An electrocardiogram is the picture or printout of the heart’s electrical activity — the line that jumps with each beat. A nurse sticks small pads on your chest and limbs; a machine reads the tiny signals and draws the trace. Doctors look at that trace to see if the heart is racing, skipping, or damaged after a shock. In hospitals everyone shortens it to ECG; in American English you will also hear EKG, from the German spelling. This word is the record, the “writing.” The machine that makes it is the electrocardiograph. Though actually, staff mix the two all day long, and in everyday speech ECG covers both the test, the machine, and the paper. You do not need the long word at the bedside; you need it when a textbook wants the precise thing. It is a medical, technical noun. It is not a treatment and it does not sit inside the body — that would be something like a pacemaker.

心電圖