Predictive Role Of Myocardial Viability For The Long-term Adverse Cardiovascular Events Following The Coronary Artery Bypass Graft

Therapy of coronary heart disease is performed on the basis ofthe individuals of different pathological bases,stages and diseases,forming an all-round therapeutic principle of from the medical drugtherapy,interventional therapy to the surgical therapy.More andmore patients with the coronary heart disease in China receivedand benefited from the coronary artery bypass graft (CABG).Withthe developments in evidence-based medicine,how to select thetherapeutic strategy and the long-term efficacy became the focalpoints to which doctors paid most attention.Due to thenon-reproducibility of heart muscle,the therapeutic principle isalways to recover the blood supply of non-dead (survived) cardiacmuscle.Therefore,the selection of various therapeutic strategiesand the evaluation on the effect after revascularization arecorrelated directly with a very important factor (survived muscle),that is,the survived cardiac muscle is an important index fordeciding the prognosis.Previous studies on the risk factors of CABG and on the survived cardiac muscle and prognosis revealed some meaningfulconclusions but were still insufficient.For instance,the analyses onthe risk factors of CABG were not performed,and did not explorethe long-term prognosis,from the myocardial survival.Due to theimportance of myocardial survival in the pathophysiology ofcoronary heart disease,we look forward to being able to knowmore information about myocardial survival and prognosis prior tothe selection of therapy.However,whether the myocardial survivalcan evaluate the long-term efficacy after revascularization andwhich method will be adopted to assess the prognosis become themajor goals of this study.Objective:To explore the relationship between the volume andposition of myocardial viability and the long-term cardiovascularadverse event.Method:Clinical data were selected from thecoronary-heart-disease patients with CABG operation and theisotopic SPECT test of survived muscle prior to the operation in theFuwai Cardiovascular Hospital,the Chinese Academy of MedicalScience from 01/01/99 to 12/31/05 (in accordance with the date ofsurgery).Total 709 patients were included in this study afterremoving the dead patients in the hospital.Regular follow-up inpatients was performed following operation.Investigate the nuclearmedicine documents of the patients above,make the semiquantitative scores of myocardial perfusion and metabolism(survival) prior to operation by the 17-segment method of ventricle,and further obtain the quantified results,based on which calculationwas carried out for the perfusion and survival in the respectivepositions of whole left ventricle and its anterior wall,lateral wall,partition,inferoposterior wall and cardiac apex.In combination withother potential risk factors,the statistical tools,e.g.the receiveroperating characteristic (ROC) curve,the COX multifactor analysis,etc.,were used to explore the relationship between the myocardialperfusion and survival and the long-term cardiac adverse events(cardiogenic death,readmission,and the combined end events)selected in advance.Results:The mean duration of follow-up was3.43±2.42 years.Using the ROC curve,the critical values ofisotopic overall survival score were determined to be 15,9 and 13,respectively,for the long-term cardiogenic death,readmission andthe combined end events after operation.Patients were groupedaccording to the determined critical value.A significant difference inthe incidence of long-term event in the two groups above and underthe critical value was revealed by analysis based on theKaplam-Meier curve,and verified by the Log-rank method.TheCOX multivariate analysis using the isotopic overallperfusion/survival as the observation point indicated that the total score of isotopic overall survival was correlated with the long-termcardiogenic death,the long-term readmission and the combinedend event,with more possible occurrence of the above eventswhen higher in the total survival scores,and was an independentpredictive factor.The isotopic overall survival percentage was alsoan independent protective factor of long-term cardiogenic deathand the combined end event,but the protective factor correlatedwith readmission was the total perfusion percentage.The COXmultivariate analysis using the isotopic 5 segment as theobservation point indicated that the cardiac apex of left ventricleand the heart muscle in lateral wall were the independent protectivefactors of long-term cardiogenic death,the perfusion in the lateralwall of left ventricle and the myocardial survival of anterior andlateral walls were the independent protective factors of long-termreadmission,and the myocardial survival of anterior and lateralwalls of left ventricle were the independent protective factors of thecombined end events.The COX multivariate analysis using thecontrol area of three vessels as the observation point indicated thatthe survived cardiac muscles in the control areas of anteriordescending branch and circumflex branch were the independentprotective factors for the long-term cardiogenic death andreadmission,and meanwhile the myocardial survival in the control area of circumflex branch was also an independent protectivefactor for the combined end events.Conclusion:1) Through theintroduction of the myocardial survival index in the nuclearmedicine,in combination with other related factors,from theisotopic overall perfusion/metabolism (survival) of ventricle,wefound that the total scores on the survived cardiac muscle of the leftventricle with nuclide have the good distinguish ability for thelong-term cardiogenic death,readmission and the combined endevents,with the higher incidence of long-term cardiac adverseevents when higher in the score.Furthermore,the critical value ofthe above scores for predicting different long-term events wasrevealed.When the score of one patient exceeds the critical value,the patient will have a not-good-enough long-term prognosis (thetotal overall-survival scores of 15,9 and 13 are the critical valuesfor predicting the long-term cardiogenic death,readmission and thecombined end events,respectively).After the overall survival andperfusion,together with other related factors,are introduced intothe COX regression equation,the overall survival and the totalscore of survival are still correlated with the long-term cardiacadverse events.2) Through the introduction of the myocardialsurvival index in the nuclear medicine,in combination with otherrelated factors,with the isotopic perfusion/metabolism in each segment of left ventricle as the observation point,it was found thatthe survived muscles in the anterior wall,cardiac apex (roughlyequivalent to the anterior descending branch) and lateral wall of leftventricle and the circumflex branch were the important independentrelated factors influencing the long-term prognosis.With respect tothe patients with myocardial infarction in the anterior wall,moreattentions are paid to the revascularization of anterior wall (i.e.anterior descending branch),and meanwhile should also be paid tothe revascularization of lateral wall,which has an importantsignificance for the long-term prognosis.The cardiac apex has theimportant significances for maintaining the geometricalconfiguration and biomechanics of left ventricle.There is a higherincidence rate of long-term cardiac events in the patients withsmaller survived cardiac muscle in the cardiac apex.