C7_biofiz Tesut Cardiac Vectorcardiograma

8/12/2019 C7_biofiz Tesut Cardiac Vectorcardiograma

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Jonctiunea (sinapsa electrica) neuro-

muscularaPotentialul electric de actiune

Semnalul electrocardiografic

Fibra cardiaca-dipol electric

Electrocardiograma

MODELUL VECTORIAL

Activitatea electrica a

tesutului muscular cardiac


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1. Terminatie nervoasa

2. Sarcolema=membrana celuleimusculare

3. Vezicula cu neurotransmitator

4. Receptor membranar de

acetilcolina (neurotransmitator)

5. Mitocondriile

Jonctiunea (sinapsa

electrica) neuro-

musculara


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Canale ionice implicate in stimularea electrica

(excitatia) celulelor musculare de catre celulele

neuronale


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Muschiul cardiac cu fibre

purkinje fibre cardiace

modificate care isi au originea in

nodul atrioventricular si se

ramifica in ambele ventricule.Aceste fibre transmit impulsul

electric de la nodul

atrioventricular catre ventricules

facand posibila contractiasimultana.


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Electrocardiogram (ECG/EKG)

Is a recording of electrical activity of heart conducted throw ionsin body to surface

Fig 13.22a

13-60


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Elements (parameters) of ECG signal


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3 distinct waves are

produced during

cardiac cycle

P wavecaused by

atrial depolarization

QRS complex

caused by

ventricular

depolarization

T waveresults from

ventricularrepolarization

ECG

Fig 13.2413-63


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Elements of the ECG:

P wave: Depolarization of both atria;

Relationship between P and QRS helps distinguish various cardiacarrhythmias

Shape and duration of P may indicate atrial enlargement

PR interval: from onset of P wave to onset of QRS

Normal duration = 0.12-2.0 sec (120-200 ms) (3-4 horizontal boxes)

Represents atria to ventricular conduction time (through His bundle)Prolonged PR interval may indicate a 1st degree heart block

QRS complex: Ventricular depolarization

Larger than P wave because of greater muscle mass of ventricles

Normal duration = 0.08-0.12 seconds

Its duration, amplitude, and morphology are useful in diagnosing

cardiac arrhythmias, ventricular hypertrophy, MI, electrolyte

derangement, etc.

Q wave greater than 1/3 the height of the R wave, greater than 0.04


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ST segment:

Connects the QRS complex and T waveDuration of 0.08-0.12 sec (80-120 msec

T wave:

Represents repolarization or recovery of ventriclesInterval from beginning of QRS to apex of T is

referred to as the absolute refractory period

QT Interval

Measured from beginning of QRS to the end of the T

wave

Normal QT is usually about 0.40 sec

QT interval varies based on heart rate


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Fig. 13.24b


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Fig. 13.24c


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Fig. 13.24d


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Elements of the ECG:

P waveDepolarization of both atria;

Relationship between P and QRS helpsdistinguish various cardiac arrhythmias

Shape and duration of P may indicate atrialenlargement


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QRS complex:

Represents ventricular depolarization

Larger than P wave because of greater muscle mass of ventricles

Normal duration = 0.08-0.12 seconds

Its duration, amplitude, and morphology are useful in diagnosing

cardiac arrhythmias, ventricular hypertrophy, MI, electrolyte

derangement, etc.

Q wave greater than 1/3 the height of the R wave, greater than 0.04

sec are abnormal and may represent MI


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PR interval:

From onset of P wave to onset of QRS

Normal duration = 0.12-2.0 sec (120-200 ms) (3-4

horizontal boxes)

Represents atria to ventricular conduction time (through

His bundle)

Prolonged PR interval may indicate a 1st degree heart

block


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Fig. 13.24g


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T wave:Represents repolarization or recovery of ventricles

Interval from beginning of QRS to apex of T is referred to as theabsolute refractory period


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ST segment:Connects the QRS complex and T wave

Duration of 0.08-0.12 sec (80-120 msec

QT IntervalMeasured from beginning of QRS to the end of the T wave

Normal QT is usually about 0.40 sec

QT interval varies based on heart rate


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Modelul vectorial


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Modelul vectorial


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C7_biofiz Tesut Cardiac Vectorcardiograma

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