electrocardiography a brief overview of ecg interpretation
TRANSCRIPT
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
Atrioventricular Node
Bundle of His
Bundle Branches Perkinje Fibres
Conduction System
• 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 CellRegular Muscle cells many moreNuclei per cell, whereas cardiacMuscle 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
• 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?