Clinical And Experimental Research On Evaluation Of Left Ventricular Function In Diabetic Cardiomyopathy Using New Speckle Tracking Echocardiography

BackgroundDiabetic cardiomyopathy(DCM) is a common complication in patients with type 2 diabetes mellitus, and it is also the main cause of death, disability and reduced life quality in diabetic patients. It is proved by many studies that DCM is not associated with coronary artery disease or hypertension, but associated with metabolic disturbance and micro-vascular lesions. And what’s more, it may eventually evolve to congestive heart failure. Therefore, the early detection and effective intervention of the occurrence and development of cardiovascular complications can improve the diabetic patients’ life quality and survival rate. The early diagnosis of DCM is then particularly important.The clinical manifestations of DCM are mainly left ventricular hypertrophy and diastolic dysfunction, and reduced left ventricular ejection fraction(LVEF) may appear in later stage. However, because of the occult onset and slow progress of DCM, most diabetic patients have no obvious clinical symptoms of cardiac dysfunction in a long period, and even conventional echocardiography can hardly make a specific diagnosis except diastolic function impairment.Three-dimensional speckle-tracking echocardiography(3DSTE) is a newly developed technique in recent years, which can be used for quantitative analysis of myocardial motion. This technique is based on real-time three-dimensional echocardiography(RT3DE) and two-dimensional speckle-tracking echocardiography(2DSTE) and has the advantages of both. It can real-timely track the cardiac speckles in three-dimensional space and avoid the acoustic speckles loss, so it will evaluate the cardiac deformation more accurately. Furthermore, compared to2 DSTE, which need manual acquisition of multiple grayscale images to calculate the strain values in different directions, 3DSTI can obtain the longitudinal, radial and circumferential strain at the same time. In this way, not only the time and effort are saved, but also the results are no longer affected by the different phase, which become more comparable.Some researchers have used 3DSTE to evaluate the cardiac function in diabetic patients since the advent of this technique. The main foci of attention are the cardiac function comparison between diabetics and normal subjects, between well- controlled and poorly- controlled diabetics, and between diabetics with or without micro-vascular lesions. However, there is lack of report about the comparison of cardiac function in type 2 diabetic patients with other concomitant diseases.Layered two-dimensional speckle tracking echocardiography(Layered-2DSTE) is the derivative and development of conventional 2DSTE. This technique can calculate the strain values of the endocardial layer and epicardial layer separately. In the course of myocardial contractility, the motion range and contribution of endocardial and epicardial layers are quite different. Therefore, compared to conventional 2DSTE, Layered-2DSTE can further subdivide the myocardium and find more subtle lesions which can’t be detected by the former. There are many published literature about the evaluation of myocardial strain using 2DSTE. However, there are just few clinical studies about the assessment of layered myocardial deformation.In this study, we first used 3DSTI to detect the left ventricular function in diabetic patients with or without hypertension, and in diabetic patients with or without obesity. And then we used Layered-2DSTE to detect the dynamic changes of left ventricular function in type 2 diabetic rats within 8 weeks after the diabetic model was established, and we hoped to provide some experimental bases for the early diagnosis of diabetic cardiomyopathy through these studies.Objectives1.To investigate the myocardial deformation in well-treated type 2 diabetic patients with or without hypertension using three-dimensional speckle-tracking echocardiography(3DSTE) and to explore variables that could affect myocardial deformation.2.To investigate LV systolic dysfunction between type 2 diabetes mellitus patients with or without obesity using three-dimensional speckle-tracking echocardiography(3DSTE) and to explore the effect of body mass index(BMI) and abdominal adipose accumulation on their cardiac structure and function.3.To detect the left ventricular function in type 2 diabetic rats within 8 weeks after the diabetic model established using conventional 2DSTE and Layered 2DSTE and to explore the early echocardiographic manifestations of myocardial damage and dynamic changes of cardiac dysfunction in diabetes.Methods1.Eighty-two patients with type 2 diabetes and controlled blood glucose, including 46 subjects with diabetes alone and 36 subjects with diabetes and well-controlled hypertension, and 40 age- and gender-matched controls were studied. Left ventricular(LV) real-time three-dimensional(3D) full-volume images were recorded and analyzed using online software. The left ventricular ejection fraction(LVEF), global longitudinal strain(GLS), global circumferential strain(GCS), global area strain(GAS) and global radial strain(GRS) were measured and compared.2.The relationships between left ventricular global strain(GLS,GCS,GAS and GRS) and3 DLVEF in diabetic patients with and without hypertension were analyzed using linear correlation.3.GLS(absolute value) was used as a surrogate marker of LV systolic function and the multivariate stepwise regression analyses were performed to explore the significant influential factors for GLS in diabetic patients with and without hypertension.4.A total of 82 type 2 diabetic patients, including 40 subjects with BMI <25 kg/m2 and 42 subjects with BMI ≥25 kg/m2, as well as 42 age- and sex-matched controls(BMI: 18.5~24.5 kg/m2) were studied. Waist circumference was measured in diabetic patients with a BMI ≥25 kg/m2 to determine whether abdominal obesity as a complication was present. LV three-dimensional full-volume images were recorded and analyzed using online software. LVEF,GLS, GCS, GAS and GRS were measured and compared.5.The multivariate stepwise regression analyses were performed to explore the significant influential factors for GLS, GCS, GAS and GRS in diabetic patients.6.Established type 2 diabetic model rats by eight-week high-fat feeding combined with 30 mg/kg streptozotocin(STZ) intra-peritoneal injection. Diabetes