEMI, Non Q MI Or also called sub-endocardial Infarction Non transmural, restricted to the sub-endocardial region - there will be no ST ↑ or Q waves ST depressions in anterio-lateral & inferior leads Prolonged chest pain, autonomic symptoms like nausea, vomiting, diaphoresis Persistent ST-segment ↓even after resolution of pain

Slide 77: 

77 77 What are these ECGs

STEMI and QWMI : 

78 STEMI and QWMI STEMI and QWMI ST ↑ signifies severe transmural myocardial injury – This is early stage before death of the muscle tissue – the infarction Q waves signify muscle death – They appear late in the sequence of MI and remain for a long time Presence of either is an indication for thrombolysis

Evolution of Acute MI : 

79 79 Evolution of Acute MI A – Normal ST segment and T waves B – ST mild ↑ and prominent T waves C – Marked ST ↑ + merging upright T D – ST elevation reduced, T↓,Q starts E – Deep Q waves, ST segment returning to baseline, T wave is inverted F – ST became normal, T Upright, Only Q+

Critical Narrowing of LAD : 

80 80 Critical Narrowing of LAD

Normal Q waves : 

81 81 Normal Q waves Notice the small Normal Q in Lead I

Pathological Q wave : 

82 82 Pathological Q wave Notice the deep & wide Infarction Q in Lead I

Slide 83: 

83 83 Very Striking

Hyper Acute MI : 

84 Hyper Acute MI Note the hyper acute elevation of ST The R wave is continuing with ST and the complexes are looking rectangular Some times tall and peaked T waves in the precardial leads may be the only evidence of impending infarct Sudden appearance LBBB indicates MI MI in Dextro-cardia – right sided leads are to be recorded

Slide 85: 

85 85 Severe Chest Pain – Why ?

Acute Anterio-lateral MI : 

86 Acute Anterio-lateral MI Note the marked ST elevations in chest leads V2 to V5 and also ST↑ in L1 & aVL T inversions have not appeared as yet R wave voltages have dropped markedly in V3, V4, V5 and V6 Small R in L1 and aVL.

Slide 87: 

87 87 Which wall MI ?

Acute Inferior wall MI : 

88 Note the ST elevations in Inferior leads- namely L2, L3 and aVF T inversions yet to appear aVL lead shows complimentary ST↓and T inversion Acute Inferior wall MI

Acute True Posterior MI : 

89 89 Acute True Posterior MI

Acute True Posterior MI : 

90 Due to occlusion of the distal Left circumflex artery or posterior descending or distal right coronary artery Mirror image changes or reciprocal changes in the anterior precardial leads Lead V1 shows unusually tall R wave (it is the mirror image of deep Q) V1 R/S > 1, Differential Diagnosis - RVH Acute True Posterior MI

Thank You!!! : 

91 Thank You!!!

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