The institutional review board approved this procedure. Written informed consent was obtained from the patient for the publication of the case details and any accompanying images.

Case History and Physical Examination

A 65-year-old man diagnosed with hypertension for the past 20 years occasionally experienced palpitations. His recent blood pressure measurements ranged from 140/80 mmHg to 160/80–95 mmHg, and his heart rate was between 85 and 105 bpm. His blood pressure was controlled by amlodipine (10 mg daily) and doxazosin (2 mg daily). Multiphasic CT revealed a 1 cm left adrenal tumor (Fig. 1a).

Fig. 1

Left adrenal tumor in a 60-year-old man with primary hyperaldosteronism a Dynamic CT section through the left adrenal gland demonstrates a slightly enhancing nodule, 1 cm in diameter (arrow), in the left adrenal gland. b Digital subtraction of left adrenal venogram demonstrates the left adrenal and tributary veins. A capsular vein is filled, but the inferior phrenic vein is not due to the valve at its junction with the adrenal vein. A bent section can be confirmed on the central side of the superior lateral tributary vein (arrowhead). c, d Volume rendering (VR) image obtained on dynamic CT showing the main trunk of the adrenal vein and tributary veins (purple), the left renal vein (cyan), an adrenal tumor (green), the left adrenal gland (yellow), and the left kidney (brown). The left anterior and right anterior oblique views on the VR images show a superior lateral tributary vein located adjacent to the adrenal tumor (arrow)

Laboratory Studies and Preparation

At baseline, plasma aldosterone and renin concentrations were 26.9 ng/dL and 0.71 pg/mL, respectively, and the serum potassium level was 3.0 mmol/L. The normal range of the aldosterone and renin is 3.1–35.4 ng/dL and 2.5—45.1 pg/mL, respectively. Captopril challenge, saline infusion, and dexamethasone suppression tests were performed. Positive results from all these tests led to the diagnosis of PA. Esaxerenone (MINNEBRO Tablets, Daiichi Sankyo Healthcare Co., Ltd.) was administered to eliminate the effects of aldosterone overproduction before RFA. Phenoxybenzamine or doxazosin was not administered preoperatively.

Segmental Adrenal Vein Sampling Technique and Results

SAVS with adrenocorticotropic hormone stimulation confirmed unilateral aldosterone excess from the superior tributary vein of the left adrenal gland [6, 7]. From the SAVS, the lateralization index of the left adrenal central vein was 17.4 (Table 1). The details of the SAVS are provided in Fig. 1b. The relationship between the positions of the main trunk of the adrenal vein, tributary veins, and adrenal tumor was evaluated by dynamic CT (Fig. 1c, d).

Table 1 Central and segmental AVSEvaluation

The effect of RFA on APA was assessed using the international consensus on surgical outcomes for unilateral PA [8]. The severity of adverse events was assessed using the Common Terminology Criteria for Adverse Events, version 5.0 [9].

Transvenous Radiofrequency Catheter Ablation of the Adrenal Adenoma and Results

The intervention was performed on an ANGIO-CT system. A radiofrequency tip catheter, the GOS catheter, was used for this procedure. The GOS catheter (Japan Lifeline Co., Ltd, Tokyo, Japan) is made of a stainless steel tube with an insulating coating (Fig. 2) [5]. First, a 7-Fr sheath was inserted at the right femoral vein by ultrasound guidance, and the left adrenal vein was catheterized using a 7-Fr guiding catheter (CX Guiding Catheter for the left adrenal vein, Large, Hanaco Medical, Tokyo, Japan). Then, a 1.7-Fr microcatheter was advanced into a tributary vein adjacent to the APA (Fig. 3a), and a 0.014-inch and 300 cm micro-guidewire (ThruwayTM Boston Scientific Co. Massachusetts) was inserted into the tributary vein. There was a bent section of the adrenal vein (Fig. 1b). Initially, we attempted to advance the GOS catheter into the adrenal tributary vein, but due to the bend in the adrenal tributary veins, it was impossible to gently advance the GOS catheter into it. Consequently, we determined that dilating the bent section using a 2.5-mm wide and 1.5-cm-long balloon catheter (Ikazuchi, KANEKA medical products, Tokyo, Japan) was preferable to forcefully advancing the GOS system, which could have resulted in damage to the tributary veins. Finally, the GOS catheter was advanced into it (Fig. 3b, c). After confirming the location of the tip of the GOS catheter on plain CT (Fig. 3d), the 0.014-inch micro-guidewire was removed, and saline was infused into the guidewire lumen at 30 mL/h. Heparin was not used in this procedure.

