Severe mitral annular calcification predicts chronic kidney disease.

BACKGROUND: Mitral annular calcification (MAC) is common in the elderly and is associated with atherosclerosis, sharing many of the same risk factors. It is also frequent among dialysis patients. We hypothesized that in general cardiology patients without kidney failure, MAC, especially when severe, may be a marker for renal dysfunction.

METHODS: Forty-one subjects were identified by searching outpatient echocardiogram reports for phrases indicating severe MAC. These were divided into subgroups based on greater or lesser overall intracardiac calcification. The "MAC mobile" subgroup had calcification largely limited to the posterior annulus with normal anterior mitral leaflet mobility. In the "MAC restricted" subgroup, calcification extended to the anterior annulus and limited anterior mitral leaflet mobility. These latter patients also had more severe aortic valve calcification. Seventy-seven controls with minimal or no intracardiac calcification were used for comparison.

RESULTS: The total MAC group had worse renal function, measured by creatinine and glomerular filtration rate (GFR), than controls (p<0.001 for both comparisons). Nearly 60% had chronic kidney disease as defined by a GFR<60 ml/min/1.73 m(2) with a relative risk of 1.8 versus controls. GFR was observed to decline in a graded fashion as calcification increased (control versus "MAC mobile" versus "MAC restricted"). Though this trend did not remain statistically significant after controlling for age and gender, GFR was substantially lower in "MAC restricted" versus "MAC mobile" patients (p=0.03).

CONCLUSIONS: Severe MAC on echocardiogram points to a strong likelihood of chronic kidney disease. Further study is needed to explore a possible graded relationship between severity of MAC and severity of renal dysfunction.