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Electrical Activity of
the Heart
By dr shazia askari
ECG(electrocardiograph)
• ECG is define as ‘’ recording of electrical activity of
heart on a graph paper.’’
Or
• Graphical...
Electrocardiograph.
• The machine which is used to record the electrical
activity of heart is ELECTROCARDIOGRAPH.
• a) ECG...
Electrocardiogram.
• The graph on which this electrical activity is recorded
is called ELECTROCARDIOGRAM.
Significance of ECG.
• ECG gives information about rate and rhythm of
the heart.
• The physical orientation of heart i.e a...
ECG paper.
• This is long role of paper ,composed of small
squares .
• One square is 1mm wide and 1 mm high.
• On ECG pape...
ECG paper.
ECG Paper.
• The time internal of each small square can be
calculated as
• 25 small sqrs are equal to 1 second.
• 1 small ...
ECG paper
• vertically the small square represent the amount of
electrical potential.
• One small sqr represent the potent...
ECG leads.
• leads are electrodes which record the
electrical potential of heart at different sites.
• There are 12 ECG le...
Bipolar limb leads.
• Lead 1 = left arm + ve , right arm _
ve
• Lead 2 = right arm _ ve ,left leg + ve..
• Lead 3 = left a...
Augmented limb leads.
• AVR attach to right arm..
• AVL attach to left arm.
• AVF attach to left foot.
Einthoven”s triangle
• Einthoven s triangle is a diagrammatic
way of illustrating that the two arms
and left leg form the ...
Einthoven “s rule.
• Einthovens law states that if the
electrical potentials of two leads are
known at any instant ,the th...
Waveforms in ECG
Lecture no 2
Always remember.
• Positive electrode is always a reference electrode.
• Depolarization wave moves toward the positive
ele...
Wave forms.
 P wave
 Atrial depolarization
 QRS complex
 Ventricular depolarization
 T wave
 Ventricular repolarizat...
Basic terminologies
 Base line : flat, straight and isoelectric line
 Wave form :deviation or movement away
from base li...
P wave
• P Wave shows atrial depolarization..
• Its duration is 0.1 sec (2 and half small sqr) and
height is 2.5 mv (2 and...
Abnormalities of P wave.
 P .pulmonale :- This is tall and peaked P wave in
lead 1 and lead 2 and 3 in right atrial hyper...
P wave.
• Inverted P wave :- may be present in .
• a) Normally in lead V 1 and V2..
• b) In dextro cardia.
• c) Incorrectl...
QRS complex.
• QRS complex represent the ventricular
depolarization.
• its normal duration is about 0. 08 seconds.( less t...
QRS complex.
• Q wave present the interventricular septal
depolarization.
• It is first wave in ECG with negative deflecti...
Low voltage QRS complex.
• when the height of R or S wave is not more than
5mm… it is seen in..
Hypothyroidism.
Pericard...
High voltage QRS complex.
• This is present in ventricular hypertrophies.
• The maximum voltage of QRS complex may be 35
m...
T Wave.
• it represent the ventricular repolarization.
• It is repolarizing wave but shows the upward
deflection because t...
T wave.
•
• T wave should not be more than one third of R
wave.
• T wave inversion represent ischemia of heart.
• Tall and...
PR interval.
• This is from beginning of P wave to the beginning
of Q wave.
• Its normal duration is from 0.12 to 0.2 sec....
Prolong PR interval.
• Prolong PR interval shows delayed conduction from
SA to AV node….
 In first degree heart , 2nd deg...
First degree heart block.
• A-V BLOCK, FIRST DEGREE
Atrio-ventricular conduction lengthened
• Interval is about 0.2 to 0.3...
Second degree heart block.
• A-V BLOCK, SECOND DEGREE
Sudden dropped QRS-complex
• PR interval is about 0.4 sec.
•
3rd degree heart block
3rd degree heart block.
• When there is AV block , atria continue to beat at
normal rhythem while new pace maker develops ...
QT interval
• Measured from beginning of Q to the
end of the T wave
. Its duration is about (10 small sqrs).
. it indicate...
RR interval.
ST segment.
• this segment present between S wave and T
wave.
• It represent the plateau phase.
• its duration is 0.04 sec...
J point.
• The exact point at which all parts of ventricles are
depolarized i.e at the just end of QRS comples and
just at...
ST segment
• Elevation . Seen in recent MI and
hyperkalemia.
• Depression. Seen in ischemia, digitalis
therapy and hypokal...
