Ann Thorac Surg 2006;81:1881-1882
© 2006 The Society of Thoracic Surgeons
Case report
Infective Endocarditis and Pseudoaneurysm: Fatal Complications of Mitral Annular Calcification
Tomohiro Tsunekawa, MD
a
,
Junjiro Kobayashi, MD
a
,
Osamu Tagusari, MD
a
,
*
,
Ko Bando, MD
a
,
Kazuo Niwaya, MD
a
,
Hiroyuki Nakajima, MD
a
,
Toshikatsu Yagihara, MD
a
,
Hatsue Ishibashi-Ueda, MD
b
,
Soichiro Kitamura, MD
a
a Department of Cardiovascular Surgery, National Cardiovascular Center, Fujishirodai, Suita, Osaka, Japan
b Department of Pathology, National Cardiovascular Center, Fujishirodai, Suita, Osaka, Japan
Accepted for publication May 24, 2005.
* Address correspondence to Dr Tagusari, Department of Cardiovascular Surgery, National Cardiovascular Center, 5-7-1, Fujishirodai, Suita, Osaka, 565-8565 Japan (Email: otagusar{at}hsp.ncvc.go.jp).
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Abstract
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We present a case of successful surgical repair for infected mitral valve and left ventricular pseudoaneurysm, which can be fatal complications of mitral annular calcification.
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Introduction
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Mitral annular calcification (MAC) is a common finding in elderly patients, and is considered a benign cardiac abnormality. However it can be a predisposing factor for infective endocarditis and pseudoaneurysm of the left ventricle. We report a successful surgical experience in a case of infected mitral valve and left ventricular pseudoaneurysm associated with mitral annular calcification. The preoperative diagnosis of infective endocarditis was difficult, even with transesophageal echocardiography, because of the morphological features of the vegetation. Coexisting hypertrophic cardiomyopathy was speculated to act as another predisposing factor for pseudoaneurysmal formation.
An 82-year-old woman was transferred to our hospital because of loss of consciousness on November 5, 2003. Cardiac tamponade was diagnosed and pericardiocentesis improved her hemodynamics. Transthoracic echocardiography showed significant calcification at the posterior mitral annulus and hypertrophy of the left ventricular myocardium. Cardiac catheterization demonstrated a 60 mm Hg pressure gradient between the inlet and apical portion of the left ventricle. In spite of these detailed examinations, the cause of cardiac tamponade was not identified. On admission, she was feverish, her white cell count was 14,740/µL, and C-reactive protein was 17.0. Antibiotic therapy with ceftazidime was administered and was continued for 2 weeks. Blood cultures were performed three times, which were all negative. Six days after admission, a thoracic computed tomographic scan revealed a highly enhanced pericardial mass adjacent to the posterior mitral annulus, which was not detected on admission (Fig 1). Transesophageal echocardiography revealed a communication between the left ventricle and the extracardiac cavity. These findings were compatible with the diagnosis of left ventricular pseudoaneurysm. On computed tomography, the diameter of the pseudoaneurysm rapidly increased from 5 cm to 10 cm in diameter within 7 days. Therefore we performed an emergency operation.
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Fig 1. Preoperative computed tomographic scan shows that the inlet of the pseudoaneurysm was located just beneath the posterior mitral annulus, which was remarkably calcified. (LA = left atrium; LV = left ventricle; PA = pseudoaneurysm.)
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The heart was approached through a median sternotomy. Dense adhesions were observed in the pericardial cavity. Under standard cardiopulmonary bypass with warm blood cardioplegia, the mitral valve was exposed through a right-sided left atrial approach. The inlet of the left ventricular pseudoaneurysm was adjacent to the posteromedial side of the mitral annulus, which was surrounded by dense calcification. No vegetation was visually recognized on the mitral valve and subvalvular apparatus. The mitral valve and large papillary muscles were resected to relieve the intraventricular obstruction. Annular decalcification was carried out after resection of the mitral leaflets. Direct closure of the inlet of the left ventricular pseudoaneurysm was performed with simultaneous annular reconstruction, which was achieved by adapting the ventricular and atrial walls with several horizontal mattress sutures using e-polytetrafluoroethylene pledgeted 4-0 monofilament. The mitral valve was replaced with a 25-mm Carbomedics mechanical valve (Sulzer Carbomedics, Inc, Austin, TX).
