Lee, Hans Joo MD^*; Puchalski, Jonathan MD^†; Sterman, Daniel H. MD^‡; Bhadra, Krish MD^‡; Kumar, Rohit MD^‡; Gillespie, Colin T. MD^‡; Haas, Andrew R. MD, PhD^‡

Post–lung-transplant bronchial stenosis (TBS) remains the leading airway complication after lung transplantation. The stenosis rate is unpredictable and varies from 7% to 18% and is a source of morbidity and mortality for lung transplant recipients.^1,2 Bronchial stenosis is considered a late complication usually occurring several months after lung transplantation.³ Anatomically, the stenosis may occur at the anastamosis, in airways distal to the anastamosis, or at both sites. The TBS etiology remains unclear, but mucosal and airway ischemia at the time of transplantation is thought to be the initial injury with an exaggerated healing response leading to stenosis.⁴

Bronchoscopic management is a common, minimally invasive approach to TBS treatment. Balloon bronchoplasty dilatation can improve airway patency and relieve TBS, but balloon dilatation alone often fails because of restenosis, and additional long-term interventions may be required.⁵

Self-expanding metal stents (SEMS) and silicone tubular stents can provide airway patency to stenotic or obstructed airways under a variety of airway conditions. In 2005, the United States Food and Drug Administration issued a black box warning against SEMS for benign airway disease.⁶ Long-term SEMS complications include fracture, migration, and granulation formation, and SEMS removal is exceedingly difficult, which may lead to life-threatening complications. Therefore, silicone tube stents are now considered as the primary intervention for benign airway obstruction as would be encountered in a lung transplant population; however, unique post–lung-transplant airway anatomic constraints often make silicone stent placement and positioning difficult.⁷

Silicone Y-stent placement has been traditionally limited to the trachea, main carina, and bilateral mainstem airways. They offer a decreased risk of migration and the ability to treat the main central airways when involved with an obstructive process.⁸ Because of post–lung-transplant anatomic constraints and failed prior tube stent placement, we sought to determine whether secondary carina Y-stent placement could offer a better TBS solution. Our hypothesis is that the Y-stent could be safely placed in the secondary carina in transplant patients and that it would result in a decrease in the number of bronchoscopy procedures related to TBS. We describe our experience using silicone Y-stents in the secondary carina for lung transplant TBS.

PATIENTS AND METHODS

We retrospectively examined prospectively collected data of all silicone Y-stents deployed for post–transplant-TBS at our institution. Six patients had 10 secondary carina silicone Y-stents placed. The collected data included the stent location and position, number and interval of bronchoscopic procedures before and after the Y-stent insertion, complications, and Y-stent removal.

All patients had an initial trial of balloon dilatation and/or tubular stent (SEMS or silicone tube) placement. The decision to deploy a secondary carina silicone Y-stent occurred only after the failure of initial treatment, with worsening clinical symptoms, spirometry, and/or complication from prior treatments (ie, stent migration; multiple stenoses). All silicone Y-stents were placed in the operating room under general anesthesia after informed consent. A Bryan-Dumon rigid bronchoscope (Woburn, MA) was used for all procedures. A Hood (Pembrooke, MA, USA) silicone Y-stent (diameter dimensions: 12 mm, 9.5 mm, 9.5 mm) was used for all patients. Measurements were obtained using flexible video bronchoscopy to determine Y-stent dimensions, and the stent was altered by shortening the stent limbs accordingly. The Bryan stent deployment system was used to deploy the stent in the bronchus intermedius (BI) or the left lower lobe bronchus. Under direct vision, the stent was grasped using forceps and manipulated into position. The upper limb stem of the stent was then placed into the upper or the middle lobe bronchus using a bronchoscope or a balloon as a guide. The balloon was used to promote full stent expansion, and the final stent position was confirmed bronchoscopically. All patients were prescribed either 3% hypertonic saline or 10% N-acetylcysteine nebulizers and albuterol 3 times daily to promote mucous clearance. Follow-up bronchoscopy was performed after Y stent insertion either for clinical symptoms (difficulty with mucus clearance, dyspnea), for decreased spirometry, or for routine surveillance to ensure no granulation tissue formation.

Patients who had Y-stent dislodgement or premature removal of their stent were all given a trial without stent replacement. Otherwise, stents were removed after sustained clinical stability of about 12 months in the expectation that airway remodeling had occurred.

