| Cardiovascular complications are the one of the main reasons for patients with diabetes to disability and death. Since 1972 Rubler described the concept of diabetic cardiomyopathy (DCM), many evidences have shown that diabetic cardiomyopathy is an independent complication of diabetes relating to metabolic disorders and microangiopathy. Those changes occurred before the lesion of coronary artery and resulted in congestive heart failure in the advanced stage. As no symptoms appeal in the early stage of its progresses and the pathological changes of the micrangium in the cardiac muscle are hardly detected in clinic, early evaluation of the cardiac function changes of diabetic cardiomyopathy is the key of its diagnosis and treatment.In the cardiac cycle, the heart pump blood function relies on the harmonizing composition of the myocardial electric activity and mechanical contraction and relaxation activity. Left ventricle (LV) plays a dominate role in the cardiac contraction and it's easily to be damaged, therefore, the LV function receives extensive attention. In clinical practices, LV ejection fraction, cardiac output and so on can reflect the LV systolic function through the appraisal of LV pumping function, but cannot directly reflect the LV myocardial contractility, until 1973 Mirsky and Parmley proposed the concept of strain and strain rate. Myocardial strain refers to the distortion in cardiac cycle, and can be used to estimate global and regional myocardial function during contraction and relaxation.Many techniques can be used to detect myocardial strain, the most often applied methods of implanted acoustic micrometer or tantalum markers are invasive, which are not widely available to be used in clinical situations. Tagged magnetic resonance imaging (tagged-MRI) has been used to take non-invasive measurements of myocardial strain, but it has the disadvantages of cost, time-consuming and low time resolution of imaging. Tissue Doppler imaging (TDI) is affected greatly by angle dependence and can only identify the deformation occurring in the direction of the ultrasound beam. On the basis of standard grey-scale images, ultrasound speckle tracking imaging (STI) can identify characteristic speckles within the myocardium and track them frame-by-frame to yield two-dimensional images of tissue deformation, reflecting the deformation of the different myocardial segments within the region of interest (ROI). Instead of focusing solely on longitudinal deformation, STI allows for the study of other components of myocardial contraction, which has high frame frequency and angle-independence. This technique is relatively unaffected by the heart swing and stretch and can accurately reflect myocardial motion and evaluate the LV global and regional systolic function.The purpose of this study is to assess LV systolic longitudinal, radial, circumferential strain, LV twist as well as LV systolic synchronicity in patients with type 2 diabetes mellitus (T2DM) and to evaluate its clinical application by STI. This study includes three parts:Part 1. Evaluation of Left Ventricular Two-dimensional Strain and Twisting Movement in Healthy Human by Ultrasound Speckle Tracking Imaging Three-five healthy volunteers were recruited into this study. Two-dimensional strain images were acquired from the LV short-axis views at the levels of mitral annulus, papillary muscle and apex, and the apical long-axis view, four-chamber view and two-chamber view of the LV respectively. EchoPAC workstation was used for offline analysis. LV peak systolic strain and its curve were acquired in short-axis and long-axis respectively as well as LV rotation and its curve. The LV twist was defined as the apical rotation relative to the base. RESULTS①LV longitudinal peak systolic strain at apical level was significantly greater than that at basal and middle levels (P<0.01), no significant difference was found among the different myocardial segments at same plane (P>0.05).②LV peak systolic radial strain was least at apical level, and significantly different with the levels of mitral valve and papillary muscle·(P<0.05～0.01). No significant difference was found among the different segments at the same plane (P>0.05).③LV peak systolic circumferential strain was gradually increasing from the mitral valve to the apex level, the average peak strain of apical level was significantly different from that of mitral level, and significant difference was also found among the different segments at same plane (P< 0.05).