Caseous calcification of the mitral valve annulus

Clinical History

56-year-old female patient presented with repeated attacks of arrhythmia associated with drowsiness and fainting. ECG findings were consistent with atrial fibrillation. The lady was also mildly hypertensive. The LAB findings were otherwise negative.

Imaging Findings

Echocardiography demonstrates large echogenic mass lesion at the level of the mitral valve annulus with associated moderate to significant mitral valve regurgitation (Fig. 1). Pre-contrast CT scan revealed the calcific nature of the mass (Fig. 2). MRI T2* also demonstrates blooming related to the calcifications (Figure 3). 4 chamber view CMR confirms the associated mitral valve dysfunction sequel to the posterior cusp shortening with subsequent regurgitation (Fig 4). Two chamber view CMR also confirms the involvement of the posterior commissure of the mitral valve (Fig. 5). Delayed enhancement CMR demonstrates intense enhancement of the mass periphery denoting heavy fibrosis of the expanded annulus walls with darker centre composed of caseous necrosis (Fig. 6). Surgical exploration of the mitral annulus revealed whitish toothpaste-like material (Fig. 7), Post-operative CT brain with multiple lacunar infarcts likely sequel to embolism occurring at the time of surgery (Fig. 8).

Discussion

Caseous calcification of the mitral annulus (CCMA) is a rare idiopathic variant of mitral annulus calcifications (CMA) occurring only in 0.06% of the population above 65 years of age [1, 2]. CCMA appears on growth pathological level as an encapsulated expansion of the mitral valve annulus affecting the posterior commissure and is full of whitish toothpaste-like material [3]. On microscopic level CCMA appears as an eosinophilic acellular material with scattered areas of calcifications [4]. Incidental discovery is the commonest presentation and is commonly misinterpreted as a cardiac tumour [1]. Less commonly CCMA presents as attacks of dyspnoea or attacks of syncope sequel to AV block [5]. Spontaneous embolization sequel to ulceration of the surface of CCMA with fistulation to the lumen of the atrium or ventricle may also be encountered [6].

Many cardiologists are not familiar with this condition and may consider it a cardiac tumour with subsequent unnecessary surgeries [3.] Multimodality imaging is required for cases of CCMA starting with transoesophageal and transthoracic echocardiography which demonstrates echogenic lobulated mass lesion with diminished mobility [7]. CT demonstrates CCMA as a dense calcified mass lesion of the posterior mitral annulus with lucent centre [8]. Cardiac MRI confirms the classical morphology and site of CCMA, MRI also demonstrates the calcific nature through blooming artefacts and can differentiate between simple CMA and CCMA through the detection of the delayed enhancement pattern of the fibrosed annulus periphery which should only be seen in CCMA [9].

CCMA is mostly managed conservatively. The indications for surgery are significant mitral valve dysfunctions, spontaneous embolization and cases where other cardiac tumours can't be totally excluded [10]. Mitral valve replacement is superior to mitral repair while the debridement of mitral annulus will be associated by higher risk of embolization [11]. Our case was managed surgically due to the significant mitral valve regurgitation. Mitral annulus debridement was done due to the inability to exclude neoplastic lesions at the time of surgery, this was followed by mitral valve replacement with the unfortunate occurrence of post-operative embolic stroke.

In summary, CCMA is a rare non-neoplastic disorder of the mitral valve annulus. Although it has very definite diagnostic imaging criteria, it is still unknown to many cardiologists and also radiologists with the subsequent possible misinterpretation and unnecessary or wrong-type mitral valve annulus surgical procedures which may end in complications, especially systemic embolization.

Differential Diagnosis List

Final Diagnosis

Caseous calcifications of the mitral valve annulus

URL:	https://www.eurorad.org/case/14104
DOI:	10.1594/EURORAD/CASE.14104
ISSN:	1563-4086