Clinical Studies Of Left Ventricular Systolic Function Using Two-dimensional Speckle Tracking Imaging

Echocardiography is now the most commonly used noninvasive tool for the assessment of cardiac anatomy and function. In addition to commonly established roles such as confirming diagnosis and disease monitoring, echocardiography plays an important clinical role in prognostic assessment. By calculating the change of left ventricular (LV) volume, LV ejective fraction (LVEF) is a clinical commonly used index, but the poor spatial resolution of ultrasound images and the operators′experience interfere with the reproducibility and accuracy. The quantification of regional myocardial function remains a challenge in clinical cardiology. Traditional methods for the evaluation of regional myocardial function using echocardiography are subjective and only partially quantitative. Tissue Doppler Imaging (TDI) is a robust and reproducible echocardiographic tool which has permitted a quantitative assessment of both global and regional function and timing of myocardial events. TDI-based strain and strain rate imaging (SRI) for LV function evaluating is a new tool for quantifying regional deformation and deformation rate by calculate the change of myocardium length. However, TDI-based strain measurements are angle dependent owing to use of the Doppler effect and simultaneous opposite deformation in the long and short axes, it can only be used to assess the longitudinal strain, but it is restricted in analyzing the myocardial strain of different directions and different levels. Speckle tracking imaging (STI) is an echocardiographic technique based on tracking of characteristic speckle patterns created by interference of ultrasound beams in the myocardium. As the tracking is based on grayscale B-mode images, it is in principle angle independent, so as a new method for quantifying global or regional LV function, it can not only evaluate the LV strain, rotation and displacement noninvasively but also analyze the characters of the cardiac movement mechanics. Previous studies indicated that STI results consist with sonomicrometry and magnetic resonance imaging (MRI) for systolic strain in the long axis and in the short axis. Moreover, STI can assess apical function which TDI difficultly to deal with. Animal experiments confirmed that there is an endocardial-epicardial gradient in both peak strain and SR values. Study to the endocardial-epicardial gradient of LV will be sensitive to objectively quantify regional and global myocardial function.The studies were divided into three parts. In the first part, the peak systolic strain of the inner and outer layers of myocardium in healthy adults were evaluated by two-dimensional ultrasound STI. The research further confirmed the feasibility of STI in assessing the LV myocardium strain. In the next two parts, we explored the strain of the inner and outer layers of LV myocardium in patients with type 2 diabetes mellitus and essential hypertension with different patterns of left hypertrophic geometric models respectively, hoping to find the abnormity of LV systolic function, providing an easy and practical ultrasonic mean for clinical diagnosis, treatment and prognostic assessment for heart disease with regional myocardial ischemia.Part I Evaluation of left ventricular systolic function in healthy subjects using two-dimensional speckle tracking imagingObjective: To explore the characters of the peak systolic strain of the inner and outer layers of myocardium and to confirm the endocardial-epicardial gradients of LV in healthy adults using STI.Methods: Study population consisted of 75 healthy volunteers (male 46, female 29, average age 39.6±15.2 years). High frame rate two-dimensional (2D)images of three consecutive cardiac cycles were recorded from the LV apical four-chamber view, two-chamber view, long-axis view and the short-axis views at the levels of mitral annulus, papillary muscle and apex of the LV respectively. 2D images were transferred to Qlab6.0 work station for offline strain analysis. The software algorithm segmented the LV wall into two equidistant layers(the inner and outer layers), moreover, the software algorithm segmented the LV long axis and short axis into 18 equidistant segments respectively(anteroseptal, anterior, lateral, posterior, inferior and interventricular). The longitudinal strain(LS) values in the inner and outer layers of myocardium were measured in the left ventricular apical views. Radial strain(RS) and circumferential strain(CS) values in the inner and outer layers of myocardium were measured in the left ventricular short-axis views using two-dimensional strain software. Acquired the peak systolic strain of each segment, calculated the average strain value of three consecutive cardiac cycles as the peak systolic strain. The average strain values of the basal segment, the middle segment, the apical segment of the LV long axis and mitral annulus, papillary