④Viewed from cardiac apex to base, the LV segmental motion performs a counterclockwise rotation at apex and a clockwise rotation at the base during the systole and apical average rotation is greater than that at mitral valve level. Rotation angle among the different ventricular segments was significantly different at mitral level and no significant difference at apical level. There was significant difference in systolic rotation angle among the different ventricular wall at papillary muscle level, and mainly for clockwise rotation. LV twist performs counterclockwise and regional torsion was heterogeneity. LV torsion angle of post-septum, posterior wall and inferior wall were greater than that of anterior wall, lateral wall and anterior-septum. Part 2. Ealuation of Left Ventricular Two-dimensional Strain and Twist in Patients with Type 2 Diabetes Mellitus by Ultrasound Speckle Tracking ImagingNinety-five subjects were included in this study: 40 T2DM with normal LV ejection fraction (LVEF≥50%) (group A),20 T2DM with abnormal LV ejection fraction (LVEF< 50%) (group B), and 35 healthy volunteers as control group. Using GE Vivid 7 ultrasound diagnostic apparatus and ultrasonic EchoPAC workstation respectively, LV peak systolic strain of six walls in apical long-axis, four-chamber, and two-chamber views were evaluated, and average peak strain in the long axis at basal, middle and apical levels, and LV global peak strain was assessed. Two-dimensional strain images were acquired from LV short-axis views. LV peak systolic global and segmental radial strain and circumferential strain at the levels of mitral annulus, papillary muscle and apex, and LV systolic global and segmental rotation at the levels of mitral annulus and apex and LV peak systolic global twist were evaluated. RESULTS①Compared with control group, all parameters of LV peak systolic longitudinal strain in group A were significantly reduced (P <0.01), LV peak systolic radial strain parameters were not significant difference (P> 0.05), peak systolic circumferential strain of part segments, average peak strain of each plane and global strain were reduced (P<0.05～0.01), and LV peak systolic rotation of all apical segments, peak systolic global rotation at the levels of mitral annulus and apex, and peak systolic global twist were significantly increased (P<0.05～0.01).②Compared with control group and group A, all parameters of LV peak systolic longitudinal strain, radial strain and circumferential strain, LV systolic global and segmental rotation and peak systolic global twist in group B were significantly reduced (P<0.05～0.01), except for a small number of myocardial segments. Part 3. Evaluation of Left Ventricular Synchrony in Patients with Type 2 Diabetes Mellitus by Ultrasound Speckle Tracking ImagingSixty patients with T2DM were divided into normal cardiac function group (group A, 40 cases, LVEF≥50%) and cardiac dysfunction group (group B,20 cases, LVEF<50%) according to LVEF, and 35 health Volunteers as control group. Two-dimensional strain images were obtained and analyzed from LV long-axis and short-axis views using GE Vivid 7 ultrasound diagnostic apparatus and EchoPAC workstation respectively, and digital data were imported Excel table. According to LV 18 segments analysis method, R-wave peak in cardiac cycle was setted as systolic starting point, the time.to peak longitudinal strain (Tsl) was derived from LV apical views, and the time to peak radial strain (Tsr) and to peak circumferential strain (Tsc), and the time to LV peak rotation (Trot) and twist (Ttw) were derived from LV axis views. The standard deviation of Tsl, Tsr, Tsc and Ttw (Tsl-SD, Tsr-SD, Tsc-SD and Ttw-SD) and the maximal temporal difference of Tsl, Tsr, Tsc and Ttw (Tsl-diff, Tsr-diff, Tsc-diff and Ttw-diff) were calculated respectively. RESULTS①For healthy subjects, there was no significant difference of Tsl, Tsr, Tsc and Ttw among different levels and different wall segments at the same plane.②In group A, Tsl-SD, Tsc-SD, and Tsl-diff were prolonged with control group (P<0.01), and other time parameters were slightly larger than control group, but the difference was not statistically significant.③In group B, Tsl and Tsr of part wall segments were significantly extended when compared with group A and control group, especially at Basal segments (P<0.05-0.01). No significant difference was found in Tsc, Trot and Ttw. Significant difference was found in above parameters of the standard deviation and the maximal temporal comparing with group A and control group (P<0.01).CONCLUSIONS①In healthy subjects, the LV longitudinal strain, radial strain, circumferential strain, rotation and twist angle among different LV myocardial segments were heterogeneity.②The abnormal myocardial deformation occurred before the development of myocardial systolic dysfunction in patients with T2DM. In patients with normal systolic function, LV peak systolic radial strain parameters were not significant difference, but longitudinal strain, circumferential strain reduced, and LV twist angle increased. The above parameters were significantly reduced in diabetic patients with heart failure.③In patients with T2DM, asynchrony of LV contraction existed with the disease progression, and the longitudinal asynchrony was more significant than that of short-axis.④Ultrasound speckle tracking imaging is non-invasive method that allows for early assessment of the impairment of global or local systolic function of LV, as well as evaluation of the LV systolic synchrony in different directions. |
PDF Full Text Request