1. BIO-ELECTRIC SIGNAL
&
ELECTRO-CARDIOGRAPHY
H.K.PIR
CSIO, CSIR COMPLEX, PUSA CAMPUS
NEW DELHI-110012

2. BIO-ELECTRIC SIGNAL

3. BIO-ELECTRIC SIGNAL
► CELL : Ionic conductor separated
from outside environment by
semi-permeable membrane
► Human Cells:
Dia : I micron to 100 microns
► Membrane Thickness : 0.01 micron

4. BIO - ELECTRIC POTENTIAL

5. ELECTROCARDIOGRAM
► InternalResting Potential: -90mv
► During Depolarisation Cell Potential Changes to
+20mv

6. Normal Impulse Conduction
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

7. Impulse Conduction & the ECG
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

8. The “PQRST”
►P wave - Atrial
depolarization
• QRS - Ventricular
depolarization
• T wave - Ventricular
repolarization

9. The PR Interval
Atrial depolarization
+
delay in AV junction
(AV node/Bundle of His)
(delay allows time for
the atria to contract
before the ventricles
contract)

11. Pacemakers of the Heart
► SA Node - Dominant pacemaker with an
intrinsic rate of 60 - 100 beats/minute.
► AV Node - Back-up pacemaker with an
intrinsic rate of 40 - 60 beats/minute.
► Ventricular cells - Back-up pacemaker with
an intrinsic rate of 20 - 45 bpm.
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12. Sequence of Impulse Travel

13. Conduction Analysis
► Normal" conduction
implies normal sino-
atrial (SA)
normal atrio-
ventricular (AV)
normal intraventricular
(IV) conduction.
► The diagram illustrates
the normal cardiac
conduction system.

14. ELECTROCARDIOGRAM

15. ECG Waves and Intervals:
► What do they mean?
► P wave: the sequential activation (depolarization) of
the right and left atria
► QRS complex: right and left ventricular
depolarization (normally the ventricles are activated
simultaneously)
► ST-T wave: ventricular repolarization
► U wave: origin for this wave is not clear - but
probably represents "after depolarizations" in the
ventricles

16. ECG Waves and Intervals:
►PR interval: time interval from onset of atrial
depolarization (P wave) to onset of ventricular
depolarization (QRS complex)
► QRS duration: duration of ventricular muscle
depolarization
► QT interval: duration of ventricular depolarization and
repolarization
► RR interval: duration of ventricular cardiac cycle (an
indicator of ventricular rate)
► PP interval: duration of atrial cycle (an indicator of atrial
rate)

17. The ECG Paper
► Horizontally
 One small box - 0.04 s
 One large box - 0.20 s
► Vertically
 One large box - 0.5 mV

18. Step 1: Calculate Rate
3 3
sec sec
► Option 1
 Count the # of R waves in a 6 second rhythm
strip, then multiply by 10.
 Reminder: all rhythm strips in the Modules are 6
seconds in length.
Interpretation?
9 x 10 = 90 bpm

19. Step 2: Determine regularity
R R
► Look at the R-R distances (using a caliper or
markings on a pen or paper).
► Regular (are they equidistant apart)? Occasionally
irregular? Regularly irregular? Irregularly irregular?
Interpretation?
Regular

20. Step 3: Assess the P waves
► Are there P waves?
► Do the P waves all look alike?
► Do the P waves occur at a regular rate?
► Is there one P wave before each QRS?
Interpretation?
Normal P waves with 1 P
wave for every QRS

21. Step 4: Determine PR interval
► Normal: 0.12 - 0.20 seconds.
(3 - 5 boxes)
Interpretation?
0.12 seconds

22. Step 5: QRS duration
► Normal: 0.04 - 0.12 seconds.
(1 - 3 boxes)
Interpretation?
0.08 seconds

23. Rhythm Summary
► Rate 90-95 bpm
► Regularity regular
►P waves normal
► PR interval 0.12 s
► QRS duration 0.08 s
Interpretation?
Normal Sinus Rhythm

24. NSR Parameters
► Rate 60 - 100 bpm
► Regularity regular
► P waves normal
► PR interval 0.12 - 0.20 s
► QRS duration 0.04 - 0.12 s
Any deviation from above is
sinus tachycardia, sinus bradycardia or an
arrhythmia

25. Arrhythmia Formation
Arrhythmias can arise from problems in the:
• Sinus node
• Atrial cells
• AV junction
• Ventricular cells

26. SA Node Problems
The SA Node can:
► fire too slow Sinus Bradycardia
► fire too fast Sinus Tachycardia
Sinus Tachycardia may be an appropriate
response to stress.

