I think clen can be use full for your heart, especially if you have problems getting winded to early during work outs. Because clen is used for asthma it really helps me breathe good in the gym, and once I get off it, my breathing feels a lot better.
I think the heart problems due to clen are from too many stimulants at once, too many peak doses of clen over working the heart to hard. I have heard from a pro who used 580mcg/day, I wouldn't really recommend ever going past 120-140mcg/day but who am I? I just think if your diet and cardio is in check you don't need much clen.