| BackgroundIschemia is the basic pathophysiological change of coronary artery disease. Ischemic myocardium can be impaired in different ways and to different extent, including morphology,function,metabolism and so on,in account for the difference of facts such as the velocity,degree and lasting time of ischemic attack and the recovery or reperfusion.Fernandes et al found it much earlier than predicted when left ventricular function changed,which was associated with artherosclerosis.Left ventricular function and regional myocardial function have close relationship with the patient's prognosis.Therefore,quantitative assessment of the regional myocardial function accurately and sensitively plays an important clinical role,for it can show reliable evidences for the diagnosis,therapy and prognosis.At present time,study of ischemic myocardial regional function with different degree coronary artery stenosis is still rare,especially for the slightly and moderately ischemic myocardium,while most studies have focused on the heavily ischemic and infarction myocardium.Percutaneous coronary intervention(PCI)has become an important therapy of the coronary artery disease(CAD)because of its many advantages such as significant curative effect,less trauma,shorter course of treatment.The main signs of PCI in present clinics include more than 70%coronary artery stenosis and vulnerable plaque, while drug is the main methods for less than 30%stenosis.However,it is still controversial how to treat the stenosis between 30%and 70%(critical stenosis).Since PCI has some serious complications and risks such as restenosis,individual risk/advantage ratio assessment may help to choose reasonable strategy for critical stenosis.Accordingly,the analysis of myocardial regional function can give some important evidence for the assessment of critical stenosis.Velocity vector imaging(VVI)technique,a novel echocardiographic technique,is based on two-dimensional gray-sale images and thus angle-independent in principle. VVI can track speckles frame by frame accurately and thus can be used to assess the function of ischemic myocardium more conveniently and accurately.Questions as follows made the formation of this study:(1)When did the regional function of myocardium begin to change and how to change as the artherosclerosis of coronary artery going on?(2)What was the differences of regional function among the ischemic myocardium with different degree of coronary stenosis?(3)How did the myocardial regional function change after PCI?In this study,the regional function of ischemic myocardium was assessed quantitatively prior and post to PCI by VVI technique.Objective(1)To assess regional function of ischemic myocardium with different degree of coronary artery stenosis by velocity vector imaging(VVI)technique,and explore sensitive parameters for the early diagnosis of ischemic myocardium;(2)To evaluate myocardial regional function after PCI,and explore echocardiographic parameters for early assessment of ischemic myocardial function after PCI therapy;(3)To discuss the value of VVI in the assessment of ischemic myocardial regional systolic and diastolic function.Methods1.Study population50 patients(41 men,mean age 61.7±10.7)with CAD according to CAG were enrolled in this study,including 30 ones with unstable angina pectoris,16 with acute myocardial infarction and 4 with old myocardial infarction.All patients took auxiliary examinations as follows:EKG,echocardiography,CAG and cTnI detection and were excluded the diagnosis of valvular heart disease,cardiomyopathy and arrhythmia.2.Methods2.1 CAG and percutanenious coronary intervention(PCI)According to CAG,all coronary arteries were divided into 4 degrees:1-degree with stenosis less than 50%;2-degree with stenosis between 50%and 74%;3-degree with stenosis between 75%and 99%;4-degree with coronary artery occluded completely.Collateral circulation was evaluated with classical Rentrop grade.Patients with stenosis more than 75%accepted PCI.2.2 EchocardiographySiemens Sequoia 512 ultrasound machine and 4V1C transducer in 2-4MHz was used in this study.Two-dimensional images of apical four-,two-chambers and long-axis view were obtained in VVI condition and with frame