| Background and Objective: Cardiac rotation about a left ventricular (LV) long axis has been described in both man and in the canine model. It has been suggested that this rotational deformation plays a major role in increasing the efficiency of systolic thickening by allowing fibre shortening to be evenly distributed across the left ventricular wall. The effect of ventricular twist has been postulated to store potential energy, which ultimately aids in diastolic recoil, leading to ventricular suction. When fiber shortening becomes non-uniform due to cardiac pathology, this pathology may be reflected in aberration of the torsional motion pattern. So it is helpful to detect the ventricular torsion.Detailed studies of the wringing motion of the normal human LV have been performed using magnetic resonance myocardial tagging, but routine clinical assessment of LV rotation by tagged MR imaging (MRI) has been difficult to implement. Although echocardiography has been used in humans for assessment of cardiac rotation, it has been limited to the measurement of the Doppler angular independence. Consequently, the effects of acute myocardial ischemia and myocardial disease such as dilated cardiomyopathy (DCM) on LV rotation remain poorly understood, stressing the need for a noninvasive and easily accessible technique capable of assessing such cardiac motion.Velocity vector imaging (VVI) is a new technique to study myocardial motion. The purpose of this study was to establish a quantification of different parameters of left ventricular wall motion from VVI. This evaluation method was to be applied to characterize the physiological contraction cycle and to determine pathophysiological changes. We hypothesized that VVI could represent an accurate tool for the assessment of LV twist and systolic wall motion asynchronization.This study include four parts: We sought to use VVI for quantitative assessment of systolic LV rotational deformation in normals and to characterize alterations of LV twist in canine after anterior acute myocardial infarction (AMI)and in DCM patients. We also evaluate desynchronization in order to provide some valuable index for CRT.Material and Methods: VVI was performed at a basal and an apical level of the left ventricle. The evaluation method was used in 60 healthy volunteers and 27 DCM patients. A suitable software was programmed for the automatic quantification of rotation and circumferential shortening between two groups. Myocardial infarction was induced by ligation of left anterior descending coronary artery in 17 adult canines. The LV rotation degree, rotation velocity, circumferencial strain and strain rate were detected at baseline, MI 10min, 60min, 4 weeks. Ts, Ts max-min and Ts-SD were examined to evaluate the desynchronization in 6 heart failure patients and follow-up the effects after CRT. Results: The software allows the quantification of left ventricular wall motion by assessment of rotation and circumferential shortening. In 60 healthy volunteers, systolic LV wringing motion as assessed by VVI occurred counterclockwise at apex and clockwise at base when viewed from the apex. The curves of rotation and circumferential shortening were regular in normal volunteers, while inordinate in DCM. The twist degree and velocity in endocardium were 18.28°±5.06° and( 187.33±40.58)°/s, significantly higher than those in epicardium (p<0.05 ). And the rotation degree and velocity at apex were higher than those at base. These characteristic could be seen in DCM patients, though the parameters decreased compared with normals, were 7.87°±2.77° and (80.17±29.64) °/s in endocardium vs. 5.50°±1.72° and( 45.50±13.69 )°/s in epicardium. In canines with myocardial infarction rotation and circumferential shortening decreased. There was significantly lower at 60min after MI compared with baseline, -2.74°±1.13° vs -4.32°±1.83°,(-41.66±15.49)°/s vs(-51.46±18.45)°/s ,-7.89±5.02 vs -9.93±7.47, -1.24±0.62 vs -1.45±0.82, respectively. The parameters increased 4 weeks later because collateral circulation formation. And the present results demonstrate in the normal, DCM patients and canine left ventricle, regional heterogeneity in twist contraction exist. There was a good correlation between LV rotational motion and LV ejection fraction. The results of synchronization evaluation showed there were interventricle and intraventricle asynchronization in 6 heart failure patients. VVI could find the position of systolic delayed and guide the electrode implant. After 3months follow up, LV remodeling relieved, heart function and the index of asynchronization were improved greatly.Conclusions: In summary, VVI is an adoptable, reliable and noninvasive investigation of left ventricular torsional deformation and asynchronization, especially using multiple segments detection. There was LV twist deformation in normals and patients. The endocardial rotation and circumferential shortening were higher than epicardial, apical were higher than basal. The rotation and circumferential shortening were decreased in AMI model and DCM patients. Also we could see there was a good correlation between LV rotational motion and LV ejection fraction. VVI can evaluate systolic wall desynchronization by Ts, Ts max-min and Ts-SD, and play an important role in CRT.
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