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Mitral Annular Calcification as a Possible Nidus for Endocarditis: A Descriptive Series with Bacteriological
Gregg S Pressman1, Mary Rodriguez-Ziccardi2, Charles H Gartman3
1Division of Cardiology, Heart and Vascular Institute, Einstein Medical Center, Philadelphia, Pennsylvania.
Background:
Mitral annular calcification (MAC) is a chronic inflammatory process with similarities to atherosclerosis. It is common in elderly patients and those with renal dysfunction. Although MAC is associated with cardiovascular morbidity, its relationship to infective endocarditis is unclear. The aim of this study was to test the hypothesis that MAC would be prevalent in patients with mitral valve vegetations and that vegetations would frequently occur on calcific nodules. A secondary aim was to look for possible bacteriological differences between vegetations attached to the calcified annulus versus leaflet vegetations.
Methods:
We retrospectively reviewed all echocardiographic studies of patients with native mitral valve vegetations from January 2007 to August 2015 (N = 56). We searched for (1) presence of MAC, (2) location of MAC, and (3) vegetation location (on calcium deposits or distant). MAC was defined as focal echo brightness in a nodular or band-like pattern. The modified Duke criteria were used to confirm the diagnosis of infective endocarditis. Transthoracic, transesophageal, and three-dimensional echocardiograms (when available) at the time of infection were evaluated by a single reader.
Results:
Twenty-eight subjects were infected with Staphylococcus aureus, 17 with a streptococcal species, and five with other organisms; blood cultures were sterile in 6. Thirty-four (61%) subjects had some degree of MAC, while 22 (39%) had none. Among those with MAC, the vegetation was located on the calcium deposits in 22 (65%), versus in 12 (35%) where it was not. Among all 56 subjects, when S. aureus was the infecting organism it was present on MAC in 16/28 (57%) versus 6/28 (21%; P = .01) for other bacterial species. By contrast, streptococcal infections more frequently involved the leaflets (16/17 [94%]) versus nonstreptococcal infections (18/39 [46%]; P = .0008).
Conclusions:
MAC may act as a nidus for infection especially with S. aureus. Differences in mechanism of attachment between S. aureus and streptococci may account for the observed difference in frequency of attachment of vegetations to MAC.
Insights
Mitral annular calcification (MAC) often serves as a site for infective endocarditis, particularly with Staphylococcus aureus. This study highlights MAC
Area of Science:
- Cardiology
- Infectious Diseases
- Medical Imaging
Background:
- Mitral annular calcification (MAC) is a chronic inflammatory process similar to atherosclerosis, prevalent in elderly and renally impaired patients.
- While associated with cardiovascular disease, MAC's link to infective endocarditis (IE) remains unclear.
- This study investigated MAC prevalence in patients with mitral valve vegetations and potential bacteriological differences.
Observation:
- A retrospective review of 56 patients with native mitral valve vegetations was conducted.
- Echocardiograms were analyzed for the presence and location of MAC and vegetations.
- Infective endocarditis diagnosis was confirmed using the modified Duke criteria.
Findings:
- Thirty-four (61%) patients had MAC, with vegetations located on calcific nodules in 22 (65%) of these cases.
- Staphylococcus aureus was more frequently found on MAC (57%) compared to other bacterial species (21%, P = .01).
- Streptococcal infections predominantly involved leaflets (94%) rather than MAC.
Implications:
- Mitral annular calcification may serve as a nidus for infective endocarditis, especially in S. aureus infections.
- Differential attachment mechanisms of S. aureus and streptococci to MAC could explain observed vegetation patterns.
- Understanding these associations can inform IE diagnosis and management strategies.