Study Of Ischemic Myocardial Regional Motion With Different Degree Coronary Artery Stenosis Using 2D-Strain And The Effects Of The Coronary Collateral Circulation On Its Function

BackgroundIn the last few years, the mortality of cornary artery disease (CAD)decrased. Heart failure (HF) becomes the major cause of morbi—mortality and hospitalization in patients aged more than 60 years. CAD become the most common reason of HF. Cardiac resynchronization therapy(CRT)has been recommended for patients with advanced chronic heart failure prolonged QRS complexes.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. So study of the dalay of myocardium motion in early coronary artery stenosis is significant.Tow-Dimention strain imaging (2D-Strain) technique, a novel echocardiographic technique, is based on two-dimensional gray-scale images and thus angle-independent in principle. 2D-Strain can track speckles frame by frame accurately and thus can be used to assess the function of ischemic myocardium more conveniently and accurately.Coronary artery disease (CAD), are the leading cause of death in industrialized countries. Bringing blood to the ischemic heart is a traditional therapeutic concept and many different surgical procedures have been devised to accomplish it. But at least 20-30% of CAD patients in whom the extent of coronary atherosclerosis is especially severe are not indicated for percutaneous coronary intervention or coronary artery bypass grafting surgery. Controlling symptoms and altering the course of advanced CAD maybe another therapeutic concept. So the induction of natural bypasses: promotion of coronary collateral growth is recognized as a source of blood supply to a myocardial area jeopardized by ischemia.Cohnheim taught that there were no anastomoses in the heart proximal to the apillary level and that the coronary arteries were true anatomic end-arteries. But this concept was disproved by Schlesinger and Zoll et al. And more than 200 years ago, Heberden described a patient who had been nearly cured of his angina pectoris by sawing wood each day, a phenomenon called "warm up" or "first effort angina" which was traditionally ascribed to coronary vasodilation with opening of collateral vessels to support the ischaemic myocardium. In fact, nascent collateral arteries occur in neonates and inhealthy individuals. Intercoronary anastomoses are prominent in fetal life and persist until about the eighth postnatal month when they diminish in size (Castorina, 1957).The functional relevance of coronary collateral vessels in humans had also been a matter of debate for many years. Well-grown versus poorly grown collateral arteries in humans have been suggested to exert a beneficial effect on infarct size, ventricular aneurysm formation, and ventricular function. Clinical practice shows that collaterals will be sufficient to maintain full systolic contractile function in some patients, whereas in others, they may be just sufficient to provide a minimum nutritional supply to hibernating myocardium. Some investigation found that only about a third has functionally sufficient coronary collaterals are able to prevent signs of myocardial angina.So the purpose of the study are to confirm the protective effects of the coronary collateral circulation to ischemic myocardial regional function with coronary artery stenosis≥75% quantitatively using 2D-strain technique and to find accurte echocardiography parameters to predict the presence of effective coronary collateral arteries.Questions as follows made the formation of this study: (1) When did the regional motion of myocardium begin to change and how to change as the artherosclerosis of coronary artery going on? (2)Dose the presence of the coronary collateral circulation protect ischemic myocardial regional function with coronary artery stenosis≥75%? (3) Which value can predict the presence of collaterals sensitively and specicialy?Objective(1) To assess ischemic myocardial regional motion with different degree coronary artery stenosis by 2D-strain technique.(2) To study the protective effects of the coronary collateral circulation to ischemic myocardial regional function with coronary artery stenosis≥75 % quantitatively using 2D-strain technique.(3) Explore sensitive parameters for the early diagnosis of the presence of coronary artery.MethodsStudy PopulationWe included 160 patients (124 men, age 57±9 years) of unstable angina pectoris (UAP) who were undergoing coronary angiography in our hospital. Exclusion criteria were presence of valvular cardiac disease, Cardiomyopathy, severe heart failure (New York Heart Association class IV) and arrhythmia. According to CAG, all coronary arteries were divided into 4 degrees: 1-degree with stenosis between 25% and 50%; 2-degree with stenosis between 50% and 74%; 3-degree with stenosis between 75% and 99%; 4-degree with coronary artery occluded completely. According to the result of angiography divided the patients into 3 groups : group 1 with normal coronary artery ; group 2with stenosis≥75% in≥1 main coronary artery involved right coronary artery, left anterior descending branch, and left circumflex branch and with the presence of coronary collateral circulation (CCC); group 3 with stenosis≥75% in≥1 main coronary artery but with no presence of CCC. The case history of all patients was reviewed, and all underwent physical examination, echocardigraphy, electrocardiography and blood testing for blood cell differential, cardiac troponin inhibitor, levels of total cholesterol, total triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, fasting plasma glucose, serum asparate aminotransferase, alanine aminotransferase, blood urea nitrogen, and creatinine. The study protocol was approved by the local ethics committee, and written informed consent was obtained from all participants.Coronary Artery AngiographyThree experienced physicians performed coronary angiography by the Judkins technique. Coronary stenosis and collateral circulation were assessed independently, and disagreements were resolved by consensus.EchocardiographyEchocardiography was performed within 24 hours before coronary angiography . It was performed using a commercially ultrasound transducer and equipment (M3S probe, Vivid7; GE Medical Systems, Horten, Norway) with subjects at rest in the left lateral decubitus position. Two-dimensional images were acquired of the standard parasternal and apical (4-chamber, 2-chamber and long-axis) views and short-axis views (mitral annulus, papillary muscle and apex) at a frame rate of 60 to 100 frames persecond. 