| BACKGROUBD Torrent-Guasp and his colleagues demonstrated that the ventricles of heart consist of a singer myofiber band starting at the pulmonary artery and forming a double helix extending to the left ventricular and ending in the aorta. The ascending segment fibers have an approximately 90 degree relative to the descending segment. When these obliquely spiraling fibers contract, they produce a twisting or wring motion of the left ventricular (LV).Rotation of the LV apex to the base, or LV torsion, is related to myocardial contractility and structure and has recently been recognized as a sensitive indicator of cardiac performance, but it has been difficult to measure. The newly developed 2-dimensional (2D) speckle tracking imaging (STI) technique has presented us with the possibility of enhancing the accuracy of displacement estimation, and has allowed LV rotation to be evaluated noninvasively. Viewed from the apex, left-handed epicardial fiber helix tries to pull the apex counterclockwise and the base clockwise. The right-handed helix in the endocardium does the opposite, but because the epicardium is farther from the centerline, its torque is greater and thus it dominates the twisting.It is well known that the assessment of the changes of LV function after myocardial infarction (MI) is very important for prognosis and therapy, such as revascularization and stem cell therapy; and the torsion behavior of MI patients are not well defined. This study was conducted to evaluate the global and regional left ventricular twist in normal and patients with anterior wall myocardial infarction (AMI) disease before and after revascularization by STI. This thesis is composed of two parts: Part 1. Assessment of Global and Regional Normal Left Ventricular Torsion Using Speckle Tracking ImagingTo assess the normal person's left ventricular global and regional torsion deformation using speckle tracking imaging (STI). 35 normal patients were included during the study. The mean values of LV rotation were obtained at three planes using STI. At the basal and apical levers 2 zones on myocardium were evaluated separately: one including inner layer and the other including outer layer. LV torsion was defined as the difference rotation degree between two levels of LV. To adjust the intersubject differences in heart rates,the time sequence was normalized.Results①During systolic, the LV performs a torsion motion with a counterclockwise rotation at the apex and a clockwise rotation at the base. The mean value of peak twist was 12.66°±4.28°. Immediately after end systole, rapid untwisting developed.②Regional torsion of LV is heterogeneity, the torsion angle was increased with distance from the base(P<0.05); post and inferior wall of LV have lager torsion angle than the anterior and anterior-septum parts (post:14.00°±5.01°; inferior:15.06°±5.66°; anterior- septum: 11.36°±4.32°; anterior:10.74°±4.17°, P < 0.01); significant differences were showed between the inner and outer layer of LV torsion (Global:17.03°±5.56°VS 11.96°±3.68°, P<0.01).③Apical rotation and global torsion of LV were significantly affected by increasing age (r=0.524, P<0.01; r=0.422, P<0.01).Part 2. Assessment of Global and Regional Left Ventricular Torsion in Patients with Anterior Wall Myocardial Infarction Disease Pre and Post Revascularization by Speckle Tracking ImagingTo evaluate the global and regional left ventricular torsion in patients with anterior wall myocardial infarction (AMI) disease pre and post revascularization by Speckle Tracking Imaging (STI). 48 AMI patients undergoing revascularization were included,30 normal patients were on control group. The values of LV rotation were obtained at each plane using STI. LV twist was defined as apical rotation relative to the base. The standard deviation of time to peak twist (Tw-SD) and the maximal temporal difference of time to peak twist (Tw-diff) of 6 segments were used as an indictor of twist dyssynchrony.Results①20 patients with good endocardium imaging were acquired after one month's follow-up.②Peak LV torsion was significantly reduced in patients with AMI than normal controls (P<0.001 ). LV torsion in the anterior and anterior-spetal regions showed a marked decease (P<0.001 ). Tw-SD and Tw-diff were significantly higher in AMI group than those in the control group(all P<0.001).③Comparing with pre-operation, one month after revascularization, LV reconstitution were reversed, LV global and segment peak torsion show obvious change, especially in the LAD territory areas (P<0.001 ). At the same time, Tw-diff reduced significantly (P<0.001). Significant correlations were noted between LV global peak twist and LVEF(r=0.78,P<0.05), LVDD(r=-0.63,P<0.05) in all subjects.CONCLUSIONSDuring systole, the LV performs a torsion motion with a counterclockwise rotation at the apex and a clockwise rotation at the base. Immediately after end systole, rapid untwisting developed. Regional torsion of LV is heterogeneity. The age-related changes of LV torsion should be fully taken into consideration when assessing LV torsion.Systolic torsion was decreased and unsynchronized in AMI patients. Revascularization therapy can improve the LV function in AMI patients. STI is a promising new method to assess LV torsional deformation and has a potential ability to quantification of left ventricular global and segment torsion in patients with coronary artery disease.
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