Mitral annulus calcification: clinical implications1
M-mode echocardiographic features of 53 patients with mitral annulus calcification (MAC) are presented with an initial clinical analysis. Direct measurement of the thickness of the calcification is described as a new technique to define the severity of this process, possibly with a prognostic value as well. Moderate to severe degree of MAC (>5 mm average thickness) was found in 69.7% of patients, all without history of rheumatic heart involvement, and only one had chronic renal failure. Detailed electrocardiographic observations showed the presence of conduction disturbances in 53.6%; 6 patients with 3° atrioventricular block and 3 with sick sinus syndrome and widespread conduction disturbances required permanent pacemaker. Electrophysiologic study of 7 patients demonstrated a significant prevalence of involvement of the conduction system below the proximal His bundle, the region more directly in contact with the calcified annulus. We believe that this quantitative method of evaluating patients with MAC is of value for noninvasive, more complete clinical study of this disease.