Health - Effects on the heart and a few concerns

[Lettish]

Swim will be using ecstasy soon. It will not be his first time, in fact, Swim is a fairly experienced user, and has used ecstasy more than a dozen times in the last few years.

Swim is not particularly fit. Swim understands ecstasy puts strain on the heart, and Swim's cardiac fitness is not exactly the best; he gets a stitch if walking too fast for a few minutes.

Swim's main question is, is there any solid evidence of a connection between ecstasy causing cardiac arrest (heart attack)? Can this happen? What are the chances of it happening? Over the next few weeks (before Swim uses ecstasy) how can he increase his cardiac fitness so that his heart is a bit more prepared and can handle the increased strain on it?