Bab7-ECG

8/16/2019 Bab7-ECG

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ECG

(Electrocardiogram)

Achmad RizalBioSPIN

ARL-EL4703-Instrumentasi Biomedis 2

Cardiac Conduction System (1)


Cardiac Conduction System (2)


The ECG (1)


The ECG (1)


The ECG (1)Electrocardiography1. Standard clinical ECG (12 leads)2. VCG (3 orthogonal leads)3. Monitoring ECG (1 or 2 leads)

8/16/2019 Bab7-ECG



Modern ECG

Figures above show how theearliest ECGs were recorded byEinthoven at 1900.Vats of salt water provided theelectrical connection to the body.The string galvanometer served asthe measurement instrument forrecording the ECG. ARL-EL4703-Instrumentasi Biomedis 8

Electrocardiograph


Holter Monitor


Dipole Model


Standard Location ?


ECG Lead Configurations• A pair of electrodes, or a combination of several electrodes

through a resistive network that gives an equivalent pair iscalled a lead.

• A vector that connects a lead electrode pair is the lead vector.• If the cardiac vector M is known, the voltage generated at any

lead can be easily computed.

8/16/2019 Bab7-ECG



Frontal Plane Bipolar LeadsEinthovenTriangle


The Einthoven Triangle


Lead I


Lead II


Lead III


Cardiac Vector Through the Cardiac CycleAs Seen By Leads I, II and III

8/16/2019 Bab7-ECG



Cardiac VectorThrough theCardiac Cycle AsSeen By Leads I,II and III


Cardiac VectorThrough the CardiacCycle As Seen ByLeads I, II and III


Cardiac Vector Throughthe Cardiac Cycle AsSeen By Leads I, II andIII


UnipolarMeasurements:Wilson Central Terminal

• Three additional leads are used for frontal planemeasurements.

• These are the measurements at the specific electrode, withrespect to a reference electrode

• One commonly used reference electrode is the WilsonCentral Terminal, obtained through a resistive network,combining limb electrodes

• The new set of leads obtained by combining the standardlimb electrodes to the Wilson terminal form the augmentedleads

• These leads provide additional vector views of cardiacdepolarization in the frontal plane. Unlike leads I, II, III, theaugmented leads utilize WCT, a central negative terminal.This virtual "electrode" is calculated by the EKG computerto measure vectors originating roughly at the center of theheart.

Note that the voltage at Wilson’s terminal is zero (why?)


Wilson’s Central Terminal


Augmented Leads: aVR

21 III

V V aVR −−=

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Augmented Leads: aVL

21 II

V

V aVL −=


Augmented Leads: aVF

2

I II

V V aVF −=


All Frontal Leads


Frontal Lead


Transversal Lead


12 LeadsECGRecording

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ARL-EL4703-Instrumentasi Biomedis 31 ARL-EL4703-Instrumentasi Biomedis 32

ECG Intrumentation

• Single Channel ECG


ECG Intrumentation

Electrode Transducer Characteristic :

acquiring signal withamplitude between0.01mV – 3mVanticipate impedance till> 5 M Ω

small current leakages< 1 µ-Aresponse frequency0.05 – 150 Hz


ECG Intrumentation

ECG Amplifier schematicsRight leg driven loop- noise reducing- patient protection- Reduce Common Mode

Voltage


ECG Intrumentation

• Instrumentation Amplifier


ECG Intrumentation

• AD620 single chip instrumentationamplifier

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ECG IntrumentationHigh Pass Filter Second Amplifier

Low Pass Filter 20 Hz

Clamper

Low Pass Filter 40 Hz

Analog subsystemARL-EL4703-Instrumentasi Biomedis 38

ECG Intrumentation

Digital Subsystem


ECG Intrumentation

Display Unit• Galvanometer • Osciloskop• CRT

• LCD• PC + Monitor • Paper chart• PDA/HP display


Some Problems in ECG

Noise & interferences


Some Problems in ECG

• Souces of interference in an ECG trace – base line wander : patient movement, electrode

reposition, dry electrode, static buildup around patient

– AC noise (50 Hz) : powerline/common modeinterfrence

– intermittent signal : lead connection not tightand secured, dry electrode, damage cable orlead wire

– Other Electrical interference (EI)

Another ECG System

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8/16/2019 Bab7-ECG



Low Power, Low Cost,Wireless ECG(Holter Monitor)

ESDDefibrillation

Protection

ADuC7022

ADF702x*

ESDDefib

Protect

RLElectrode

RAElectrode

RLElectrode

AD623G=10.6

High-PassPole0.5Hz

0.47μF

5pF

681kΩ

499kΩ

5.23kΩ 5.23kΩ

475Ω 10kΩ

108pF

Anti-aliasFilter-3dB, 1592 Hz

AdditionalDigitalFilter

Level ShiftAnti-Alias

TotalGain ~ 220

G =22.05

AD8641

AD8603

Dependent on FrequencyBand Used( WMTS or ISM)


Low Cost, Low Power AED

Filter and

ProtectionNetwork

ADR365

AD7685

HighVoltage

Discharge

Power Control

ADP1712

AD8220/4 AD8606

AD8605

PatientPads

Li IonBattery

ADuC70xxor

Blackfin®

LCD Display

Single poleanti-alias

filter

Digital Filtering

Blanking


Exercise Heart Rate Monitor (Example: treadmill with heartrate monitor)

AD8692AD8692

REF

REF REF

AD8553

AD8691

High PassFilter

ADuC70xxREF

InputProtection

+5V

40 HzLowPass Filter

Documents

Bab7-ECG