Download - 203 MDE ECG1 lectuers.pdf
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ElectrocardiogramElectrocardiogram
The tracing made by an electrocardiograph
Electrocardiograph
an instrument for recording thechanges of electrical potential occurring
during the heartbeat used especially in
diagnosing abnormalities of heart action
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Sinoatrial Node (SA)the impulse generating tissue
located in the right atrium of theheart
Atrioventricular Node (AV)the tissue between the atria and the
ventricles of the heart, conducts thenormal electrical impulse from the atria
to the ventricles
Cardiac conduction systemCardiac conduction system
SA AV His bundle Purkinje fibers
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Electrocardiogram (ECG) (cont.)Electrocardiogram (ECG) (cont.)
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ECG Waves and IntervalsECG Waves and Intervals
P wave: the sequential activation (depolarization) of the right and
left atria QRS complex: right and left ventricular depolarization
ST-T wave: ventricular repolarization
U wave: probably represents "afterdepolarizations" in theventricles
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 andrepolarization
RR interval: duration of ventricular cardiac cycle (an indicator ofventricular rate)
PP interval: duration of atrial cycle (an indicator of atrial rate)
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ECG Signal CharacteristicsECG Signal Characteristics
Signal is generated in the heart
Amplitude range: -5 mV to +5 mV (usually thepacked up signal on the body surface is 1 mV)
Frequency range: 0.05 to 1500 Hz Acquisition by surface electrodes
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Lead configurations for ECG AcquisitionLead configurations for ECG Acquisition
1. Bipolar limb leads (Einthoven)
2. Unipolar limb leads or Augmented limb
leads (Goldberg)
3. Unipolar chest leads (Wilson)
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Bipolar limb leads (Einthoven)Bipolar limb leads (Einthoven)
Lead I Lead II Lead III
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Signal shape of Bipolar l imb leadsSignal shape of Bipolar l imb leads
(Einthoven)(Einthoven)
Lead I
Lead II
Lead III
U i l li b l d A t d li b l d
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Unipolar Unipolar limb leads or limb leads or Augmented limb leads Augmented limb leads
(Goldberg)(Goldberg)
Lead aVR Lead aVL Lead aVF
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Signal shape ofSignal shape of Unipolar Unipolar limb leadslimb leads
Lead aVR
Lead aVL
Lead aVF
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Signal processing of ECGSignal processing of ECG