The incidence and clinical course of caseous calcification of the mitral annulus: a prospective echocardiographic study.

Background: Mitral annular calcification (MAC) is a common echocardiographic finding. Caseous calcification of the mitral annulus (CCMA) is, on the other hand, a less known, rarely described variant, seen as a round mass with a central echolucent area composed of a puttylike admixture of fatty acids, cholesterol, and calcium. The aims of this study were to assess the prevalence of CCMA, assess its morphologic changes over the course of time, and evaluate the patients' characteristics and clinical outcome on follow-up.

Methods: Between January 2002 and December 2004, 20,468 consecutive patients, referred for transthoracic echocardiography, were included in the study. All patients underwent echocardiographic examinations. Four echocardiographic laboratories participated in the registry. CCMA was defined as a large, round, echodense mass with smooth borders located in annular region, without acoustic shadowing and with central areas of echolucencies resembling liquefaction.

Results: A total of 2169 (10.6%) patients were given the diagnosis of MAC by 2-dimensional echocardiography. A total of 14 patients (0.64% of all MACs, 0.068% of all studies) were given the diagnosis of echocardiographic findings compatible with CCMA. Six (43%) patients underwent transesophageal echocardiography (TEE) to better evaluate the nature of the mass. A complete TEE examination was performed using 2-dimensional and color flow Doppler, and the best visualizations of the mass were performed by midesophageal 4-chamber view, midesophageal 2-chamber view, and midesophageal long-axis view. More detailed imaging of the masses, above all a better visualization of the central areas of echolucency, the assessment of the posterior mitral leaflet motion, and the assessment of the correct location of the mass was achieved by TEE views. All calcifications were confined to the mitral annulus. The most common symptom was palpitation, which occurred in 43% of the patients. During a mean follow-up of 3.4 +/- 1.2 years, one patient died. The cause was unrelated to the annular mass; it was the result of neoplasm. During the follow-up period, in 6 (43%) cases, the studies changed, in regard to the features of CCMA, in comparison with baseline studies, thus likely suggesting a changeable condition.

Conclusions: This study confirms prior observations that CCMA is a rare and benign condition. It illustrates the potential role of TEE in confirming the precise location of the lesion and in more clearly defining the extent of the involvement of the posterior mitral leaflet. There were no typical clinical characteristics in patients with CCMA although the absolute number of patients with CCMA was too small to be statistically significant. However, CCMA does tend to occur in older patients and all 14 patients with CCMA in this study had hypertension. CCMA may be a dynamic process based on the observation that 3 patients with MAC progressed to CCMA and 3 patients with CCMA reverted back to MAC during the study period. To avoid diagnostic mistakes such as tumor, abscess, or thrombus among echocardiographers, it is important for us to consider a more widespread knowledge of this rare lesion.