Fibrosing Mediastinitis Causing Acute Ostial Left Main Myocardial Infarction

ABSTRACT: This report describes an unusual etiology of acute coronary syndrome. A 48-year-old female presented with anginal chest discomfort and was found to have evidence of acute pulmonary edema requiring mechanical ventilation. She underwent emergency coronary angiography and stenting of the culprit left-main artery ostial discrete stenosis. Subsequent echocardiography and magnetic resonance imaging revealed severe aortic regurgitation and periaortic valve tissue infiltrates. Pericardiectomy and mediastinal mass biopsy were performed which indicated the pathology of fibrosing mediastinitis.

J INVASIVE CARDIOL 2010;22:456–460

Key words: acute myocardial infarction, fibrosing mediastinitis

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Fibrosing mediastinitis is an uncommon chronic inflammatory condition of diverse etiology which is characterized by proliferation of acellular collagen and fibrous tissue within the mediastinum. This condition can present in myriad manner depending upon the organ structures involved. We report the first case of acute ostial left main myocardial infarction (MI) due to extrinsic compression from fibrosing mediastinitis. Case Report. An 48-year-old Chinese female presented to our emergency department with a history of chest discomfort of 1-week duration and was found to be in a state of cardiogenic shock. She was also found to have pulmonary edema requiring mechanical ventilation. She had no known cardiovascular risk factors, but gave a history of recent admission to another hospital for fever and cough. Her 12-lead electrocardiogram (ECG) showed hyperacute ST-segment elevation in leads V1 to V4 and aVR (Figure 1). A provisional diagnosis of acute anterior STEMI was made and she underwent immediate cardiac catheterization. Diagnostic coronary angiography revealed a left-dominant circulatory system with a discrete 90% ostial left main stenosis (Figure 2). Intravascular ultrasound (IVUS) revealed extrinsic oval compression of the ostium of the left main artery (Figure 3). There was no evidence of atheroma formation in the coronary artery intima. Primary percutaneous coronary intervention (PCI) was performed with the implantation of a 4.5 x 16 mm Liberté® stent (Boston Scientific Corp., Natick, Massachusetts) across the ostial stenosis at a pressure of 18 atmospheres (Figure 4). Repeat IVUS interrogation confirmed good stent expansion and apposition with no evidence of intimal dissection (Figure 5). Post-PCI ECG showed resolution of the raised ST segments (Figure 6). The patient was stabilized hemodynamically and extubated 2 days later. There was mild elevation of the cardiac enzymes with a peak creatine kinase of 593 U/L, CK-MB of 90.9 µg/L and troponin-T of 0.88 µg/L, which were indicative of myocardial necrosis. Dual antiplatelet therapy of aspirin and clopidogrel was planned for 1 year. On further investigation, her two-dimensional echocardiography showed a thickened aortic valve with periaortic valve tissue infiltration (Figure 7a). There was severe aortic regurgitation from possible flail aortic valve leaflets (Figure 7b) and severe mitral regurgitation. The left heart chambers were dilated with mildly impaired left ventricular systolic function (visual left ventricular ejection fraction was estimated to be 55%). Moderate pulmonary hypertension was also present, with a calculated pulmonary artery systolic pressure of 64 mmHg. A magnetic resonance (MR) imaging study of the thorax showed an infiltrative mediastinal mass with patchy gadolinium-DTPA uptake at the base of the heart and great arteries (Figure 8). Pericardiectomy and mediastinal mass biopsy were performed to establish the etiology. The surgical gross findings included pericardial dense fibrosis with inflammation, but no appearance of malignant tumor tissues. The exuberance of inflammation and fibrosis probably led to constriction of the left main artery and evidence of early constrictive pericarditis. Histologic examination showed a chronic fibroinflammatory process with fibroadipose tissue seen with scattered lymphoid aggregates. There was no evidence of malignancy (Figure 9). A diagnosis of fibrosing mediastinitis was made and the rheumatology department was consulted. The treatment plan was to control the acute inflammatory process with high-dose prednisolone and methotrexate for 3 months followed by repeat coronary angiography and an MRI scan. This will be followed by aortic valve replacement and possible aortic graft replacement and coronary artery bypass surgery. The patient remained well on therapy until the 10th week of treatment, when she complained of weakness and collapsed from sudden death. No post-mortem examination was performed.

