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Predeployment Length Modification of a Self-expanding Metallic Stent

Hoag, Jeffrey B. MD, MS*; Juhas, William RN; Morrow, Kathy CRT; Standiford, Steven B. MD, FACS; Lund, Mark E. MD, FCCP* †

doi: 10.1097/LBR.0b013e31817c0383
Case Reports
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Bronchopleural and alveolopleural fistulae from surgical and nonsurgical causes present unique management issues. A myriad of strategies have been employed to diminish airflow through the fistulous tracts. Frequently, treatment approaches need to be individually tailored on the basis of fistula size and location and to limit morbidity associated with treatment options. In unstable patients, a combination or staging of minimally invasive and surgical approaches may be necessary. Unfortunately, necessary resources may not be readily available for emergent intervention in all cases. We describe a novel approach of predeployment length modification of a self-expanding metallic airway stent. Deployment of this modified stent completely abrogated airflow through the intractable alveolopleural fistula that caused profound respiratory failure.

*Drexel University College of Medicine

Cancer Treatment Centers of America, Philadelphia, PA

Sources of Support: None.

Reprints: Mark E. Lund, MD, FCCP, Drexel University College of Medicine, Pulmonary, Critical Care, and Sleep Medicine, Mailstop 107, 245 N 15th Street, Philadelphia, PA 19102 (e-mail: Mark.Lund@Drexelmed.edu).

Received for publication March 10, 2008; accepted March 25, 2008

Conflict of Interest: Dr Lund has been a member of the Clinical Advisory Board for Alveolus Inc. Dr Hoag, Dr Standiford, Mr Juhas, and Ms Morrow have no conflicts to disclose.

Abronchopleural fistula (BPF) is an abnormal communication between the proximal tracheobronchial tree, defined as the mainstem, lobar, or segmental bronchus, and the pleural space. BPF carries a high mortality1–3 and frequently presents a management quandary. An alveolopleural fistula (APF) occurs when the pleural connection is distal to a segmental bronchus.4 In patients with respiratory failure, the occurrence of an APF significantly complicates the management of the underlying disease process.

Both BPF and APF develop as a complication of surgical and nonsurgical processes.4–6 Spontaneous or chemotherapy-induced tumor necrosis are known to cause pneumothorax.7–9 These spontaneous pneumothoraces can cause persistent air leaks that are always because of APF.10 APF after pulmonary resection may not require reoperation, although this may not be the case with profound air leaks that may be seen in parenchymal necrosis tumor.8 On the other hand, BPF most frequently requires surgical correction.4,11 Both medical and surgical techniques have been used to diminish abnormal airflow through pulmonary fistulae. Because of the instability of patients with these devastating complications, surgical correction is frequently performed as a staged procedure.5

Covered self-expanding metallic (SEM) airway stents are well known for their ability to reduce or eliminate airflow through a fistula.12–17 Although a myriad of stent sizes are commercially available, immediate access within a given facility or a geographic region for an odd, rarely used size may not be obtainable in an emergent setting. To date, the peer-reviewed literature is lacking in experience with real-time modification of covered metallic airway stents. Herein, we report a case in which length modification of a predeployed, covered, SEM airway stent helped terminate massive airflow through an APF in a patient with acute respiratory failure and pneumothorax refractory to multiple chest tube evacuation.

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CASE PRESENTATION

A 33-year-old woman with stage IV, estrogen, progesterone, and HER-2/neu negative breast carcinoma presented with increasing respiratory distress and hypoxemia. The patient had a preexistent interstitial process that on biopsy was a cryptogenic organizing pneumonialike sequelae.18 She had multiple pulmonary metastases. These metastatic nodules were traced over serial computerized tomography scans to subsequently cavitate with chemotherapy. Rupture of these cavitated metastases initially created small, loculated pneumothoraces, with the largest one being in the right upper lobe (RUL) (Fig. 1). Ten days after initial stabilization with medical management, she developed acute respiratory failure from a right-sided tension pneumothorax. On successive days, a total of 3 chest tubes were placed as the right lung failed to expand. She continued to have a massive air leak while breathing spontaneously for 7 days. Profound refractory hypoxemia on 100% FiO2 nonrebreather mask persisted. Despite her markedly advanced disease and overall poor prognosis, the patient requested all palliative care for the quality of life.

