Opinions please

Megan
My first doctors appointment was yesterday. I'm suppose to be 6 weeks 3 days according to when I started bleeding from my chemical pregnancy on June 13th. They did a transvaginal ultrasound and saw the yolk sac and there was a small fetal pole that she measured and it was measuring at 5 weeks and 3 days. She told me she was going to try and get a heart rate and she did and it was 84. They told me to come back in a week for a follow up ultrasound and decided not to do any blood work or anything else until next week. I know this heart rate is low but could it be because I'm early or do they think I'm going to miscarry?