Download - ECG
THE NORMAL ELECTROCARDIOGRAM
Shahd AlAli
• QRS complex: ventricular depolarization• QT interval: mechanical contraction of the ventricles • T wave: ventricular repolarization- can indicate a recent
MI• ST segment: isoelectric
The U wave• The U wave is a small (0.5 mm) deflection immediately
following the T wave, usually in the same direction as the T wave. It is best seen in leads V2 and V3.
Caused by:• Delayed repolarisation of
Purkinje fibres• Prolonged repolarisation of
mid-myocardial “M-cells”• After-potentials resulting from
mechanical forces in the ventricular wall
U waves are prominent if > 1-2mm or 25% of the height of the T wave. Causes: • Bradycardia • Severe hypokalemia
• Depolarization from the endocardium > epicardium• Repolarization from the epicardium > endocardium
• Q wave: 1st negitive after the p wave • R : 1st positive after p wave• S : 1st negative after r wave
ECG leads
•3 bipolar leads ( I,II,III)•3 augmented leads (aVR, aVF, aVL)•6 precordial leads
ECG bipolar leads
Lead II shows the best picture of the heart
Augmented Limb leads Opposite
Precordial leads • V1-V6
• V1 : 4th intercostal space, right parasternal• V2 : 4th intercostal space, left parasternal• V3 : between V2, V4• V4 : 5th intercostal space, midclavicular line • V5 : anterior axillary • V6 : mid-axillary
Cardiac abnormalities • Lead I• Lead III, aVF
• We don’t diagnose it with Lead II
Normal ECG
Left Ventricular hypertrophy
Right Ventricular Hypertrophy