muscle and apex of the LV short axis in the inner and outer layers were calculated as the LV global LS, RS and CS of each level.Results: (1) The LV longitudinal strain curve had two peaks, the peak systolic LS values were negative. In the inner layers of myocardium, the peak systolic LS values of different segments and the peak global LS values at different levels showed higher than those of the outer layers(P<0.05), and the LS values gradually increased from base to apex(P>0.05). At the same level, the LS values of different segments had no significant difference in the inner or outer layers. (2) LV radial strain curve of each segment was a positive peak curve, the peak systolic RS values were positive. The peak systolic RS values of different segments and the peak global RS values at different levels of the inner layers showed higher than those of the outer layers(P<0.05). The RS values at different levels had significant difference, the value at the level of papillary muscle was the largest, the peak systolic RS values of different segments at the same level had no significant difference. (3) LV circumferential strain curve of each segment was a negative peak curve, the peak systolic CS values were negative. The peak systolic CS values of different segments and the peak global CS values at different levels of the inner layers showed higher than those of the outer layers(P<0.05), especially in anteroseptal and posterior segments(P<0.01). At levels of mitral annulus and papillary muscle, the CS values of anteroseptal and inferior were relatively high, the CS values of lateral and posterior were relatively low (P< 0.05). The peak systolic CS value of anteroseptal at level of apex showed higher than those of the other segments, but there were no significant difference.Conclusions: Independent of insonation angle for assessing myocardial strain, STI has the potentiality to be used clinically to evaluate the regional and global myocardial function of LV, study to the endocardial-epicardial gradient of LV will be sensitive to objectively quantify regional myocardial systolic function.Part II Evaluation of left ventricular systolic function in patients with type 2 diabetes mellitus using two-dimensional speckle tracking imagingObjective: To evaluate the characters of the peak systolic strain of the inner and outer layers of myocardium and to explore the application value in assessing the long-axis and short axis systolic function of LV by STI in patients with type 2 diabetes mellitus.Methods: 38 patients with type 2 diabetes mellitus (male 21, female 17, average age 59.2±9.0 years) as DM group, 29 age- and gender- matched healthy volunteers (male 18, female 11, average age 58.3±9.6 years) as the control group. The patients′blood glucose was well controlled within normal level. Two-dimensional, M-mode and Doppler echocardiographic examination were performed and some parameters were acquired, including LV end-diastolic diameter (LVDd), LV end-systolic diameter (LVDs), diastolic interventricular septal thickness (IVST), diastolic posterior wall thickness (PWT), left ventricular ejective fraction (LVEF), the early rapid filling velocity of mitral valve (E), peak velocity of the late filling wave due to atrial contraction (A), E /A velocity ratio, peak myocardial early diastolic velocity at the mitral annulus (Em), late diastolic velocity (Am), Em /Am ratio. High frame rate two-dimensional (2D) images of three consecutive cardiac cycles were recorded from the LV apical four-chamber view, two-chamber view, long-axis view and the short-axis views at the levels of mitral annulus, papillary muscle and apex of the LV respectively. 2D images were transferred to Qlab6.0 work station for offline strain analysis, acquired the peak systolic strain of each segment and calculated the average value of three consecutive cardiac cycles as the peak systolic strain. The average strain values of the basal segment, the middle segment, the apical segment of the LV long axis and mitral annulus, papillary muscle and apex of the LV short axis in the inner and outer layers were calculated as the LV strain of each level in the inner and outer layers respectively. The LV global LS, RS and CS were the average values of the LV strain of each level in the inner and outer layers respectively.Results: (1) The LV wall thickness, LV diameter and LVEF had no significant difference between two groups; E /A and Em /Am in DM group showed lower than those in the control group (P<0.05). (2) LV longitudinal strain curve in DM group was similar to that in the control group, but the average LS values of the basal segment, the middle segment, the apical segment and the LV global LS value in DM group were lower than those in the control group (outer layer: P<0.05, inner layer: P<0.01). In DM group, the peak systolic LS values of different segments of the inner layers showed higher than those of the outer layers (P>0.05). (3) LV radial strain curve in DM group was