Adrenal vein sampling (AVS) is used to distinguish unilateral from bilateral causes of primary aldosteronism (PA). The use of adrenocorticotropic hormone (ACTH) stimulation during AVS remains controversial. ACTH increases successful cannulation at the expense of producing discordant AVS results. This study compares basal and post-ACTH aldosterone and cortisol values to evaluate the role of ACTH in AVS, and correlates the results of AVS to surgical outcomes in patients with discordant lateralisation.
An audit was conducted of 127 AVS performed at two tertiary hospitals. Information was collected on patient demographics, screening tests, AVS results pre- and post-ACTH stimulation, adrenal imaging and surgical outcomes including adrenal histology and biochemistry where available. Successful cannulation and lateralization were defined by the selectivity index (SI) and the lateralization index (LI) respectively. The diagnosis of aldosterone producing adenoma was supported by a contralateral suppression index (CSI) <1.
ACTH increased SI in all cases with more successful cannulations of both adrenal veins and an overall increase in bilateral cannulation success from 43% pre-ACTH to 65% post-ACTH. The number of unilateral cases fell from 71% basally to 55% post-ACTH. Among 10 patients with discordant results, 6 underwent unilateral adrenalectomy of whom 4 were found to have adenoma on histology. Patient who had clinical and/or biochemical improvement either had post-ACTH LI >2 and/or CSI <1. Of all these discordant cases, the majority lateralized to the right side at baseline.
ACTH increased cannulation success rate in AVS but at the cost of reduced lateralization. Basal LI appears to be the more reliable lateralization indicator, although a lower post-ACTH LI threshold of >2 and contralateral suppression also support the diagnosis of aldosterone-producing adenoma. Discordant cases remain clinical dilemmas so strategies to reduce or understand ACTH-induced discordance are needed.