I had the same experience. At 20 week ultrasound, my baby's heart had high density echo spots as well. My IPS results was very good. Still I was very nervous because I was over 40 years old. However, it turned out to be fine. My baby is 8 months old now. He is very healthy and energetic.
My doctor told me that was one of the 10 soft markers they use for checking abnormality. But itself, it should not be a big concern. The Ultrasound lady told me that the machine is much more sensitive now. They are picking up more.