Download Electrocardiography

Electrocardiography
A Brief Overview of ECG
Interpretation
Normal to Abnormal
• Only way to understand abnormal is to first
look at the “normal”.
• First: looking at cardiac electrical
conduction.
Conduction System
Sinoatrial Node
Bundle of His
Atrioventricular Node
Bundle Branches
Perkinje Fibres
Conduction System
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Sinoatrial Node (60-80 bpm)
Atrioventricular Node (40-60 bpm)
Bundle of His (20-40 bpm)
Bundle Branches
Purkinje fibres
Cardiac Cells
Normal Conduction
• SA node starts action
• Accepted by AV node, starts inferior action
• Passes to bundle of His, down Purkinje
fibres
• Action potential restarts
Cardiac Cell
Regular Muscle cells many more
Nuclei per cell, whereas cardiac
Muscle cells only have one.
Much more like smooth muscle,
Under involuntary control.
Cardiac Cell
Muscle Cell
Conductivity
• Contractile and Conductive cells
• Focused impulse is generated (a
pacemaker of any other site) then
surrounding tissue will rhythmically
contract.
• Bad when not starting at node.
Normal ECG
Normal ECG
Dysrhythmias
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Look at P Wave
Look at QRS complex
Look at T Wave
Look for U Waves
Rhythm Rate
• In order to tell what the rate of the heart is
from the ECG:
• Count the # of QRS complexes in a six
second strip and multiply by ten.
Dysrhythmias
• Rate
• P Waves (present, inverted, absent,
retrograde, ratio)
• PR Interval (5 small squares)
• QRS (3 small squares)
• Rhythm (regular/irregular)
Interpret me!
Now me!
Heart Disease
• #1 killer in Canada
Blocked Coronary Artery
• depending on the
amount of damage,
conductive system
may be impaired.
• electrical impulses do
not travel across dead
tissue.
Defibrillation
• Reboot the computer
Defibrillation
• Definition - the application of an external
electrical shock to the heart muscle
which terminates the electrical activity of
the heart. This allows the natural
pacemakers of the heart to restore
normal rhythm.
• Time from collapse to defibrillation is
critical factor to survival
Ventricular Tachycardia
Ventricular Fibrillation
Non-Shockable Rhythms
12 Lead
• Normally look at Lead II (over Left
shoulder)
• Sometimes need to look at more aspects
of heart
• Used to diagnose myocardial infarction,
other cardiac dysrhythmias
• Looks at 12 Different aspects of the heart
12 Lead
Questions?