Success Rate of Adrenal Venous Sampling and its Determining Factors: Experience of a Single Center in Malaysia

BACKGROUND: Primary hyperaldosteronism has been regarded as the commonest and potentially curable cause of secondary hypertension in up to 80% of cases if this condition is detected early. Laparoscopic adrenalectomy proved to be a promising curable method for primary hyperaldosteronism secondary to aldosterone producing adenoma, while primary hyperaldosteronism secondary to bilateral adrenal hyperplasia requires optimization of medical treatment. Adrenal venous sampling (AVS) has been recommended by the Endocrine Society's guideline in addressing the subtypes of primary hyperaldosteronism. Therefore, determining success rate of AVS in our center is crucial in the management of primary hyperaldosteronism and to prevent redundant procedures. The objectives of this study were to evaluate the success rate of AVS in our center and the associated factors that correlate with the success rate.

METHODS: A retrospective study in a single center, all adult patients who were diagnosed with primary hyperaldosteronism and underwent AVS in our center between 2014 until 2022 were included. Successful samples defined by a selectivity index of ≥2, that is, the ratio of adrenal vein cortisol level to the peripheral vein cortisol level, were evaluated. The baseline demographic characteristics of each patient, technical parameters of AVS, and anatomical parameters of right adrenal vein from the venographic images were evaluated and analyzed to correlate with the outcome of AVS. A P-value of <0.05 was considered statistically significant.

RESULTS: The overall success rate of AVS in our center was 61.3%. The success rate significantly increased to 80.6% in the trained interventional radiologist (IR) group, which represents a single IR who had completed specific training in AVS, compared to non-trained IR group which consisted of a total of 10 IRs without specific AVS training (P = 0.046). The right AVS had lower success rate than the left AVS (64% vs. 94.6%). The type of right adrenal vein pattern showed significant association with the outcome of AVS (P = 0.014). There were 6 types of right adrenal vein patterns observed in our study; Type 1 - gland-like pattern with numerous branches, Type 2 - delta pattern, Type 3 - triangular pattern with central "blush", Type 4 - no discernible pattern and Type 5 - spidery or stellate pattern. The sixth pattern was the hepatic radicles blush with hepatic drainage, for which blood sampling were also collected due to its appearance was frequently indistinguishable from the Type 1 pattern. The results showed Type 2 pattern had the highest incidence (30.5%; 32/105 samples) and Type 5 had the highest success rate (100%; 11/11 samples), while the hepatic radicles blush pattern had the highest incidence in fail samples resulting in the highest failure rate (94.7%; 18/19 samples). The visualization of the inferior emissary vein (IEV) from the venographic images during right AVS had a significant association with the successful AVS (97.5% success rate; 39/40 samples; P = 0.003). Contrariwise, blood sampling withdrawn from the right adrenal vein in the presence of hepatic drainage communication associated with the failure AVS (86.7% failure rate; 26/30 samples; P = 0.001).

CONCLUSIONS: The overall success rate of both AVS in our center was 61.3%, and the success rate was higher in the trained IR group than the non-trained IR group. The visualization of IEV and the type of right adrenal vein patterns were the key determining factors with significant association to the successful right AVS. Conversely, blood sampling withdrawn from the hepatic radicles and hepatic drainage had significant association with the failure right AVS.