Sokolow-Lyon index

How to calculate the Sokolow-Lyon-Index for left ventricular hypertrophy?

For the assessment of the left ventricular myocardium, the amplitude of the R wave in either v5 or v6 (the higher amplitude counts) is added to the amplitude of the S wave in v1. If the sum is greater than 3.5 millivolts, the index is positive. This is suggestive of hypertrophy of the left ventricular myocardium.