Discussion

We report the first case of an acute ostial left main artery narrowing from fibrosing mediastinitis in a young patient without significant underlying coronary artery disease. Fibrosing mediastinitis is an uncommon chronic inflammatory disorder of diverse etiology. It is characterized by an excessive fibrotic reaction in the mediastinum, which can result in compromise of airways, great vessels and other mediastinal structures. Although many cases are idiopathic, many are thought to be caused by abnormal immunologic response to histoplasma, mycobacteria, nocardia infection, Hodgkin’s disease, sarcoidosis and some collagen vascular autoimmune disorders.^1,2 There is also an association with other inflammatory disorders like retroperitoneal fibrosis, sclerosing cholangitis, orbital pseudotumor and Riedel’s thyroiditis. These entities cause encasement of mediastinal structures. There are two possible types of fibrosing mediastinitis: focal and diffuse.^1,2 The focal type usually manifests on computed tomography (CT) or MR images as a localized, calcified mass in the paratracheal or subcarinal regions of the mediastinum or in the pulmonary hila. The diffuse type manifests on CT or MR images as a diffusely infiltrating, often non-calcified mass that affects multiple mediastinal compartments. Imaging studies play a vital role in the diagnosis to confirm the diagnosis of an infiltrative process in mediastinum and in the management of fibrosing mediastinitis.³ Histopathology indicates dense bundles and sheets of hyalinized collagen admixed with a relatively sparse inflammatory infiltrate.^1,2 Involvement of the coronary arteries by fibrosing mediastinitis is rare. Reed et al,⁴ in an autopsy report, described a patient who presented with congestive heart failure and ureteric obstruction which exhibited fibrosing mediastinitis and massive periaortic fibrosis in the infrarenal abdominal aorta. The coronary arteries were markedly sclerotic with some distal involvement. Another interesting report by Saxena et al⁵ described a thick fibrotic ring involving the aortic root and the left coronary orifice. Aleksic et al⁶ described a female patient who underwent coronary artery bypass surgery done for involvement of the left anterior descending artery and left circumflex artery from mediastinal fibrosis involving the aorta. Both CT and MR imaging play a vital role in the diagnosis and management of fibrosing mediastinitis. CT is considered the mainstay for diagnostic evaluation of patients with suspected fibrosing mediastinitis because MR imaging depicts calcification poorly. Chest radiographic findings are usually nonspecific.³ Fibrosing mediastinitis often has an unpredictable course, with both spontaneous remission and exacerbation of symptoms being reported. Loyd et al⁷ reported a mortality rate of > 30%, which is much higher than that reported in other studies. Causes of death in fibrosing mediastinitis are usually recurrent infection, hemoptysis or cor pulmonale. The mortality rate among patients with subcarinal or bilateral mediastinal involvement may be higher than that among patients with more localized mediastinal or hilar fibrosis. There are three possible avenues for treatment: systemic antifungal or corticosteroid treatment, surgical resection and local therapy for complications. Most of the available data in this regard are based on either case reports or small series; prospective, randomized, controlled trials have not been performed.⁷ Most studies have shown little or no beneficial effect of corticosteroids therapy.⁸ If disease is localized, surgical resection of affected tissue may be curative or may result in amelioration of signs and symptoms. A complete resection may require extensive vascular or airway reconstruction — techniques that are available at only a few medical centers. Bilateral mediastinal involvement is generally thought to preclude a surgical approach. On the whole, the results of surgical therapy have been disappointing, and resection is often associated with high morbidity and mortality.⁷ Increasingly, symptomatic patients are treated with local therapies directed toward reopening occluded or severely stenosed airways, pulmonary arteries or vena cavae.³ Extensive complex surgery was originally planned for the patient, but she demised unexpectedly. The cause of her death is likely from her underlying severe valvular heart condition, although other causes such as coronary in-stent restenosis or stent thrombosis cannot be excluded. This case report describes an uncommon cause of left main coronary ostial stenosis from fibrosing mediastinitis manifesting as acute coronary syndrome. Prompt revascularization and corrective surgery in appropriate patients are keys to improving outcomes.

References

1. Dehner LP, Coffin CM. Idiopathic fibrosclerotic disorders and other inflammatory pseudotumors. Sem Diagn Pathol 1998;15:161–173. 2. Flannery MT, Espino M, Altus P, et al. Hodgkins disease masquerading as sclerosing mediastinitis. Suth Med J 1994;87:921–923. 3. Rossi SE, Page McAdams H, Rosado de Christenson ML, et al. Fibrosing mediastinitis. RadioGraphics 2001;21:737–757. 4. Reed GW, Stinely RW. Massive periaortic and periarterial fibrosis: Report of a case. N Engl J Med 1959;261:320–333. 5. Saxena P, Tesar PJ. Mediastinal fibrosis causing myocardial ischemia. Ann Thorac Surg 2005;80:2368–2370. 6. Aleksic I, Saldana F, Busch T et al. Unsuspected idiopathic mediastinal fibrosis complicating coronary bypass operation. Ann Thorac Surg 1999;67:224–225. 7. Loyd JE, Tillman BF, Atkonson JB, Des Prez RM. Mediastinal fibrosis complicating histoplasmosis. Medicine (Baltimore) 1988;67:295–310. 8. Dunn EJ, Ulicny KS Jr, Wright CB, Gottesman L. Surgical implications of sclerosing mediastinitis: A report of six cases and review of the literature. Chest 1990;97:338–346.

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From National University Heart Centre, National University of Singapore, Singapore. The authors report no financial relationships or conflicts of interest regarding the content herein. Manuscript submitted February 11, 2010, provisional acceptance given February 22, 2010, final version accepted March 12, 2010. Address for correspondence: Domingo T. Addatu, Jr., MD, National University Heart Centre 5, Lower Kent Ridge Road, Singapore 119074. E-mail: jhunemd@yahoo.com or jaddatu74@gmail.com