Have you ever experienced weird issues with your heart once you got pregnant?

So I myself have a strange issue with my heart. I talked to my doctor and apparently due to the increase in blood and hormones and such it can cause an underlying heart problem to finally appear on the surface. He told me to if I choose to keep the baby be very careful with activities and basically try and stay calm. Oh boy here we go is all I had to say to that. I want a baby badly but I'm also nervous about the strain it can cause on my heart and the potential for capitulation...any who, have you had this happen to you?