SAT-548 Significance of Adrenal Vein Aldosterone Gradient in the Diagnosis of Unilateral Subtype of Primary Aldosteronism

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Context: Adrenal vein sampling (AVS) is the standard method for subtype diagnosis in primary aldosteronism (PA), while success rate of its procedures, especially in right adrenal vein (AV), has limited. However, unilateral subtype of PA can be completely cured by surgical treatment and hence diagnostic approach for PA should be established especially when patients with apparent adrenal disease on computed tomography (CT) lack complete AVS result. In recent years, segmental AVS demonstrates that apparent aldosterone gradient in each adrenal vein branch is specific finding in aldosterone producing adenoma. Since we have reported that plasma aldosterone concentrations different in the proximal and distal regions of the left AV in some of the patients with PA, we hypothesized that solo finding of adrenal aldosterone gradient in the left AV (left AV gradient) should be the clue for unilateral subtype of PA. Objective: The aim was to investigate whether left AV gradient indicate the left unilateral subtype of PA. Design and Setting This study was a part of the Kyushu Adrenal Network Database for Advanced medicine (Q-AND-A) study, a cross-sectional and retrospective study in a single referral center. Participants and AVS procedure: Of 194 PA patients who underwent AVS with cosyntropin stimulation between January 2007 and April 2019, 111 patients had available and successful AVS data. Blood samples in left adrenal veins were obtained from following two positions; the common trunk and the central adrenal vein. We calculated left AV gradient by the ratio of aldosterone-to-cortisol ratio on the higher position in left AV to that on the lower position. We determined the presence of left AV gradient if it was greater than four. Main outcome measures: Prevalence of unilateral subtype in patients with left AV gradient who had unilateral disease on CT. Results: Of 111 patients with complete AVS data, 43 who had left unilateral disease on CT were analyzed in present study. Twenty-nine patients were diagnosed as left unilateral subtype on AVS and 14 were bilateral subtype. Aldosterone gradient was observed only in patients with unilateral subtype (41% [12/29]), not in patients with bilateral subtype (0% [0/14]). Of 29 patients with unilateral subtype on AVS, clinical parameters, including plasma aldosterone concentrations, plasma renin activity, and serum potassium levels, were not different in those with and without left AV gradient. The receiver operative curve analysis for the diagnosis of unilateral subtype on AVS showed that the optimal cutoff value of left AV gradient was 3.3 with a sensitivity of 45% and specificity of 100%. Conclusion: The presence of left AV gradient is the reliable finding for the diagnosis of left unilateral subtype in patients with PA who have unilateral disease on CT. However, further study in a larger number of cases is required to validate this finding.