Ann Thorac Surg 2006;81:1075
© 2006 The Society of Thoracic Surgeons
Original article: General thoracic
Invited commentary
Douglas E. Wood, MD
Division of Cardiothoracic Surgery, University of Washington, 1959 NE Pacific, Room AA-115, Box 356310, Seattle, WA 98195-6310
(Email: dewood{at}u.washington.edu).
Replacement of the carina is one of the most difficult challenges facing the thoracic surgeon. Primary airway tumors of the carina are rare, but surgical resection offers the best hope for curative intent in nearly all cases. The longitudinal extent of carinal resection is limited to approximately 4 cm due to the complexity of airway reconstruction at the tracheal bifurcation. Although the anatomy of the carina creates additional anatomical considerations for reconstruction, the absence of a suitable airway substitute is no different for long-segment tracheal resection. Clearly there is a need for a conduit to replace the central airway to allow more aggressive resection of both tracheal and carinal neoplasms. Investigators have tried a variety of techniques ranging from novel efforts of airway lengthening, prosthetic replacement, a diverse spectrum of tissues for autograft and allograft replacement, and efforts at tissue engineering. Unfortunately, none have become reliable airway substitutes due to anastomotic complications, infection and fistula development, and ischemia or rejection resulting in progressive contracture with disabling stenosis or malacia.
The authors [1] have published an experimental model that is encouraging for surgeons involved in airway surgery. An aortic autograft or allograft is similar in size to the trachea and mainstem bronchi, is readily available, can provide aerostatic tubular continuity of the airway, and may provide a scaffold for regeneration of tracheal wall morphology.
However there are three major hurdles lying between this small series in an animal model and the clinical application in humans. First, most airway tumors can be managed by resection and reconstruction using native trachea, a time-tested and reliable technique with good outcomes. In addition, more extensive tumors are not only limited by the longitudinal extent of the tumor, but they also have unresectable radial extension or metastatic disease, or both. Therefore the cohort of patients eligible for aortic replacement of the trachea or carina is infinitesimally small, making it very difficult for any center to adequately test the technique in humans and gain a clinical experience that could be applicable in other thoracic centers.
Second, harvesting of an autograft adds substantial complexity and attendant morbidity to an already intricate operation and would need to be balanced against simpler palliative treatment with interventional bronchoscopy, radiation, and chemotherapy. In this animal model there is substantial perioperative mortality. Given that current carinal resection has a mortality of at least 15%, one would expect this to be higher from both short-term and long-term consequences of the airway graft. One could easily postulate that current palliative treatments, however flawed, may be preferable to aortic airway replacement, yet the rarity of these cases would prevent any meaningful ability to compare outcomes.
Finally, and perhaps most importantly, the amazing finding in this animal study is the long-term regeneration of a viable, stable, mucosally lined airway, allowing ultimate decannulation. Nearly all other clinical and research experience suggests that similar airway replacements develop an ischemic inflammatory response, resulting in scar contracture with stricture or malacia requiring a permanent airway stent if the patient survives the hazards of anastomotic complications. If the finding of tracheal regeneration can be duplicated by others and transferred to human results, this would be a true breakthrough. I hope that the authors will continue this line of investigation and learn the mechanism of the tissue regeneration found in long-term survivors of this animal protocol, because this would be a profound advance with an effect far beyond tracheal or carinal replacement.
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References
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- Seguin A, Martinod E, Kambouchner M, et al. Carinal replacement with an aortic allograft Ann Thorac Surg 2006;81:1068-1075.[Abstract/Free Full Text]
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