Mitral annular calcification: significant and worth acting upon. Mitral annular calcification (MAC) is a degenerative process which commonly occurs in the elderly and has multiple etiologies. Patients with MAC have a higher prevalence of left atrial enlargement, left ventricular enlargement, atrial fibrillation, conduction defects, mitral regurgitation, mitral stenosis, hypertrophic cardiomyopathy, and bacterial endocarditis than those without it. In addition, patients with the disorder have a higher incidence of cardiovascular events, thromboembolic cerebrovascular events, permanent pacemaker implantation, and valve replacement. This review discusses the significance of these warning signs, explores updated diagnostic procedures for MAC, and recommends some therapeutic strategies. 