Postural tachycardia syndrome (POTS) is a form of orthostatic intolerance, the development of symptoms that come on when standing up from a reclining position, and that may be relieved by sitting or lying back down. The primary symptom of an orthostatic intolerance is lightheadedness, fainting and an
Postural tachycardia syndrome (POTS) is a form of orthostatic intolerance, the development of symptoms that come on when standing up from a reclining position, and that may be relieved by sitting or lying back down. The primary symptom of an orthostatic intolerance is lightheadedness, fainting and an uncomfortable, rapid increase in heartbeat (tachycardia), a common response to a rapid drop in blood pressure as mediated by baroreceptors in the carotid bulb and aortic arch. There are several inconstant secondary symptoms. A syndrome is simply a constellation of symptoms, not all of which may be present in all cases, and as is the case in POTS, a syndrome may also have a wide variety of underlying causes.
A subset of POTS patients suffer from a low blood volume. Would you predict that this particular subset of patients has elevated or suppressed plasma levels of renin and aldosterone? Explain your answer.
The nuance of dysregulation of the RAA axis is complex in these patients, however, plasma angiotensin 2 (Ang2) is found to be significantly higher in these POTS patients. This may be due to the finding that angiotensin converting enzyme 2 (ACE2) is significantly reduced in these patients. ACE2 is part of the recovery arm of the RAA axis homeostatic system in which Ang2 is converted to angiotensin 1-7, a member of the angiotensin peptide family that has the opposite effects of Ang2, leading to vasodilation. How does this finding, elevated Ang2, potentially explain the occurrence of tachycardia in these patients?
Trending now
This is a popular solution!
Step by step
Solved in 2 steps