27. Atrial Cell Problems
Atrial cells can:
► fire occasionally from Premature Atrial
a focus Contractions (PACs)
► firecontinuously due Atrial Flutter
to a looping
re-entrant circuit

28. ►A re-entrant
pathway occurs
when an impulse
loops and results
in self-
perpetuating
impulse
formation.

29. Atrial Cell Problems
Atrial cells can also:
• fire continuously Atrial Fibrillation
from multiple foci
or
fire continuously Atrial Fibrillation
due to multiple
micro re-entrant
“wavelets”

30. Teaching Moment
Atrial tissue
Multiple micro re-
entrant “wavelets”
refers to wandering
small areas of
activation which
generate fine chaotic
impulses. Colliding
wavelets can, in turn,
generate new foci of
activation.

31. AV Junctional Problems
The AV junction can:
► fire continuously due Paroxysmal
to a looping re-entrant Supraventricular
circuit Tachycardia
► block impulses coming AV Junctional
from the SA Node Blocks

32. Ventricular Cell Problems
Ventricular cells can:
► fire occasionally from Premature Ventricular
1 or more foci Contractions (PVCs)
► fire continuously from Ventricular Fibrillation
multiple foci
► fire continuously due Ventricular Tachycardia
to a looping re-
entrant circuit

33. Arrhythmias
►Sinus Rhythms
►Premature Beats
►Supraventricular Arrhythmias
►Ventricular Arrhythmias
►AV Junctional Blocks

34. Sinus Rhythms
►Sinus Bradycardia
►Sinus Tachycardia

35. Rhythm #1
• Rate? 30 bpm
• Regularity? regular
• P waves? normal
• PR interval? 0.12 s
• QRS duration? 0.10 s
Interpretation? Sinus Bradycardia

36. Sinus Bradycardia
► Etiology:
SA node is depolarizing slower than normal,
impulse is conducted normally (i.e. normal
PR and QRS interval).

37. Rhythm #2
• Rate? 130 bpm
• Regularity? regular
• P waves? normal
• PR interval? 0.16 s
• QRS duration? 0.08 s
Interpretation? Sinus Tachycardia

38. Sinus Tachycardia
► Etiology:SA node is depolarizing faster than
normal, impulse is conducted normally.
► Remember: sinus tachycardia is a response
to physical or psychological stress, not a
primary arrhythmia.

39. Premature Beats
►Premature Atrial Contractions
(PACs)
►Premature Ventricular Contractions
(PVCs)

40. Rhythm #3
• Rate? 70 bpm
• Regularity? occasionally irreg.
• P waves? 2/7 different contour
• PR interval? 0.14 s (except 2/7)
• QRS duration? 0.08 s
Interpretation? NSR with Premature Atrial
Contractions

41. Premature Atrial Contractions
►Deviation from NSR
These ectopic beats originate in the atria
(but not in the SA node), therefore the
contour of the P wave, the PR interval, and
the timing are different than a normally
generated pulse from the SA node.

42. Premature Atrial Contractions
► Etiology:
Excitation of an atrial cell forms an
impulse that is then conducted normally
through the AV node and ventricles.

43. Teaching Moment
► When an impulse originates anywhere in the
atria (SA node, atrial cells, AV node, Bundle of
His) and then is conducted normally through
the ventricles, the QRS will be narrow (0.04 -
0.12 s).

44. PVCs
► Etiology:One or more ventricular cells
are depolarizing and the impulses are
abnormally conducting through the
ventricles.

45. Teaching Moment
► When an impulse originates in a ventricle,
conduction through the ventricles will be
inefficient and the QRS will be wide and
bizarre.

