A Ruptured Mitral Valve Aneurysm as Complication of a Bicuspid Aortic Valve Endocarditis.

We present a case of a ruptured mitral valve (MV) aneurysm as a complication of a bicuspid aortic valve (BAV) endocarditis. It is about a young 35-year-old man, admitted to Cardiology Unit because of unexpected heart failure picture. We found a BAV endocarditis complicated by anterior MV-anterior leaflet aneurysm formation and subsequent severe MV regurgitation caused by aneurysm perforation. It was a particular and rare situation characterized by an infection of anterior mitral leaflet secondary to an infected regurgitant jet of a primary aortic infective endocarditis due to a BAV. A resulting aneurysm formation on the atrial side of the mitral anterior leaflet leads later to mitral perforation. In this article, we review the more relevant medical literature on this topic.

Introduction

To the best of our knowledge, only 29 cases of mitral valve (MV)-leaflet aneurysm associated with infective endocarditis (IE) have been reported. Of these patients, 75% underwent surgical treatment, usually because of severe MV regurgitation caused by perforation of the MV aneurysm (MVA). We present here a case of bicuspid aortic valve (BAV) endocarditis complicated by anterior MV-anterior leaflet aneurysm formation and subsequent severe MV regurgitation caused by aneurysm perforation. In addition, we review the relevant medical literature.

Case Report

A 35-year-old man young man was admitted to Cardiology Unit because of an unexpected heart failure picture without fever. There was no cardiovascular disease in his clinical history. Two months before, he suffered from fever (38°C) for about 2 weeks. Medium doses of levofloxacin were given orally, but a blood culture had not been taken. Physical examination found a diastolic murmur on the left sternal border and olosystolic murmur at the apex. Blood pressure was low with a high differential measurement (100/50). There were bilateral rales at lung auscultation. Electrocardiogram showed sinus rhythm with a heart rate of 95 beats/min and normal atrioventricular and intraventricular conduction; ventricular repolarization was substantially normal. Oxygen saturation in ambient air was slightly reduced (SO2: 93%). Chest X-ray showed a clear picture of lung congestion [Figure 1]. Transthoracic echocardiogram (TTE) revealed an unusual bulging of the anterior leaflet of MV with a severe eccentric posterior regurgitation [Figure 2, Videos 1 and 2]. This finding was associated with a severe aortic regurgitation due to an anterior-posterior BAV. Left ventricular ejection fraction was 55%, but there was a right ventricular dysfunction with an estimated systolic pulmonary pressure of 50 mmHg. Transesophageal echocardiography (TEE) revealed a saccular structure in the anterior leaflet that bulged into the left atrium throughout the cardiac cycle and was perforated [Figure 3 and Video 3]. A BAV was also confirmed on TEE with a severe aortic regurgitation and a torrential color jet that hit the mitral anterior leaflet aneurysm [Figure 4, Videos 4 and 5]. Two clear elongated vegetations were found floating inside an aneurysm with a severe eccentric jet from the perforated zone [Video 6]. IE was suspected, but multiple blood cultures resulted all negative. Furthermore, medical therapy for heart failure was started and resulted rapidly in a clinical stabilization.

Figure 1

Chest X-ray showing pulmonary congestion.

Figure 2

Transthoracic echocardiogram, parasternal L-A view showing the anterior leaflet saccular aneurysm of the mitral valve.

Figure 3

Transesophageal echocardiography, 4-C mid-esophageal view showing the perforated anterior leaflet aneurysm of the mitral valve.

Figure 4

Transesophageal echocardiography image demonstrating the anterior-posterior bicuspid aortic valve.

In conclusion, it was a particular and rare situation characterized by an infection of anterior mitral leaflet secondary to an infected regurgitant jet of a primary aortic IE due to a BAV. A resulting aneurysm formation on the atrial side of the mitral anterior leaflet led later to mitral perforation.

