Partially Successful Adrenal Vein Sampling With and Without Cross-Sectional Imaging in Primary Aldosteronism Subtyping

BACKGROUND: Adrenal vein (AV) sampling (AVS) is used to guide therapy in primary aldosteronism (PA). When a single AV is successfully cannulated, the relative aldosterone secretion index (RASI), which compares the aldosterone/cortisol ratio in that AV versus the periphery, has been proposed as sufficient for PA subtyping, particularly when <1. Data on RASI reliability have, however, been inconsistent. METHODS: This retrospective cohort study included patients with PA who underwent AVS before and after cosyntropin stimulation at a referral center between January 2015 and December 2024. To simulate partially successful AVS, RASI was calculated in patients with successful bilateral AV cannulation and compared across PA subtypes and postoperative outcomes, with assessment of distributional overlap. RESULTS: Of 460 patients (mean age 53±12 years; 58% men), bilateral AVS was successful in 437 patients at baseline and in all patients after cosyntropin stimulation. Without cosyntropin, 98% of dominant AV and 97% of nondominant AV RASI from lateralized PA overlapped with bilateral PA RASI. Similar patterns were observed postcosyntropin. In adrenalectomized patients, RASI did not distinguish between those with and without PA cure. Previously proposed RASI thresholds misclassified up to 74% of lateralized PA and 64% of bilateral PA. When corroborated with cross-sectional imaging, the prediction of correct lateralization improved, particularly when using RASI from cosyntropin-stimulated AVS. CONCLUSIONS: Considering the substantial overlap of RASI across PA subtypes, partially successful AVS has limited utility and is unreliable in guiding adrenalectomy for PA.