Experimental Study Of Regional Wall Motion By Doppler Tissue Lmaging

Background and objective: Hie technique of Doppler tissue imaging (DTl) can provide the real-time information of the direction and velocity of regional wall motion, which gives us a new method for quantitative analysis of myocardial function. Clinical application of DTl has been intensively studied, but the main attention is paid on the systolic wave (S), early diastolic wave (E1) and atrial systolic wave (A'). The DTI spectrum analysis of ischemic myocardium is not fine. Our objective is to determine the difference between the motion of the regional wall along the long and short axes and the alteration of the DTl spectra in the acute myocardial ischemia. We have laid the emphasis on the analysis of wave of the isovolumic contraction (FVC) in the study.Methods: In 6 anesthetized dogs, various degrees of left ventricular (LV) function and various velocities of LV posterior walls (LVPW) motion were induced by intravenous administration of dobutamine (DBA). We recorded the DTl spectra of LVPW motion along the long and short axes in different conditions induced by different dosages of DBA. Simultaneously the LV pressure curve and its first derivative (dP/dt) curve were recorded. The correlation between the velocities and+dP/dtmax, ~dP/dtn,aX were evaluated. In baseline the velocities along the long and short axes were compared .In 6 open-chest dogs, various degrees of regional wall motion abnormalities were induced by occluding 1-2 branches of LCX and LDA. Before and after the occlusions, the DTI spectra of LV anterior walls (LVAW) and LVPW were recorded and the velocities of the walls were compared. Results: In baseline, the peak IVC along the long axis was significantly greater than IVC along the short axis(19.6*5.5 vs 17.4*3.2cm/s, p<0.05). The peak S along the long axis was significantly greater than S along the short axis(17.2*6.7 vs 11.8+1.9cm/s, p<0.05) . The peak A' along the long axis was significantly greater than A' along the short axis (13.1 *2.6 vs 12.4*2.8cm/s, p<0.05). Whereas no significant difference was seen in the peak E' in either axis(13.1 *6.07 vs 11.5 *4.1cm/s, p>0.05). The peak IVC and peak S along the short axis were correlated well with and +dP/dtmax (r=0.8124, +dP/dtmax= -3270+654IVC and r=0.8431, +dP/dtn,ax=-316+725S, p<0.05). After coronary arteries occlusion, ischemia resulted in significant reduction of velocities of peak IVC| ,S and A' (4.6 *5.38 vs 16.60*4.11cm/s, 7.16*1.80 vs 11.30+ 1.58cm/s and 6.71+4.81 vs 11.08* 3.35cm/s, respectively, p<0.05), but the velocity of peak IVC2 increased significantly(l9.57 *3.58 vs 5.97 + 6.25cm/s, p<0.01). The peak E' became negative. The absolute time and relative time of peak IVCi were shortened(12.08* 13.36 vs 34.17+ 15.19ms and 0.033 + 0.037 vs 0.097*0.037, p<0.01)but peak IVC2 was prolonged significantly(55.55*15.11 vs 11.67 *12.31ms and 0.151* 0.039 vs 0.034+0.037, p<0.01 ).Conclusions: There are different wall motion velocities along the long and short axes and of normal and ischemic myocardium. The difference can be rapidly and sensitively detected by DTI, which makes it possible to analyze the alteration of regional wall function quantitatively. DTI is a reliable method for diagnosing heart diseases.