Fig. 2

GOS system (Japan Lifeline Co., Ltd, Tokyo, Japan). a The GOS catheter has an original spiral-slit cut and is sufficiently flexible to follow the curvature of the venous vasculature. It was designed for a 6-Fr sheath, with a 1.65 mm shaft diameter and a guidewire lumen compatible with a 0.016 inch micro-guidewire. The estimated cauterization area with the catheter is approximately 18 mm in the longitudinal direction and 17 mm in the short-axis direction. b The catheter also has an inner cooling mechanism. c The ablation was performed using a 500-kHz radiofrequency generator. A ground pad was attached to the right back. The roller pump was capable of perfusing saline at 20 mL/min in the inner cooling mechanism of the catheter

Fig. 3

Transvenous catheter radiofrequency ablation of an aldosterone-producing adenoma of the left adrenal gland a The superior lateral tributary vein was catheterized using a 7-Fr guiding catheter (large arrow) inserted into the left adrenal vein, a 1.7-Fr microcatheter (arrow), and a 0.016 inch microwire (arrowhead). b The flexure part of the adrenal tributary vein is dilated using a 2.5 mm diameter, 1.5 cm length balloon catheter (Ikazuchi, KANEKA medical products, Tokyo, Japan) to provide a lumen for insertion of the GOS catheter (arrow). c The GOS catheter was advanced to the end of the superior lateral adrenal tributary vein over the wire (arrow). Then, the catheter tip was pulled back approximately 4 mm by each cauterization, and a total of four cauterizations were performed. The relationship between the catheter tip and the adenoma was not clear in the images, but it was possible to ascertain their relative positions to some extent by comparing the plain CT with the preoperative CT. d Volume rendering image obtained from non-enhanced CT images showing the GOS catheter (orange), tip of the catheter (red) (arrow), adrenal tumor (green) (arrowhead), and adrenal gland (yellow), providing a good view of the relationship between the tumor and catheter tip. e, f After system removal, dynamic CT using 60 mL of iodine-contrast medium was performed. On axial and coronal dynamic CT images, the left adrenal lesion is not detected as an enhanced tumor (arrow). Some edematous changes are seen around the adrenal gland. The lower part of the adrenal gland shows normal enhancement (arrowhead). g, h Five months after the procedure, a dynamic CT for screening of coronal arterial stenosis was performed. While the lower part of the adrenal gland shows enhancement (arrowhead), the left adrenal lesion did not show contrast enhancement (arrow)

The patient was deeply sedated under blood pressure and heart rate control with continuous administration of β-blockers and a radial arterial catheter placed to monitor blood pressure. Then, the APA and surrounding adrenal gland were cauterized at 7000 J two times each in sequence. In the catheter tip used in this report, thermocouples were placed inside the electrodes, allowing the electrode temperature to be measured. The temperature at the tip was measured, while the ablation was performed. The output time was 7−11 min for each ablation and 80 min in total. For blood pressure and pulse rate control, 1308 mg of esmolol hydrochloride (Brevibloc, Maruishi Pharmaceutical. Co., Ltd, Japan) was continuously administered, a total of 190 mg of esmolol hydrochloride as bolus injections, and 32 mg of phentolamine mesylate (Regitin injection, Novartis Pharma K.K., Tokyo, Japan). For pain, 100 mg of tramadol hydrochloride (Tramal injection, Nippon Shinyaku Co., Ltd. Japan) and 1000 mg of acetaminophen (Acelio bag for intravenous injection, Terumo Corp. Tokyo, Japan) were administered.