rate kept 60-100Hz. All patients were examined before CAG and patients who accepted PCI were also examined 1 week and 1 month after PCI respectively.2.3 Data processingAccording to a 16-segment model of left ventricle recommended by the American Society of Echocardiography(ASE),all segments of the left ventricular were separated into 5 groups:0 group with no coronary artery stenosis;1 group with stenosis less than 50%;2 group with stenosis between 50%and 74%;3 group with stenosis between 75%and 99%,while the 4 group having a completely occluded coronary artery.The segmental myocardial systolic peak velocity(Vs),strain(ε)and strain rate (SRs),early diastolic velocity(Ve)and strain rate(SRe),late diastolic velocity(Va)and strain rate(SRa),the parameter ratio of diastole and systole(Ve/Va,SRe/SRa)and segmental ejection fraction(SEF)were analyzed with VVI offline software.3.Statistical analysisSoftware SPSS(version 13.0)was used for statistical analysis.All results are expressed as mean±standard deviation(SD).Difference among inter-groups before PCI were tested by ANOVA and q test,while comparisons among intra-groups at different times were done by using repeated-measures ANOVA.All tests were 2-sided and P＜0.05 was considered significant.Results1.General statesAmong 50 patients,9 had singal coronary artery stenosis,7 had double arteries stenosis while 34 had three arteries stenosis.24 patients(48%)had collateral circulation,and 1-,2-,3-degree collateral circulation were respectively 16%,16%, 16%.All of the collateral circulation happened where the stenosis of coronary artery was higher than 75%.32 patients accepted PCI,6 were given coronary artery bypass (CABG)while 12 took drug only.766 myocardial segments were analyzed pre-PCI,which included 154 of 0 group, 132 of 1 group,93 of 2 group,357 of 3 group and 30 of 4 group.248 segments were analyzed after PCI,including 41 of 0 group,37 of 1 group,14 of 2 group,144 of 3 group and 12 of 4 group.2.Regional function of ischemic myocardium in different degrees before PCI2.1 VelocityVs and Ve of 1-4 group,Va of 3-4 group,Ve/Va of 2-3 group were lower than the same parameter of 0 group(P＜0.05);2.2 Strain(ε)εof 2 and 4 group were much lower than that of 0,1 and 3 group(P＜0.05);2.3 Strain rate(SR)SRe,SRe/SRa of 1 group,SRs,SRe and SRe/SRa of 2-4 group were lower than that of 0 group(P＜0.05);SRs,SRa of 2 group,SRs and SRe of 4 group were lower than that of 1 group(P＜0.05);SRe and SRa of 2 group were lower than that of 3 group(P＜0.05);SRs,SRe of 4 group were lower than that of 3 group,and SRe was also lower than that of 2 group(P＜0.05).2.4 Segmetal ejection function(SEF)SEF of 3 group was lower than that of 0 and 1 group(P＜0.05);SEF of 4 group was lower than that of 0-3 group(P＜0.05);3.Changes of myocardial regional function after PCI 0 group:compared to pre-PCI,SRs increased 1 week and 1 month after PCI (P＜0.05);1 group:Ve/Va increased and Va decreased 1 week after PCI(P＜0.05),but there was no significant difference of parameters between pre-PCI and 1 month after PCI;2 group:Ve decreased 1 week after PCI(P＜0.05),but there was no significant difference of parameters between pre-PCI and 1 month after PCI;3 group:Ve/Va and SRe/SRa were higher than that of pre-PCI(P＜0.05);SRs increased 1 week after PCI but decreased 1 month after PCI(P＞0.05),however,the difference was not considered significant;SRs of 1 month was lower than that of 1 week after PCI(P＜0.05).4 group:there was no significant difference of parameters among pre-PCI,1 week and 1 month after PCI.Conclusions(1)Myocardial diastolic function is impaired while coronary artery stenosis＜50%; Abnormal systolic function appears when coronary arteriostenosis≧50%.(2)As stenosis,myocardial regional function has a bidirectional change: decreased first,then increased and decreased at last.(3)After PCI,regional systolic function of severe ischemic myocardium decreased and diastolic function increased;the regional function of normal and slightly ischemic myocardium also showed some improvement after therpy.(4)VVI technique provides a new method for assess ischemic myocardial regional function before and after PCI accurately and sensitively.
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