3 consecutive cardiac cycles were acquired during breath hold. The images were stored digitally for subsequent offline analysis.Echocardiography AnalysisEchocardiography results were analyzed offline by use of the analysis software (EchoPAC PC SW-Only v.7.0.x; GE-Vingmed, Norway). By a point-and-click approach, we placed some points on the images along the left-ventricular subendocardium at the end of the systolic phase, from the interventricular septum to the lateral wall in the apical 4-chamber view, from the inferior to anterior wall in the apical 2-chamber view, from the posterior wall to the anterior septum in the apical long-axis view and the same of the short-axis of LV. The software can divide the ventricular walls into 6 segments automatically. Then strain and strain rate datas of the myocardial segments were acquiered by the software and were exported to Microsoft Excel for further analysis.The following parameters of the myocardial segments were calculated: the systolic peak strain (Sps), strain rate (SRs), end systolic strain (Ses), early diastolic strain rate (SRe) and late diastolic strain rate (SRa) in longitudinal(L), radial(R), circumferential (C) directions and the rotation (Rot), rotation rate.Statistical AnalysisValues are expressed as mean±standard error (SD). One-way ANOVA with LSD correction (equal variances assumed) and DunnettC test (equal variances not assumed) used as appropriate. The diagnostic use of the parameters were assessed by the use of receiver operating characteristic (ROC) curves. Statistical analysis involved use of SPSS 16.0 (SPSS Inc., Chicago, IL, USA). A P < 0.05 was considered statisticallysignificant.ResultsGeneral statesAmong 160 patients, 24 had singal coronary artery stenosis, 41 had double arteries stenosis while 65 had three arteries stenosis, 30 proved to be normal.1669 myocardial segments were used to analyzed the relation between the stenosis degree of cornary artery and changes of dyssynchrony of LV, which included 590 of 0 group, 314 of 1 group, 202 of 2 group, 421 of 3 group and 142 of 4 group in longitudinal direction and 598 of 0 group, 307 of 1 group, 139 of 2 group, 484 of 3 group and 141 of 4 group in radial, circunficial, roatation direction.According to the result of PCI, there are 48 collateral artarys. All of them happened where the stenosis of coronary artery was higher than 75% include left anterior descending branch (LAD) to right coronary artery (RCA) 14 , RCA to LAD 18, RCA to left circumflex branch (LCX) 5, LCX to RCA 7, LCX to LAD 2, LAD to LCX 2.Time data of ischemic myocardium in different degreesCompared with 0 group, time of RSes, CSps, CSes, CSRe, Rotps, Rotes, Rotsra of 2 group, time of RSes, RSRe, CSRs, LSes, LSRe, LSRs of 3 group, time of CSRs of 4 group increased significantly (p<0.05); Compared with 2 group, time of LSps, LSes, LSRs, RSes, RSRs, CSps, CSes, CSRs, CSRa, Rotps, Rotsrs, Rotsre of 3 group decreased markedly (p<0.05). Compared with 3 group, LSes, LSRe, LSRs of 4 group increased markedly (p<0.05).Regional function of ischemic myocardium with or without collateral arterysIn longitudinal direction, compared with 1-group, the systolic peak strain and end systolic strain of 2-group and 3-group, the systolic strain rate and late diastolic strain rate of 2-group, the systolic strain rate, early diastolic strain rate and late diastolic strain rate of 3-group decreased significantly (p<0.05); Compared with 2-group, the systolic peak strain, end systolic strain and the systolic strain rate decreased significantly (p<0.05).In radial direction, compared with 1-group, the early diastolic strain rate and late diastolic strain rate of 2-group and the end systolic strain, the systolic strain rate, early diastolic strain rate and late diastolic strain rate of 3-group decreased significantly (p<0.05); compared with 2-group, the end systolic strain and the systolic strain rate of 3-group decreased significantly (p<0.05).In circumferential direction, compared with 1-group, the early diastolic strain rate of 2-group and the systolic peak strain, end systolic strain, systolic strain rate, early diastolic strain rate and late diastolic strain rate of 3-group decreased significantly (p<0.05); compared with 2-group, the systolic peak strain, end systolic strain, systolic strain rate and early diastolic strain rate decreased significantly (p<0.05).About the rotation, compared with 1-group, the early diastolic rotation rate and late diastolic rotation rate of 2-group and systolic peak rotation, end systolic rotation, systolic rotation rate and early diastolic rotation rate decreased significantly (p<0.05).The predictive value of the parameters to collateral presenceWe calculated the sensitivity, specificity, Youden index, area of ROC of the parameters to predict the presence of collateral circulation.ConclusionsWhen coronary arteriostenosis(?)50%, 4 directions motion have become delayed. With the degree of stenosis, regional myocardium systole and dystole bidirectional as: delayed, then get better and delayed at last. Coronary collateral circulation provides a protection to ischemic myocardial regional function. 2D-strain technique may serve as an efficient method to assess ischemic myocardial regional function...