Radiation after Masectomy with LVEF issue

I am concerned about the effect that Radiation will have to my heart since a MUGA detected LVEF was low (49%). My Radiation Oncologist tells me that heart damage after radiation to the chest wall today is very rare - but that doesn't mean it doesn't happen. I was diagnosed with ILC, had a masectomy, pathology report shows there were at least 4 tumors and the margins were positive. I definately want Radiation since there was cancer in the margins, but since it is the left side of my chest I am quite concerned about radiation to the left side of my chest wall. Is there anyone out there who can give info about this?