was confirmed by random blood glucose concentrations of higher than 16.7mmol/L for consecutive three days.7.Conventional echocardiography was used to detect the rats’ left ventricular structure and function 2 weeks, 4 weeks and 8 weeks after the diabetic models were established.8.Conventional 2DSTE and Layered-2DSTE were used to detect the rats’ left ventricular segmental radial strain(RS), radial strain rate(RSr), circumferential strain(CS) and circumferential strain rate(CSr) 2 weeks, 4 weeks and 8 weeks after the diabetic models were established.9.Myocardial HE and Masson staining was performed after echocardiography examination to observe the changes of myocardial cells and collagen fibers 2 weeks, 4 weeks and 8 weeks later.ResultsPart 11.No significant differences were found in 3DLVEF among the controls and the diabetic patients with or without hypertension(p>0.05).2.GLS was significantly lower in patients with diabetes only when compared to controls(p<0.001). Patients with diabetes and hypertension showed significantly lower LV systolic strains in all directions when compared to the controls and patients with diabetes only(p<0.001 or p<0.05).3.The results of linear correlation analysis indicated that in diabetic patients with and without hypertension, the 3D-LVEF showed a moderate positive correlation with four strain parameters(absolute value), and the correlation with GLS was the highest.4.The results of multiple stepwise regression indicated that FPG and LVEDV were common significant influential factors for GLS in diabetic patients with and without hypertension. In patients with diabetes only, the important influential factors also included RWT, while in patients with diabetes and hypertension, E/Emwas another influential factor.5.The significantly lower values of LS,CS,AS and RS in multiple segments were observe in diabetic patients with and without hypertension when compared to the controls.Part 21.Compared with the controls with similar BMI, diabetic subjects without overall obesity had significantly lower GCS, GAS, and GRS(p<0.05), as well as markedly lower GLS(p<0.001).2.However, 3D-LVEF and all global strains in diabetic subjects with overall obesity were not only markedly lower compared with controls(p<0.002 and p<0.001), but also significantly lower than those in diabetic subjects without overall obesity(p<0.002 and p<0.05).3.The results of multiple stepwise regression indicated that Hb A1 c and BMI had negative impacts on all LV strains in two groups of diabetic patients(obese and non- obese). RWT also showed negative effects upon GLS, GAS, and GRS. Additionally, E/E’ was negatively correlated with GCS.4.The diabetic subjects with overall and abdominal obesity had significantly reduced GLS, GCS, GAS, and GRS compared with those with overall obesity only(all p<0.05).5.Compared with the controls with normal BMI, diabetic subjects without overall obesity showed significantly lower LS in all segments and significantly lower CS,AS and RS in partial segments. However, diabetic subjects with overall obesity showed significantly lower LS, CS, AS and RS in all segments when compared to the controls.Part 31.72 hours after STZ injection, the rats in model group showed the typical symptoms of polydipsia, polyphagia and polyuria. The random blood glucose concentrations of higher than 16.7mmol/L for consecutive three days indicted that the rats progressed to full type 2diabetes.2.Compared with the control group, the rats in the model group showed significantly lower mass and heart rate, but significantly higher blood glucose and blood lipid 2 weeks, 4 weeks and 8 weeks after the diabetic models were established.3.The results of conventional echocardiography: The model rats showed significantly higher values of LV size and wall thickness, but significantly lower LVEF and FS when compared to the control group 2 weeks, 4 weeks and 8 weeks after the diabetic models were established.4.The results of 2DSTE: The model rats showed significantly lower radial strain rate(RSr) in few segments when compared to the control group in 2 weeks later. However, in 4 and 8 weeks later, the segments with significantly lower radial strain(RS) and radial strain rate(RSr) in model rats increase remarkably.5.The results of 2DSTE: Similar to the RS and RSr, the model rats showed no significant decrease in circumferential strain(CS) and circumferential strain rate(CSr) when compared to the control group in 2 weeks later. However, in 4 and 8 weeks later, the segments with significantly lower CS and CSr in model rats showed increase obviously.6.The results of Layered 2DSTE: The model rats showed significantly lower endocardial CS in multiple segments when compared to the control group in 2weeks later. However, the epicardial and whole-layer CS showed no significant decrease when compared to the control group at the same time.7.The results of self control in diabetic model rats: The left ventricular systolic and diastolic function in diabetic rats was significantly decreased in 4 and 8 weeks later when compared to the last time point.8. The results of pathological examination: Hypertrophy and degeneration of myocardial cell and collagen accumulation increased gradually with the DM duration 2 weeks, 4 weeks and 8 weeks after the diabetic models were established.Conclusions1.Both clinical and experimental results indicated that T2 DM could lead to decrease in left ventricular systolic strain even if the LVEF was still in normal range.2.Type 2 diabetic patients with normal LVEF showed multidirectional(longitudinal, circumferential, area and radial) decrease in LV global and segmental strain. And it worsened with coexistent hypertension, though blood glucose and blood pressure were well controlled. The sensitivity of 3DSTE was able to detect these subclinical changes.3.Compared with the normal subjects with similar BMI, non-obese type 2 diabetic patients with normal LVEF demonstrated subclinical LV deformation and dysfunction, whilst coexistent obesity resulted in further damage to myocardial contractility. 3DSTE was a sensitive method for detecting these abnormalities.4.The decrease in strain and strain rate detected by 2DSTE could reflect the progressive downward trend of the LV segmental systolic and diastolic function in diabetic rats in 8 weeks. Layered 2DSTE could detect the subtle abnormality in endocardial myocardium which appeared earlier than the epicardial and whole-layer myocardium.