ObjectiveTo observe the three-dimensional shape of mitral valve elongation and the hemodynamic changes of the left ventricular outflow tract by real time three-dimensional echocardiography（RT-3 DE）

and to analyze the causes of left ventricular outflow tract dynamic obstruction caused by anterior mitral valve elongation.MethodsEighteen patients with mitral valve elongation confirmed by echocardiography（study group）and 23 normal healthy adults（control group）were selected. On the basis of conventional two-dimensional echocardiography

RT-3 DE was used to observe the threedimensional shape and hemodynamic changes of malformed mitral valve

and the length of residual part of anterior mitral valve elongation（AMV-e L）

the length of anterior mitral valve（AMV-L）

left ventricular outflow velocity（LVOT-V）

pressure gradient（LVOT-P）

interventricular septal thickness（IVS-D）

left ventricular posterior wall thickness（LVPW-D）

left ventricular end diastolic diameter（LVD-D）

left ventricular end systolic diameter（LVS-D）

mitral velocity（MV）

left ventricular ejection fraction（LVEF）and heart rate（HR）were measured and compared in the two groups.The correlation between parameters of mitral value elongation and left rentricular outflow tract dynamic parameters.ResultsThere were statistically significant differences in AMV-L

LVOT-V

LVOT-P

IVS-D and LVPW-D between the two groups（all P<0.05）

but there were no significant difference in LVD-D

LVS-D

MV

LVEF and HR between the two groups.The systolic anterior motion of anterior mitral valve elongation was found in the study group.The AMV-L of the study group was positively correlated with AMV-e L、LVOT-V and LVOT-P（r=0.925

0.916

0.923

all P<0.05）.ConclusionMitral valve elongation can lead to left ventricular outflow tract obstruction.The systolic anterior motion of anterior mitral valve elongation is the cause of left ventricular outflow tract obstruction.