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ECGChapt. 11,12,13

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ECG= Combination of Depol. And Repol. waves

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P‐R interval: bw

A &V excitation

Q‐T interval: V contraction

Isoelectric

قطعه

فاصله

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Biphasic record

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Current leadDepolrized

zone Polarized (Rest) zone

Importance of electrode location

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I + III = II

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Factors that change the direction of the mean electrical vector

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The Nobel Prize in Physiology or Medicine 1924

Willem Einthoven

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ECG Leads: placement of Recording Electrodes

•

ECG chest lead (unipolar

leads)

–

These leads measure the electrical activity in a horizontal plane

that perpendicular to the frontal 

plane

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Augmented vector

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Right to LeftBase to ApexEndocard. to Eipcard.

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Normal range-20 to +100

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Q wave

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DR

جهت انتشار امواج در بطن

جهت بردار الكتريكي

Long duration of action potentialin septum and endocardium

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Atrial

Depol. And repol.

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Plotting the Mean Electrical Axis

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Electrical Axis Deviation

•

Heart position

•

Hypertrophy

•

Block

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Left axis deviation (Left ventricle hypertrophic)

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Right axis deviation (right ventricle hypertrophic):Pulmonary valve stenosisTetralogy

of FallotVSD

High QRS

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tetralogy of Fallot

A: Pulmonary stenosis

B: Overriding aorta

C: ventricular septal

defect (VSD)

D: Right ventricular hypertrophy

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Left axis deviation (Left bundle branch block)

Long QRS

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Right axis deviation (right bundle branch block)

Long QRS

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Short waves:

short QRS

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QRS abnormalities:

Change in voltage:Hypertrophy/InfarctionSlow conduction

Change in duration:Slow conduction/ Purkinje System Blockdestruction of cardiac muscle in various areas

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Current leadInjured zone Normal  zone

Current of injury:

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Current of injury:

J pointIsoelectric line

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New collateral coronary blood flow develops

If the muscle does not die, it will continue to show an injury potential as long as the ischemia exists

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Q wave:

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T-

inversion

Slow Conduction of the Depolarization WaveShortened Depolarization in Portions of the Ventricular Muscle

Digitalin

toxicity

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1. Abnormal rhythmicity

of the pacemaker2. Shift of the pacemaker from the sinus node to another place in the heart3. Blocks at different points in the spread of the impulse through the heart4. Abnormal pathways of impulse transmission through the heart5. Spontaneous generation of spurious impulses in almost any part of the heart

Cardiac Arrhythmias

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Tachycardia>100

Bradycardia<60

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Atrioventricular

Block

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Atrial

premature beat

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A-V node premature beat

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PVC

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Paroxysmal Tachycardia

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Long QT syndrome Ventricular action potentials

QT

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Pathway around the circle is too longVelocity of conduction becomes decreasedRefractory period

of the muscle might become greatly shortened.

Re-entry

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Reentry Mechanisms

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Atrial

fibrilation

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Atrial

flutter

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Interpretation of Normal and Abnormal Cardiac  Rhythm from ECG

•

Sinus rhythm = 60 –

100 beats/min

•

Bradycardia

= heart rate < 60 beats/min

•

Tachycardia = heart rate >100 beats/min

Atrial

rate = 250-350 beats/min

Ventricular rate = 100 –

200 beats/min

Ventricular rate >250 beats/min