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Pseudoaneurysm of mitral–aortic intervalvular fibrosa: two case reports and review of literature

Thaslim Ahamed Kassim , Robert C. Lowery , Ali Nasur , Sanul Corrielus , Gaby Weissman , Pamela Sears-Rogan , Michael Greenberg , Steven Singh
DOI: http://dx.doi.org/10.1093/ejechocard/jep189 E7 First published online: 8 December 2009

Abstract

The aim of this study was to identify the echocardiographic characteristics of pseudoaneurysm of the mitral–aortic intervalvular fibrosa, which is a rare and life-threatening complication of infective endocarditis. We have demonstrated the difference in clinical presentation and management of acute and chronic types of this pseudoaneurysm, together with a review of literature of the topic. We present two cases, one acute and the other an example of a chronic pseudoaneurysm of the mitral–aortic intervalvular fibrosa. The abscess may enlarge rapidly and rupture, resulting in haemorrhage with a catastrophic outcome. Rarely, the pseudoaneurysm will undergo a subclinical course, thicken and organize into a chronic aneurysm. Transoesophageal echocardiogram demonstrates a false lumen below the aortic valve annulus at the mitral–aortic intervalvular fibrosa with marked pulsatility with systolic expansion and diastolic collapse. The successful management of acute pseudoaneurysm necessitates extensive resection and replacement of the infected areas around the pseudoaneurysm. In chronic pseudoaneurysm, there is structural integrity around the calcified pseudoaneurysm, potentially minimizing the need for an extirpative surgery. Pseudoaneurysm of the mitral–aortic intervalvular fibrosa is a rare complication of infective endocarditis, but delay in diagnosis can lead to devastating outcome.

  • Pseudoaneurysm
  • Infective endocarditis
  • Echocardiogram

Introduction

Pseudoaneurysm of the mitral–aortic intervalvular fibrosa is a rare but potentially fatal complication of infective endocarditis.1 Pseudoaneurysm of the mitral–aortic intervalvular fibrosa may also occur as a result of transmural myocardial infarction, chest trauma, or cardiac surgery.24 Complications of intervalvular pseudoaneurysm may include rupture into the left atrium with resultant heart failure5 or the pericardium with ensuing cardiac tamponade6 and sudden death. Our initial case is the first described case of pseudoaneurysm of the mitral–aortic intervalvular fibrosa to develop as a complication of an infected haemodialysis catheter. Our second patient developed the pseudoaneurysm of the mitral–aortic intervalvular fibrosa as an outcome of aortic valve endocarditis that was not treated sufficiently.

Case report 1

A 53-year-old hypertensive African-American male patient with a past medical history of end-stage renal disease was admitted to the hospital with complaints of fever, vomiting, and watery diarrhoea for 3 days. A jugular venous catheter had been placed 8 months prior. On physical examination, he had low-grade fever of 101°F and a pulse rate of 110 bpm. There were no signs of systemic embolization and no audible murmurs on auscultation. Laboratory data showed a leucocytosis of 17 800/cu mm and elevated creatinine of 2.5 mg/dL; chest X-ray showed a normal cardiac silhouette and no evidence of pulmonary vascular congestion. He was started on vancomycin and piperacillin-tazobactum for presumed bacteraemia after blood cultures were obtained.

Blood cultures were positive for methicillin-resistant staphylococcus aureus, and antibiotics were changed to vancomycin and amikacin on the basis of sensitivity studies. Subsequent blood cultures were negative, and his condition improved. Despite clinical improvement, the patient continued to have persistent leucocytosis (more than 15 000/cu mm) and developed a new systolic murmur. A transthoracic echocardiogram (TTE) was performed for the evaluation of infective endocarditis, which demonstrated moderate mitral regurgitation, marked left atrial dilatation, and a mild aortic regurgitation. The mitral valve was partially calcified with an immobile anterior lateral leaflet. The aortic valve was structurally normal and mildly calcified (Figure 1).

Figure 1

Transthoracic echocardiogram showing partially calcified mitral valve with an immobile anterior lateral leaflet.