Lecture 3
ECG
Electrophysiology
 If an electrode is placed so that wave of
depolarization spreads toward the recording
electrode, the E...
Waves in limb leads.
Waves in augmented limb leads
1. ECG recording of electrical activity not the
mechanical function
2. ECG is not a direct depiction of abnormalities
3. E...
Lecture 4
ECG helps to know?
How to calculate heart rate.
heart rate define as the no of heart beats per
minute.it can be determine by ECG VIA TWO
RULE...
Rule of 300
Take the number of “big boxes” between
neighboring QRS complexes, and divide this
into 300. The result will be...
What is heart rate???????
Heart rate?
Heart rate ?
Rule of 10 sec
As most EKGs record 10 seconds of rhythm per
page, one can simply count the number of
beats present on the ...
Rhythm.
• This is checked by the intervals between two R
waves or two S waves.
• If the no of small or large sqs are equal...
Normal sinus rhythm
Sinus arrhythmia
• There is sinus rhythm , but the RR interval
(heart rate) varies with respiration.
• Heart rate increase...
Cardiac Rhythm:
Supraventricular
Atrial flutter.
• When atrial rate is between 200 to 300 betas /min
• During atrial flutter AV node is not able to transmi...
ATRIAL FLUTTER
Impulses travel in regular and circular course in
atria – No interval between T and P.
Atrial fibrillation.
• A totally irregular and rapid atrial rate in which there
is a contraction of only small portion of ...
ATRIAL
FIBRILLATION
Impulses have random pathways in atria.
VENTRICULAR
TACHYCARDIA
•
Impulse originate at ventricular pacemaker –
odd/wide QRS complex - often due to
myocardial infa...
Ventricular fibrillation.
• Rapid ,irregular and ineffective contractions
of small segments of ventricles is termed as
ven...
VENTRICULAR FIBRILLATION
hapazerd ventricular depolarization – ineffective at
pumping – death within minutes
•
•
Cardiac axis
• The flow of current from one point to another is
representing by an arrow. This is called Vector.
• The dir...
Vector Analysis
QRS axis.
By near-consensus, the normal QRS axis is defined as
ranging from -30° to +90°.
-30° to -90° is referred to as a...
Axis deviation
• Deviation to R: increased activity in R vent. –
obstruction in lung, pulmonary emboli, some heart
disease...
The quadrant approach
RAD Negative in I, positive in
AVF
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Electrocardiogram

  1. 1. Electrical Activity of the Heart By dr shazia askari
  2. 2. ECG(electrocardiograph) • ECG is define as ‘’ recording of electrical activity of heart on a graph paper.’’ Or • Graphical representation of electrical activity of heart.
  3. 3. Electrocardiograph. • The machine which is used to record the electrical activity of heart is ELECTROCARDIOGRAPH. • a) ECG machine. • b) power lab.
  4. 4. Electrocardiogram. • The graph on which this electrical activity is recorded is called ELECTROCARDIOGRAM.
  5. 5. Significance of ECG. • ECG gives information about rate and rhythm of the heart. • The physical orientation of heart i.e axis. • Its a diagnostic tool for various heart conditions like hypertrophies , ischemia, infarction , arrhythmias conduction problems and pace maker activity. • ECG does not provide information about mechanical activity.
  6. 6. ECG paper. • This is long role of paper ,composed of small squares . • One square is 1mm wide and 1 mm high. • On ECG paper there are thick lines, between two thick lines there are 5 small squares. • The speed of ECG machine is 25 mm per second.
  7. 7. ECG paper.
  8. 8. ECG Paper. • The time internal of each small square can be calculated as • 25 small sqrs are equal to 1 second. • 1 small sqr is equal to 1/25 second. • i.e 0.04 seconds.
  9. 9. ECG paper • vertically the small square represent the amount of electrical potential. • One small sqr represent the potential of 0.1 mv. • 10 small squares represent the potential of 1 mv.
  10. 10. ECG leads. • leads are electrodes which record the electrical potential of heart at different sites. • There are 12 ECG leads. a) 3 bipolar limb leads. b) 3 augmented limb leads.(unipolar). c) 6 chest leads.
  11. 11. Bipolar limb leads. • Lead 1 = left arm + ve , right arm _ ve • Lead 2 = right arm _ ve ,left leg + ve.. • Lead 3 = left arm _ ve , left leg +ve.
  12. 12. Augmented limb leads. • AVR attach to right arm.. • AVL attach to left arm. • AVF attach to left foot.
