Conduction disturbances associated with mitral anular calcification.

To investigate the apparent association of mitral anular calcification (MAC) and electrocardiographic abnormalities, the relation between the location of two-dimensional (2D) echoquantified MAC and conduction disturbances was studied in 140 patients with MAC (MAC group) and 135 age- and sex-matched patients without MAC (control group). The MAC group was subclassified regarding the site and severity of calcium in the mitral anulus. The site of MAC was defined as Type I of MAC near the conduction system and Type II of MAC away from the conduction system. The severity of MAC was graded on 2D echocardiography as mild (localized within 1 segment) and moderate to severe (more than 1 segment). Seven patients with MAC, and only one control subject, had pacemakers in place. Conduction disturbances were present in 44 (31%) of 140 patients with MAC and in 37 (27%) of the 135 control patients (no significant difference). But there were more conduction disturbances in the patients with Type 1 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. Intraventricular conduction delay also was more prevalent in the patients with Type I MAC than in the control group (Type I: 12% vs control: 4%; p less than 0.05). These data suggest that moderate to severe degrees of MAC located near the conduction system are associated with conduction disturbances, especially intraventricular conduction delay.