Mitral annular calcification is a predictor for incident atrial fibrillation

Background: Mitral annular calcification (MAC) has been associated with adverse cardiovascular disease outcomes and stroke in longitudinal and community-based cohorts. Prospective data are limited on its association with atrial fibrillation (AF). Methods: We examined the association between MAC and the long-term risk of AF over 16 years of follow-up in participants in the original cohort of the Framingham Heart Study who attended a routine examination between 1979 and 1981. MAC was assessed by M-mode echocardiography. Cox proportional-hazards models were used to estimate hazard ratios (HR) for incident AF. Results: Of 1126 subjects who had adequate echocardiographic assessment and were AF-free at baseline, 149 (13%) had MAC. There were 217 cases of incident AF (42 in subjects with MAC). The age- and sex-adjusted incidence rate was 362 per 10,000 person-years in subjects with MAC compared with 185 per 10,000 person-years in those without MAC. In multivariable- adjusted analyses, MAC was associated with an increased risk of AF (HR 1.6, 95% CI 1.1-2.2). This association was attenuated upon further adjustment for left atrial size (HR 1.4, 95% CI 0.9-2.0). Conclusions: The association between MAC and incident AF may be mediated partially through left atrial enlargement. These data suggest the importance of better understanding the mechanisms involved in cardiac valvular calcification.