Determination of adrenal hypersecretion in primary Aldosteronism without aldosterone-production adenomas

Of the total 2753 hypertensive patients referred to our center for screening PA from January 2018 to July 2019, we retrospectively reviewed the AVS data of 292 patients who were suspected to have secondary hypertension and excluded 14 patients who failed in AVS, 17 patients with Cushing syndrome / Adrenal medullary hyperplasia, 80 patients with Conn syndrome, and 40 patients without complete biochemical result. The remaining 141 patients were analyzed for the following parameters: age, sex, body mass index (BMI), serum potassium, serum sodium, urinary potassium, urinary sodium, estimated glomerular filtration rate (eGFR), renin, aldosterone, aldosterone to renin ratio (ARR) value after the confirmation test, CT imaging, and AVS examination. Blood pressure was obtained in three consecutive measurements after taking a 5-min rest. Blood samples were obtained in the sitting/recumbent position during 8:00 am to 10:00 am. All antihypertensive drugs that can interfere with the renin-angiotensin-aldosterone system were discontinued for at least 2–4 weeks before the screening test. Patients with hypokalemia were treated with potassium sparing agents. Inclusion criteria— mainly referred to Endocrine Society guideline [17]: ① Blood pressure ≥ 140/90 mmHg or under treatment, and/or hypokalemia (serum potassium ≤3.5 mmol/L); ②Elevated ARR; ③Suspicious positive or positive results of confirmatory test, confirmatory test is excluded if clinical symptoms are typical, renin is inhibited and PAC > 20 ng/dL; ④ CT indicates normal appearing adrenals, minimal unilateral adrenal limb thickening, unilateral microadenomas (≤1 cm), or bilateral macro- or microadenomas (or a combination of the two). Exclusion criteria: ①APA: unilateral macroadenoma (diameter > 1 cm) and the opposite side was normal [18, 22, 23];②Aldosterone-producing adrenal carcinomas (diameter > 4 cm), glucocorticoid remediable aldosteronism (GRA) and familial hyperaldosteronism;③Any other secondary hypertension: renal parenchymal hypertension, renal artery stenosis, Cushing’s syndrome, adrenal medullary hyperplasia, coarctation of aorta, obstructive sleep apnea hypopnea syndrome, etc.;④AVS procedure failed. Major complications: ①Ischemic heart disease [22]: (1) typical clinical symptoms; (2) new ischemic ECG changes; (3) new pathological Q waves; (4) new imaging evidence of myocardial loss or abnormal ventricular wall motion; (5) coronary angiography or intracavitary imaging abnormalities or autopsy confirmed coronary thrombus; ②Hypertensive Nephropathy [24]: (1) hypertension; (2) microalbuminuria> 20 mg/d or ACR > 30 mg/mmol; (3) excluded due to renal parenchymal diseases (glomerulopathy or tubulopathy diseases). This study complied with the tenets of the Declaration of Helsinki and was approved by the ethics committee of institute. Written informed consent was obtained from all patients.

AVS has been performed through the upper extremity route (median cubital vein or basilic vein). Briefly, A French 6 sheath was inserted through the percutaneous forearm vein approach. A 5F MPA (125 cm, Cook Medical, Bloomington, IN, USA) catheters were advanced slowly to the right atrium, then into the inferior vena cava (IVC), bypassing the right ventricle. The right adrenal vein was catheterized, and the position of the catheter tip was verified by gentle injection of a small amount of nonionic contrast medium and documented radiographically. Blood was obtained from the right adrenal vein. Then, a TIG catheter (Terumo Corporation, Tokyo, Japan) was used to catheterize the left adrenal vein. Heparin (50 U/Kg) was administered to avoid adrenal venous thrombosis during AVS procedure [25, 26].