46. Ventricular Conduction
Normal Abnormal
Signal moves rapidly Signal moves slowly
through the ventricles through the ventricles

47. Atrial Fibrillation
►Deviation from NSR
 No organized atrial depolarization, so
no normal P waves (impulses are not
originating from the sinus node).
 Atrial activity is chaotic (resulting in an
irregularly irregular rate).
 Common, affects 2-4%, up to 5-10% if
> 80 years old

48. ELECTROCARDIOGRAM

49. ELECTROCARDIOGRAM

50. Orientation of the 12 Lead ECG
► 12-lead ECG provides spatial information about the
heart's electrical activity in 3 approximately orthogonal
directions:
► Right
► Left
► Superior
► Inferior
► Anterior
► Posterior
► Each of the 12 leads represents a particular
orientation in space, as indicated below (RA = right
arm; LA = left arm, LF = left foot):

51. Orientation of the 12 Lead ECG
►Bipolar limb leads (frontal plane):
► Lead I: RA (-) to LA (+) (Right Left, or lateral)
► Lead II: RA (-) to LF (+) (Superior Inferior)
► Lead III: LA (-) to LF (+) (Superior Inferior)
► Augmented unipolar limb leads (frontal plane):
► Lead aVR: RA (+) to [LA & LF] (-) (Rightward)
► Lead aVL: LA (+) to [RA & LF] (-) (Leftward)
► Lead aVF: LF (+) to [RA & LA] (-) (Inferior)
► Unipolar (+) chest leads (horizontal plane):
► Leads V1, V2, V3: (Posterior Anterior)
► Leads V4, V5, V6:(Right Left, or lateral)

52. Einthoven's Triangle
Each of the 6 frontal plane
leads has a negative and
positive orientation (as
indicated by the '+' and '-'
signs). It is important to
recognize that Lead I (and to
a lesser extent Leads aVR and
aVL) are right Ûleft in
orientation. Also, Lead aVF
(and to a lesser extent Leads
II and III) are superior
Ûinferior in orientation. The
diagram further illustrates the
frontal plane hookup.

53. STANDARD LIMB LEADS

54. ELECTROCARDIOGRAPH

55. ELECTROCARDIOGRAPH

56. ELECTROCARDIOGRAPH

57. ELECTROCARDIOGRAPH

58. LOCATION OF CHEST ELECTRODES IN 4TH AND 5TH
INTERCOSTAL SPACES:
V1: right 4th intercostal
space
V2: left 4th intercostal
space
V3: halfway between V2
and V4
V4: left 5th intercostal
space, mid-clavicular
line
V5: horizontal to V4,
anterior axillary line
V6: horizontal to V5, mid-
axillary line

59. ELECTROCARDIOGRAPH
Voltages Present at the Input of ECG:
 1mv Heart signal (Wanted)
0 – 10 v ac common mode 50Hz (Unwanted)
0 – many microvolts differential 50 Hz ac
0 – 500 mv dc

60. ELECTROCARDIOGRAPH

61. ELECTROCARDIOGRAPH
Good Design Advantages:
 Patient Protection
 Distortion Elimination
 Defibrillator Protection
 High Common Mode Rejection
 Constant Trace Intensity

62. ELECTROCARDIOGRAPH
Electrical Specification:
 Common Mode Rejection Ratio: 114 db or
greater
 Isolation Impedance: 30 MΩ from patient to
chassis
 Input Impedance: Buffer Amplifier Greater than
50 MΩ shunted by 1500 pf
 Frequency Response: 3db down at 100Hz

63. ELECTROCARDIOGRAPH

64. ELECTROCARDIOGRAPH

65. ELECTROCARDIOGRAPH
Maintenance:
 Test Equipment Required:
 Stylus Pressure Gauge (0 – 5 gms)
 Signal Generator
 Multimeter
 Oscilloscope

66. ELECTROCARDIOGRAPH
 Performance checks:
1. Stylus Pressure: 2 – 3 gms
2. Trace Intensity
3. Centering
4. Gain
5. Internal Calibration STD 1mv
6. Gain Balance

67. ELECTROCARDIOGRAPH
Preventive Maintenance:
► Electricalchecks
► Mechanical Inspection
► Cleaning
► Lubrication: Every 2000 years

68. ELECTROCARDIOGRAPH
► ECG OPERATION:
► Electrode Colour Coding:
For hewlett-packard/Burdick ECG’S
• RA White
• La Black
• LL Red
• RL Green
• V Brown

69. ELECTROCARDIOGRAPH
► Electrode Colour Coding:
For European ECG Mc/s
• RA Red
• LA Yellow
• LL Green
• RL Black
• V Brown/White

