Rescue of Pulmonary Artery Intra-Stent Re-Stenosis by Unzipping an Undersized Stent in an Adult Patient With Fibrosing Mediastinitis
For patients with fibrosing mediastinitis (FM)—a rare condition where thick scar tissue builds up in the chest cavity—pulmonary artery stents can be life-changing. They open narrowed blood vessels to restore oxygen flow and ease breathlessness. But what if the stent is too small for the vessel? This was the dilemma facing a 71-year-old man with FM, whose undersized stent led to dangerous re-narrowing—and whose case now offers hope for similar patients.
The Patient’s Story: A Small Stent, Big Problems
The man, treated at Gansu Provincial Hospital in Lanzhou, China, had a history of FM—a disease where fibrous tissue invades the mediastinum (the space between the lungs) and compresses nearby blood vessels. Six months before admission, he’d received a 6mm-diameter stent (PALMAZ®BLUE™) in his right interlobar pulmonary artery to fix severe narrowing. One month prior, a 9mm stent was placed in his left superior pulmonary vein.
But by the time he returned to the hospital, his symptoms had spiraled: he could barely walk short distances without gasping for air (World Health Organization [WHO] functional class III, meaning marked activity limitations). Tests revealed:
- Low blood oxygen (89.3% saturation, a sign of type I respiratory failure).
- Elevated heart stress markers (N-terminal pro B-type natriuretic peptide: 146 pg/mL).
- A loud second heart sound (pulmonary hypertension) and right axis deviation on an electrocardiogram.
Imaging—computed tomographic pulmonary angiography (CTPA) and selective pulmonary artery angiography—confirmed the worst: the 6mm stent in his right interlobar pulmonary artery had re-narrowed (intra-stent re-stenosis). Further analysis of old scans revealed a critical mistake: his actual interlobar pulmonary artery was 10mm in diameter. The original 6mm stent was drastically undersized.
The Solution: “Unzipping” the Small Stent to Make Room
The team—led by Dr. Yun-Shan Cao of Gansu Provincial Hospital and colleagues from Xianyang Central Hospital, Shanghai Chest Hospital, Tufts Medical Center, and Tianjin Medical University Eye Hospital—decided to “unzip” (gently expand) the undersized stent. Using three balloons of increasing size (5mm, 7mm, 8mm) inflated to 10–14 atmospheres (atm), they carefully stretched the 6mm stent open.
Once the stent was fully unzipped, they implanted a properly sized 10mm-diameter stent (Express™ Vascular LD) at 18 atm. Pulmonary artery angiography (PAG) showed the new stent was perfectly expanded—no tears, leaks, or complications.
The Outcome: A Year of Healing
The results were transformative. Right away, the man’s breathlessness eased. One year later:
- He’d improved to WHO functional class I (no activity limitations).
- His six-minute walking distance jumped from 272 meters (admission) to 365 meters (follow-up).
- Mean pulmonary artery pressure (a key marker of lung health) dropped from 41 mmHg to 20 mmHg.
- Tricuspid annular plane systolic excursion (TAPSE, which measures right heart function) rose from 15mm to 19mm (normal: 17–24mm).
- CTPA showed no re-stenosis in the new stent.
Why This Case Matters for FM Patients
FM is a tough disease to treat. In North America, it’s most often caused by Histoplasma capsulatum (a fungal infection). In China, tuberculosis is the top trigger. Drug therapy relieves symptoms but doesn’t fix vascular narrowing. Surgery is high-risk due to scar tissue. Percutaneous stenting is a newer option—but size is everything.
Undersized stents are a known cause of re-stenosis. While “unzipping” small stents has been used in children with congenital pulmonary stenosis (to adapt to growth), this case is one of the first to show it works in adults with FM—a group where scar tissue makes vessel expansion far harder.
The team’s success hinged on one key step: precise imaging. By comparing old and new CTPAs, they realized the original stent was too small—a mistake that could have been avoided with better pre-op planning.
What This Means for Patients and Doctors
For patients with FM who develop stent re-stenosis, this case offers a new path: instead of removing the old stent (a risky procedure), doctors can unzip it and implant a properly sized one. The team cautions that the approach isn’t for everyone—it requires careful imaging and expertise—but it’s a promising option for adults with FM-induced pulmonary artery stenosis.
As the authors write: “Unzipping an undersized stent and implanting a proper-sized one may be safe and feasible for adult patients with FM-induced pulmonary artery stenosis.”
About the Study
This case was published in the Chinese Medical Journal in 2021 by a team of cardiologists and researchers from China and the U.S. Funding came from the National Natural Science Foundation of China, the Chinese Academy of Sciences “Light of West China” Program, and other regional grants.
doi.org/10.1097/CM9.0000000000001493
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