Just come across your post. Having lupus does not mean that a patient will go on to have heart problems.
The commonest manifestation of lupus in the heart is inflammation of the pericardium or lining , which is called pericarditis. This involves the sac that surrounds the heart, and not the heart muscle.
APS - antiphospholipid syndrome or Hughes syndrome - or sticky blood as some patients call it - can cause problems which may affect the heart amongst other things. Having said this, people who don't have lupus can have APS so this is another reason why it doesn't follow that because you have lupus you will have heart problems.
So, the heart is not routinely an affected organ in lupus but pericarditis is often extremely distressing. It can be extremely painful - from my own experience. Fortunately it does respond well to steroid treatment.
I hope this helps. Take care.