70. ELECTROCARDIOGRAPH

71. ELECTROCARDIOGRAPH
Corrective Maintenance & Repair:
► Ckt Board Component Replacement:
1. Do not apply excessive heat
2. Apply heat to the component leads and
remove the component with a perpendicular
pull from the board
3. Do not force replacement component leads
into a hole clogged with excessive solder
► Stylus Replacement
► Pressure Roller Assembly

72. BIO-ELECTRIC SIGNAL

81. Lead Selection Ckt
► Lead Selection ckt: IC104,105,106,107
► Clock pulse & Control pulse are provided to 4-
bit binary up down counter IC 106 (4029)
► Counter counts up when ADV is pressed &
counts down when Rev is pressed
► IC107 (4051) enables one of the eight LED’S to
indicate lead selection.
► IC104 (4011) & IC105 (4001) ensures only one
clock pulse is produced whenever one of the
switches is pressed.

83. Microcontroller based ECG
BPL 6108T

84. Microcontroller based ECG
BPL 6108T

85. salient features
► CARDIART 6108T is a portable 12-lead
electrocardiograph with a single channel printing
system, capable of processing all ECG leads
simultaneously.
► Automatic and manual recording modes.
► Built in rechargeable battery for mains independent
use.
► With a fully charged battery, it is possible to take 200
complete ECGs in auto mode.
► Printing the ECG on 50-mm paper using quality thermal
printer.
► The acquired and memorized signal in automatic mode
can be printed on paper for an unlimited number of
times.

86. salient features
• Compact design and low weight for portability.
• The “active recording” time: the time necessary to
acquire and memorize the ECG signal is only 10
seconds. Consequently, effects of interference and
muscle tremors are reduced.
• Selectable parameter measurement program.

87. TECHNICAL SPECIFICATIONS
► Power supply : 230V 10%
► Power consumption : Less than 12W
► Battery : Internal rechargeable
NiMH 9.6V 1500mAH
►Recording system : Thermal printer,
8 dots/mm
►ECG Leads : Standard 12 leads
Acquired 8 leads
Reconstructed 4 leads
(III, aVR, aVL, aVF)

88. TECHNICAL SPECIFICATIONS
►Recording sensitivity
Manual mode: 2.5 - 5 -10 - 20
mm/mV 5%
Auto mode: dependent on the
signal strength,
Optimizes automatically
to 2.5 -5 -10 - 20
mm/mV 5%

89. ► Signal Memory : 10 Seconds for each
lead in Auto mode
► Operating modes: Manual – acquisition
and printing in real time
Auto - simultaneous
acquisition
► Safety Standard: Compliant to Class II
type IEC-601-1 &
601-2-25 Standards

90. ► CARDIART 6108T complies with IEC standard for safety
and electromagnetic compatibility.
► Place the electrocardiograph as far as possible from
electrical lines or from source of static electricity. The ECG
signal can be disturbed if the electrocardiograph is
situated in proximity to source of high voltage or electrical
lines.
► Avoid placing electrocardiograph close to other diagnostic
or therapeutic equipment like X- ray machines, ultrasound
machines, electrically operated beds etc that could be a
source of excessive interference and ECG signal
distortion.
► Avoid the use of mobile phones in the vicinity.
► Keep electrocardiograph away from other electrical
equipment, switch OFF such equipment when recording
an ECG.

91. Charging the internal batteries
► CARDIART 6108T uses NiMH rechargeable internal
batteries and are protected against
► over current by means of polymer resettable fuse. To
charge the batteries connect the
► “battery charger” to the connector on the back of the
device. The “battery charger “ is
► protected against short circuits by an internal fuse.
► Caution: All devices are delivered with the batteries
“fully charged

92. System Block Diagram

93. Battery Charger circuit

94. ECG section
► The major activities of this section are as below:
► High voltage protection of the circuits when the
patient is given shock from a defibrillator.
► Deriving standard bi-polar and uni-polar ECGs from
the electrodes connected to the human body.
► Rejection of common mode ac interference signal.
► Fixed gain amplification of low level ECG signals.
► Lead off or poor contact identification.
► Removing the low frequency or dc from the ECG
signal through ac coupling.
► Second stage amplification and DC level shifting to
provide proper interface to ADC.

95. Defibrillator protection circuit

96. First Stage Amplifier

97. Second stage amplifier

98. ECG to ADC interface

99. Right leg drive

100. Print head Interface circuit

101. Motor control circuit

102. Print format: