The Study Of Mechanism Of Ischemic Mitral Regurgitation By Echocardiography

Background: Ischemic mitral regurgitation (IMR) is a common complication of coronary artery disease with a poor prognosis. The exact mechanisms of IMR are complex and not well defined, which prevent a better therapeutic approach to this disease. The aim of study is to detect the influence of left ventricle and mitral apparatus remodeling on mitral regurgitation in different conditions by echocardiography, and investigate the mechanism of IMR.This study include four parts.Part one Analysis of ischemic mitral regurgitation correlation factors Objectives:To investigate the mechanism of IMR. Methods: The correlations among the mitral regurgitation, left ventricle and mitral apparatus remodeling in normal group, myocardial infarction without regurgitation group and myocardial infarction with regurgitation group were detected by echocardiogaphy, and the measurements are as follows: the degree of mitral regurgitation expressed as jet/left atrial area, end diastolic and systolic volume index(EDVI, ESVI), ejection fraction (EF), sphericity index expressed as diastolic and Systolic L/D, wall motion index(WMI) of the myocardium underlying papillary muscle, mitral leaflet closure(MLC), coaptation height(CH), chordae tendineae(CT), mitral annular area(MAA), the length between the Posterior or anterior papillary muscle tips and the contralateral anterior mitral annular(APM-AMA, PPM-AMA), the distance between the Posterior and anterior papillary muscle (APM-PPM) and the changes of apillary muscle position. Results: Remodeling was found in left ventricle in myocardial infarction patients with lower EF, higher EDVI and ESVI, smaller L/D and lower WMI The remodeling degree of regurgitation group was higher than that of non- regurgitation group. Remarkable remodeling was found in mitral apparatus in regurgitation group with insufficient systolic leaflet body displacement toward the annulus, with coaptation limited to leaflet tips and increase in MLC, CH, MAA, APM-PPM, APM-AMA, PPM-AMA, and decrease in MA contraction, and lateral and posterior displacements of the papillary muscle. The degree of regurgitation were correlated with MLC, CH, EDVI, ESVI, EF, L/D, MAA, MAcontraction, APM—PPM, APM-AMA, and decrease in MA contraction, and lateral and posterior displacements of the papillary muscle. Multivariate analysis based on stepwise multiple linear regression showed that EDVI is the major determinant of MR in left ventricle remodeling indexes, and MLC, PPM-AMA ,MAA are the major determinants of MR in mitral apparatus remodeling indexes, and MLC, PPM-AMA, MAA are the major determinants of MR in left ventricle and mitral apparatus remodeling indexes. Conclusions: left ventricle without mitral apparatus remodeling was not always induced IMR, only when left ventricle with mitral apparatus remarkable remodeling can induce IMR, and MLC, PPM-AMA, MAA are the major determinants of MR. Part two Influence of myocardial infarction locationon ischemic mitral regurgitationObjectivesrTo investigate the influence of myocardial infarction(MI) location on ischemic mitral regurgitation. Methods: 20 normal control subjects and 87 patients with prior MI, including 51 patients with anterior MI and 36 patients with inferior MI were detected by echocardiogaphy, and the measurements are as follows: the degree of mitral regurgitation expressed as jet/left atrial area, end diastolic and systolic volume index(EDVI, ESVI), ejection fraction (EF), sphericity index expressed as diastolic L/D, wall motion index(WMI)of the myocardium underlying papillary muscle, mitral leaflet closure(MLC), mitral annular area(MAA), the length between the posterior or anterior papillary muscle tips and the contralateral anterior mitral annular(APM-AMA, PPM-AMA). Results: The percentage of MR jet area and incidence of Moderate or greater MR were higher in in patients with inferior MI than anterior MI. Significantly left ventricle remodeling was found in patients with inferior and anterior MI, and lower EF and higher ESVI were found in patients with anterior MI. Mitral apparatus remodeling was also found in in patients with inferior and anterior MI. The increase in MLC, PPM-AMA,MAA were significantly higher in patients with inferior MI, but the increase in APM-AMA had no different between patients with inferior and anterior MI. Multivariate analysis based on stepwise multiple linear regression showed that MLC, MAA, EDVI were the major determinants of MR in patients with anterior MI, and MLC, MAA, PPM-AMA werethe major determinants of MR in patients with inferior MI. Conclusions:The difference in IMR between inferior and anterior MI is due to the different influence on mitral apparatus. The changes in MAA, PPM-AMA were significantly greater in inferior MI, so the IMR.were more severe. Part three The effect of mitral annular dilation in the mechanismof functional mitral regurgitationObjective:To investigate the effect of mitral annular dilation in the mechanism of functional mitral regurgitation. Method: 20 control subjects, 30 patients with lone AF and 30 patients with coronary artery disease or dilated cardiomyopathy were detected by echocardiogaphy, and the measurements are as follows: the degree of mitral regurgitation expressed as jet/left atrial area, end diastolic and systolic volume index(EDVI, ESVI), ejection fraction (EF), sphericity index expressed as diastolic L/D, mitral leaflet closure(MLC), mitral annular area(MAA), the length between the posterior papillary muscle tips and the contralateral anterior mitral annular (PPM-AMA). Results: EDVI, ESVI, EF, Systolic L/D and PPM-AMA in AF group were similar to those in normal group except MA dilated. EDVI, ESVI, EF, Systolic L/D, MLC, MA and PPM-AMA changed significantly in FMR group with MA was similar to that of AF group. Multivariate analysis based on stepwise multiple linear regression showed that MLC, MAA, PPM-AMA were the major determinants of MR, and the influence of MAA was smaller. Conclusion: Isolated annular dilation doesn't seem to cause moderate or severe MR. Part four Influence of papillary muscle functionon ischemic mitral regurgitationObjectives:To investigate the influence of papillary muscle function on IMR. Methods: 41 patients with inferior MI were detected by echocardiogaphy, and the measurements are as follows: the degree of mitral regurgitation expressed as jet/left atrial area, end diastolic volume index(EDVI), ejection fraction (EF), sphericity index expressed as diastolic L/D, mitral leaflet closure area(MLC), mitral annular area(MAA), the length between the Posterior or anterior papillary muscle tips and the contralateral anterior mitral annular(APM-AMA, PPM-AMA), the posterior papillary muscle function.The patients were divided into two groups according the sphericity index. Results: Left ventricle and mitral apparatus remodeling were moresevere in group two than that in group one include EDVI, EF, L/D, MLC, MAA, PPM-AMA and PPM function. PPM function was correlated with the degree of regurgitation in group two but not with total group. Multivariate analysis based on stepwise multiple linear regression showed that MLC, MAA, PPM-AMA were the major determinants of MR but not PPM function.Conclusions: papillary muscle dysfunction wasn't the main cause of IMR. In an given condition it can relieve the degree of IMR.