Conduction disturbances related to the site and severity of mitral anular calcification: a 2-dimensional echocardiographic and electrocardiographic correlative study.

To investigate an apparent association of mitral anular calcium (MAC) and electrocardiographic abnormalities, the relation between location of 2-dimensional (2-D) echo-quantified MAC and conduction disturbances was studied in 140 patients with MAC (MAC group) and in 135 age- and sex-matched patients without MAC (control group). The MAC group was subclassified regarding site and severity of calcium in the mitral anulus. The site of MAC was defined as Type I, near the primary conduction system--MAC located in the medial segment and/or extending to the anterior mitral leaflet; and Type II--MAC located at the central and/or lateral segments away from the primary conduction system. The severity of MAC was graded on 2-D echocardiography as mild (localized within 1 segment) and moderate to severe (greater than 1 segment). Seven patients with MAC, and only 1 control subject, had pacemakers in place. Conduction disturbances were present in 44 (31%) of 140 patients with MAC, and in 37 (27%) of 135 control patients (difference not significant). But there were more conduction disturbances in patients with Type I MAC (53%) than in those with Type II MAC (26%) (p less than 0.01). Specifically, complete left bundle branch block and intraventricular conduction delay were more prevalent when MAC was near the conduction system. Conduction disturbances also were more prevalent in patients with Type I MAC than in the control group: intraventricular conduction delay (Type I, 12% versus control, 4%; p less than 0.05) and total conduction disturbances (53 versus 28%; p less than 0.01). These data suggest that moderate to severe degrees of MAC located near the conduction system are associated with conduction disturbances, especially intraventricular conduction delay.