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Cross-sectional echocardiographic observations on the mechanism of preservation of the opening snap in calcific mitral stenosis.

Cross-sectional echocardiography (CSE) was performed on 19 patients with mitral stenosis (MS). Nine patients (group 1) had little or no mitral valve (MV) calcification; ten patients (group 2) had heavy MV calcification. An opening snap was present in each of the patients in group 1. Of the group 2 patients, five (group 2A) had an opening snap and five (group 2B) did not. CSE in the long axis revealed in group 1 patients a mobile MV with sharp anterior arching of the anterior leaflet in early diastole; in group 2A, dense echoes suggestive of calcification were noted near the tip of the MV, while the body of the leaflet was relatively thin and it arched anteriorly sharply in early diastole; and in group 2B, dense echoes were noted at the tip and body of the MV with reduction in mobility of the valve, and the sharp anterior arching of the anterior leaflet in early diastole was absent. Preservation of the OS in calcific MS depends on the distribution of calcification. Heavy calcification confined to the tip of the MV allows the anterior leaflet to arch anteriorly in early diastole, allowing preservation of the OS, whereas heavy calcification of the tip and body of the MV reduces the pliability of the valve with consequent disappearance of the OS.