Mitral stenosis: Left atrial dynamics reflect altered passive and active emptying

Abstract

To assess the passive and the active phases of left atrial (LA) emptying, LA volumes and function were studied in 15 patients with mitral stenosis (MS) in sinus rhythm and in 11 normal subjects (NL) with two-dimensional echocardiography with simultaneous electrocardiograms. LA and left ventricular (LV) volumes were measured with the biplane area-length method. LA maximal and minimal volumes were measured at mitral valve opening and closure, respectively. In addition, LA volume was measured at onset of atrial systole (beginning of the P wave on the electrocardiogram). LA volumes were larger in MS compared with NL: Maximal 122 ± 65 cm³ versus 46 ± 12 cm³, p < 0.001; onset of atrial systole 108 ± 63 cm³ versus 29 ± 12 cm³, p < 0.001; minimal 90 ± 60 cm³ versus 18 ± 7 cm³, p < 0.001. LA passive emptying volume (maximal minus volume at onset of atrial systole) was not statistically different in MS compared with NL, while LA active emptying volume (volume at onset of atrial systole minus mimimal) was larger in MS compared with NL (17 ± 5 cm³ versus 11 ± 5 cm³, p < 0.05). The net result was normal LA total emptying volume (maximal minus minimal) MS 32 ± 11 cm³, NL 28 ± 5 cm³. In contrast, the LA emptying fractions were significantly decreased in MS compared with NL (passive 0.13 ± 0.08 versus 0.39 ± 0.1, p < 0.0001, active 0.19 ± 0.08 versus 0.38 ± 0.07, p < 0.0001, total 0.30 ± 0.1 versus 0.62 ± 0.07, p < 0.0001). Thus in MS in sinus rhythm the increased LA volumes compensated for the decreased LA emptying fractions and maintained LA total emptying volume.