Child physiology

[fatonfire]

A low PVR , flow through a defect e.g. VSD and blood flow to lungs will be high.
High blood flow to lungs increases left atrial pressure. why does this cause pulmonary vasoconstriction?

Thanks

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[FindMeOnTheLinks]

Too much blood flow to the lung results in a V/Q defect. The pulmonary vasoconstriction is a reflex to prevent this. I'm a little hazy on the mechanism but I think the increased blood flow stretches the vessel walls, opening mechanically gated calcium channels in the smooth muscle cells, and the calcium causes constriction. Could be off on that though.


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