As stated a chest x-ray is a preliminary, and usually the first test to help diagnose a heart problem. I remember lying on a gurney half-dead with a prior heart attack and the doctor with his very poor English was trying to explain the results of the x-ray. I wasn't very interested and don't remember much of it.
My heart showed a left ventricle dilation and that caused the heart to have weak contractions. The heart was not pumping sufficient blood supply and blood from the lungs was backed up causing fluids to leak into lung tissues.
The risk is the greatest if your heat is pathologically enlarged (left ventricle), and that can cause abnormal heart rhythm. The enlargement caused my mitral valve to have a problem. The mitral valve is the one-way opening for blood flow to move from the upper chamber to the lower chamber, and the enlarged LV deformed the opening so now it doesn't close tightly over the opening and some blood flows back into the upper chamber during the pumping phase. My heart was dilated.
Enlargement of the heart can be due to thickened heart walls that don't relax sufficiently enough fill properly and that can reduce the amount of blood pumped into circulation. That often is due heart muscle disease.
To help answer you questions: what was/are your symptoms, what medication, any excessive alcohol consumption, smoking, drugs, etc. It probably can be effectively treated and not death issue unless you are in your in 9th decade of age.
Thanks for sharing, and if you have any other questions or comments you are welcome to follow-up. Take care.
Well an x-ray is not really enough information, what you need is an echo scan to evaluate the condition of the heart and the dimensions. Enlargement can be quite normal for someone who does a lot of physical activities, i.e. sports. It doesn't mean death, if it's caused by something other than sporting activities, there are quite a few causes, even high blood pressure. The appropriate medication will allow the heart to return to normal size. You need more tests yet, otherwise everything will be guess work. Have they organised an echo scan?