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): /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

Sinus rythm 1 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

Clockwise rotation

Counterclockwise rotation

Illustration of LVH

ST depression and T inversion

T wave inversion

ST SEGMENT AND ACS