Adrenal vein sampling (AVS) is crucial for differentiating between unilateral and bilateral causes of primary aldosteronism (PA). However, there is a lack of uniform agreement regarding the use of adrenocorticotropic hormone (ACTH) stimulation during AVS. This study compares basal and post-ACTH aldosterone and cortisol values to evaluate the role of ACTH stimulation in AVS.
An audit was conducted of 127 AVS procedures performed at Austin Health (Jan 2001–Dec 2015) and Monash Health (Jan 2010-Dec 2015). Both centres performed AVS pre- and post-ACTH using sequential catheterization. Patient demographics, screening aldosterone and renin concentrations, AVS aldosterone and cortisol levels pre- and post-ACTH stimulation, adrenal imaging and surgical outcomes including adrenal histology were retrieved. Successful cannulation and lateralization were defined by the selectivity index (SI) and the lateralization index (LI) respectively.
ACTH significantly increased the rate of successful cannulation (SI > 2 pre- or > 3 post-ACTH), from 70% to 95% on the left (p<0.001), and from 54% to 68% on the right (p=0.03). However ACTH stimulation significantly lowered the LI (p=0.03). Using LI> 3 pre-ACTH and LI > 4 post-ACTH as thresholds for lateralization, the number of unilateral cases decreased from 70% pre-ACTH to 56% post-ACTH. 17 cases would have been re-classified as bilateral despite basal lateralization. Eight of these patients elected to undergo unilateral adrenalectomy, six of whom were found to have adenomas on histology and had a biochemical cure together with normalization or improvement in blood pressure. All six patients had post-ACTH LI > 2.
ACTH stimulation increased the rate of successful cannulation in AVS but masked lateralization in six cases of proven adenoma. Basal LI appears to be the more reliable indicator of lateralization although a post-ACTH LI using a lower threshold of >2 also supports the diagnosis of an aldosterone-producing adenoma.