FIGURE 1.

FIGURE 1.

In the operating room, we undertook a trial blockade of the right mainstem bronchus (RMS) to evaluate her tolerance of unilateral, left lung ventilation with an ultimate plan to place a stent from her trachea into the left mainstem bronchus. The patient was managed with a laryngeal mask airway with spontaneous ventilation under inhalational anesthesia. Profound oxygen desaturation ensued after temporary occlusion of the RMS. At this stage, selective occlusion of the RUL bronchus was considered, as most of the cavitating lesions were located in this lobe. The patient tolerated the trial of RUL bronchus well and the air leak diminished. We elected to occlude the RUL with an RMS/right bronchus intermedius (RBI) stent. Evaluation of the RMS and proximal RBI revealed that a stent of 16 to 18 mm and no longer than 40-mm length was required. Immediately available were 16 to 18 mm×60 to 80 mm in both Ultraflex (Boston Scientific, Boston, MA) and Aero (Alveolus Inc., Charlotte, NC) stent models. It was determined that the patient could not be safely managed for rigid bronchoscopy secondary to inability to maintain spontaneous ventilation with adequate procedural sedation. This precluded the use of silicone stents that are easily length modified. The volume of her leak was believed to preclude safe use of positive pressure ventilation. Two other regional centers of excellence in interventional pulmonology and our local sales representative were contacted; nevertheless, an appropriate-sized stent remained elusive. We had no immediate availability of endobronchial valves or other occluding devices.

After extensive discussion and consideration of the design of both available SEM stents, it was decided to modify the length of an Aero stent predeployment to allow the use of a 60-mm stent in a 40-mm placement. After modification of the length of the Aero stent, it was deployed in the RMS/RBI without difficulty. Immediately after deployment and partial occlusion of the RUL, there was a significant reduction in the air leak. Repositioning the stent to completely occlude the RUL eliminated the leak through the fistula (Fig. 2).

FIGURE 2.

FIGURE 2.

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MODIFICATION OF SEM STENT LENGTH

Stent Selection

Consideration of both commonly used SEM stents was undertaken. The “woven” design of the Ultraflex concerned us because of the potential of unraveling after modification. Loss of overall structural integrity was believed probable after cutting the end of the woven nitinol structure.

The structure of the Aero is unique. It is laser fashioned from a single piece of nitinol. Concentric rings of nitinol are held in position by “long axis” nitinol strands. It was this “unibody” construction with concentric rings that we believed made the Aero more amenable to length modification (Fig. 3). Each concentric ring is 5 mm in length, allowing rapid approximation of the length to be removed. The lack of significant foreshortening with deployment was also reassuring that the trimmed length would approximate the final length. Furthermore, the complete enclosure of the nitinol metal in the coating suggested a further ability to have the adapted stent maintain structural integrity.

FIGURE 3.

FIGURE 3.

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Partial Deployment

To maintain the integrity of the portion of the stent to be placed within the RMB, the predeployed original constrained position had to be kept (Figs. 4A, 5A). The sheath laying over the Aero stent was slowly withdrawn proximally using the trigger grip. Additional control was provided by holding the distal end of the inner catheter with the other hand to prevent its rapid withdrawal. By slowly withdrawing the sheath and allowing the individual rings to expand, the precise length was obtained (Figs. 4B, 5B, 5C). In this manner, 4 spiral rings, 20 mm of the stent, were exposed.

FIGURE 4.

FIGURE 4.

FIGURE 5.

FIGURE 5.

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Modification of Length

After the required number of rings was exposed, the remaining constrained portion of the stent was secured by hand. Using straight sharp-sharp iris scissors, the stent was slowly cut using the end of the outer sheath as a guide. The cut was placed between the exposed rings and the constrained portion of the stent. This provided a “window” that allowed cutting the hydrophilic coating and several long axis nitinol connectors. The now fully expanded, severed distal end of the stent was removed and discarded (Figs. 4C, 5D).

