Cyanosis in Right heart failure?

[infinity89r]

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Goljan says that cyanosis occurs particularly in right heart failure because there is increased time for peripheral tissues to extract oxygen which leads to a decreased oxygen saturation. Isn't that a paradox? I mean even if there is increased extraction of oxygen in the tissues and saturation in the venous system goes down, won't gas exchange in the lungs equilibrate it back to alveolar oxygen levels? I don't understand what I'm missing there. Can someone please explain? Its in page 164 in the 3rd edition of Rapid Review Pathology.

 

[pathtopenn]

I think u are just thinking a little too hard. The right heart is going to pump into the pulmonary circulation the deoxygenated blood. So the definition of heart failure is the pump failure thus less output from the rt ventricle into the pulmonary circulation. Less output leads to less reoxygenation of the blood. Less oxygenated blood in circulation cause more TPR to adjust perfusion to the more important areas. Thus cyanosis occur because those are not the area that is the most important (ie heart, brain). Good luck!

 

[JohnGT]

The above description is correct. Right heart failure decreases the ability to advance blood flow from the right heart into the pulmonary circulation for gas exchange. Therefore, overall oxygen content on the arterial side remains low because oxygen saturation has decreased. Cyanosis is simply a physical finding that reflects this decreased oxygen content.

In children, this type of cyanosis is found in patients with a hypoplastic right heart or in other structural diseases such as TOF or severe pulmonary valve stenosis. Similarly, you will see cyanosis in children with other Right to Left shunting; because again, the overal oxygen saturation and content on the arterial side is decreased.

BTW, the increased extraction of oxygen in peripheral tissues during a "cyanotic state" is due to the effects of local metabolites and the oxyhemoglobin dissoc curve.

 

[Chirurg]

I think u are just thinking a little too hard. The right heart is going to pump into the pulmonary circulation the deoxygenated blood. So the definition of heart failure is the pump failure thus less output from the rt ventricle into the pulmonary circulation. Less output leads to less reoxygenation of the blood. Less oxygenated blood in circulation cause more TPR to adjust perfusion to the more important areas. Thus cyanosis occur because those are not the area that is the most important (ie heart, brain). Good luck!

this sounds good.
and also OP:
as Goljan says in 1 of his lectures qouting someone else: Right Heart Failure is a diagnosis of signs (Cyanosis, raised JVP, oedema) while Left Heart Failure is a diagnosis of Symptoms ( Shortness of Breath, Weakness etc)