Evaluation Of LV Remodelling And Mechanics In Patients With Mitral Regurgitation Using Two-dimensional Speckle Tracking Imaging

Evaluation of LV remodelling and mechanics in Patients with Mitral Regurgitation using Two-dimensional Speckle Tracking ImagingPrimary mitral regurgitation (PMR) is defined as the pathology of ?1 of the components of the valve (leaflets, chordae tendineae, papillary muscles, annulus), which causes valve incompetence with systolic regurgitation of blood from the left ventricular to the left atrium. Patients with severe PMR can tolerate volume overload for many years. Alterations of LV geometry occur due to chronic volume overload. LV structure and function are closely related. Therefore, assessment of alterations in LV structure and function in patients with PMR may shed important light on the interplay of structure and function in PMR.Two-dimensional speckle tracking imaging (2D-STI) has been widely used to assess left ventricular (LV) function. It can obtain LV global and regional longitudinal, radial as well as circumferential strains at the same time, which assists in evaluating LV contraction systemically. However, whether LV strain data should be indexed to LVEDV remains controversial.Mitral replacement and repair are the main surgical interventions for severe PMR, however, LV dysfunction occurs postoperatively in some patients, accompanied with poor long-term survival. Although some patients had impaired LV function, LV ejection fraction remains normal or even slightly higher. The low-impedance left atrium contains mitral regurgitation from LV, leading to a decrease in LV end-systolic dimension. Under these circumstances, LVEF could not accurately reflect LV myocardial contraction. Accurate evaluation of LV function preoperatively in PMR allows to make clinical decision and choose optimal time for surgery.This study evaluated the alterations in LV remodelling and mechanics preoperatively in chronic severe PMR by using transthoracic echocardiography and two-dimensional speckle tracking imaging. We intended to explore the following questions:1. Is the indexation of LV global strains to LVEDV necessary in patients with PMR? 2. The alterations in LV remodeling and mechanics and their interplay in the presence of volume overload? 3. Is there any clinical application values on the prediction of postoperative LV function using 2D STI?Three parts are included in this study.Part 1 Is the Indexation of LV Global Strains Necessary in Patients with Mitral RegurgitationWe studied 72 cases using transthoracic echocardiography, including 41 patients with severe PMR and 31 normal subjects. LV global longitudinal strain (GLS), mid-ventricular radial strain (mid-RS) and circumferential strain (mid-CS) were derived from two-dimensional speckle-tracking imaging. LV cavity size and geometry were assessed by EDVI, ESVI, SVI, LVEF, MRVI, LV wall thickness to radius (T/RED) and LV short-axis to long-axis ratio (S/LED) at end-diastole. Results As expected, the study population has a wide data range with respect to EDVI (77±36mL/m2), ESVI (30±23mL/m2), SVI (47±19mL/m2), T/RED (0.38±0.08), S/LED (0.71±0.14) respectively. By linear regression analysis, LV GLS, mid-RS, mid-CS correlated significantly with LVEF (GLS:r=-0.5, GRS:r=0.48, GCS:r=-0.61, all p<0.001) but not with EDVI, SVI, MRVI (all P=NS).Part 2 Assessment of LV Geometry and Mechanics in Mitral Regurgitation using 2-dimensional Speckle Tracking Imaging41 chronic severe PMR patients and 31 normal subjects were prospectively studied using transthoracic echocardiography and 2D-STI. LV cavity size and geometry were assessed by EDD, ESD, IVST, PWT, LV mass, EDVI, ESVI, EF, SVI, LV wall thickness to radius (T/RED, T/RES) and LV short-axis to long-axis ratio (S/LED, S/LES) at end-diastole and end-systole. LV global and regional systolic longitudinal, radial and circumferential strains were measured from apical 4-chamber view and three short-axis views. Results PMR group had significantly increased EDD?ESD?EDVI? ESVI?LVMI?SVI (all p<0.001) but with the same LVEF than those of normal group (p=0.599). PMR group had lower T/RED and T/REs but increased LV S/LED and S/LES (all p<0.001). Global systolic longitudinal, radial and circumferential strain did not differ between the two groups (all p>0.05). At regional level, LV longitudinal and radial strain decreased in the basal segments (all p<0.05) when comparing with normal group, however, PMR group had significant increased longitudinal strain in apex as well as radial strain in middle septum. Stepwise regression analysis confirmed LV longitudinal strain in apex and radial strain in base correlated with T/RED. And basal septum longitudinal strain are affected by T/Red?EDVI as well as S/LesPart 3 Prediction of Early Postoperative LV Contraction in Patients with Mitral Regurgitation using 2-dimensional Speckle Tracking Imaging41 consecutive patients with chronic severe PMR scheduled for mitral valve replacement. Two-dimensional speckle-tracking imaging was performed to obtain LV global longitudinal, mid-ventricular radial strain and strain rates before surgery. MR severity was quantified by using the proximal isovelocity surface area method, and the effective regurgitant orifice (ERO) was estimated. The modified biplane Simpson's method was used to obtain LV end-diastolic volume (EDV), LV end-systolic volume (ESV), and LV ejection fraction (LVEF). Echocardiography was repeated in all patients within 2 weeks after surgery. The study population was divided into two groups, according to postoperative decrease in LVEF:group A, with postoperative LVEF decreases< 10%, and group B, with postoperative LVEF decreases> 10%. The values predicting a postoperative LVEF decrease of >10% was estimated by binary logistic regression equation. And the critical values were obtained using receiver operating characteristic (ROC) curves. Results The LV radial strain rate at the level of mid-ventricular short-axis plane was the strongest predictor of a postoperative LVEF reduction of>10%, with the best discriminant value< 1.652 s-1 (area under the receiver operating characteristic curve,0.847; sensitivity and specificity were 70% and 88.24%, respectively.)ConclusionsLV global strains are able to assess LV contraction in patients with a wide range of volume status of mitral regurgitation and normal subjects. The previous notion of indexing LV strain data to LVEDV appears to be unnecessary and could distort its interpretation. The increase in LV end-diastolic dimension and short-axis contraction assists in coping with LV volume overloading.2D STI could predict postoperative LVEF reduction at an early stage in severe PMR patients.