I agree with Jaxxon. It's important for you to feel comfortable with the diagnosis and treatment. I would ask for copies of the reports and find out what the doctor means by a "weak" heart. If he/she is referring to cardiomyopathy (weaking of the heart's pumping chamber), I'd want to know what I could do to improve my condition. Many times, cardiomyopathy can be improved, but it's a good idea to know what's going on before you move forward. Jaxxon gave you great advice - let the doctor and/or staff know that you are concerned and would like to know more. Regardless of how your proceed, I think you should ask for copies of the test results.
Are you taking any medications? It's common to take medications for a weakened heart muscle. Some doctors put their patients on an ACI inhibitor, beta blockers, and/or combinations of heart medications. Let us know what you find out.
Check with your doctor about ways to improve your hearth health. I suppose if a doctor told me I had a "weak heart," I certainly would be nervous, but they would know best how much of a concern that is. I would think with exercise and proper nutrition, you could strengthen even a "weak" heart, but again, be sure to check with your doctor. Be honest with them, and let them know you are worried about such a diagnosis, and be proactive and see if they can give you any tips on how to improve your situation.
Best of luck :)