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ECG(Electrocardiogram)
Achmad RizalBioSPIN
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Cardiac Conduction System (1)
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Cardiac Conduction System (2)
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The ECG (1)
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The ECG (1)
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The ECG (1)Electrocardiography1. Standard clinical ECG (12 leads)2. VCG (3 orthogonal leads)3. Monitoring ECG (1 or 2 leads)
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Modern ECG
Figures above show how the earliest ECGs were recorded by Einthoven at 1900.Vats of salt water provided the electrical connection to the body. The string galvanometer served as the measurement instrument for recording the ECG. ARL-EL4703-Instrumentasi Biomedis 8
Electrocardiograph
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Holter Monitor
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Dipole Model
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Standard Location ?
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ECG Lead Configurations • A pair of electrodes, or a combination of several electrodes
through a resistive network that gives an equivalent pair is called 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.
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Frontal Plane Bipolar LeadsEinthovenTriangle
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The Einthoven Triangle
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Lead I
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Lead II
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Lead III
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Cardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and III
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Cardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and III
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Cardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and III
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Cardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and III
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UnipolarMeasurements:Wilson Central Terminal
• Three additional leads are used for frontal plane measurements.
• These are the measurements at the specific electrode, with respect to a reference electrode
• One commonly used reference electrode is the Wilson Central Terminal, obtained through a resistive network, combining limb electrodes
• The new set of leads obtained by combining the standard limb electrodes to the Wilson terminal form the augmented leads
• These leads provide additional vector views of cardiac depolarization in the frontal plane. Unlike leads I, II, III, the augmented leads utilize WCT, a central negative terminal. This virtual "electrode" is calculated by the EKG computer to measure vectors originating roughly at the center of the heart.
Note that the voltage at Wilson’s terminal is zero (why?)
acquiring signal with amplitude between 0.01mV – 3mVanticipate impedance till > 5 MΩsmall current leakages < 1 µ-Aresponse frequency 0.05 – 150 Hz
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ECG Intrumentation
ECG Amplifier schematicsRight leg driven loop- noise reducing- patient protection- Reduce Common Mode
Voltage
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ECG Intrumentation
• Instrumentation Amplifier
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ECG Intrumentation
• AD620 single chip instrumentation amplifier
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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
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ECG Intrumentation
Display Unit• Galvanometer• Osciloskop• CRT• LCD• PC + Monitor• Paper chart• PDA/HP display
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Some Problems in ECG
Noise & interferences
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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 mode interfrence
– intermittent signal : lead connection not tight and secured, dry electrode, damage cable or lead wire
– Other Electrical interference (EI)
Another ECG System
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Glossary of Terms• AED : Automated External Defibrillator – Auto diagnosis with voice
directed treatment.• EKG/ECG: ElectroCardioGram – skin surface, heart monitor• Holter Monitor: Portable device for continuously monitoring the electrical
activity of the heart for at least 24 hours. Can be external or implantable.
• Defibrillation : Delivering a therapeutic dose of electrical energy to the heart.• T-wave alterans : A change in the shape of the heartbeat signal on an every
other beat basis that is not apparent to the naked eye.• Right Leg Drive : An operational amplifier deriving common mode voltage is
used to invert the common-mode signal and drive it back into thepatient through the right leg.
• RFI : Radio Frequency Interference• ESD : Electro Static Discharge