  13. 13. Einthoven”s triangle • Einthoven s triangle is a diagrammatic way of illustrating that the two arms and left leg form the apices of triangle surrounding the heart. • It is an equilateral triangle.
  14. 14. Einthoven “s rule. • Einthovens law states that if the electrical potentials of two leads are known at any instant ,the third can be determine by simply summing the first two.
  15. 15. Waveforms in ECG Lecture no 2
  16. 16. Always remember. • Positive electrode is always a reference electrode. • Depolarization wave moves toward the positive electrode gives positive deflection. • Depolarization wave move away from positive electrode gives the negative deflection.
  17. 17. Wave forms.  P wave  Atrial depolarization  QRS complex  Ventricular depolarization  T wave  Ventricular repolarization
  18. 18. Basic terminologies  Base line : flat, straight and isoelectric line  Wave form :deviation or movement away from base line may be upward or downward  Segment : A line between two waves  Interval : a wave form plus a segment this shows time duration  Complex : combination of several wave form without segment.
  19. 19. P wave • P Wave shows atrial depolarization.. • Its duration is 0.1 sec (2 and half small sqr) and height is 2.5 mv (2 and half small sqr). • Presence of p waves in ECG strip shows the sinus rhythm.
  20. 20. Abnormalities of P wave.  P .pulmonale :- This is tall and peaked P wave in lead 1 and lead 2 and 3 in right atrial hypertrophy. (pulmonary hypertension).  P. mitrale ;_ It is biphasic or broad P wave seen in left atrial hypertrophy.(mitral stenosis). -. Best seen in lead 2.
  21. 21. P wave. • Inverted P wave :- may be present in . • a) Normally in lead V 1 and V2.. • b) In dextro cardia. • c) Incorrectly placed electrodes.
  22. 22. QRS complex. • QRS complex represent the ventricular depolarization. • its normal duration is about 0. 08 seconds.( less than 2 small sqr) and hight is about 5 to 20 small sqrs. • It is a wide complex because it mask the atrial repolarization. • Q wave is first wave of this complex but often absent.
  23. 23. QRS complex. • Q wave present the interventricular septal depolarization. • It is first wave in ECG with negative deflection. • Q wave greater than 1/3 the height of the R wave, greater than 0.04 sec are abnormal and may represent the old infarction. .
  24. 24. Low voltage QRS complex. • when the height of R or S wave is not more than 5mm… it is seen in.. Hypothyroidism. Pericardial effusion. Thick chest wall. Problem in ECG machine.
  25. 25. High voltage QRS complex. • This is present in ventricular hypertrophies. • The maximum voltage of QRS complex may be 35 mv(35 small square). • V1 and V2 show high voltage QRS complex in right ventricular hypertrophy.( s wave) • V5 and V6 show such QRS complex in left ventricular hypertrophy. (r wave)
  26. 26. T Wave. • it represent the ventricular repolarization. • It is repolarizing wave but shows the upward deflection because the part depolarized in the last is first to be repolarized,, that is base of heart depolarized in the last but is first to be repolarized.
  27. 27. T wave. • • T wave should not be more than one third of R wave. • T wave inversion represent ischemia of heart. • Tall and peaked R wave is present in hyperkalemia. • Flattened R waves in pericarditis and myocarditis.
  28. 28. PR interval. • This is from beginning of P wave to the beginning of Q wave. • Its normal duration is from 0.12 to 0.2 sec.. • It represent the conduction time of impulse from SA node to the ventricles and AV delay.
  29. 29. Prolong PR interval. • Prolong PR interval shows delayed conduction from SA to AV node….  In first degree heart , 2nd degree and complete heart block. Digitalis therapy.  Hyperkalemia.
  30. 30. First degree heart block. • A-V BLOCK, FIRST DEGREE Atrio-ventricular conduction lengthened • Interval is about 0.2 to 0.3 sec.
  31. 31. Second degree heart block. • A-V BLOCK, SECOND DEGREE Sudden dropped QRS-complex • PR interval is about 0.4 sec. •
  32. 32. 3rd degree heart block
  33. 33. 3rd degree heart block. • When there is AV block , atria continue to beat at normal rhythem while new pace maker develops in purkinjie system with a rate of 15 to 50 beats /min. • With a sudden block purkinje system cannot take over pace maker activity immediately ,it takes about 16 to 30 sec. during which ventricles fail to contract and person faint. • This delayed pickup of heart beat is called stokes Adams syndrome.
  34. 34. QT interval • Measured from beginning of Q to the end of the T wave . Its duration is about (10 small sqrs). . it indicates total systolic time of ventricles.
