Saturday, December 7, 2013

Chemoreflex function in heart failure

Harold D. Shultz and Shu-Yu Sun


There are peripheral and central chemoreceptors in the human body, located in the carotid and aortic bodies as well as the ventral surface of the medulla, that both play a role in regulating both the respiratory and sympathetic cardiovascular outflow. The peripheral receptors primarily respond to hypoxemia, where as the central receptors are most sensitive to hypercapnia.  However, both are able to influence acute ventilation and cardiovascular outflow in order to regulate O2 and CO2 levels in the plasma.  It was previously thought under normoxic conditions the chemoreflex played little or no role in regulating sympathetic tone, recently however it has been shown that blocking peripheral chemoreceptors activity via hyperoxima decreases sympathetic nerve activity.  This evidence leads us to believe that the chemoreflex may play a role in elevated sympathetic tone in heart failure patients, even without hypoxia. A study done with HF induced rabbits shows that peripheral chemoreflex control over renal sympathetic nerve activity and ventilation is increased, increased sensitivity of the peripheral chemoreflex therefore provided a potential mechanism for sympathetic activation in heart failure patients. After many experiments it was found that attenuated NOS activity is one of the main reasons HF patients have enhanced peripheral chemoreceptor sensitivity.

~JI

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