similar to that in the control group, but the average RS values at each short axis level and the peak global RS values were higher than those in the control group ( P<0.05), and the peak systolic RS values of different segments of the inner layers showed higher than those of the outer layers( P>0.05). (4) LV circumferential strain curve in DM group was similar to that in the control group, the average CS values of each short axis level and the peak global CS values were higher than those in the control group( P>0.05).Conclusions: Analysis of the strain of the inner and outer layers of LV myocardium with STI in patients with type 2 diabetes mellitus can help to identify LV systolic dysfunction and to provide a new noninvasive method for the diagnosis of sub-clinical cardiomyopathy.Part III Evaluation of left ventricular systolic function in patients with essential hypertension using two-dimensional speckle tracking imagingObjective: To evaluate the characters of the peak systolic strain of the inner and outer layers of myocardium and to explore the application value of STI in evaluating LV systolic function in hypertension patients with different patterns of left ventricular hypertrophic (LVH) geometric models.Methods: 36 patients with essential hypertension (male 19, female 17, average age 58.7±8.3 years), 33 age- and gender- matched healthy volunteers (male 20, female 13, average age 57.9±6.5 years) as the control group. All patients were divided into two groups according to left ventricular mass index (LVMI)(group A 20 patients: NLVH,group B 16 patients: LVH), male LVMI>134 g/m2, female LVMI>110 g/m2 defined as LVH. Echocardiographic examination were performed and some paremeters were acquired, including LVDd, LVDs, IVST, LVPWT, LVEF, E /A and Em /Am. High frame rate two-dimensional images of three consecutive cardiac cycles were recorded from the LV apical four-chamber view, two-chamber view, long-axis view and the short-axis views at the levels of mitral annulus, papillary muscle and apex of the LV respectively. LS, RS and CS in the inner and outer layers of myocardium were measured in the left ventricular long-axis and short-axis views using two-dimensional strain software. The LV strain values at each level of the long axis and the short axis in the inner and outer layers were calculated, the LV global strain values of the long axis and the short axis were the averages of the LV strain value of each level.Results: (1) There were no significant difference in IVST, LVPWT, LVMI between group A and the control group; IVST, LVPWT, LVMI in group B were significantly higher than those in group A and the control group (P<0.01); There were no significant difference in LVEF among three groups; Compared with the control group, the LV global diastolic function in group A and group B was significantly decreased (E /A: 1.29±0.53 vs 0.93±0.22 and 0.89±0.41; Em /Am: 1.24±0.32 vs 0.83±0.35 and 0.81±0.23) (P<0.05). (2) LV longitudinal strain curves in group A and group B were similar to that in the control group, the peak systolic LS values of different segments of the inner layers were higher than those of the outer layers (P>0.05). Compared with the control group, the average LS values of the basal segment, the middle segment and the apical segment of the LV long axis were decreased in group A (P>0.05); The average LS values at each level and the LV global LS values in group B were significantly decreased than those in the control group (outer layer: P<0.05, inner layer: P<0.01); (3) LV radial strain curve in hypertension patients was similar to that in the control group. In group A, the average RS values of short axis levels and the LV peak global RS values of the inner layers were higher than those of the outer layers (P<0.05), and the peak systolic RS values were higher than those in the control group (outer layer: P<0.05, inner layer: P<0.01); In group B, there was no significant difference in the peak systolic RS values between the inner and outer layers, compared with the control group, the peak systolic RS value at level of the mitral annulus was higher than that in the control group (P<0.01); The peak systolic RS values of the inner and outer layers in group A were significantly increased than those in group B (P<0.05). (4) LV circumferential strain curve in hypertension patients was similar to that in the control group, the peak systolic CS values of short axis levels and the LV peak global CS values of the inner layers were higher than those of the outer layers (group A P<0.01; group B P<0.05); There were no significant difference among three groups.Conclusions: Radial contractility appears to compensate for reduced longitudinal contractility in subclinical LV dysfunction occurring in the absence of ischemia or LV hypertrophy. STI has the potentiality to be used clinically to evaluate the LV systolic function in hypertension patients with different patterns of left ventricular hypertrophic geometric models.