ECG Laboratory Class Introductory Notes Dr. Eric Downer edowner@tcd.ie
Electrocardiogram (ECG) Uses of electrical events through heart: 1. Orientation of heart and the localisation of areas that do not conduct electrical activity normally 2. Amplitude of current associated with depol is proportional to amount of depol tissue myocardial hypertrophy/ atrophy 3. eliable measurement of heart rate (60/ - interval) Objectives of lab class 1. ecord ECG and measure parameters 2. Be familiar with waveform deflections recorded from each electrode 3. Assess electrical orientation of heart 4. Heart sounds
Cardiac conducting system
The ECG interval approx 0.18 sec T interval approx 0.4 sec
Electrical Activity STAT wave: atrial depolarization ELECTICAL EVENTS OF THE CADIAC CYCLE
Electrical Activity STAT wave: atrial depolarization or segment: conduction through AV node and A-V bundle Atria contract. ELECTICAL EVENTS OF THE CADIAC CYCLE
Electrical Activity STAT wave: atrial depolarization or segment: conduction through AV node and A-V bundle Atria contract. ELECTICAL EVENTS OF THE CADIAC CYCLE wave
Electrical Activity STAT wave: atrial depolarization or segment: conduction through AV node and A-V bundle Atria contract. ELECTICAL EVENTS OF THE CADIAC CYCLE wave wave
Electrical Activity STAT wave: atrial depolarization or segment: conduction through AV node and A-V bundle Atria contract. ELECTICAL EVENTS OF THE CADIAC CYCLE wave wave S wave S
Electrical Activity STAT wave: atrial depolarization or segment: conduction through AV node and A-V bundle Atria contract. ELECTICAL EVENTS OF THE CADIAC CYCLE wave ST segment wave S Ventricles contract. S wave S
Electrical Activity STAT wave: atrial depolarization or segment: conduction through AV node and A-V bundle Atria contract. T wave: ventricular epolarization T epolarization ELECTICAL EVENTS OF THE CADIAC CYCLE S wave ST segment wave S Ventricles contract. S wave S
Electrical Activity STAT wave: atrial depolarization The end T S or segment: conduction through AV node and A-V bundle Atria contract. T wave: ventricular epolarization T epolarization ELECTICAL EVENTS OF THE CADIAC CYCLE S wave ST segment wave S Ventricles contract. S wave S
Electrical Activity STAT wave: atrial depolarization The end T S or segment: conduction through AV node and A-V bundle Atria contract. T wave: ventricular epolarization T epolarization ELECTICAL EVENTS OF THE CADIAC CYCLE S wave ST segment wave S Ventricles contract. S wave S
Electrical Activity STAT wave: atrial depolarization The end T S or segment: conduction through AV node and A-V bundle Atria contract. T wave: ventricular epolarization T epolarization ELECTICAL EVENTS OF THE CADIAC CYCLE S wave ST segment wave S Ventricles contract. S wave Atrial contraction precedes ventricular contraction by approx 160msec S
ECG leads Electrode on right and left wrists Electrode on left ankle ight ankle (earth) Einthoven leads: I, II, III (standard limb leads) Augmented limb leads Chest leads: V1-V6
Einthoven lead configurations
ight arm I Left arm II III Left leg ight leg (earth)
- - Augmented Leads I av avl + - II III avf + +
av + + avl Notes: Current flow towards +ve, upward deflection Current flow away from +ve electrode, downward deflection + avf
Chest lead placement
Electrical Axis of the Heart Mean S amplitude from leads I, II and III Mean S = + -S Mark on corresponding side of triangle Drop a perpendicular line and show point of intersection
Heart Sounds 1 2
ECG lead arrangements
Biopolar Leads
Augmented Leads av + + avl + avf
Vectors
1. Electrical axis of 60 0 2. Electrical axis of -15 0 Left axis deviation L. Ventricular hypertrophy hypertension 3. Electrical axis of +170 0 ight axis deviation. Ventricular hypertrophy ulmonary hypertension
Heart Sounds 1 2