Download this article's Factoid (PDF & PPT for Gold Subscribers)

Vascular stent implantation is feasible and likely to provide clinical benefit in select patients who have central vascular obstruction due to fibrosing mediastinitis (FM), according to the first analysis of a large group of patients suffering from this extremely rare condition. The research was published online March 21, 2011, ahead of print in Circulation.

FM is a complication of infection with Histoplasma capsulatum that can lead to obstructions in the pulmonary and systematic vasculature and large airways. Months, years, or even decades after the initial infection, individuals who are susceptible to FM develop uncontrolled fibrosis around previously infected mediastinal lymph nodes. Symptoms include cough, dyspnea, hemoptysis, chest pain, and recurrent pulmonary infections.

For their single-center study, Erin L. Albers, MD, of Vanderbilt University School of Medicine (Nashville, TN), and colleagues conducted a retrospective review of 58 consecutive patients who underwent cardiac catheterization for FM between 1996 and 2008. Approximately half (53%) had bilateral disease. In all, 40 (69%) received an intervention, and a total of 77 stents were used to treat 59 lesions: 26 in the pulmonary artery, 21 in the pulmonary vein, and 12 in the superior vena cava.

Stenting Improves Symptoms, Survival

Stenting resulted in significant reductions in pressure gradients and increases in vessel caliber at all locations (P < 0.001 for both). After a median of 115 months (range, 5-122 months), symptomatic recurrent stenosis required further intervention in 28% of the 40 patients who underwent stenting.

Three of the stented patients were lost to follow-up, leaving 37 for whom follow-up was available for at least 1 month. The majority (87%) reported improvement immediately after stent placement, with the benefit lasting from 2 months to 12 years.

Complications related to catheterization occurred in 26% of the entire cohort, with major complications requiring immediate intervention observed in 10%. These included significant vessel injury, reperfusion pulmonary edema, thrombosis requiring anticoagulation, and stent malposition. One patient with severe bilateral disease who underwent catheterization with stent placement died 19 days later from a cerebrovascular accident (CVA).

Among the 40 patients who received stents, 15% died during follow-up, including the patient with a CVA. The remaining deaths occurred between 11 months and 9.5 years after the procedure. In contrast, 5 of the patients who did not undergo intervention (29%) died during follow-up; 4 of the 5 patients (80%) had bilateral disease.

Patients with bilateral disease showed a trend for better survival at 5 years with stenting (89.5% vs. 52.5% with no intervention; P = 0.282).  Fewer deaths occurred in the unilateral disease subgroup, which derived no survival benefit from stenting.

The decision to proceed with stenting in patients with FM should only be made after thorough preprocedural evaluation, the paper recommends. “Specifically, the presence of bilateral vascular involvement should strongly influence referral for intervention, because patients in this cohort are likely to receive the most clinical benefit,” the investigators write, adding that CT angiography was the definitive diagnostic test at their center. Other tests such as echocardiography, nuclear medicine perfusion scanning, and combined ventilation/perfusion studies were performed as indicated or provided by the referring institution.

Effective Treatment for a Rare Condition

“What speaks to the  rarity [of FM] is that at Vanderbilt, which is in a relatively high prevalence area for this uncommon infection, the investigators report an experience over 12 years of 58 patients,” David Kandzari, MD, of Piedmont Heart Center (Atlanta, GA), told TCTMD in a telephone interview. “And this is the largest case series reported for this type of therapy.”

Sorin J. Brener, MD, of Weill Cornell Medical College (New York, NY), also characterized the study as unique. “What’s novel about this [research] is it’s a large experience,” he said in a telephone interview with TCTMD. “No one [else] has seen 58 lesions caused by FM. It’s very, very rare.”

In an e-mail communication, Dr. Albers described his center’s experience: “Being that histoplasmosis is endemic in our region of the country, our institution has a long history of studying and treating this disease and its complications, including FM. We find that stent placement is not only technically feasible, but that it can provide sustained clinical improvement in selected patients with FM, specifically those with bilateral pulmonary vascular involvement.”

Few Other Options

Dr. Albers said the success of percutaneous stent placement is all the more important because FM is not an easy condition to treat. “Medical treatment for FM (steroids and/or antifungal therapy) is helpful in only a handful of cases,” he noted. “Surgical intervention is generally quite limited due to the destruction of tissue planes by the invading mass, but there have been a few reports of the use of synthetic grafts to bypass obstructed pulmonary vasculature. Overall, these options are applicable to only a few patients.”

According to Dr. Brener, medical therapy is directed at relieving symptoms related to obstruction, typically congestion. “Either you get superior vena cava syndrome or swelling of the face and neck, and it’s just [treatable with] diuretics, which doesn’t really solve the problem. Surgery can be attempted to remove the fibrous tissue that encases the veins, but it’s an extremely big and complex operation,” he explained.

Dr. Kandzari said FM makes surgical intervention difficult, “because of the extensive, widespread scarring that’s pervasive throughout the chest and thorax, and in many instances it precludes transplantation because it’s an infectious agent.”

Refer to Experienced Centers

Experienced centers are best prepared to handle such a rare condition, Dr. Kandzari advised. “Given the condition itself and its complexities, the considerations for treatment probably span those of the cardiologist and also the thoracic surgeon for identifying the best therapy,” he said, adding that percutaneous interventions are best done by a cardiologist in these patients, “in part because of the technical skills required but also because of the need to understand pulmonary physiology and hemodynamics in such cases.”

Dr. Albers agreed. “Stent placement in FM is often more challenging than typical stent placement, so special care needs to be taken. Interventionalists with special expertise in large vessel stent placement should be sought [to work on patients with FM], especially in the case of pulmonary vein involvement,” he said, pointing out that these cases are handled at Vanderbilt by a pediatric interventional cardiologist who has extensive experience with pulmonary artery and pulmonary vein intervention.