Mitral annular calcification as a cause of mitral valve gradients

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Abstract

Background

Mitral annular calcification (MAC) is common, particularly in the elderly. While thought to occasionally produce significant mitral regurgitation, it is considered a rare cause of mitral stenosis.

Methods

Echocardiogram reports from general cardiology outpatients were searched for phrases regarding severe MAC and, separately, for mitral stenosis. Rheumatic disease or other mitral valve (MV) pathology was excluded. Mean MV and aortic valve (AV) gradients were recorded. The presence or absence of anterior MAC was noted and a semi-quantitative assessment of anterior mitral leaflet (AML) mobility was made. Ten patients with annuloplasty rings served for comparison.

Results

Group A (22 patients with moderately/severely reduced AML mobility) had a mean MV gradient of 7 mm Hg (range 3–14) vs. 3 mm Hg (range 1–5) in group B (21 patients with normal/mildly reduced AML mobility), p < 0.0001. Annuloplasty patients had a mean MV gradient of 3 mm Hg, p < 0.001 vs. group A but similar to group B. Mean AV gradient was 27 mm Hg (range 4–48) in group A vs. 14 mm Hg in group B (range 3–40), p = 0.013. No patient had more than mild mitral regurgitation.

Conclusion

MAC producing a potentially important MV gradient is not rare in the general cardiology population. Reduced AML mobility appears to be necessary for a gradient > 5 mm Hg. Significant AV gradients are commonly associated, reflecting greater overall cardiac calcification. These patients can be easily identified by looking for reduced AML mobility as part of widespread cardiac calcification.

Introduction

Mitral annular calcification (MAC) is a common finding on echocardiography, particularly in the elderly [1]. The etiology is unclear although it is associated with the same risk factors as atherosclerotic disease of which it may be a subclinical form [2]. In addition it appears to be related to abnormal calcium and phosphorus metabolism with a high incidence noted in end-stage renal disease [3].

Generally, this process is regarded as benign although it is thought to produce significant mitral regurgitation on occasion [4]. Mitral stenosis due to annular calcification is reported to be quite rare [5], [6], [7], [8], [9], [10], [11], [12], [13]. However, we have noted a number of patients undergoing routine echocardiography who have a significant resting gradient across the mitral valve (MV) with the only apparent etiology being MAC. We therefore evaluated a series of echocardiograms demonstrating severe MAC for features associated with a resting MV gradient.

Section snippets

Materials and methods

Outpatient echocardiogram reports were searched for key phrases regarding severe annular calcification and, separately, for mitral stenosis; patients with rheumatic disease or other identifiable mitral valve disease were excluded. All outpatient studies were performed in the setting of a private general cardiology practice between 1/1/03–10/1/05. Several inpatient studies were included as they came to our attention for purposes of substantiating our observations. Forty-three cases (40

Results

A total of 4270 patients underwent echocardiography in our outpatient lab over this time period. Of those, 3096 were age 65 or older. Forty patients were reported to have severe MAC, representing 0.9% of the total group and 1.3% of those 65 and over. All but three had severe posterior MAC. Nineteen subjects were identified who had reduced AML mobility due to annular calcification (group A included these as well as three additional inpatients). They represented 0.4% of the total number of

Discussion

Mitral annular calcification is commonly observed on echocardiograms, particularly in the elderly [1]. While this is usually an incidental finding it has occasionally been associated with significant mitral regurgitation [4]. As demonstrated in our cohort of unselected outpatients it can also produce a clinically relevant resting gradient across the mitral valve, with approximately 0.5% of our outpatients affected. This is more likely when the MAC is severe and especially when there is reduced

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