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Vanderbilt University Medical Center Nashville, TN
Correspondence to: James E. Loyd, MD, Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, Nashville, TN 37232-2650;
To the Editor:
We read with interest the report by Guerrero and colleagues (March 2001)1 describing treatment of pulmonary artery stenosis in a patient with fibrous mediastinitis. Unique safety issues are present and should be addressed when considering intravascular stents for pulmonary vascular compromise caused by fibrous mediastinitis, also known as mediastinal fibrosis. Unlike most other causes that occlude only the pulmonary arteries, such as pulmonary embolism, mediastinal fibrosis may concomitantly affect pulmonary veins, airways, or arteries, of one or both lungs, in any combination.2 Benefit would not likely ensue from the restoration of arterial blood flow to a lung that has an obstructed airway, and could even cause severe shunting. Alternatively, restoring flow through the pulmonary artery of a lung in which pulmonary veins are also obstructed could lead to pulmonary edema. Pulmonary venous occlusion, especially in the presence of concomitant arterial occlusion, can be difficult to verify and should be meticulously evaluated by specialized techniques, such as balloon wedge angiography and measurement of pressure gradients. Since disorders causing large pulmonary vein occlusion are uncommon in adults, those individuals with the most experience using relevant diagnostic approaches are often invasive pediatric cardiologists who commonly encounter congenital pulmonary venous disorders.
The authors1 underestimate the prevalence of mediastinal fibrosis. They report that only "fifteen other cases of fibrous mediastinitis with pulmonary artery compression have been described in the literature." In one review2 more than a decade ago with 71 reported cases of mediastinal fibrosis, pulmonary vascular involvement was described for 40 patients. Underreporting probably occurs at present because the condition has already been adequately described.
In the "Discussion" section, the authors1 state, "patients with fibrous mediastinitis generally have a benign clinical course until a mediastinal structure is compressed," a statement that raises the issue of the definition of mediastinal fibrosis. Although there is not a universally accepted definition, it surely should not include all patients who have any fibrosis within the mediastinum. A reasonable definition also requires the involvement of a major vessel or airway,2 so as to distinguish patients with true mediastinal fibrosis from patients with inconsequential limited scarring. Our experience in the last decade with several dozen patients has demonstrated that those with unilateral autoamputation of one lung by mediastinal fibrosis usually have a relatively benign course, even for many decades.3 Exceptions to this observation include the few patients in whom serious hemoptysis from systemic vascular hypertrophy to the obstructed lung develops.
The character of the mediastinal fibrosis lesion is so dense, ie, typically described by a surgeon as having the consistency of concrete, it is surprising that balloon dilation and stenting can successfully restore vascular patency in this condition. For our first case using pulmonary venous stents for a young man with bilateral pulmonary venous obstruction from mediastinal fibrosis,3 because we suspected the fibrotic veins were too rigid to successfully dilate, we were prepared to use a Rotablator tissue extraction device (Boston Scientific; Natick, MA), but were pleased to learn that it was not required. Our experience is similar to that of the authors, with successful stenting of seven vessels (four pulmonary arteries and three pulmonary veins) in four patients with mediastinal fibrosis.4
Further emphasis regarding different causes of mediastinal fibrosis5 is also important, as discussed by Sherrick et al in reference 5 of the authors.1 The patient in the current report has mediastinal fibrosis typical for that which occurs as a late complication of histoplasmosis, because it is focal, lymph node-based, calcified, and invasive. Despite the authors’ suggestion that steroids may be helpful here, this condition has never been shown to respond to steroids or any other medical therapy. In contrast, another form of mediastinal fibrosis may have features that resemble retroperitoneal fibrosis and is characterized by noncalcified, diffuse disease, which usually encompasses the entire trachea and may even extend outside the thorax to be palpable in the neck. This form of mediastinal fibrosis should be distinguished because it does appear to respond to corticosteroids or tamoxifen, at least in several published case reports.
We believe that attempts to stent vessels to palliate disease are clearly indicated in patients with bilateral pulmonary vascular disease from mediastinal fibrosis, in whom the outcome is universally poor and operative reconstruction risk is high.2 Stenting of vessels for patients with unilateral disease may be appropriate, but the risk/benefit ratio is less clear because many of these patients may have prolonged survival with acceptable functional status. Indeed, their functional status may be analogous in many respects to that of a single lung transplant recipient. Another consideration should include the possibility that the relative risk of a stent for a pulmonary vein (compared to that for a pulmonary artery) may be higher, because a stent complication of thrombosis might cause systemic embolism, and thereby possibly jeopardize extrapulmonary structures.
Finally, we were disappointed that the authors or reviewers did not use this opportunity to include any discussion regarding the physiologic mechanisms of dyspnea in their interesting patient or why the procedure might be associated with its resolution.
References
University of Washington School of Medicine Seattle, WA
Correspondence to: Riyad Karmy-Jones, MD, FCCP, Harborview Medical Center, Box 359796, 325 Ninth Ave, Seattle, WA 98104-2499
To the Editor:
I would like to thank Drs. Robbins, Davis, Doyle, and Loyd for their interest in our article. Briefly, we felt confidant, based on echocardiography and CT review, that the pulmonary veins were not involved in our patient, and bronchoscopy documented that the right mainstem bronchus was patent. We suspect that the patient’s improvement was due to a combination of reduced dead-space ventilation and some reduction in right-heart strain. The authors have succinctly reviewed the topic as well as their experience in stenting. We agree that each patient’s workup must be thorough and treatment individualized. Institutionally we managed two more patients in this manner, including one referred after a failed stent. Clearly, although more experience needs to be gained, interventional approaches are becoming recognized as a valuable tool in the management of these complex cases.
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