I can't speak to ECG's, but rather like an animated time series except in the reverse direction.

As you say, the norm is right to left, highest priority (now) on the far right, like this: https://square.github.io/cubism/

It must be an acquired taste, or contextually dependent, because even though I do plenty of metrics visualization which is right-to-left, left-to-right for a high-level view of behavior feels fine to me.