I Have Been A Competitive Bodybuilder For 30 Plus Year.

I have been a competitive bodybuilder for 30 plus year. I had open heart surgery back in July. I was released to workout. Now I feel I am making good progress. I can lift pretty hard in all areas except chest. I have been letting the sternum continue to heal. Can I train hard without hurting the new coronary arteries. Are they going to pop off while doing leg presses? Am I safe to trains moderately hard. What about GH FOR HEALING tissue