You can choose whatever software for presenting ECG signal. I did the image by Matlab 2015a in Ubuntu 10.10.3/Debian 8.1. However, assume that you do not have here the original signal. You need to vector smartly to get nice output. I am interested how much different vector/visual techniques maintain the original signal. The thread To convert only black color to white in Matlab is about some tools to measure how much you lose signal from one technique. The optimum would use such methods that you could maintain the signal quality and return from the bigger image the smaller image.
How can you scale this image for A3 or bigger for printing?