Identification of subsets of Aldosterone-Producing Adenoma (APA) with dynamic Adrenal Vein Sampling (AVS)

Abstract

Many APA escape identification with available imaging techniques because of their small size. Demonstration of lateralization of aldosterone (A) oversecretion with AVS is crucial for the correct diagnosis, but proved to be difficult, because of the variable and pulsatile pattern of A secretion in APA. Based on the assumption that APA can be ACTH-responsive, stimulation of A secretion before AVS has been proposed to increase the lateralization of A secretion, but data are scant. Therefore, we prospectively investigated the usefulness of dynamic testing in patients (pts) with primary aldosteronism (PA) undergoing AVS. We performed bilateral AVS in 19 consecutive PA pts and used ROC curves-derived criteria for interpretation of results. After 30’ quiet supine resting, blood was simultaneously obtained from both sides for measurement of Cortisol (C) and A. A dynamic test (ACTH 250 μg as an i.v. bolus) was then performed and sampling was repeated again after 30’. Selectivity was assessed by the Cside/CIVC ratio and adverse effects were recorded. AVS resulted to be selective in 85% of pts and no adverse effect occurred. APA was diagnosed in 15 pts (66% left, 33% right) and confirmed at surgery and follow-up; idiopathic hyperaldosteronism was found in two. Only 80% of APA responded to ACTH with an increase of A in the ipsilateral adrenal vein, but on average the increase [AAPAside/(CAPAside/CIVC(inferior vena cava)) 1067±249 pg/ml (m±SEM):, before vs 1378±288 after stimulation] was not statistically significant because of the wide spread of values. In contrast, A increased significantly (p<0.05) in the adrenal vein blood contralateral (ctl) to APA(Actlside/(Cctlside/CIVC(inferior vena cava)) (148±27 pg/ml, before vs 994±480 after stimulation). Due to these concomitant changes no significant enhancement of lateralization was seen with dynamic testing in the APA. While confirming that AVS is safe and accurate for identifying unilateral causes of PA, at a power of 80% (b=0.20; a=0.05) these results do not support the usefulness of dynamic testing to improve the diagnostic accuracy of AVS. Importantly, they showed that dynamic AVS allows identification of ACTH-responsive and non-responsive APA thus opening the way to their molecular characterization.