Treatment

Five days after admission, the patient underwent aortic valve replacement with 23 mm bileaflet mechanical prosthesis (St. Jude Medical) and MV replacement with a 27 mm bileaflet mechanical prosthesis (St. Jude Medical). At operation, one vegetation was found on the coronary cusp of the BAV, and the valve appeared to be thicken and coarse. Noncoronary cusp was perforated. A cystic cavity of 15 mm on the anterior mitral leaflet was clearly visualized from the left atrium and was perforated. The MV leaflet was smooth, and a visible evidence of endocarditis (one vegetation) was found. It was no possible to repair the two valves. After the operation, although cultures of the removed aortic leaflets and MVA were negative and further pathology showed no evidence of inflammatory infiltrate, which was due to the administration of enough doses of antibiotics before the operation, vancomycin was still intravenously given to prevent the recurrence of infection (1.0 g q12 h for 2 weeks). The patient recovered uneventfully and was discharged asymptomatic on the 10th postoperative day. Three months later the patient remained asymptomatic, and TTE showed a perfect result of the performed treatment.

Discussion

In 1729, Morand described the first case of MVA as a saccular structure that bulged into the left atrium with systole expansion and diastolic collapse.[1] MVAs are rare, with an incidence of 0.2%–0.3% on echocardiographic examinations in general. Of the several causative mechanisms reported for MVA (among them connective-tissue disorders, pseudoxanthoma elasticum, and myxomatous valve degeneration), IE is the most prevalent. Substantially, they recognize two pathogenic mechanisms. Less frequently an infected aortic regurgitation jet striking the ventricular surface of the anterior mitral leaflet can result in the formation of an aneurysm of this leaflet.[2] Nevertheless, in the most patients with aortic valve endocarditis, the infection may spread to the mitral-aortic intervalvular fibrosa.[3] Piper et al.[4] defined “mitral kissing vegetation” the large aortic vegetations prolapsing into the left ventricular outflow tract during diastole and contacting the anterior mitral leaflet thus causing it to be secondarily infected. This process causes an abscess, aneurysm and eventually perforation into the left atrium. Aneurysm perforation occurred in 72% of the reported cases. Guler et al. affirmed that larger aneurysm size does not necessarily correlate with a higher risk of perforation.[5] The moment of aneurysm perforation might be a crucial point for peripheral embolization. Although TTE may occasionally identify subtle valvular abnormalities, the better resolution provided by TEE yields a more definitive identification of these rare lesions. MVA can be confused with several abnormalities including myxomatous degeneration of the MV, MV prolapse, flail mitral leaflet, papillary fibroelastoma, myxomas involving the MV, and nonendothelialized cyst of the MV. Color flow Doppler distinguishes an aneurysm from other abnormalities by demonstrating direct communication between an aneurysm and the left ventricle. Early detection and prompt intervention are important to prevent the complications of valvular aneurysms, which include rupture, embolism, and endocarditis. In the reported cases of IE with MVAs, most patients (75%) ultimately underwent surgical treatment, although the timing of surgery was usually unclear. Ruparelia et al. suggested to planning surgery as soon as the abnormality is observed, to prevent aneurysm rupture, the development of severe mitral regurgitation, and embolization.[6] On the other hand, Vilacosta et al. suggested the possibility of conservative management, with surgical intervention only in case of cardiac deterioration.[7] Other authors have recommended a similar approach. The latest 2015 European Society of Cardiology IE guidelines[8] suggest that in the presence of signs of locally uncontrolled infection (increasing vegetation size, abscess formation, false aneurysms, creation of fistula) and persistent fever, surgery is recommended as soon as possible. Rarely, when there are no other reasons for surgery and fever is easily controlled with antibiotics, small abscesses or false aneurysms can be treated conservatively under close clinical and echocardiographic follow-up. Therefore, unless severe comorbidity exists, the presence of locally uncontrolled infection is an indication for early surgery in patients with IE. Heart failure or locally uncontrolled infection both have I(B) recommendation in the latest European Society of Cardiology IE guidelines[8] for urgent surgery. When surgeons plan surgery in complicated aortic valve IE, they should consider possible extravalvular involvement, in particular on the aortic root and the mitral-aortic intervalvular fibrous body. Given the extent of abnormalities associated with MV-leaflet aneurysm development, surgical MV replacement is often necessary; however, repair should be performed if possible, because of the lower risk of recurrent IE. Therefore, in patients with MVAs, repair or replacement of the valve during aortic valve replacement/repair should be performed.

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Conflicts of interest

There are no conflicts of interest.