What are heart problems that a pregnant women could have?

This is my 4th pregnancy, i had two miscarriages, I'm only 10weeks but i was told that i might have a heart problem because i keep fainting for two weeks already. I was told that, thats not good, so my doctor is going to sent me to a another doctor for tests. My family has heart problems history but not when they been pregnant, on both sides of my parents.