| ST-segment elevation myocardial infarction(STEMI)is one of the most severe types of myocardial infarction.The incidence of STEMI in China is increasing year by year.STEMI can easily lead to myocardial microcirculation obstruction,segmental wall movement abnormalities,decreased cardiac function,complicated with aneurysm and mural thrombus,further arrhythmia and chronic heart failure,seriously affecting the life quality of patients.Emergency percutaneous coronary interention(e PCI)is an important means of reperfusion therapy for STEMI patients,which can effectively open culprit vessels.Although culprit vessels are recanalized to thrombolysis in myocardial infarction(TIMI)flow grade 3,the myocardial microcirculation perfusion which is related to left ventricular remodeling and adverse cardiovascular events has not fully recovered.Therefore,early,rapid and accurate evaluation of cardiac structure,function and myocardial microcirculation perfusion in STEMI patients is of great significance in adjusting treatment strategies,evaluating the effect of reperfusion therapy and determining prognosis.Contrast echocardiography can enhance the cardiac cavity and myocardium,which can not only improve the accuracy and repeatability of cardiac structure and function assessment,but also evaluate the recovery of myocardial microcirculation perfusion after reperfusion,providing a new perspective of risk stratification and optimizing therapeutic schedule for patients.In this context,the aim of this study was to evaluate the cardiac structure,function and myocardial perfusion of STEMI patients using contrast echocardiography.First,the accuracy and repeatability of two-and three-dimensional echocardiography combined with contrast echocardiography to evaluate the left ventricular structure and function were investigated by using beagles’ pathological specimens as the gold standard,so as to provide a reference for the subsequent screening of the most appropriate method to evaluate the left ventricuclar structure and function of STEMI patients.Second,to probe the incremental value of the method which is screened from the first part in evaluating left ventricular structure and remodeling parameters in STEMI patients.Third,to evaluate the myocardial perfusion of STEMI patients with TIMI flow grade 3 following e PCI by myocardial contrast echocardiography and to explore the relevant influential factors.Finally,to investigate the predictive value of qualitative and quantitative parameters of myocardial contrast echocardiography for cardiac events by following up STEMI patients with TIMI flow grade 3 following e PCI.This study is divided into four parts.Part 1 Evaluation of left ventricular structure and function by two-and three-dimensional contrast-enhanced transthoracic echocardiography:an experimental studyObjective: To discuss the accuracy and repeatability of left ventricular structural and functional measurements by two-and three-dimensional contrast-enhanced transthoracic echocardiography(2D c TTE and 3D c TTE).Methods: M-mode in parasternal long-axis views were obtained from 12 beagles,and the apical four-chamber,three-chamber and two-chamber views and the three-dimensional full-volume images of the left ventricle were collected with unenhanced and contrast-enhanced transthoracic echocardiography.The intimal display rates in apical four-chamber,three-chamber and two-chamber views of the left ventricular segments were evaluated by two-and three-dimensional unenhanced echocardiography(2D TTE and 3D TTE),2D c TTE and 3D c TTE.Left ventricular end-diastolic longitudinal dimension(LVLD)was measured with 2D TTE and 2D c TTE.Left ventricular end-diastolic volume(LVEDV),left ventricular end-systolic volume(LVESV)and left ventricular ejection fraction(LVEF)were measured respectively with Teichholz method of M-mode,biplane Simpson method of 2D TTE and 2D c TTE.Left ventricular three-dimensional full-volume images were processed and analyzed by Tom Tec software,and LVEDV,LVESV and LVEF were measured respectively with 3D TTE and 3D c TTE.The measurements of pathological specimens were taken as the gold standard,the accuracies of measuring LVLD and LVEDV by different methods were evaluated.All indexes were measured again by the same observer and different observers,and the reproducibility of different methods for measuring different indexes were evaluated.Results:(1)The intimal display rate of the left ventricular segments was higher with 2D c TTE and 3D c TTE than that with 2D TTE and 3D TTE,and 2D c TTE was the best(P<0.05).