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Mitral annular calcification and the risk of stroke in an elderly cohort
E J Benjamin1, J F Plehn, R B D'Agostino
1Framingham Heart Study, Mass.
Insights
Mitral annular calcification doubles stroke risk, even after accounting for traditional risk factors. This finding highlights mitral annular calcification as a significant independent predictor of stroke incidence in the elderly population.
Area of Science:
- Cardiology
- Neurology
- Geriatrics
Background:
- Previous studies suggested a link between mitral annular calcification (MAC) and stroke risk.
- The independence of this association from established stroke risk factors remained unclear.
Purpose of the Study:
- To investigate the relationship between mitral annular calcification and the incidence of stroke.
- To determine if MAC is an independent risk factor for stroke.
Main Methods:
- Echocardiography was used to assess MAC presence and severity in 1159 subjects from the Framingham Study.
- Stroke incidence was analyzed over eight years using a proportional-hazards model, adjusting for traditional stroke risk factors.
Main Results:
- Mitral annular calcification prevalence was 10.3% in men and 15.8% in women.
- MAC presence was associated with a 2.10-fold increased relative risk of stroke (P = 0.006).
- Each millimeter of MAC thickness correlated with a 1.24-fold increased stroke risk (P < 0.001), independent of other factors.
Conclusions:
- Mitral annular calcification is associated with a doubled stroke risk in an elderly, population-based cohort.
- This association persists independently of traditional stroke risk factors.
- The causal role of MAC in stroke risk requires further investigation.
Background:
Previous clinical studies have suggested that there is an association between mitral annular calcification and the risk of stroke, but it is unclear whether this association is independent of the traditional risk factors for stroke. We examined the relation between mitral annular calcification and the incidence of stroke in a population-based study.
Methods:
Subjects in the Framingham Study receiving a routine examination underwent M-mode echocardiography to determine the presence and severity (thickness in millimeters) of mitral annular calcification. The incidence of stroke during eight years of follow-up was analyzed with a proportional-hazards model adjusting for the calcification, age, sex, systolic blood pressure, diabetes mellitus, cigarette smoking, atrial fibrillation, and coronary heart disease or congestive heart failure.
Results:
Among 1159 subjects whose echocardiograms could be assessed for mitral annular calcification and who had no history or current evidence of stroke at the index examination (51 percent of all subjects), the prevalence of mitral annular calcification was 10.3 percent in the men and 15.8 percent in the women. Multivariate analysis demonstrated that the presence of mitral annular calcification was associated with a relative risk of stroke of 2.10 (95 percent confidence interval, 1.24 to 3.57; P = 0.006). There was a continuous relation between the incidence of stroke and the severity of mitral annular calcification; each millimeter of thickening as shown on the echocardiogram represented a relative risk of stroke of 1.24 (95 percent confidence interval, 1.12 to 1.37; P less than 0.001). Furthermore, even when subjects with coronary heart disease or congestive heart failure were excluded from the analysis, subjects with mitral annular calcification still had twice the risk of stroke.
Conclusions:
In an elderly, longitudinally followed population-based cohort, mitral annular calcification was associated with a doubled risk of stroke, independently of traditional risk factors for stroke. Whether such calcification contributes causally to the risk of stroke or is merely a marker of increased risk because of its association with other precursors of stroke remains unknown.