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Title: Endothelial function, the renin-angiotensin-aldosterone axis (RAAS) and hypertension : diagnostic strategies and therapeutic role of potassium supplementation
Author: Graham, U.
ISNI:       0000 0004 2724 7396
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2012
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There is limited evidence of the effect of potassium on endothelial function. Three studies suggest a beneficial effect. Potassium raises aldosterone which has a negative effect on cardiovascular health. We aimed to determine the effect of potassium on endothelial function and the renin-angiotensin-aldosterone system in patients with moderate cardiovascular disease risk. We investigated potential new diagnostic and therapeutic interventions in patients with primary hyperaldosteronism (P A). Lastly we reviewed the outcomes in patients with P A who underwent adrenal venous sampling (A VS). The first study was a randomised controlled crossover study with 40 patients at > 1 0% cardiovascular disease risk. Patients took either 64mmol potassium or placebo for 6weeks with 6week washout. Endothelial function was assessed using pulse wave analysis measuring change in augmentation index to endothelial dependent (salbutamol) and independent (GTN) vasodilation. The second study explored the diagnostic potential of the 250mcg synacthen test in 9 P A patients, 26 essential hypertensives and 26 normotensives. We explored the aldosterone response to gonadotrophin releasing hormone (GnRH) in 6 patients with P A and 15 controls. The final study was a retrospective review of A VS results and adrenalectomy outcomes in 100 patients with PA. Potassium significantly improved systolic blood pressure and but did not affect endothelial function. Plasma renin activity and aldosterone both increased with potassium. Patients with P A had an exaggerated response to synacthen and GnRH ,- compared to controls. Our retrospective analysis found a cortisol corrected aldosterone affected to unaffected adrenal ratio of>2.0 with concordant C'T fmdings accurately classified 95% of P A patients. With adrenalectomy, 97% of patients with unilateral disease had improved blood pressure. Potassium had no effect on endothelial function but lowered systolic blood pressure. The increase in aldosterone did not have a negative impact on the vasculature. The synacthen and GnRH tests offer potential new diagnostic and therapeutic options in P A.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available