| Backgrounds and Objectives: There is a main research field for the cardiologist to quantify objectively myocardial function. Strain measures the extent of myocardial deformation whilst strain rate measures the rate of the deformation. Both strin and strain rate have been shown to provide new quantitative indexes about the clinical assessment of regional myocardial systolic and diastolic function. Myocardial strain and strain rate can be detected through those methods such as radiation contrast, the implantation of cardiac ultrasonic minicrystal, and magnetic resonance imaging (MRI). Strain and strain rate also can be estimated by several echocardiographic methods. The simplest way is using parasternal short-axis M-Mode view, calculatting wall thickening rate during systole. This however only gives estimates of anteroseptal and posterior wall thickening. Straight anatomy M-mode has been developed years ago. It can place the sample line in 360°radius so as to obtain M-mode image in arbitrary point or angle, which can improve the accurateness and so improve the application of M-mode echocardiogram. However, this method only provides uni-dimensional semi-quantitative assessment of myocardial thickening or thinning, without any information concerning about longitudinal and circumferential function. The most widely used and validated technique is tissue Doppler-derived strain so far. But it is only able to estimate strain along the ultrasound beam due to the angle dependency and thus cannot reliably measure strain in the azimuth or perpendicular plane (dependent on Cosθof the angle of insonation), which limits the usage of this technique primarily to longitudinal fibers, not able to quantify deformation in the radial and circumferential plane.Two-dimensional strain echocardiography (2DSE) is a novel method of the quantitative assessment of myocardial function. This technique is not encumbered by angle dependency and based on tracking of natural acoustic markers formed by speckle patterns arising from interference of ultrasound backscattered from tissue structures in B mode images. Since the speckle can be tracked in any direction, it is possible to measure its movement in both axial and perpendicular planes, allowing estimation of radial and circumferential strains. This removes the previous limitation of only being able to measure strain along the beam of ultrasound. In addition to the circumferential deformation parameters, ventricular rotation and twist can also be calculated using this technique. It is possible for clinician to estimate special movement of heart.In the present study, 2DSE was used in quantifying the systolic motion of patients with coronary heart disease (CHD), whose left ventricular (LV) wall motion was estimated normal by conventional echocardiography, trying to estimate its application and difference in evaluating LV wall abnormal motion in longitudinal, radial and circumferential dimensions and ventricular rotation, and to investigate its feasibility and clinical value in identifying ischemic myocardium.Methods: (1) Sixty-nine doubtful CHD patients sufferring from coronary arteriography in General Navy Hospital from Oct 2007 to May 2008 were involved in this study, which were divided into two groups, one was CHD group (n=38) and the other control group (n=31). And there was no other heart disease in all the objects. (2) Vivid 7 color Doppler Ultrasound Diagnostic Instrument was used and an M3S transducer in harmonic 1.7~3.4 MHz mode was adopted, frame frequency of which was above 80 frames/s. The two-dimensional images from LV short-axis views at the levels of mitral annulus, papillary muscle and apex, and LV apical four-chamber view, two-chamber view and long-axis view in 3 continuous cardiac cycles were recorded. (3) LV ejection fraction (LVEF) and fraction shortening of short axis (FS) was calculated by bi-plane Simpson's method by conventional echocardiography. (4) Using EchoPAC personal computer, longitudinal strain and strain rate (SL, SrL), circumferential strain and strain rate (SC, SrC), radial strain and strain rate (SC, SrC) of LV segments, global systolic strain (GLS), and torsion and torsional rate were obtained in each plane, and the corresponding curve was accessed.Results: (1) Twenty-seven of all the 38 patients in CHD group (27/38) had at least one coronary artery stenosis≥75%, while 24 patients in the control group (24/31) with stenosis≤20% in each of the three coronary arteries. Thirty-two patients in CHD group (32/38, 84.21%) had left anterior descending coronary (LAD) narrow. (2) Conventional echocardiographic parameters such as LV diameter, left atria diameter, LVEF, FS, E/A ratio and E-wave deceleration time had no statistical difference between the two groups (P>0.05). (3) Tracking success rate of 2DSE is 96.46% to 97.26%, and unsuccessful tracking happened more often at mitral annulus level than others. (4) In control group, strain (S) and strain rate (SR) of the longitudinal, circumferential and radial dimensions in LV have certain regularity, and there has no statistical differences of longitudinal and radial S and SR among LV walls (P>0.05). In CHD group, except that radial SR in papillary muscle and apex level increased, the absolute value of longitudinal, circumferential and radial S and radial SR in mitral annulus level were lower than that in control group, and the homogeneity disappeared, and there has significant difference at several segments (P<0.05 or P<0.01). The longitudinal S had highest rate to detect the abnormal segments in CHD group and radial SR lowest. (5) The absolute value of torsion and torsional rate in each plane in CHD group were lower than that of control subjects, and there was significant difference between the two groups at global torsion rate (P<0.05). (6) Global systolic strain (GLS) in CHD group was significantly increased (P<0.05), and has good correlations with LVEF and FS (P<0.05). (7) The area under curve (AUC) of each receiver operating characteristic (ROC) curve of S and SR were compared to evaluate their diagnostic efficacy of CHD. The results showed that the AUC of SrL and SC were maximum. The cut value of SrL﹣0.855 s-1 has the highest Yuedden index (0.530) to diagnose CHD, with sensitivity 81.6% and specificity 71.4%. While the cut value of GLS﹣22.85% has the lowest Yuedden index (0.249) to diagnose CHD, with the highest sensitivity of 84.2%. (8) The AUC of SL to the diagnosis of LAD stenosis was maximum. The cut value of SL was﹣15.77% at anterior wall and anteroseptal, which had the highest Yuedden index (0.563), with sensitivity of 74.2% and specificity of 82.1%.Conclusion: (1) 2DSE has the higher sensitivity than conventional echocardiography in the diagnosis of CHD. The detection rate of indexes to abnormal segments from highest to lowest in the three dimensions is: longitudinal dimension>circumferential>radial, and detection rate of strain was higher than that of strain rate. The detection rate of longitudinal strain was the highest and radial strain rate the lowest. (2) Of all those parameters such as torsional angle and torsional rate in both globe and in each plane, the global torsional rate has the highest sensitivity in the diagnosis of CHD. (3) Global longitudinal strain (GLS) is a sensitive index to evaluate wall motion abnormality in CHD group, and has good correlations with LVEF and FS. (4) The efficacy of longitudinal strain rate (SrL) and circumferential strain (SC) were the maximum to the diagnosis of CHD. The cut value of SrL was﹣0.855s-1 with the highest Yuedden index (0.530). (5) The efficacy of longitudinal strain (SL) was the maximum to diagnose the stenosis of left anterior descending. At anterior wall and anteroseptal, the cut value of SL was﹣15.77% with the highest Yuedden index (0.563). |
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