Successful sampling was determined by high selectivity index (cortisol in the adrenal vein/ cortisol ≥2 subclavian vein without adrenocorticotropic hormone simulation). To correct for the dilution effect of the inferiorphrenic vein flow into the common phrenic trunk, the right and left adrenal vein aldosterone concentrations were divided by the respective cortisol concentrations. Plasma cortisol was used to calibrate the aldosterone level to obtain the local standardized concentration of aldosterone. The catheterization was successful if the concentration of intravenous cortisol / inferior vena cava cortisol (SI) ≥ 2 and a lateralization index≥2 was indicated the unilateral aldosterone hypersecretion based on an expert consensus on the use of AVS for PA subtype [17].

Captopril challenge test (CCT) and saline infusion test (SIT) were used as confirmatory tests for PA diagnosis. Aldosterone and renin level were tested by Chemiluminescence Immunoassay (CLIA) (DiaSorin, Saluggia, Italy). Positive results were determined according to Endocrine Society guideline [17].

IBM SPSS Statistics 20 was used for statistical analyses. We used F-test or Kruskal–Wallis test to compare various parameters according to the data distribution. Quantitative values between groups were compared by t test and the Mann-Whitney test, while Chi-square test was used for categorical variables. Variables associated with lateralized AVS in the bivariate analysis (p < 0.05) were entered in logistic regression models, and stepwise forward selection was performed to find whether variables were independently associated with lateralized AVS (Wald test p < 0.1). C-Statistic was used to evaluate the discrimination ability of regression models. p < 0.05 was considered statistically significant.

Database retrieval yielded 292 AVS in 2753 patients during the study period (Fig. 1). Of these 292 patients, 97 (33.2%) did not fulfill the inclusion criteria, 40 (13.7%) were without complete biochemical result, and 14 (4.8%) had a failure of AVS. The remaining 141 patients were included: 90 (63.8%) had a lateralization; 51 (36.2%) had non-lateralized AVS. Among them, 33 patients met the criteria for spare confirmatory tests. Among the remaining 108 patients, 25(23.1%) underwent SIT and 83(76.9%) underwent CCT.

According to the presence or absence of lateralization examined by AVS, patients were divided into lateralized PA and non-lateralized PA. Except for the difference in the lateralization ratio, there was no difference in other clinical parameters and proportion of complications between the two groups (Table 1).

Age, serum potassium, eGFR, PAC, and ARR after confirmatory tests were used to distinguish the lateralized AVS in patients with UAH. Thus, a multivariable logistic regression model was used to predict the lateralized AVS based on these variables (Table 2). This model has statistical significance (χ² = 7.519 p < 0.01) and good fitting effect(χ² = 10.79 p = 0.21). Only one combination variable was entered in the model: ARR after confirmatory tests (the coefficients: 1.010, 95% CI: 1.000 to 1.021, p < 0.044). 13.9% (15 of 108) of PA patients without APA showed a sensitivity of 22.1%, a specificity of 100%, while the specificity of serum potassium and PAC was lower (Table 3). In addition, several models for predicting AVS avoidance reported by other studies were used to evaluate our results. It showed a poor prediction (Supplementary Table S1).

We further examined whether UAH patients with ARR > 10 (ng/dL)/(mU/L) were susceptible to target organ damage and PA-associated complications (Supplementary Table S2). The PAC was significantly higher, while direct renin concentration was significantly lower in UAH patients with ARR > 10 (ng/dL)/(mU/L) compared to that in UAH patients with ARR ≤10 (ng/dL)/(mU/L) (p < 0.01). However, serum potassium level was not different between the two groups. Importantly, the incidence of ischemic heart diseases and hypertensive nephropathy was higher in UAH patients with ARR > 10 (ng/dL)/(mU/L) (p < 0.05). Correlation analysis showed a significant association between PAC and aldosterone concentration of the adrenal vein (r = 0.299 p < 0.01), and serum creatinine level and ACR (urinary albumin/creatinine ratio) were significantly correlated with the PAC (r = 0.218 p < 0.05, r = 0.233 p < 0.05), respectively (Supplementary Table S3).