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Figure 1 Example of electrocardiographic analysis of clinical arrhythmias: leads aVF, V₁ and V₄ of a normal sinus beat, followed by the first beat of repetitive monomorphic ventricular tachycardia. A = total QRS duration, measured from the earliest onset in lead V₄ to the latest activation in lead aVF (ms); B = R-wave duration, determined in lead V₁ from the QRS onset to the R-wave transaction point of the R-wave with the isoelectric line (ms); C = R-wave amplitude, measured from the peak to the isoelectric line (mV); D = S-wave amplitude measured from the cusp to the isoelectric line (mV).