From a cardiography report from Bolivia - Nastro Nx, followed by a number. There is no additional context; this appears in a paragraph of data, including the patient's name, height, weight, operator's initials, et cetera. It appears that Nx is used instead of No. (number). Is this just there to confuse the uninitiated? All I can find on a web search regarding "Nastro" is the name of a researcher in Italy. Does anyone have any suggestions regarding meanings and possible translations into English? Thank you in advance!