(2)The measurement of LVLD by 2D c TTE was more relevent with the measurement by pathological specimen than that by 2D TTE(0.851 vs.0.748).The measurements of LVEDV by M mode,2D TTE,2D c TTE,3D TTE and 3D c TTE correlated with the measurements by pathological specimens(0.612,0.806,0.857,0.728 and 0.869,respectively).2D c TTE and 3D c TTE can provide more accurate measurements,and 3D c TTE was the most precise method.(3)For intra-and inter-observers,the coefficients of variation of LVEDV,LVESV,LVEF with 2D c TTE and 3D c TTE were lower than those with M-mode,2DTTE,3DTTE.Conclusions: Contrast-enhanced transthoracic echocardiography can improve image quality of 2D TTE and 3D TTE with more accurate and repeatable measurements,2D c TTE is best at the display of segmental ventricular endocardium while 3D c TTE is best at the evaluation of left ventricular volume,providing a new method for clinical precise evaluation and dynamic monitoring of left ventricular structure and function.Part 2 The incremental value of contrast-enhanced two-dimensional transthoracic echocardiography for determination of left ventricular structure and remodeling measurements in STEMI patientsObjective: To explore the differences of left ventricular structure and remodeling measurements evaluated by unenhanced and contrast-enhanced two-dimensional transthoracic echocardiography,and to investigate the incremental value of contrast-enhanced transthoracic echocardiography.Methods: Sixty-nine patients with STEMI who underwent unenhanced and contrast-enhanced two-dimensional echocardiography were enrolled.The apical four-chamber,three-chamber and two-chamber views of the left ventricle were collected with unenhanced and contrast-enhanced modes.According to the endocardial display in the unenhanced mode,all patients were divided into two groups: excellent image quality and poor image quality.The endocardial segment display rate and mural thrombus diagnosis rate were compared in each group with unenhanced and contrast-enhanced modes,and the improvement of left ventricular overall image quality and left ventricular apex display with contrast-enhanced mode were evaluated in the poor image quality group.LVEDV,LVESV and LVEF were measured respectively by biplane Simpson method with unenhanced and contrast-enhanced modes.The left ventricular global longitudinal strain(GLS)was measured by a CMQ software in Qlab with unenhanced and contrast-enhanced modes,respectively.The differences and repeatability of left ventricular remodeling measurements of LVEDV,LVESV,LVEF and GLS in each group were compared with unenhanced and contrast-enhanced modes,and the feasibility and accuracy of GLS in contrast-enhanced mode were evaluated.Results:(1)Of the 69 patients included,23(33.33%)were in the group with excellent image quality and 46(66.67%)were in the group with poor image quality.Regardless of the image quality in the unenhanced mode,the display rate of endocardial segment in the contrast-enhanced mode was higher than that in the unenhanced mode(P<0.05).(2)For the group with poor image quality,the overall image quality of the left ventricle and the display of the left ventricular apex were significantly improved in the contrast-enhanced mode(P<0.05).The diagnosis rate of mural thrombus in the contrast-enhanced mode was higher than that in the unenhanced mode,but there was no significant difference between the two groups(P>0.05).(3)For the group with poor image quality,LVESV in contrast-enhanced mode was higher than that in unenhanced mode,while LVEF and GLS were lower than those in the unenhanced mode(all P<0.05).(4)The correlation between GLS measured in contrast-enhanced and unenhanced mode was 0.912,and most of the measurements in the two modes were within the consistency threshold,proving that measuring GLS in the contrast-enhanced mode was feasible.For the group with poor image quality,compared with GLS measured in the unenhanced mode,the correlation between GLS and LVEF measured in the contrast-enhanced mode was higher(0.731 vs.0.709).(5)For the patients with excellent image quality,the interclass correlation coefficients of most parameters were increased slightly in the contrast-enhanced mode,especially among interobservers.For those with poor image quality,the intra-and inter-observers’ interclass correlation coefficients of left ventricular remodeling mearsurements were increased significantly in the contrast-enhanced mode.Conclusions: Contrast-enhanced two-dimensional echocardiography can more clearly display the left ventricular structure of STEMI patients and obtain more repeatable left ventricular remodeling measurements such as LVEDV,LVESV,LVEF and GLS,especially for patients with poor image quality.Part 3 Prevalence and influential factors of myocardial perfusion abnormalities in acute STEMI patients with TIMI flow grade 