A novel high-frequency optical coherence tomography imaging with isotonic electrolyte solution in a patient with a history of contrast-induced nephropathy

We report a case of a 59-year-old man with contrast-induced nephropathy (CIN) following a previous percutaneous coronary intervention (PCI), who underwent elective PCI using a novel high-frequency optical coherence tomography (HF-OCT) system with isotonic electrolyte solution (IES) (acetated Ringer’s solution) as a contrast-sparing flushing agent. HF-OCT enabled high-quality intravascular imaging without the use of conventional contrast medium. Complex PCI was successfully performed in the left anterior descending artery, including intravascular lithotripsy and stent implantation, under the guidance of HF-OCT with IES. Only 5 ml of contrast was used throughout the procedure, and the patient experienced no recurrence of CIN. This case demonstrates that HF-OCT with IES is a feasible and safe imaging strategy in patients with contraindications to contrast media. A 59-year-old man with acute coronary syndrome was admitted to our hospital two months earlier, and the culprit lesion in the middle mid-right coronary artery (RCA) was treated with a coronary stent. Preprocedural serum creatinine level was 1.62 mg/dl, and estimated glomerular filtration rate (eGFR) was 35.5 ml/min/1.73 m². After the index procedure, he developed CIN with his creatinine level increasing to 3.29 mg/dl and eGFR decreasing to 16.4 ml/min/1.73 m² 4 days later. The elective PCI for residual tight stenosis with severe calcification in the left anterior descending artery was scheduled. In performing complex PCI in a patient with CIN, we employed a novel HF-OCT system (Gentuity LLC, Sudbury, Massachusetts, USA) with IES (acetated Ringer’s solution) to minimize contrast medium. This HF-OCT system enables faster pullback speeds (up to 100 mm/s) and long imaging distance using a reduced-size 1.8-F imaging catheter [1,2]. We have previously reported that this system could provide coronary artery images of comparable quality to those obtained with conventional contrast medium flushing by using IES instead [3]. A 6-Fr guiding catheter (Ikari left 3.5, Heartrail Ⅱ; TERUMO Corporation, Tokyo, Japan) without side holes was used for the selective left coronary artery angiography. Referring to the prior coronary angiography, a guidewire was advanced across the lesion (Fig. 1a, arrow) without contrast injection, and HF-OCT imaging was performed using IES with a 6-Fr guide extension catheter (Guideplus ST; Nipro Corporation, Osaka, Japan). In accordance with our previous report, IES was manually injected into the coronary artery using a 20 ml syringe to obtain OCT imaging [3]. For the distal lesion, predilation was performed with a 2-mm balloon (Zinrai 2 × 15 mm; Kaneka Corporation, Osaka, Japan), followed by stent implantation (Xience Skypoint 2.25 × 23 mm; Abbott Vascular, Santa Clara, California, USA). On OCT, severe calcification with a calcification score of greater than or equal to 3 was identified in the proximal lesion (Fig. 1e, arrowheads). Predilation was performed with a 2-mm balloon, and intravascular lithotripsy was performed using Shockwave C2 (Shockwave Medical, Santa Clara, California, USA) with a total of 60 pulses (Fig. 1b). Using HF-OCT with IES, we confirmed that cracks had formed in the calcified plaque (Fig. 1f, arrowhead). Further predilation with a 3-mm scoring balloon (Lacrosse Aperia NSE 3 × 13 mm; Nipro Corporation) was conducted, and a stent was deployed (Xience Skypoint 3.5 × 48 mm; Abbott Vascular) (Fig. 1c). Postdilation was performed with a 4-mm balloon (Hiryu Plus 4 × 8 mm; TERUMO Corporation). HF-OCT confirmed good stent expansion with no malapposition, dissection, or hematoma (Fig. 1g). Finally, simultaneous HF-OCT imaging and coronary angiography were performed, allowing the PCI procedure to be completed with only 5 ml of contrast medium. The final angiography revealed no significant abnormalities, with good expansion of the treated lesion (Fig. 1d). The patient was successfully discharged without any recurrence of CIN. In the present case, the total contrast volume was only 5 ml, achieved by the 100 mm/s pullback speed of the HF-OCT system and an IES flush. Our previous study confirmed that HF-OCT with IES provides image quality comparable to conventional contrast OCT [3]. These findings suggest that HF-OCT with an IES flush is a practical strategy to minimize contrast exposure, particularly in patients at risk of CIN. While conventional OCT systems can be used with noncontrast flushes such as dextran, saline, or Ringer’s solution, these approaches are constrained by slower pullback speeds (20–40 mm/s), often necessitating multiple flushes or supplemental contrast. In contrast, the HF-OCT system achieves 100 mm/s pullback with an imaging length up to 100 mm, enabling high-quality visualization with a single IES flush. This advantage underscores the clinical value of HF-OCT with IES in minimizing contrast exposure, particularly in patients with renal dysfunction or a history of CIN.Fig. 1: Angiographic and HF-OCT findings of the patient with a history of contrast-induced nephropathy treated using an isotonic electrolyte solution (acetated Ringer’s solution) flush with a novel HF-OCT system. (a) Coronary angiography performed at the time of percutaneous coronary intervention 2 months earlier showed severe stenosis in the left anterior descending artery (arrow). (b) IVL was performed because HF-OCT revealed severe calcification. (c) A single long stent was implanted to fully cover the lesion. (d) Final angiography confirmed no significant abnormalities with only a 5 ml of contrast medium. (e) HF-OCT image of the severely calcified proximal lesion (arrowheads) before IVL obtained using an IES flush. (f) HF-OCT after IVL showing cracks in the calcified plaque (arrowhead), also obtained with an IES flush. (g) Postintervention HF-OCT demonstrating good stent expansion without major malapposition, dissection, or hematoma, acquired using an IES flush. HF-OCT, high-frequency optical coherence tomography; IES, isotonic electrolyte solution; IVL, intravascular lithotripsy.Acknowledgements Conflicts of interest There are no conflicts of interest.