  35. 35. RR interval.
  36. 36. ST segment. • this segment present between S wave and T wave. • It represent the plateau phase. • its duration is 0.04 sec .
  37. 37. J point. • The exact point at which all parts of ventricles are depolarized i.e at the just end of QRS comples and just at the begining of ST segment. • At the point potential of ECG is zero with no current is flowing through heart.
  38. 38. ST segment • Elevation . Seen in recent MI and hyperkalemia. • Depression. Seen in ischemia, digitalis therapy and hypokalemia.
  39. 39. Lecture 3 ECG
  40. 40. Electrophysiology  If an electrode is placed so that wave of depolarization spreads toward the recording electrode, the ECG records a positive (upward) deflection.  If wave of depolarization spreads away from recording electrode, a negative (downward) deflection
  41. 41. Waves in limb leads.
  42. 42. Waves in augmented limb leads
  43. 43. 1. ECG recording of electrical activity not the mechanical function 2. ECG is not a direct depiction of abnormalities 3. ECG does not record all the heart’s electrical activity
  44. 44. Lecture 4
  45. 45. ECG helps to know?
  46. 46. How to calculate heart rate. heart rate define as the no of heart beats per minute.it can be determine by ECG VIA TWO RULES.  Rule of 300  10 Second Rule
  47. 47. Rule of 300 Take the number of “big boxes” between neighboring QRS complexes, and divide this into 300. The result will be approximately equal to the rate. Although fast, this method only works for regular rhythms.
  48. 48. What is heart rate???????
  49. 49. Heart rate?
  50. 50. Heart rate ?
  51. 51. Rule of 10 sec As most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats present on the EKG and multiply by 6 to get the number of beats per 60 seconds. This method works well for irregular rhythms
  52. 52. Rhythm. • This is checked by the intervals between two R waves or two S waves. • If the no of small or large sqs are equal between two R or S waves,, the rhythm is said to be normal. • If not the rhythm is said to be irregular. • Irregular rhythm is called Arrythmias.
  53. 53. Normal sinus rhythm
  54. 54. Sinus arrhythmia • There is sinus rhythm , but the RR interval (heart rate) varies with respiration. • Heart rate increase during inspiration and decrease during expiration.
  55. 55. Cardiac Rhythm: Supraventricular
  56. 56. Atrial flutter. • When atrial rate is between 200 to 300 betas /min • During atrial flutter AV node is not able to transmit all the impulses to ventricles so ventricular rate is 1/3 or ¼ of atrial rate. • P wave is like saw tooth. • Present is IHD , rheumatic heart disease.
  57. 57. ATRIAL FLUTTER Impulses travel in regular and circular course in atria – No interval between T and P.
  58. 58. Atrial fibrillation. • A totally irregular and rapid atrial rate in which there is a contraction of only small portion of atrial musculature. • P waves replace by irregular F waves , bcoz whole atria is not contracting. • QRS complex and T waves r normal but rhythm is irregular.
  59. 59. ATRIAL FIBRILLATION Impulses have random pathways in atria.
  60. 60. VENTRICULAR TACHYCARDIA • Impulse originate at ventricular pacemaker – odd/wide QRS complex - often due to myocardial infarction , rate is about 120/ to 220/ min.
  61. 61. Ventricular fibrillation. • Rapid ,irregular and ineffective contractions of small segments of ventricles is termed as ventricular fibrillation. • Peripheral pulse is absent bcoz cardiac out put is zero.
  62. 62. VENTRICULAR FIBRILLATION hapazerd ventricular depolarization – ineffective at pumping – death within minutes • •
  63. 63. Cardiac axis • The flow of current from one point to another is representing by an arrow. This is called Vector. • The direction of flow of current i.e the arrow point is always towards the positive direction. The range of cardiac axis is 0 to +90 degrees. Beyond this limit it is said to be deviated.
  64. 64. Vector Analysis
  65. 65. QRS axis. By near-consensus, the normal QRS axis is defined as ranging from -30° to +90°. -30° to -90° is referred to as a left axis deviation (LAD) +90° to +180° is referred to as a right axis deviation (RAD)
  66. 66. Axis deviation • Deviation to R: increased activity in R vent. – obstruction in lung, pulmonary emboli, some heart disease • Deviation to L: increased activity in L vent. – hypertension, aortic stenosis, ischemic heart disease
  67. 67. The quadrant approach
  68. 68. RAD Negative in I, positive in AVF

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