Abstract Body: Introduction
Unilateral primary aldosteronism (PA) is diagnosed when aldosterone production lateralizes during adrenal vein sampling (AVS). In lateralizing PA, if aldosterone secretion is autonomous, it should suppress the contralateral adrenal gland. Contralateral adrenal gland suppression of aldosterone is often overlooked in lateralizing or unilateral PA diagnosis, which may explain why adrenalectomy (ADX) does not always lead to a biochemical or clinical cure.
Hypothesis
Is heterogeneity in aldosterone dysregulation and clinical outcomes in unilateral PA after ADX related to the magnitude of contralateral adrenal gland suppression of aldosterone secretion?
Methods
Adults with hypertension and confirmed primary aldosteronism (PA) who underwent successful adrenal vein sampling (AVS) were included. Bilateral PA (n=28) was defined by a post-ACTH lateralization index (LI) < 4; unilateral PA (n=17) by LI > 4. Unilateral cases were further stratified by contralateral suppression index (CSI), calculated by dividing the aldosterone-to-cortisol (A/C) ratio of the non-dominant adrenal vein by the A/C ratio of the inferior vena cava (IVC): true unilateral (CSI < 1, n=10) and asymmetric bilateral (CSI > 1, n=7). We assessed pre-adrenalectomy (ADX) urinary aldosterone excretion, sodium suppressibility of aldosterone, 6-month post-ADX blood pressure outcomes, and changes in WHO-defined daily dose (DDD) of antihypertensive therapy. Medically treated bilateral PA patients underwent the same assessments.
Results
True unilateral PA had the highest 24-hour urine aldosterone excretion (median 35.2, interquartile range [19.7, 54.0]), while asymmetric bilateral was similar to bilateral PA 19.1 [18.1, 21.8] vs. 20.3 [16.6, 32.7]. An index (urine sodium/urine aldosterone) showed sodium suppressibility of aldosterone was similar in asymmetric bilateral and bilateral PA 12.4 [10.3, 16.8] vs 12.5 [10.2, 17] but was lowest in true unilateral PA 6.3 [6.0, 8.4]. At 6 months post-ADX, SBP reduction was larger in true unilateral compared to asymmetric bilateral PA -35.0 [-58, -11.5] vs -6 [-16.8, -2] though the drop in DDD was more in the latter -1.5 [-3.5, 0.6] vs -2.3 [-3.0, 2.3].
Conclusions
Our data suggests heterogeneity in aldosterone dysregulation and clinical outcomes amongst those with lateralizing or unilateral PA with those manifesting lesser suppression of contralateral adrenal gland aldosterone secretion closely mirroring the non-lateralizing or bilateral PA.