RESULTS

Ten silicone secondary carina Y-stents were deployed in 6 lung transplant patients (Table 1). Four patients had grade IV stenoses and 2 had grade II stenoses. Spirometry and clinical improvements were seen in 5/6 patients after Y-stent placement. Six Y-stents were placed in the right mainstem/right upper lobe/BI (RMS/RUL/BI), 2 in the BI/right middle lobe/right lower lobe (BI/RML/RLL), and 2 in the left mainstem/left upper lobe/left lower lobe (LMS/LUL/LLL) (Fig. 1). One of the 6 patients did not tolerate his secondary carina Y-stent within days after placement because of RUL limb granulation tissue formation. The stent was removed in 2 days and replaced with another secondary carina Y-stent with a longer RUL limb, which also caused obstructing granulation tissue within 2 days. This Y-stent was removed and the TBS was managed without a Y-stent.

TABLE 1

FIGURE 1

There was a significant prolonged Y-stent placement therapeutic effect in all but 1 patient. There was both a reduction in the procedure number performed and an increase in interval days between procedures for the 5 patients who tolerated their stent. The mean number of procedures before secondary carina Y-stent insertion was 15.6, but only 4.8 after Y-stent insertion. The mean interval number of days between procedures was 24.5 days before the Y-stent insertion and 85.8 days after the Y-stent insertion. There were no complications in any patients during Y-stent insertion (Fig. 2).

FIGURE 2

One patient required secondary carina Y-stent replacement after inadvertent Y-stent dislodgement during a follow-up surveillance bronchoscopy and symptomatic restenosis within 2 days. One patient had an initial Y-stent placed in the BI/RML/RLL, which was removed after a lobectomy was performed for RUL airway obliteration. After RUL lobectomy, a recurrent stenosis developed in the BI, requiring a new Y-stent in the BI/RML/RLL. Another patient had a Y-stent replaced in the same location after obstructing granulation tissue developed in the LUL limb. The granulation tissue was debulked and injected with steroids (triamcinolone acetonide 10%), and a replacement Y-stent with a longer LUL limb was deployed without granulation tissue recurrence. While this patient developed obstructing granulation tissue requiring stent revision, small-to-moderate amounts of asymptomatic nonobstructing granulation tissue developed in 4 of the 6 patients. This granulation tissue was detected by routine surveillance bronchoscopy at 2- to 3-month intervals and was easily removed with standard biopsy forceps without stent revision or removal.

Stent Removal

Only 1 of the 6 patients had a successful Y-stent removal without TBS recurrence. As presented above, 1 patient did not tolerate 2 different Y-stents within days because of a robust granulation response and another management approach was required. One patient had a Y-stent removal trial and failed, and was eventually retransplanted for a combination of TBS and chronic rejection. Another patient had a lobectomy with Y-stent removal, and a new Y-stent was placed for a new TBS. Two patients have not had a Y-stent removal trial and both are asymptomatic with stable spirometry.

DISCUSSION

Post–lung-TBS can be a devastating complication for lung transplant recipients that can lead to reduced lung function, multiple procedures with complex airway interventions, reduced quality of life, and potentially increased mortality. Current treatment strategies include balloon bronchoplasty, stent placement, reconstructive surgery, and retransplantation. Balloon bronchoplasty can be successful, but the result is often temporary with restenosis common.^5,9 Surgical reconstruction is particularly risky in this patient population because of mmunosuppression, poor wound healing, postsurgical adhesions, and poor pulmonary reserves. Therefore, endobronchial airway stents form the backbone to prevent TBS recurrence and maintain airway patency.

In TBS, airway stenting has many anatomic constraints that prevent effective stent deployment. The TBS position and extension into donor airways determines what type of stent may be optimal in a given anatomic location. As the donor lung bronchial circulation is not reestablished, the donor airway is kept as short as possible to minimize airway ischemia. This often results in the RUL airway or the left hilum being within several millimeters of the anastamosis. If a pure anastamotic stenosis develops with normal distal airways, deployment and maintenance of stent position without migration or coverage of any distal airways can be problematic. If the stenosis extends further into the donor airways beyond the anastamosis, these anatomic relationships and optimal stent choice, placement, and maintenance become even more difficult to rectify.

