A Case of Prosthetic Valve Endocarditis with Pseudoaneurysm Formation Caused by Haemophilus parainfluenzae

Correspondence to Hack-Lyoung Kim, M.D., Ph.D. Division of Cardiology, Department of Internal Medicine, Seoul National University Boramae Medical Center, Seoul National University College of Medicine, 20, Boramae-ro 5-gil, Dongjak-Gu, Seoul 156-707, Korea Tel: +82-2-870-3235, Fax: +82-2-831-0714, E-mail: khl2876@gmail.com Copyrightc 2014 The Korean Association of Internal Medicine This is an Open Access article distributed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by nc/3.0/) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 가성동맥류를 동반한 Haemophilus parainfluenzae 인공판막 심내막염


INTRODUCTION
Haemophilus parainfluenzae (H.parainfluenzae), a rare cause of infective endocarditis, is responsible for only about 1% of all causes of endocarditis in adults [1].Pseudoaneurysm formation associated with infective endocarditis is a relatively infrequent but potentially lethal complication.The most frequent site of pseudoaneurysm formation is the mitral-aortic interventricularfibrosa (MAIVF), and its predisposing factors are infective endo-carditis of the aortic valve or aortic valve surgery [2].Here, we describe a case of pseudoaneurysm formation associated with an infected artificial graft following the Bentall procedure caused by H. parainfluenzae.

CASE REPORT
A 77-year-old male was hospitalized with acute chest pain that had started three hours earlier.His medical history was not  significant.He was diagnosed with an acute type A aortic dissection and underwent emergency surgery successfully with replacement of both the ascending aorta and aortic valve (the Bentall procedure).Although his chest pain improved after surgery, the patient complained of sustained general weakness and ill-defined malaise.Serial blood cultures and transthoracic echocardiography (TTE) showed no abnormal findings during the postoperative period.Four months after surgery and during hospitalization, the patient became drowsy and developed a high grade fever.His blood pressure dropped to 79/49 mmHg, his body temperature was 39.1ºC, and his white blood cell count was 13,500/mm 3 with 91% neutrophils.The patient's C-reactive protein level was markedly elevated to 17.84 mg/dL.Brain magnetic resonance imaging demonstrated multiple small enhancing lesions in both cerebral hemispheres, suggestive of embolic infarction (Fig. 1).Under strong suspicion of infective endocarditis causing cerebral embolization, TTE and subsequent transesophageal echocardiography (TEE) were performed.The prosthetic aortic valve functioned well and had no visible vegetations.However, a pseudoaneurysm was noted in the region of the MAIVF (Fig. 2).Surgical correction was not considered because of high operative risk and the family's refusal.
Blood samples for culture were obtained, and treatment was initiated with vancomycin and cefepime.Six days later, Gram-neg-ative bacteria, which were later identified as H. parainfluenzae, were detected in all three sets of blood cultures.The antibiotic regimen was changed to cefotaxime.Despite treatment, progressive multiorgan failure developed and the patient died on day six of TEE.

DISCUSSION
H. parainfluenzae, which is part of the normal flora of the nasopharynx, has been implicated as a rare cause of infective endocarditis.H. parainfluenzae is a slow-growing organism, and blood cultures do not usually become positive within 7 days of sample collection [3].Similarly, the onset of Haemophilus endocarditis is most often subacute, the symptoms often develop insidiously over several weeks, and the time to diagnosis varies widely [1].Systemic embolization is another characteristic of Haemophilus endocarditis.It has been reported that arterial emboli occur frequently in up to 60% of patients with Haemophilus endocarditis.Although embolic infarction and the deposition of immune complexes can occur everywhere, including the spleen, kidneys, coronary vessels, and cerebrovascular system, embolization to the central nervous system is a major cause of morbidity and mortality in patients with H. parainfluenzae endocarditis [1,4,5].Some of these characteristics were seen in our case: (1) The MAIVF is a thin fibrous structure between the aortic and mitral valves where the anterior mitral leaflet connects with the non-coronary cusp of the aortic valve [2].This subaortic structure can be infected as a complication of aortic valve endocarditis.The MAIVF is an avascular structure and prone to infection.The direct extension of inflammation from the aortic valve to the MAIVF is common.Less frequently, an infected aortic regurgitating jet flow striking the MAIVF causes damage to the area and makes it vulnerable to infection [9].For these reasons, involvement of the MAIVF has been reported in 44% of patients with aortic valve endocarditis [9].Pseudoaneurysm formation in the MAIVF is a rare complication that has been reported to be a sequela of infective endocarditis of the aortic valve, aortic valve surgery, or chest trauma.This complication can be fatal because of the risk of rupture, especially when the pseudoaneurysm is large, and surgical correction is usually warranted as soon as the diagnosis is made [2].In our case, however, surgery was not performed because the surgical risk was high and because the patient's family refused surgery.
The diagnostic value of TTE is limited in the detection of vegetations and complications associated with infective endocarditis.It has been reported that the recognition of a pseudoaneurysm by TTE is possible only in about half of all patients [2,9].TEE is superior to TTE in the visualization of vegetations, abscesses, fistulas, and pseudoanuerysms associated with infective endocarditis.Its sensitivity and specificity are 100 and 83%, respectively, in identifying complications of infective endocarditis [10].In our case, the image produced by TTE was good, and we were able to identify the pseudoaneurysm easily and to confirm it by TEE.
To the best of our knowledge, our patient is the first case of

-Figure 2 . 3 )
Figure 2. Echocardiography revealed a pseudoaneurysm (red arrows) with a flow-communicating pulsatile cavity in the region of the mitral-aortic interventricularfibrosa. Transthoracic echocardiograms (parasternal long axis view) without (A) and with color Doppler (B), and transesophageal echocardiograms without (C) and with (D) color Doppler.LV, left ventricle; Ao, aorta; LA, left atrium.

H
. parainfluenzae PVE following the Bentall procedure that was complicated by a pseudoaneurysm and cerebral emboli.H. parainfluenzae PVE is rare, and the slow-growing nature of the mi-croorganism may delay an accurate diagnosis.Thus, there may be life-threatening complications such as rupture of the pseudoaneurysm and cerebral emboli.Therefore, attention should be paid to Haemophilus-mediated infective endocarditis, especially in patients with prosthetic valves who present with an unusual clinical course or metastatic infection.중심 단어: 가성동맥류; 심내막염; Haemophilus parainfluenzae; 인공판막