Yeah big heart ??? I dunno cardio is good, if you have a bad heart maybe ask a doctor what ya can do. I know I got lucky when I was doing meth for 2 years, my heart did nt really get big as most ppl experience this, but my heart is bigger than it was, from dope and working out... but the Dr says its in good shape, resting heart beat is 66-68 bpm, and I have the blood preassure of a 90 pound female..... yeah.... If you have any real concerns though mayne hit up your Dr. fo sho... Dont want to die on a treadmill... lol