On transoesophageal echocardiogram (TEE), the mitral valve leaflets appeared moderately thickened, and there was mild annular calcification with extension of calcium into posterior leaflet. An eccentric, posteriorly directed jet of moderate mitral regurgitation was detected by colour flow Doppler. An abscess cavity was identified as systolic expansion and diastolic collapse within the area of the mitral–aortic intervalvular fibrosa, with flow extending into the left atrium (see Supplementary data online, Video S1). There was echo-dense material within the aneurysm suggestive of vegetations or thrombus. The patient was transferred to a medical centre with cardiothoracic surgery facility for an immediate operation. A cardiac catheterization was performed which showed moderate aortic insufficiency and moderate mitral insufficiency with no evidence of any coronary artery disease.

Direct observation at surgery revealed that the region of the mitral–aortic intervalvular fibrosa was destroyed and there was perforation of the aortic annulus (Figure 2). Surgery included resection and reconstruction of mitral and aortic annuli and replacement of mitral and aortic valves. Initially, the patient did well and was readied for discharge. He was re-admitted to the intensive care unit some 4 weeks after surgery owing to a late sternal wound infection. However, he subsequently died 8 weeks post-operatively, and his death was attributed to pneumonia.

Figure 2

Destroyed mitral–aortic intervalvular fibrosa with perforation of the aortic annulus.

Case report 2

The second patient is a 55-year-old African-American male who had been diagnosed five years ago with aortic valve endocarditis and an ‘annular abscess’. He had been scheduled for surgery at that time. However, he was later incarcerated and received no further treatment until he saw a physician in an outpatient clinic setting after his release from prison. Physical examination demonstrated a heart murmur, which by TTE was found to be an aortic root aneurysm. A magnetic resonance imaging study of the heart (Figure 3) was obtained which showed the anatomic findings of a pseudoaneurysm of the mitral–aortic intervalvular fibrosa. He was taken to the operating room and an aortic valve sparing procedure was performed. The orifice of the pseudoaneurysm of the mitral–aortic intervalvular fibrosa was closed using a biological patch.

Figure 3

Magnetic resonance imaging showing the organized pseudoaneurysm of the mitral–aortic intervalvular fibrosa with opening from the aortic outflow tract. AoV, aortic valve; LA, left atrium; RA, right atrium; RV, right ventricle.

Discussion

Pseudoaneurysm of the mitral–aortic intervalvular fibrosa is uncommon but one of a number of potentially catastrophic complications of infective endocarditis.1 It most commonly occurs with aortic valve endocarditis and often may be associated with infected prosthetic valves.7 The mitral–aortic intervalvular fibrosa, also known as the mitral–aortic membrane, is a fibrous region of the heart between the left half of non-coronary cusp and the adjacent left coronary cusp of the aortic valve and the anterior mitral leaflet. It is of great functional and clinical importance due to its location between the mitral and aortic valve and the role it plays in maintaining the functional integrity of both the valves.8 The mitral–aortic intervalvular fibrosa is a relatively avascular structure, and as such, it offers very little resistance to infection, leading to the formation of abscess.9 The involvement of the mitral–aortic intervalvular fibrosa and the anterior mitral valve leaflet in infective endocarditis occurs either due to direct extension of infection from the aortic valve or as a result of infected aortic regurgitant jet striking these structures.10 The abscesses may subsequently perforate and result in haemorrhage into the ventricle outflow tract and left atrium or, as our second example shows, can organize chronically into a pseudoaneurysm of the mitral–aortic intervalvular fibrosa.11

The thin nature and fragility of the mitral–aortic intervalvular fibrosa increase its susceptibility to dilatation following endocarditis, mitral and aortic valve surgeries, or thoracic trauma, leading to the appearance of pseudoaneurysm. A detailed anatomical knowledge of the mitral–aortic intervalvular fibrosa and its surrounding area is necessary during cardiac surgeries to prevent complications such as pseudoaneurysm of the mitral–aortic intervalvular fibrosa.

