Steroids increasing the size of your heart is an urban myth. Steroids increase the size of muscles and your heart is technically a muscle but you would need to be taking absurd dosages for really long periods of time to actually increase the size of your heart.
Steroids are well known to increase blood pressure if you aren't taking the proper support supplements with your cycle. In particular, you need to add an AI and a good liver aid supplement into your cycle.
Here is a great video for you to watch where I talk about support supplements for the steroid cycle to stay healthy and side effect free while on cycle ->
http://www.evolutionary.org/forums/...upplements-stay-health-while-cycle-45316.html
The first thing I talk about in the video is the importance of an aromatize inhibitor (AI) to keep estrogen in the low-normal range. This will prevent side effects like gynecomastia, water retention and libido issues. The AI should be started on day 1 of the cycle and used throughout the entire cycle. Aromasin at 10mg every other day is a good dosage.
The second I talk about is the importance of using an anti-prolactin drug whenever using a nandrolone (deca, npp) or nandrolone derivative (trenbolone). Cabergoline or pramipexole at 0.5mg every third day is a good dosage.
The third topic I discuss is the benefit of using a good liver aid supplement like N2guard from n2bm.com when ever using oral steroids.
Finally, I talk about blood pressure and cholesterol and stresses the importance of routinely checking both while on a steroid cycle. If either are significantly out of the normal range, book an appointment with your doctor and get him to write you a blood pressure and/or cholesterol medication prescription.