Rescue of Pulmonary Artery Intra-Stent Re-Stenosis by Unzipping an Under-Sized Stent in an Adult Patient with Fibrosing Mediastinitis
Fibrosing mediastinitis (FM) is a rare fibro-inflammatory disease that affects the mediastinum, leading to the compression of vital structures such as the pulmonary arteries and veins. This condition can result in severe complications, including pulmonary vascular stenosis, which can significantly impair respiratory function. The management of FM-induced pulmonary artery stenosis has evolved over the years, with percutaneous pulmonary vascular stent implantation emerging as a promising therapeutic modality. However, the success of this approach depends on the appropriate sizing of the stent, as under-sized stents can lead to intra-stent re-stenosis, a challenging complication to manage.
This article presents a case study of a 71-year-old male patient with FM-induced pulmonary artery stenosis who developed intra-stent re-stenosis following the implantation of an under-sized stent. The patient was successfully treated by unzipping the under-sized stent and implanting a properly sized stent, resulting in significant clinical improvement. This case highlights the feasibility and safety of unzipping an under-sized stent in adult patients with FM-induced pulmonary artery stenosis.
Clinical Presentation and Initial Management
The patient, a 71-year-old male, was admitted to the hospital with progressive exertional dyspnea. He had a history of FM-induced pulmonary vascular stenosis, which had previously been managed with stent implantation. Six months prior to admission, a 6-mm diameter stent (6 mm × 18 mm; PALMAZ®BLUETM, Cordis, Shanghai, China) had been implanted in the right interlobar pulmonary artery due to severe stenosis. Additionally, one month before admission, a 9-mm diameter stent (9 mm × 29 mm; ExpressTM Vascular LD, Boston Scientific, Marlborough, MA, USA) had been implanted in the left superior pulmonary vein.
Upon admission, the patient reported aggravated dyspnea. Physical examination revealed an accentuation of the second heart sound at the pulmonary valve auscultation area and right axis deviation. Laboratory tests showed a D-dimer level of 0.4 mg/mL and an N-terminal pro B-type natriuretic peptide level of 146 pg/mL. Arterial blood gas analysis indicated a blood oxygen saturation of 89.3%, consistent with type I respiratory failure. The patient was classified as World Health Organization (WHO) functional class III.
Diagnostic Evaluation
Computed tomographic pulmonary angiography (CTPA) and selective pulmonary artery/vein angiography were performed to evaluate the patient’s condition. These imaging studies revealed intra-stent re-stenosis in the right interlobar pulmonary artery. The CTPA images obtained before and after the initial stent implantation were reviewed, and it was determined that the interlobar pulmonary artery had a diameter of 10 mm. The previously implanted 6-mm diameter stent was deemed under-sized, which likely contributed to the development of intra-stent re-stenosis.
Interventional Procedure
Given the diagnosis of intra-stent re-stenosis, the decision was made to unzip the under-sized stent and implant a properly sized stent. The procedure was performed using a series of balloons with increasing diameters: 5 × 30 mm (SterlingTM, Boston Scientific), 7 × 30 mm (SterlingTM, Boston Scientific), and 8 × 30 mm (MUSTANGTM, Boston Scientific). These balloons were inflated to pressures ranging from 10 to 14 atmospheres (atm) to gradually expand the under-sized stent. Pulmonary artery angiography (PAG) confirmed that the 6-mm diameter stent was completely unzipped.
Following the unzipping of the stent, a 10 × 25 mm stent (ExpressTM Vascular LD, Boston Scientific) was implanted into the unzipped stent at a pressure of 18 atm. Additional PAG images showed that the 10-mm diameter stent was well expanded, and no complications were observed. The procedure was successful in restoring the patency of the right interlobar pulmonary artery.
Clinical Outcomes
The patient’s symptoms improved significantly following the implantation of the 10-mm diameter stent. At the one-year follow-up, the patient’s functional status had improved to WHO functional class I. The six-minute walking distance increased from 272 meters upon admission to 365 meters at follow-up. Right heart catheterization revealed a decrease in mean pulmonary artery pressure from 41 mmHg to 20 mmHg, and tricuspid annular plane systolic excursion increased from 15 mm to 19 mm. CTPA imaging confirmed the absence of intra-stent re-stenosis, indicating the long-term success of the intervention.
Discussion
Fibrosing mediastinitis is a rare but serious condition that can lead to significant morbidity due to the compression of mediastinal structures, including the pulmonary arteries and veins. The etiology of FM varies geographically, with Histoplasma capsulatum infection being the primary cause in North America and tuberculosis infection being more prevalent in China. The management of FM is challenging, as medical therapy is often limited in efficacy, and surgical interventions carry a high risk of complications due to the abnormal anatomy caused by fibrous tissue infiltration.
Percutaneous pulmonary vascular stent implantation has emerged as a valuable therapeutic option for FM-induced vascular stenosis. However, the success of this approach depends on the appropriate sizing of the stent. Implanting an under-sized stent can lead to intra-stent re-stenosis, which poses a significant challenge in the management of these patients. The case presented here demonstrates the feasibility and safety of unzipping an under-sized stent and implanting a properly sized stent in an adult patient with FM-induced pulmonary artery stenosis.
The technique of unzipping an under-sized stent has been previously reported in the context of congenital pulmonary artery stenosis in children, where it is used to accommodate body growth. However, its application in adult patients with FM-induced pulmonary artery stenosis has not been well-documented. The success of this procedure in the present case suggests that unzipping an under-sized stent and implanting a properly sized stent may be a viable option for managing intra-stent re-stenosis in adult patients with FM.
Conclusion
This case report highlights the successful management of intra-stent re-stenosis in an adult patient with FM-induced pulmonary artery stenosis by unzipping an under-sized stent and implanting a properly sized stent. The procedure resulted in significant clinical improvement and long-term patency of the pulmonary artery. This approach may offer a safe and effective therapeutic option for adult patients with FM-induced pulmonary artery stenosis who develop intra-stent re-stenosis. Further studies are warranted to validate these findings and explore the broader applicability of this technique in the management of FM-induced vascular stenosis.
doi.org/10.1097/CM9.0000000000001493
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