Pathologic examination revealed infiltration by neutrophils and structural destruction of the posterior mitral leaflet. The anterior mitral leaflet and subvalvular apparatus were intact. The vegetation was located mainly at the base of the posterior mitral leaflet, especially on the ventricular surface, and its shape was smooth and flat (Fig 2). These findings confirmed the diagnosis of infective endocarditis (IE) associated with MAC [1]. The causative organism was not identified even from the resected specimen. Postoperative antibiotic therapy with ampicillin sodium was continued for 2 weeks. After commencing anticoagulation therapy with warfarin sodium, the patient was discharged on foot. One year after the operation her condition was good and she showed no recurrence of endocarditis or left ventricular pseudoaneurysm.
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Fig 2. (A) Photomacrograph of posterior mitral leaflet. The upper row shows the ventricular surface. The lower row shows the atrial surface. The vegetation was relatively smooth and flat and was located mainly on the ventricular surface of the base of the posterior mitral leaflet. (B) Photomicrograph of posterior mitral leaflet. The right side of the specimen was attached to the mitral annulus. Structural destruction and hemorrhage are recognized at the ventricular surface of the basal portion. Infiltration by neutrophils is shown at the same position. (Hematoxylin-eosin stain; original magnification, x20.) (Bar is 1 mm in length).
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Comment
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Mitral annular calcification is a common cardiac abnormality in elderly patients [2], and it is generally considered a benign finding. However it can be a predisposing factor for infective endocarditis. A prospective study demonstrated a three-fold higher incidence of infective endocarditis in elderly patients with MAC than in those without [3]. Protrusion of annular calcium may result in turbulent blood flow and ulceration of the overlying leaflet, and these can provide an ideal nidus for infection. The pathologic findings of IE with MAC are relatively uniform, and IE often involves the base of the posterior mitral leaflet [1]. Furthermore, the inflammatory process readily extends through the myocardium directly to the pericardium, because the infectious focus is just adjacent to the mitral annulus [1], resulting in para-annular destruction, such as intramural atrial hematoma and left ventricular pseudoaneurysm [4, 5].
The echocardiographic diagnosis of IE with MAC is difficult because the vegetations are masked by artifacts and shadowing of the calcification [6]. In addition, in our case, the smooth flat shape of the vegetation per se could have been a disadvantage in echocardiographic diagnosis. This disadvantage led to a delay in diagnosis with time for pseudoaneurysmal formation.
Another reason for pseudoaneurysmal formation in this patient may have been coexisting hypertrophic obstructive cardiomyopathy. Calcification of the mitral annulus seems to be accelerated by conditions that elevate the left ventricular pressure, such as systemic hypertension, aortic valve stenosis, and hypertrophic obstructive cardiomyopathy [7]. Elevated end-diastolic pressure increases the mitral annular stress and not only accelerates calcification of the annulus, but also induces perforation of the left ventricle.
This article reports the successful surgical repair of a pseudoaneurysm that a patient had develop with IE associated with a calcified mitral annulus. The diagnosis of IE associated with MAC is difficult, and close observation is necessary because its sequelae are potentially catastrophic (eg, pseudoaneurysm and cardiac rupture).
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References
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- Burnside JW, Desanctis RW. Bacterial endocarditis on calcification of the mitral annulus fibrosus Ann Int Med 1972;76:615-618.[Medline]
- Pomerance A. Pathological and clinical study of calcification of the mitral valve ring J Clin Pathol 1971;23:354-361.
- Aronow WS, Koenigsberg M, Kronzon I, Gutstein H. Association of mitral annular calcium with new thromboembolic stroke and cardiac events at 39-month follow-up in elderly patients Am J Cardiol 1990;65:1511-1512.[Medline]
- Schecter SO, Fyfe B, Pou R, Goldman ME. Intramural left atrial hematoma complicating mitral annular calcification Am Heart J 1996;132:455-457.[Medline]
- Eicher JC, Falcon-Eicher S, Soto FX, et al. Mitral ring abscess caused by bacterial endocarditis on a heavily calcified mitral annulus fibrosusdiagnosis by multiplane transesophageal echocardiography. Am Heart J 1996;131:818-820.[Medline]
- Eicher JC, De Nadai L, Soto FX, et al. Bacterial endocarditis complicating mitral annular calcificationa clinical and echocardiographic study. J Heart Valve Dis 2004;13:217-227.[Medline]
- Roberts WC, Perloff JK. Mitral valvular diseasea clinicopathologic survey of the conditions causing the mitral valve to function abnormally. Ann Intern Med 1972;77:939-975.[Medline]
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Abstract
Introduction
