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Patient
Young woman 23 years of age, asymptomatic, with no prior history and a normal cardiac ultrasound;
Trace
QRS amplitudes are normal in all leads; R wave is maximum in leads II, aVF and V5; the amplitude of the R wave is < 14 mm in lead I, < 13 mm in aVL, < 20 mm in aVF, < 5 mm in V1 and < 25 mm in V6. The amplitude of the S wave is < 20 mm in V1 and < 25 mm in V2; the R/S ratio is less than 1 in V1 and greater than 1 in V5; the Sokolow and Lewis indices are negative;
Exergue
Measuring the amplitude of the QRS and calculating various indices (Lewis, Sokolow) is an integral component of the systematic analysis of an ECG because it allows the diagnosis of ventricular hypertrophy.
The voltage of the QRS-complexes is expressed in mV, while the amplitude is measured in mm using the horizontal lines. The amplitude of the QRS-complexes is extremely variable depending on the leads and according to numerous factors.