Research Of Viable Myocardium In Patients With Myocardial Infarction By Doppler Tissue Imaging

Background and objectiveMyocardial infarction(MI) is very frequent at present . The cellular metabolism and heart functions of patients with MI are seriously impaired,leading to high morbidity and mortality at last. With the development of coronary artery bypass graft(CABG) operations and percutaneous transluminal coronary angioplasty (PTCA),it was discovered that some impaired myocardium function could be recovered after CABG or PTCA therapy,so the viable myocardium was put forward .After recanalization of blood vessel and flow,the action of viable myocardium could be obviously improved ,however the segments without it became stable or worse.So the accurate judgement of viable myocardium become very important in choice of treatment plan, danger ranking and prognosis estimation.Recently, there are several methods in evaluating of viable myocardium by echocardiography: stress echocardiography, colour kinesis and acoustic quantification,myocardial contrast echocardiography, acoustic density, Doppler tissue imaging. Doppler tissue imaging is a new, quantitative, noninvasive method to analysis myocardial motion.It can display moving times, directions and velocities of different myocardial segments and detect regional wall motion abnormality(RWMA).To assess regional contraction function,the traditional method of Doppler tissue imaing is measuring systolic peak velocity values,but wall motion at isovolumic contraction period is rarely studied.It has been reported after some animal experiments that wall moving velocities during isovolumic contraction period were the best indexes in evaluating contraction function of ischemia myocardium and it could allow rapid estimation of the transmural extent of viable myocardium after reperfusion for AMI.It need be fartherly studied whether this method could estimate myocardial viability in patients with myocardial infarction by transthoracic approach.However,there are few similar researches domestically and abroadly yet.The purpose of this study were:â‘ to assess the character and regularity of left ventricular segments moving by measuring wall motion of normal subjects and OMI during isovolumic contraction period with Doppler tissue imaging.â‘¡to evaluate the relations of ventricular function and isovolumic contraction regional motion indexes in patients with OMI.â‘¢compared with viable fraction gained by NTG^99mTc-MIBI SPECT,to discuss the clinical value of appraising myocardial viability by isovolumic contraction regional motion indexes during quiescent condition.Materials and methodsThirty normal subjects(20men,10women,mean age 54±10 years) and thirty patients with OMI(22men,8women,mean age 57±12years) were included.The normal subjecs were all approved by history, physical sign, electrocardiogram,X ray and echocardiography.The OMI patients(NYHA class III—IV) were all confirmed to be the old anterior septal myocardial infarction by case history, electrocardiogram, echocardiography and coronary arteriongraphy.In the OMI subjects,there were 10 patients(8men,2women,mean age 54±9 years) undertaking radionuclide imaging.Echocardiography was performed with Doppler tissue imaging with probe frenquency 2.0⁴.0MHz.The sample volumes were separately located at LV post septal wall,lateral wall,anterior wall,inferior wall, anterior septal wall and posterior wall in two levels(basal,middle). The systolic velocities (Vs),the isovolumic contraction peak positive and negative myocardial velocities(VIVC1,VTVC2),during times(TIVC1,TIVC2),velocity time integrals (VTIIVC1,VTIIVC2)and the difference(DIVC) between VTVC1 and VIVC2 were measured.Parameters of LV function and the other measured indexes included:â‘ ejective fraction of LV (LVEF,along apical four-chamber view by Simpson's equation);â‘¡fractional shortening of LV (LVFS,parastermal long axis view of LV by M-mode echocardiography);â‘¢stroke volume (SV, parastermal long axis view of LV by M-mode echocardiography);â‘£LV end-diastolic diameter (LVEDD, parastermal long axis view of LV by M-mode echocardiography);(5)LV end-diastolic pressure (LVEDP,through cardiac catheter ventriculography);â‘¥viable fraction (VF, by NTG^99mTc-MIBI SPECT).Results1. Normal subjects showed that VIVC1 > VIVC2, TIVC1 > TIVC2, VTIIVC1> VTIIVC2 (p<0.05) at every segment wall besides LV posterior wall. The defferences of VIVC1 and VIVC2 in different walls and segments were usually inapparent. (P>0.05) .2. Patients with OMI showed that Vs,VIVC1 and DIVC was significantly decreased and VIVC2,TIVC2 and VTIIVC2 was significantly increased than that of the normal subjects(p<0.05).In contrast, TIVC1 and VTIIVC1 were stable (P>0.05). Compared with normal subjects, infarction segment walls changed obviously,but others in patients with OMI were steady (P>0.05) .In OMI group, minor axis DIVC values were seriously decreased contrasting to long axis ones(p<0.05)3. Minor axis DIVC values were correlated linearly with VF,LVEF,LVFS,LVEDD and LVEDP,while long axis DIVC values were only correlated with VF.4. Associated with myocardial viability result of VF, the sensibility and specificity of evaluating viable myocardium was 75% and 75% when minor axis DIVC values were more than -1.50; the sensibility and specificity was 77.8% and 87.5% while long axis ones were more than 0.92.Conclusions1. In normal subjects,the LV regional segments motion often showed certain regulation wave during isovolumic contraction period.2. The indexes of isovolumic contraction could discover local moving abnormality and the minor axis DIVC values could reflect heart function generally and sensitively.3. DIVC values could not only differentiate viable myocardium but also estimate the degree of myocardial viablity. 4. Detecting indexes of isovolumic contraction by DTI could reflect heart function sensitively and DIVC could become a new index in assessing viable myocardium at quiescent condition.