I will answer this for you.
Steroids do not cause heart disease.
Steroids can cause elevated ldl (bad cholestorol) which can lead to artheriosclerosis, and heart disease.
This by itself is a risk factor, but the is culminated by gentically inherited risks, i.e. did your father have heart disease? did he die of an MI before 65 y.o.?
Now most BB these days do not eat good food, year round. Bodybuilders these days typically have weight shifts of up to 80 lbs in the off season. - that is a lot of food, and all that stored fat, when it is burned off, has to be reabsorbed back from the fat cell, into the blood stream, then utilized as energy.
Now if you can imagine that some of this ends up lining the blood vessels twice over, and going through the kidneys, e.t.c, this isn't a very healthy thing to be doing on a regular basis!
The other unhealthy practice of BB is the binging post contest - where rapid weight gain occurs.
Most of this is water weight, that is sucked interstitially due to negative oncotic pressure in the blood (that is to say the body has become used to a certain body mass and has adjusted the amount of protein in the blood to achieve a balance in simple diffusion) the influx of calories increase solute interstitially well over solute intervascularly thereby pulling water with it.
This ends up spilling back ward a bit into the intervascular space further complicating things by increasing myocardial stretching of the right side of the heart - which can damage the elastisity of the heart (starlings rule) decreasing ejection fractions by as much as 20%!
Basically this practice isn't healthy!
Now of course the additions of GH, and insulin, igf-1 e.t.c. don't help matters by further increasing the cardiac problems, as an overly large heart loses it's ability to properly contract the left ventrical fully, further decreasing ejection fraction, yet, because the heart is larger, demand for oxygen is greater, yet supply is less due to the decrease in cardiac output and ejection fraction.
Now add to this the arteriosclerosis, (narrowing of the coronary arteries that supply the heart with blood) and you see we have a big problem just waiting to happen!
As for kidney damage, well the overuse of diuretics in the sport can't have helped things, I know Flex Wheeler probably injured his kidneys way worse from his automobile accident, as trama causes the release of myoglobin from the musculature, which ends up clogging the tubules, and nephrons in the kidneys, causing permament damage.
This probably was the beggining of his problems, which were made worse by his abuse of diuretics, and other drugs.
Kidneys are also tied directly to cardiac health as well.
So the moral of the story, is, watch your cholestorol levels closely, eat clean, don't binge - especially after a contest, -no large shifts in weight in the off season, avoid 17-AA steroids which are the worst effectors of lipid levels, and GH and insulin.
Get a stress test by the time you turn 35, and then every 5 years thereafter.