Mitral valve leaflet diverticulum with vegetation—a rare complication in rheumatic heart disease

Abstract

Diverticulum of mitral leaflet is a rare complication, which is recognized by its central clearing with characteristic diastolic collapse and systolic expansion on echocardiogram. It is found to be commonly associated with infective endocarditis while various other mechanisms of its formation have been suggested. The present case with an underlying history of rheumatic heart disease complicated by infective endocarditis well demonstrates the formation of mitral leaflet diverticulum and its possible complications. Surgical findings revealed diverticulum of the anterior mitral leaflet, and the patient underwent double valve replacement.

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Introduction

Diverticulum arising from the heart is an uncommon finding, which has been rarely seen involving the mitral valve leaflet. Diverticulum is to be distinguished from mitral valve vegetation, papillary fibroelastoma, atypical myxoma, and abscess. It has been described most commonly in association with infective endocarditis.

Case report

A 43-year-old lady, who was a known case of rheumatic heart disease, severe aortic regurgitation, and moderate aortic stenosis, was on regular medical follow-up in view of asymptomatic status. She presented with complains of fever for 7 days, associated with New York Heart Association (NYHA) class III dyspnea and pedal edema. There was no history of joint symptoms, rash, or abnormal body movements. She was average built with mild pallor and bilateral pitting-type pedal edema, with no skin rash or subcutaneous nodules. The patient had documented febrile episodes and tachycardia at rest. Jugular venous pressure (JVP) was elevated, with blood pressure of 110/40 mmHg recorded in the right upper arm. Cardiovascular system examination revealed cardiomegaly, soft first heart sound, and narrow split second heart sound with harsh blowing–type ejection systolic murmur, grade 3/6, at the right second intercostal space and grade 3/4 early diastolic decrescendo murmur in the left 3rd intercostal space, close to the sternal border. Also, third heart sound was appreciated at the apex in the left lateral position and infrascapular bilateral fine crepitations were present. Blood investigations revealed a total leukocyte count of 15,000 (normal range 4000–11,000/cm m³), erythrocyte sedimentation rate (ESR) of 70 (normal 0–7 mm/h), C-reactive protein (CRP) 61 (normal < 3), negative antistreptolysin O (ASO) titer and serum procalcitonin level of 0.114 (normal 0.09) ng/ml. Chest X-ray postero-anterior view showed cardiomegaly with a cardiothoracic ratio of 0.55 with grade II pulmonary venous hypertension. Twelve-lead surface electrocardiogram (ECG) showed sinus tachycardia with a rate of 120/min, PR interval 180 ms, QRS duration 90 ms, axis + 15°, and left ventricular hypertrophy. Transthoracic echo showed dilated left ventricle with thickened and restricted leaflets involving both aortic and mitral valves, likely rheumatic etiology. There was severe aortic regurgitation and moderate stenosis with a 6 × 3 mm vegetation attached to the ventricular side of the aortic valve. The aortic regurgitation jet was eccentric, which was directed towards the anterior mitral leaflet (AML). At the site of jet hitting on AML, a 8 × 6 mm diverticulum was seen, with mouth towards the ventricular side and the diverticulum bulging into the left atrium (Videos 1, 2, 3, and 4). Diverticulum was identified by leaflet hooding and characteristic central clearing with systolic expansion. It was associated with moderate mitral regurgitation, and a vegetation of 8 × 6 mm size was attached to the ventricular side of mitral valve. There was also a suspicion of aortic root abscess on echocardiogram which was subsequently confirmed on cardiac computerized tomography (CT). Three sets of blood cultures were sent, which showed a persistent growth of alpha hemolytic streptococci. She was started on penicillin and gentamycin, based on culture sensitivity report, and received full course of guideline-based antibiotics. As no neurological symptoms were present, head CT was not done. The patient had a symptomatic improvement with resolution of fever, pedal edema, and improved breathlessness within 4–5 days of starting of antibiotics and supportive heart failure medication. Subsequent follow-up echo showed persistent vegetations on both mitral and aortic valves with no significant change in vegetation size. Within 1 month of completion of antibiotics, the patient presented with sudden onset headache, vomiting, and loss of consciousness, with no neurological deficit. Magnetic resonance imaging (MRI) brain showed a focal area of hemorrhage in left occipital white matter. Digital subtraction angiography (DSA) revealed saccular diverticulum involving temporal branch of the left posterior communicating artery, possibly mycotic in origin. Repeat procalcitonin and blood cultures were negative. In view of mycotic aneurysm, even after 4 weeks of antibiotics, the patient was given penicillin and linezolid for 4 weeks as per the previous culture sensitivity report. Following antibiotic therapy, there was a complete resolution of saccular diverticulum involving artery on repeat DSA, while repeat echo revealed persistent vegetation involving both aortic and mitral valves with persistent mitral valve diverticulum involving AML.

