Yes...due mostly to those variables -- mainly excessive dosages, non stop usage and the excessive weight that results from it. I'd say overweight people are more suseptible to heart disease than some 200 pound bodybuilder who does a light cycle twice a year. (Not to mention what else some of these guys use that strain the heart such as stims, slin and GH).
And as anyone who is familiar with my work knows, I believe dosages of over a gram a week TOTAL is absurd for non pros. If you can't make progress on 600 mgs a week, you suck anyway. And cycles should not exceed 2 months.