Surprisingly low aldosterone levels in peripheral veins following intravenous sedation during adrenal vein sampling: implications for the concept of nonsuppressibility in primary aldosteronism.

BACKGROUND: Constituitively high and nonsuppressible aldosterone levels are considered to be the hallmark of primary aldosteronism. We observed a high proportion of primary aldosteronism patients with surprisingly low aldosterone levels in peripheral veins during adrenal vein sampling (AVS) and sought to further characterize the phenomenon.
METHODS: Database analysis of patients with primary aldosteronism at the University of Calgary who underwent AVS under intravenous sedation. Aldosterone levels following sedation were compared with aldosterone measured at diagnosis in the free-living state. A validation analysis was performed on a similar database from the University of British Columbia.
RESULTS: Seventy-two percent of 127 patients had AVS aldosterone levels more than 30% lower than their outpatient aldosterone measure (468 vs. 278 pmol/l, P < 0.001). Thirty-nine percent of patients had aldosterone levels less than 200 pmol/l and 13% had levels less than 140 pmol/l during AVS. Repeat analysis on the UBC cohort produced similar results with 88% having an aldosterone more than 30% lower than the outpatient measure (median aldosterone 568 vs. 201 pmol/l, P < 0.001).
CONCLUSION: A majority of primary aldosteronism patients have markedly lower aldosterone levels during sedated AVS compared with those found during outpatient diagnosis. In the absence of confounding medications, hypokalemia, circadian timing, postural variation and with low correlation to measures of hypothalamic-pituitary-adrenal activity, this suggests that many primary aldosteronism patients may, at times, have aldosterone levels that are surprisingly low-normal. This finding challenges the concept that a persistently high and nonsuppressible aldosterone level is a sine qua non of primary aldosteronism.