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Advancing Sheath

The outer sheath was now slowly readvanced over the space left by the discarded stent. It was reapproximated to the distal tip of the stent deploying device. The remaining nondeployed stent was now completely enclosed by the sheath (Fig. 4D). This allowed insertion of the stent in a usual fashion through the oropharynx and trachea, and the positioning of the modified stent within the bronchial tree was uncomplicated (Fig. 6).

FIGURE 6.

FIGURE 6.

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DISCUSSION

BPF and APF are dreaded complications of a multitude of thoracic procedures and diseases because of the difficulty in management and poor outcomes. Although not formally tested, factors associated with poor outcomes include fistula size, time of onset from surgery, bronchial stump length, and etiology of stump failure. On the basis of these factors, certain therapeutic options may be favored over the others.

Surgical approaches for management of BPF include thoracoplasty, chest wall fenestration, and omental wrapping by a variety of techniques, although these procedures carry significant morbidity and mortality themselves. Surgical therapy for a postresection APF is rarely indicated.4,11,19 Isolated lung ventilation strategies, chest tube management, and high-frequency ventilation have all been attempted with variable success.

Endobronchial management of BPF was first described in the year 1977.20,21 A full review of the topic was recently published.5 Briefly, these less invasive approaches have included tracheobronchial stenting using SEM stents13–17 and silicone stents.12,22,23 Occlusion with fibrin1,24–26 or synthetic glues27,28 with and without vascular coils for scaffolding, scar-promoting procedures with neodymium:yttrium aluminum garnet (Nd:YAG) laser,29 or sclerosant injection30,31 at the fistula site have also been reported. More recently, the use of 1-way valves has been used with success.32,33 Additionally, animal models have suggested the potential application of laser welding of patch material to the bronchial wall.34

Because of the paucity of randomized, controlled trials in APF treatment techniques, small case series and anecdotal experience provide limited options to bronchoscopists.

In our patient, the massive volume loss through the APF complicated her underlying interstitial disease process. The patient experienced a rapidly progressive hypoxemic respiratory failure. Because of the concern of exacerbating tidal volume loss through the fistula, we did not use positive pressure ventilation. Similarly, independent lung ventilation was not an option as demonstrated by temporary occlusion of the RMS with a bronchial blocking balloon. Finally, the patient was clinically unsuitable to tolerate thoracoscopy after a tenuous operative course to place her 3 chest tubes. We, therefore, elected to seal the fistula with a covered SEM stent. Because of limitations in stent size in our institution and other local centers, we made the decision to attempt length modification rather than abandon the attempt to close the air leak and stabilize the patient. We were afraid that without this maneuver, the additional length of the stent would have blocked the lower trachea and the left main bronchus. A silicone “Y” stent was not considered, as it was not safe to perform a rigid bronchoscopy.

To our knowledge, the length modification of an SEM stent has not been performed previously. We describe a strategy for the predeployment length modification of covered SEM airway stents. This method allows for the emergent management of a rapidly deteriorating patient when essential stent sizes are unavailable. Although long segments of stenosis can be managed with nesting of short stents, a stent that is too long usually offers no benefit. Inappropriately long stents will occlude the distal airways or will project into the trachea. Stents with significant projection into the trachea can partially occlude or severely compromise the tracheal lumen or contralateral mainstem bronchus. Furthermore, the stent may cause mucosal injury to the tracheal wall, particularly with cough. With the above method of modification, an Aero stent can be shortened by 5-mm increments to the appropriate length.

In our patient, this stent modification technique allowed the desired portion of the stent to remain in the constrained position and subsequently be safely deployed. The stent remained stable after deployment with continued occlusion of the RUL fistula. There was no recurrence of right-sided fistula leakage over the remainder of the patient's course, although the patient expired 10 days later from a contralateral tension pneumothorax.

We believe that the best option is to always place the appropriate length stent without modification. If an emergent indication is present and the available stents are too long, this technique can be used to fit the stent to the patient. It would be our recommendation that as soon as feasible, the stent be replaced with the correct size.

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CONCLUSIONS

Length modification of the Aero stent before deployment is possible. The modification of this SEM stent can be considered when a proper length stent is not available in an urgent or emergent situation. Further evaluation is required to determine the long-term safety and stability of such an approach.

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REFERENCES

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Keywords:

interventional pulmonology; bronchoscopy; airway stent; self-expanding metallic stent

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