The patient was planned for double valve replacement in view of heart failure and persistent aortic root abscess. Intraoperative transesophageal echocardiogram (TEE) revealed thickened and restricted aortic and mitral valves with severe aortic regurgitation and moderate mitral regurgitation; vegetation involves both mitral and aortic valves; and the anterior mitral leaflet showed diverticulum at the site of aortic jet hitting on leaflet. The patient underwent double valve replacement with 23 size tilting disc mechanical prosthesis at mitral position and 21 size tilting disc mechanical prosthesis at aortic position. Intraoperatively, abscess was found to extend from the annulus fibrosa posteriorly around the aorta, further up to the left atrium and right atrium junction of the aortic root. The annulus fibrosa was split between aortic and mitral valves and abscess was seen extending into the aortic root. Aortic leaflets, with abscess tissue, were excised and the left atrium was opened by the superior septal approach. Stitches were taken for aortic valve replacement from the mitral annulus to the aortic annulus, crossing annular fibrosa defect. Other opening of abscess cavity, which was lateral to aortic annulus, was closed with stitches. Grossly, AML measured 2.5 × 2.3 cm and basal part showed hooding, suggestive of a large diverticulum. Excised aortic and mitral leaflet tissue and excess abscess tissue were sent for histopathology. Both valve tissues on histopathology showed sclerosis, mild inflammation, focal fibrinoid deposits, and thin-walled neovascularization, suggestive of rheumatic etiology. Abscess tissue showed no growth on culture and sensitivity, as the patient received a complete course of antibiotics prior to surgery. Post surgery the patient was started on ecosprin and warfarin and is subsequently doing well on follow-up.

Discussion

Diverticulum arising from the heart is an uncommon finding. These lesions usually arise from the left atrial or ventricular wall leading to outflow tract obstruction or valvular regurgitation. Diverticulum of leaflet has been described in case reports to be mostly associated with mitral valve, with reported incidence of 0.2–0.29%. It usually involves the anterior mitral leaflet, but rarely posterior leaflet involvement has been described [1, 2]. Renwick and Stewart, in 1957, were the first to describe an acquired-mitral valve diverticulum presenting as acute mitral regurgitation [3]. It is found to be commonly associated with infective endocarditis, but reports of noninfective etiology for diverticulum formation have been described.

Mechanisms hypothesized for diverticulum formation are (i) aortic regurgitant jet, (ii) contact between vegetations of the aortic valve and the anterior mitral leaflet (kissing lesions), and (iii) spread of the infectious process to the adjacent mitral valve tissue. It is hypothesized that this pouch forms as a consequence of myxomatous changes in the valve, leading to an area of focal weakness [4]. Weakening of mitral leaflet tissue secondary to any cause, i.e., infective endocarditis, aortic regurgitation jet, aging, and connective tissue diseases like Barlow syndrome, Marfan syndrome, or osteogenesis imperfecta can result in acquired mitral leaflet diverticulum [3]. Case series by Vilacosta showed that in patients with mitral leaflet aneurysms, majority had infective endocarditis with aortic regurgitation [5]. Pressure of ventricular systole on an area of weakened valve may lead to an “out pouching” or diverticulum in the valve. When the diverticulum reaches a certain size, this leads to disruption in coaptation of the mitral valve or perforation of leaflet, leading to the mitral regurgitation [6].

Diverticulum is to be distinguished from mitral valve vegetation, papillary fibroelastoma, atypical myxoma, and abscess [7]. On echocardiography, diverticulum shows central clearing with characteristic diastolic collapse and systolic expansion [8]. The patient with suspected leaflet diverticulum should be evaluated for site, relation to aortic regurgitation jet, if present, size and characteristic findings distinguishing them from abscess and other mass. TEE is the mainstay for diagnosis of a diverticulum, though transthoracic echocardiogram (TTE) can give a fair insight into the same, as in the present case.

Thinning of the diverticulum wall may further result in aneurysm formation, which can lead to perforation due to systolic pressure, giving rise to clinically significant mitral regurgitation [9]. In addition, thrombus formation or vegetation may develop within the aneurysm, which may lead to embolism. Uncomplicated diverticulum can be serially followed up, as suggested by some authors, but if complicated by rupture or regurgitation, it needs to be corrected with repair or valve replacement [10].

Conclusion

Leaflet diverticulum is a rare entity which needs to be evaluated for underlying etiology. TEE is a major diagnostic utility, but TTE can give fair insight into the same. Current case scenario reveals a patient with rheumatic valve, which was complicated by infective endocarditis and subsequently resulted in formation of a leaflet diverticulum. Underlying mechanism was likely the high-pressure aortic regurgitation jet hitting on AML, resulting in focal weakness and diverticulum formation. In view of heart failure, infective endocarditis, and moderate-to-severe valvular lesions involving both aortic and mitral valves, the patient underwent double valve replacement.

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The authors declare that there is no conflict of interest.

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