Our original approach before 2005 was to place an uncovered SEMS across the TBS, which would rarely migrate, would allow aeration of donor airways (RUL or LUL) through the SEMS struts, and would effectively improve patient symptoms and spirometry. Unfortunately, in some patients, a robust granulation response would develop leading to further interventions and complications.¹⁰ Because of these SEMS complications and the 2005 Food and Drug Administration black box warning regarding SEMS in benign disease, this approach was abandoned in favor of silicone tube stent placement.

All of the patients in this case series underwent standard balloon bronchoplasty, TBS electrocautery incision, intrastenosis steroid injection, and/or deployment of other silicone endobronchial stents without the ability to maintain airway patency. Therefore, secondary carina Y-stent placement was conceived out of necessity in these patients after approaches and standard silicone tube stent deployment failed either because of the inability of the stent to remain in position or because of TBS extension into distal airways where tube stent configuration would not be feasible. We demonstrate here that secondary carina Y-stent deployment significantly decreased the number of procedures and increased the time between procedures for 5 of our 6 patients and stabilized their airways. Furthermore, the secondary carina Y-stents did not become dislodged as did silicone tube stents in several patients. The 3-limb Y-stent configuration not only provided a better anchor and positional stability, but also offered the ability to stent multiple adjacent TBS areas.

Our data also demonstrate that there is no perfect stent for any application. One patient developed rapid and robust granulation tissue within days of Y-stent placement precluding successful secondary carina Y-stent utilization. In addition, a second patient developed obstructing granulation tissue 5 months after Y-stent placement that required granulation tissue debulking and deployment of a new Y-stent with a modified limb to prevent granulation tissue formation. The remaining 4 patients all developed small-to-moderate amounts of asymptomatic nonobstructing granulation tissue easily removed during surveillance bronchoscopy. These findings demonstrate that there is a role for surveillance bronchoscopy in these patients to ensure no stent-related complications are developing. Moreover, mucoid obstruction of silicone stents is a concern, which can lead to respiratory distress, especially in a single-lung transplant patient whose native lung is often severely compromised. However, we encountered no mucoid impactions through mucolytic medication nebulizers 3 times daily in all patients. Although it was technically more difficult to place secondary carina Y-stents compared with its initial design for the trachea and mainstem airways, this was not prohibitive and was performed safely with no procedural complications. Other investigators have described using silicone Y-stents safely in the secondary carina for malignancy.¹¹

We arbitrarily chose approximately 1 year for Y-stent removal without any specific criteria other than clinical stability. In previously published data, there have been other SEMS and silicone tube stent series that were removed in this time frame without TBS recurrence. Thistlethwaite et al¹² described their experience with silicone stent removal in a series of 22 stents placed for TBS: 18 were successfully removed in about 12 months (mean duration, 362.3 d; range, 185 to 567 d). In our patient series, only 1 of our 6 patients had their Y-stent removed without TBS recurrence. This patient had a grade II injury, which may be a factor in successful stent removal as the degree of airway injury and stenosis is less extensive. Three patients developed restenosis and required Y-stent reinsertion, and each of these patients presented with a grade IV anastamotic injury (extensive bronchial wall necrosis extending 2 cm from anastomosis) and type IV stenosis (diffuse bronchial stenosis). Similarly, Thistlethwaite et al describe difficulties with permanent stent removal in diffuse bronchial stenosis (type IV). Consequently, the degree and type of injury before stent placement may predict successful remodeling and stent removal. A larger study will be needed to further examine this observation.

Our study has several limitations; the most obvious is its retrospective nature and the potential bias by the investigators determining the frequency of subsequent interventions. However, there is no evidence-based protocol on the threshold for bronchoscopy in TBS management or bronchoscopic maintenance for any airway stent. Another limitation is that there were no objective measures (spirometry) or validated quality-of-life evaluations before/after Y-stent placement. We conjectured that the decrease in flexible and rigid bronchoscopies after our intervention translated into a meaningful quality-of-life improvement. Future prospective studies need to consider these limitations in their design.

CONCLUSIONS

To our knowledge, this is the first description of using the silicone Y-stent in the secondary carina for post–lung-transplant TBS. A combination of the unique anatomic anatamosis and airway configurations with the type and degree of stenosis lends to a secondary carina Y-stent offering a novel intervention for select patients. When the Y-stents were tolerated, they reduced the number of therapeutic procedures required to manage TBS and increased the interval between procedures after stent placement.

REFERENCES