cardiac echogenic focus

I need help, I'm 22 weeks pregnant and  I'm freaking out. Has anyone been told or ever been told that their unborn child has cardiac echogenic focus. I have googled it and they keep saying its a soft mark in the heart that could mean Down syndrome. I did the test for Down syndrome through blood and my results came back negative. My doctor told me there's nothing to worry about, she's not worried cause I'm having a healthy pregnancy. But I don't believe her. She said it goes away sometimes after birth or next ultrasound. I keep thinking about this over and over and over again everyday, I'm really scared. I will love my child regardless but still it's scary news and situation . I just need to know if everyone had gone through this, maybe give me some insight. I would really appreciate it. Has anyone gone through it and see that it's gone and there baby was fine?   Thank you