Methods

From 1995 to 2009, 98,260 consecutive patients who had a transthoracic echocardiographic study at Rabin Medical Center were prospectively entered into a comprehensive clinical database. Of these, 80 consecutive patients aged <50 years were diagnosed with MAC. Baseline characteristics of these patients were compared with those of 843 consecutive patients >50 years with MAC.

Exclusion criteria included prosthetic mitral valve, history of rheumatic heart disease, and congenital cardiac malformations. Echocardiographic studies were performed by an experienced sonographer and reviewed by a cardiologist specialized in echocardiography. The database included clinical, laboratory, and echocardiographic parameters. The echocardiographic parameters included left ventricular (LV) dimensions obtained from the parasternal long-axis view with measurement of end-diastolic interventricular septum thickness, LV posterior wall thickness, and LV end-diastolic and end-systolic diameter; LV function, based on the assessment of LV contractile performance and wall motion in multiple 2-dimensional views graded as good (LV ejection fraction ≥50%), mild LV dysfunction (LV ejection fraction of 40% to 49%), moderate LV dysfunction (LV ejection fraction of 30% to 39%), and severe LV dysfunction (LV ejection fraction <30%); MAC, defined as a dense, localized, highly reflective area at the base of the posterior leaflet of the mitral valve; mitral and aortic valve stenosis assessed according to the present guidelines for the assessment of valve stenosis ; aortic, mitral, and tricuspid regurgitation assessed semiquantitatively according to the present guidelines for the evaluation of native valves ; and systolic pulmonary pressure estimated by the peak velocity of the tricuspid regurgitant jet added to an estimate of right atrial pressure.

This registry was approved by the ethics committee of the Rabin Medical Center.

Results

We identified 80 patients with MAC who were aged <50 years; of these, 19 patients were excluded owing to rheumatic heart disease and 5 owing to missing data. The mean age was 44.2 ± 6.9 years with a male-to-female ratio of 2.5:1.

The prevalence of cardiovascular risk factors and established cardiovascular disease was substantially greater than expected for this age group ( Table 1 ). Fifty-two percent of the patients had chronic kidney disease (creatinine clearance <60 ml/min). Of these, 62% had end-stage kidney disease (creatinine clearance <15 ml/min) and 24% underwent renal transplantation. Twenty-five percent of the patients (all with chronic kidney disease) had hyperphosphatemia, whereas 13% had hypercalcemia. Four patients (7%) had no cardiovascular risk factors.

Baseline characteristics of patients with versus without chronic kidney disease are listed in Table 2 . The prevalence of cardiovascular risk factors was similar between patients with and without chronic kidney disease, except for hypertension, which was significantly more prevalent in patients with chronic kidney disease than those without (72% vs 33%, p = 0.03). Furthermore, the prevalence of coronary artery disease and previous stroke was not different between the 2 groups.

Echocardiographic parameters of young patients with MAC are summarized in Table 3 .

Twenty-five percent of the patients had significant mitral regurgitation (18% with moderate and 7% with severe regurgitation), and 5% had moderate or severe mitral stenosis. Aortic valve disease was present in 66% of the patients (14% postaortic valve replacement, 16% moderate or severe stenosis, 5% moderate or severe regurgitation, 2% combined moderate or severe stenosis and regurgitation, and 28% aortic valve calcification). Significant tricuspid regurgitation (moderate or severe) and estimated systolic pulmonary hypertension >50 mm Hg were detected in 14% and 20% of the patients, respectively.

Nine patients (16%) had moderate or severe LV dysfunction, which was due to regional wall motion abnormalities secondary to previous infarcts in 6 patients, global dysfunction in 2 patients, and severe aortic stenosis in 1 patient. LV hypertrophy was observed in 32 patients (56%), 6 of whom (19%) had hypertrophic cardiomyopathy. Eleven patients (20%) exhibited LV dilation; of these, 2 had significant mitral valve regurgitation and 2 had significant aortic valve regurgitation.

During a median follow-up period of 7 years (interquartile range 6.25 to 12 years), 23 patients (41%) died with a mean age of death of 46 years (range 35 to 57 years; of whom 13 had chronic kidney disease, 5 severe aortic stenosis, 1 familial hyperlipidemia treated with plasmapheresis, and 1 malignancy).

The baseline characteristics of young patients versus older patients with MAC in our cohort are presented in Table 1 . The proportion of men was significantly greater in young patients with a male-to-female ratio of 2.5:1 compared with 0.6:1 in older patients. Chronic kidney disease and smoking were 1.5-fold and 1.8-fold more common in young patients than in older patients (52% vs 34%, p = 0.009 and 39% vs 22%, p = 0.003, respectively), whereas dyslipidemia and hypertension were more prevalent in older patients. Diabetes rates were similar between the groups. Coronary artery disease was more prevalent in older patients, while the prevalence of previous stroke did not differ between the groups.