I'll be resuming my ECT treatment this week after having to stop due to unexpected surgery. I have ultra brief, unilateral ECT. I have has no memory loss at all. I've had 4 treatments so far and anticipate up to 12.
If you are concerned about memory loss ask for the ultra brief pulse, unilateral. I think it has been the only thing that's worked for me in years.
BTW You might want to read the book called Shocked by Kitty Dukakis. It's honest and very helpful.