| Part I.Impact of Intramyocardial Hemorrhage And Microvascular Obstruction On Cardiac Mechanics In Acute Phase Of ST-Elevation Myocardial Infarction : A Speckle-Tracking Echocardiography StudyObjective:Intramyocardial hemorrhage(IMH)and microvascular obstruction(MVO)are two major mechanisms of reperfusion injury of the left ventricle(LV)after acute ST-elevation myocardial infarction(STEMI).Cardiac magnetic resonance(CMR)are currently the reference standard for detecting these two reperfusion injuries.We sought to assess the impact of IMH and MVO on LV cardiac mechanics using two-dimensional speckle tracking echocardiography(2DSTE)during the acute phase of STEMI,and explore the predictive ability of strain parameters in identifying MVO and IMH.Method:Our study enrolled 81 patients admitted to our hospital for acute STEMI.All patients underwent CMR within 8 days(median 4.9 days)after reperfusion therapy.Echocardiography examination was performed on the same day with CMR.Myocardial segments were divided into 6 groups based on CMR findings:(1)Normal segments without infarction,(2)segments with non-transmural infarct(NTI)but no CMR evidence of reperfusion injury(NTI MVO-/IMH-),(3)NTI segments with MVO but no IMH(NTI MVO+/IMH-),(4)segments with tansmural infarct(TI)but no reperfusion injury(TI MVO-/IMH-),(3)transmural infarct segments with MVO but no IMH(TI MVO+/IMH-),and(4)TI segments with IMH in addition to MVO(TI MVO+/IMH+).2DSTE derived segmental peak systolic circumferential(CS),radial(RS),and longitudinal(LS)were measured using a GE Echo PAC 110 work station,and the results were compared among groups.Results: There were 58 patients presented with MVO or IMH in the study population.Of the 1458 segments analyzed,there were 882(60.5%)remote non-infarct segments(remote segments),151(10.4%)non-NTI segments,and 425(29.1%)TI segments.In NTI segments,MVO was present in 9 segments(NTI MVO+/IMH-group),and the rest(n=142)showed no reperfusion injury(NTI MVO-/IMH-group).IMH was absent in all NTI segments.In TI segments,148(34.8%)showed no reperfusion injury(TI MVO-/IMH-group),81(19.1%)had MVO without IMH(TI MVO+/IMH-group),and 196(46.1%)showed MVO with IMH(TI MVO+/IMH+ group).The amplitudes of all strain measurements decreased with the increase of infarct transmurality.The presence of MVO in NTI segments didn't result in the decrease of strains(P>0.05).In TI segments,the presence of MVO alone was not associated with the decrease of strain measurements(P>0.05),while IMH decreased CS significantly(P=0.004).The ROC curve analysis showed that the sensitivity and specificity of CS using the cut-off of >-11.66% to diagnose IMH were 78.00% and 79.45%,respectively(AUC=0.86,P=0.0001).Conclusions: In the acute phase of STEMI,myocardial strain decreased with the increase of infarct tansmuarlity.Reperfusion MVO and IMH injury have differential impact on cardiac mechanics.IMH preferentially affects CS,presumably related to its location in the mid-myocardial layer.Part II.Accessing Myocardial Viability And Predicting Left Ventricular Remodeling After Acute Myocardial Infarction: A Speckle-Tracking Echocardiography StudyObjective:In the acute phase of myocardial infarction,the stunned myocardium may presented with functional recovery in the follow-up,while the infarct region may become thinner and expanded which will result in the remodeling of left ventricle.Our study aims to explore the value of 2D-STE derived strain parameters in predicting myocardial segmental functional recovery and LV remodeling.Method : We enrolled in 81 patients with firstacute ST-elevation myocardial infarction(STEMI).All patients underwent CMR within 8 days(median 4.9 days)after reperfusion therapy to evaluated scar percentage and reperfusion injury(defined as MVO or IMH).Echocardiography examination was first performed on the same day with CMR.The baseline LVEF,left ventricular end-systolic volume(LVESV),left atrial volume,index for diastolic function,and wall motion score index(WMSI)were measured.2DSTE analysis was performed using a GE Echo PAC 110 work station to calculate segmental and global CS,RS and LS.After a mean follow-up of 14 months,echocardiography was performed again for assessing segmental WMSI and LVESV.Recovery of myocardial function were defined as the increment of WMSI by ?1 grade,and LV remodeling was defined as the increase of LVESV by >15% compared with baseline.Major adverse cardiac event(MACE)were defined as death,and the attack of heart failure.Results:The percentage of segmental function recovery decreased with the increase of infarct transmurality and the presence of reperfusion injury.The segments with functional recovery was associated with higher amplitude of strain measurement at baseline compared with those without functional recovery(P<0.05).The ROC analysis showed a cutoff value of ?-7.77% for CS to predict the functional recovery with a sensitivity and specificity of 77.17% and 61.40% respectively(AUC= 0.74,p<0.001).On a global level,patients with MACE and LV remodeling was associated with higher proportion of reperfusion injury,higher scar percentage,depressed LV diastolic function,higher WMSI,lower LVEF as well as global strains.Multivariate regression showed that CMR scar percentage and GCS were the independent predictive factors for LV remodeling.ROC analysis reveal the highest AUC of CMR scar percentage for predicting LV remodeling using the cutoff point of >23%,with a sensitivity of 79.49% and specificity of 88.57%(AUC=0.88,P=0.0001).A cutoff value of GCS?-17.48% also predicted LV remodeling with a sensitivity of 88.33% and specificity of 69.23%(AUC=0.8,P=0.0001).Conclusions: The STE strain in acute phase of myocardial infarction could be used to predict segmental functional recovery.The depressed global strain at baseline was associated with a higher possibility of MACE and LV remodeling at follow-up.CS may be the best index for predicting segmental functional recovery and LV remodeling. |
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