How is adrenal venous sampling (AVS) performed in the workup of hyperaldosteronism?

Updated: Oct 19, 2018
  • Author: George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London); Chief Editor: Robert P Hoffman, MD  more...
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Answer

ACTH may be infused into a peripheral vein (at a dosage of 50 mcg/h, starting 30 minutes before sampling) to mask the effects of confounding ACTH peaks during sampling. To reduce the risk of adrenal hemorrhage, adrenal venography is avoided.

If cosyntropin stimulation is not used, AVS is best performed in the morning after an hour of supine rest, to avoid false positive results due to diurnal fluctuation in ACTH concentrations. Additional measures, such as use of benzodiazepines and local anesthesia before venipuncture, should be taken to minimize emotional and pain-related stress.

Hypokalemia should be adequately corrected before AVS. Mineralocorticoid receptor antagonists and amiloride should be withdrawn for 4-6 weeks before AVS. Particularly, the former may allow a rise in renin secretion, which can stimulate aldosterone secretion from the unaffected contralateral adrenal gland, thus minimizing the lateralization. Peripheral α1-adrenergic receptor blockers and the long-acting dihydropyridine or nondihydropyridine calcium-channel blockers (verapamil) are recommended because of their minimal effect on renin secretion.

If cosyntropin stimulation is not used, then bilateral simultaneous AVS should be performed.

An adrenal vein cortisol-to-inferior vena cava cortisol ratio (selectivity index/SI) is used to confirm adequate cannulation of adrenal veins. The cut-off value for the SI should be 2 or higher for AVS performed under unstimulated conditions and 3 or higher for AVS performed during cosyntropin stimulation.

The lateralization index (LI), calculated from the PAC and plasma cortisol concentration (PCC) in both adrenal veins and defined as the ratio of the higher (dominant) over the lower (nondominant) PAC/PCC ratio is used for the assessment of lateralization of aldosterone hypersecretion. Although data on LI cut-off values are controversial, LI cutoff of 4 during cosyntropin stimulation and of 2 for unstimulated AVS have been recommended as the criteria to document lateralization of aldosterone excess. AVS studies using cosyntropin stimulation are considered equivocal when the LI is 2-4.


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