Thursday, March 5, 2015

Study group discussion: Cardiac embryology and fetal heart sounds

Cardiac Embryology review question! Which blood vessel does the 6th arch artery give rise to?

Pulmonary arteries!

Common carotid artery derived from..??

3rd arch

Right!

Here's a mnemonic on the derivatives of arch arteries http://medicowesome.blogspot.ae/2013/11/aortic-arch-derivatives-mnemonic-images.html

The coronary arteries develop from which structure?

From aortic sinuses of valsalva..??

Endothelial tissue grows out of the aortic wall and connects with the subepicardial vessel plexus while the heart is developing to form coronary arteries.. Is that right??

Ya.. At first the cells are derived from venous sinus  then they transform to become arteries.

When does heart start pumping ?

I am guessing its 4wks?

First heart beat by 4 weeks!

When does the fetal heart beat for the first time in utero? And when is the heartbeat detected by ultrasound? I know 4 weeks is when the heart starts pumping but is it the same time we detect through USG?

I think there are 2 different terms!!
Fetal heart motion around 5-6 weeks
Fetal heart sounds can be heard around 8-10 weeks

Ohh.

Fetoplacental unit establishes around 21-22 days following fertilization.
Fetal heart motion: 9 weeks by doppler USG.
Fetal heart sounds 18-20 weeks by stethoscope.

When does the  fetal movements start?

18-20 weeks?

That's probably right. I know mothers start noticing moviments from 20th week on. a bit later if it is their first child and they don't how to recognise the sensation.

Yep. Multigravidas appreciate fetal movements earlier than primis

In 16 to 18 wks - That's for multigravida.

But fetal movements start at 8-9 weeks. They are perceived late I guess!

In what case foetal heart fails to mature enough such that we can't detect sounds even at 8w?

One case would be hydatidiform mole. No heart sounds heard.

I don't know what is a hydatidiform mole.

Hydatidiform mole isn't a fetus. It's a edematous condition of the Placental villi. You'll learn this is second year, Pathology!
There is no fetus or fetal parts. Not compatible with life... You'll have to read it up from books.

Here are some study links!
Embryology and gestational trophoblastic disease 

Difference between complete and partial mole mnemonic

Hydatidiform mole (Complete vesicular mole) mnemonic

Why is such a gap between starting of heart beats and its detection by US ??

I mean heart starts beating at around 4w and heart beats are detected at around 8w .. why so ?

That's a very interesting question.. But I have no idea regarding that!

Theories:
Maybe because motion is there but structurally heart is immature so no sound is there (av valve)

I think we don't have equipment to detect faint sounds. We could detect heart sounds along with the motion if we had the technology!
Maybe you guys will invent a fetoscope that detects it earlier in the future! :D

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