Patients usually present with symptoms and signs of infective endocarditis. Enlargement of the pseudoaneurysm may compress the left coronary artery and result in angina-like symptoms.12 Communication of pseudoaneurysm with the left ventricle or ascending aorta results in heart failure.5 The pseudoaneurysm of the mitral–aortic intervalvular fibrosa can very rarely rupture towards anterior chest wall and produce a fistula.13 Embolization of thrombotic material in the pseudoaneurysm of the mitral–aortic intervalvular fibrosa may result in stroke.14

Diagnosis of pseudoaneurysm of the mitral–aortic intervalvular fibrosa

Pseudoaneurysm of the mitral–aortic intervalvular fibrosa should be ruled out in all infective endocarditis patients undergoing TTE.15 Patients with aortic valve endocarditis and eccentric jets of mitral regurgitation on TTE should undergo evaluation by TEE to exclude pseudoaneurysm of the mitral–aortic intervalvular fibrosa.16 The diagnostic sensitivity of TTE to detect pseudoaneurysm of the mitral–aortic intervalvular fibrosa is 43%, and it may increase to 90% when TEE is performed.15,17 Transoesophageal echocardiogram demonstrates a false lumen below the aortic valve annulus at the mitral–aortic intervalvular fibrosa. The most distinct echocardiographic feature of pseudoaneurysm is the marked pulsatility with systolic expansion and diastolic collapse.18 This distinguishes it from aortic ring abscess, which does not show this phenomenon. Rupture of pseudoaneurysm of the mitral–aortic intervalvular fibrosa can be identified by colour Doppler, which shows a pseudoaneurysm communicating with left atrium or aorta or the left ventricular outflow tract.15

Cardiac magnetic resonance imaging can identify and give more detailed information about pseudoaneurysm of the mitral–aortic intervalvular fibrosa with better resolution.1 Ghersen et al.19 have documented the usefulness of electrocardiographic gated multi-dimensional commuted tomography in the diagnosis and dynamic evaluation of pseudoaneurysm of the mitral–aortic intervalvular fibrosa. Pre-operative three-dimensional TEE also has been used to gather information about exact anatomical relationships of pseudoaneurysm of the mitral–aortic intervalvular fibrosa to surrounding tissue and various shunts operating through the mitral–aortic intervalvular fibrosa.20

Acute pseudoaneurysm of the mitral–aortic intervalvular fibrosa complicating infective endocarditis requires immediate and extensive surgery. It is necessary to thoroughly debride the infected area and reconstruct with artificial material.7 We have been able to find only one case report of pseudoaneurysm of the mitral–aortic intervalvular fibrosa treated with systemic antibiotics which resulted in complete clinical recovery. Subsequent echocardiography in that patient showed pseudoaneurysm of the mitral–aortic intervalvular fibrosa remaining stable with contraction of vegetation.19

Our second case illustrates a different scenario in the natural history of this disease process. Because of the imposed lack of treatment, the endocarditis was able to progress to a chronic pseudoaneurysm of the mitral–aortic intervalvular fibrosa. The aneurysm itself was calcified and not easily amenable to resection. However, the tissue surrounding the orifice had developed sufficient structural integrity so as to allow placement of a bovine pericardial patch and closure of the aneurysm with prevention of further communication with the aortic blood stream. Subsequent surveillance with echocardiography or magnetic resonance imaging will be necessary.

Conclusion

These cases underscore the importance of timely echocardiography and timely surgical intervention in patients in whom there is a high risk of or an increased index of suspicion for infective endocarditis with abscess. Echocardiographers should also focus their attention on subaortic structures and anterior mitral valve leaflet. In case of any doubt regarding thickening of aortic root/base of anterior mitral leaflet, TEE is the next study of choice and should be done without further delay. Early recognition and treatment of infective endocarditis and any possible abscesses may allow for surgical correction before the development of the much more complex entity of pseudoaneurysm of the mitral–aortic intervalvular fibrosa.

Supplementary data

Supplementary data are available at European Journal of Echocardiography online.

Conflict of interest: none declared.

References

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