Download The ECG in clinical practice: making the diagnosis at a glance

The ECG in clinical practice:
making the diagnosis at a glance
Prepared and presented by Dr Lukoji
Specialist Physician
DEFINITION:
• Graphic recording of the
electrical activity (potential) of
the heart on a standard paper
grid.
CONDUCTION SYSTEM (FLIP CHART)
• Sinus node (initiate the electrical impulse): 6080/minutes: fires the impulse to the atria
• AV node (CS in RA): only electrical connection
between atria and ventricles: transmit the
impulse from the atria to the ventricle: slows
down the impulse (filter and regulator)
• Bundle of His: made out of 2 branches: LBB and
RBB
• Purkinje network: within the ventricle
CONDUCTION SYSTEM
How ECG is generated:
• Impulse depolarizes successively the atria
then the ventricles follow by repolarization for
each .
• Depolarization and repolarization are then
recorder graphically as an ECG in form of a
curve by means of electrodes attached to the
patient’s body surface at conventional spots.
• Depolarization and repolarization generate
waves on the tracing.
ECG curve
Deconstructing the ECG curve:
•
•
•
•
•
•
•
P wave: atrial depolarization
QRS complex: ventricular depolarization (varies)
T wave: ventricular repolarization
Isoelectric line
Calibration signal (rectang=10mm=1mv)
ECG generally prints at a speed of 25mm/sec
Leads: standards (I,II,III), augmented (aVF, aVL,
aVR) &precordial (V1 to V6)
• Leads#electrodes
Electrodes placement
• Proper placement is key to accurate tracing
hence accurate diagnosis.
• Ensure proper skin preparation
• Ensure patient is calm (explain)
• Connect electrodes at appropriate spots
(chest electrodes!)
The precordial leads: correct
placement
ECG stepwise analysis
•
•
•
•
•
Check calibration
Check paper speed
Check patient identity
If needed have a caliper and lens
I take a minimum of 5 minutes to analyze each
ECG (you do not need to hurry, details are key for
accurate diagnosis)
• Get senior colleague opinion if doubt
(overdiagnosis or underdiagnosis)
• Automated interpretation from ECG machine is
often misleading: beware!!!
What to look for: general impression
and rhythm analysis
•
•
•
•
•
•
•
•
•
•
•
What is the rhythm: NSR or not?
What is the heart rate?
P wave duration
Intervals measurement: P, PR, QRS, QT
QRS axis
QRS duration
QRS amplitude: low voltage, sokolow, RSS
QRS infarction signs
Rotation and transition zone
ST and T segment
T-U wave
1
•
•
•
•
•
Sinus rythm
P positive in lead I and II
Every P wave is followed by QRS complex
PR interval is constant
QRS interval is constant
2. Heart rate:
300/large square between R-R interval
P wave duration
Prolong P wave: P mitrale
Right atrial hypertrophy: P pulmonale
PR interval
Prolonged PR
Short PR duration (pre-excitation
syndrome)
Short PR duration
Prolong QRS duration
how prolonged QRS occurs
Bundle branch block
Bundle branch block
Clockwise rotation
Counterclockwise rotation
Illustration of LVH
ST depression and T inversion
T wave inversion
ST SEGMENT AND ACS