Original sentence: The original machine, weighing some 60 lb (27 kg), delivered the Lown waveform at energy levels up to 100 joules for exposed heart application, and 200–400 joules for transthoracic application.Up until the late 1950's, fibrillation of the heart could be treated only by drug therapy
Edited sentence: The original machine, weighing some 60 lb (27 kg), delivered the Lown waveform at energy levels up to 100 joules for exposed heart application, and 200–400 joules for transthoracic application.Up until the late 1950s, fibrillation of the heart could be treated only by drug therapy