Adrenal Venous Sampling in Primary Aldosteronism: The Usefulness of Contralateral Suppression Index

Table 1

Results of aldosterone and cortisol obtained from adrenal vein sampling under cosyntropin continuous stimulation.

Vein	Aldosterone (ng/dL)	Cortisol (μg/dL)	Selectivity index	Contralateral suppression index
IVC	30.5	34.0	—	—
Right AV	39.0	32.6	0.95	NA
Left AV	47.3	193.0	5.67	0.273

A, aldosterone; AV, adrenal vein; C, cortisol; IVC, inferior vena cava; IV, right iliac vena; NA, not applicable. Selectivity index: cortisol on adrenal vein divided by cortisol on inferior vena cava. A ratio of at least 5 : 1 is needed for one to be confident that the adrenal veins were successfully catheterized. Thus, only the left side was adequately sampled (selectivity index of 5.67). Contralateral suppression index: aldosterone/cortisol on the adequately catheterized side divided by aldosterone/cortisol on the inferior vena cava. The contralateral aldosterone-to-cortisol ratio (0.245) is less than the IVC aldosterone-to-cortisol ratio (0.897), with a ratio less than 1.0 (0.273 in this case), which is indicative of suppression of aldosterone secretion by the noninvolved adrenal gland. It is not applicable because the right adrenal vein was not successfully catheterized.