3 following e PCIObjective: To evaluate the myocardial perfusion of STEMI patients with TIMI flow grade 3 following e PCI by myocardial contrast echocardiography and to explore the influential factors of myocardial perfusion defect.Methods: From April 2018 to December 2019,67 STEMI patients with TIMI flow grade 3 following e PCI were prospectively enrolled.The general clinical data,laboratory test results and coronary angiography related indicators were recorded.All patients underwent routine echocardiography and myocardial contrast echocardiography within 7 days after e PCI.Left ventricular end-diastolic and systolic diameters,LVEDV,LVESV,LVEF,GLS and wall motion score index(WMSI)were evaluated.Myocardial perfusion was evaluated qualitatively according to the replenishment time after high-mechanical index flash.Normal myocardial perfusion(n MP)rated as 1 point was replenished within 4 s while delayed myocardial perfusion(d MP)rated as 2 points was replenished within 4-10 s.Myocardial perfusion obstruction(MPO)rated as 3 points was failed to replenish more than 10 s.Myocardial perfusion score index(MPSI)was calculated by adding the perfusion score in all segments divided by the total number of evaluable segments.All the patients were divided into three groups: n MP group,d MP group and MPO group.Results:(1)Among the 67 patients included,there were 27 MPO cases(40.30%),24 d MP cases(35.82%)and 16 n MP cases(23.88%),respectively.(2)Compared with the n MP group,N terminal B-type natriuretic peptide(NT-pro BNP)and hypersensitive C-reactive protein were higher in d MP and MPO groups(all P<0.05).The proportion of peak ultra-Tn I≥50 ng/ml and white blood cell count in MPO group were higher than those in the n MP group(P<0.05).(3)The proportion of TIMI flow grade 1 in d MP group before e PCI was significantly higher than that in n MP group(P<0.05).The proportions of left anterior descending(LAD)culprit vessel in d MP and MPO groups were significantly higher,while the proportions of right coronary artery culprit vessel in d MP and MPO groups were significantly lower than that in n MP group(all P<0.05).The proportion of distal vascular lesions in the n MP group was higher than that in MPO group(P<0.05).(4)Compared with the n MP group,LVEDV,LVESV,WMSI and MPSI were higher in d MP and MPO groups,while LVEF and GLS were lower(all P<0.05).Compared with the d MP group,WMSI and MPSI increased and GLS decreased in the MPO group(all P<0.05).(5)Univariate and multivariate logistic regression analyses showed that white blood cell count,peak ultra-Tn I≥50 ng/ml,LAD culprit vessel,LVEDV,LVESV,LVEF,WMSI and GLS were risk factors for MPO,but only peak ultra-Tn I≥50 ng/ml(OR=6.777,P=0.018)and WMSI(OR=1.649,P=0.002)were independent predictors for MPO.Receiver-operating characteristic curve analysis yielded a cut-off value of WMSI≥1.32 best predicted MPO with 92.60% sensibility and 62.50% specificity,and area under the curve was 0.809(P<0.05).Conclusions: After e PCI,a large proportion of STEMI patients with TIMI flow grade 3 still had abnormal myocardial perfusion,especially with LAD lesion.Peak ultra-Tn I≥50 ng/ml and WMSI were independent predictors for MPO.Myocardial contrast echocardiography can be used to evaluate the severity of myocardial perfusion abnormalities and provide a basis for optimizing clinical treatment strategies.Part 4 The predictive value of qualitative and quantitative myocardial contrast echocardiography for cardiac events in STEMI patients with TIMI flow grade 3 following e PCIObjective: To investigate the predictive value of qualitative and quantitative parameters of myocardial contrast echocardiography for cardiac events in STEMI patients with TIMI flow grade 3 following e PCI.Methods: From April 2018 to January 2020,64 STEMI patients with TIMI flow grade 3 following e PCI were prospectively enrolled.The general clinical data,laboratory test results and coronary angiography related indicators were recorded.All patients underwent routine echocardiography and myocardial contrast echocardiography within 7 days after e PCI.LVEDV,LVESV,LVEF,GLS and WMSI were evaluated.Myocardial perfusion was evaluated qualitatively according to the replenishment time after high-mechanical index flash.Normal myocardial perfusion rated as 1 point was replenished within 4 s while delayed myocardial perfusion rated as 2 points was replenished within 4-10 s.Myocardial perfusion obstruction rated as 3 points was failed to replenish more than 10 s.MPSI was calculated by adding the perfusion score in all segments divided by the total number of evaluable segments.Quantitative perfusion parameters(A and β)were analyzed using a 17-segment model by ROI software in Qlab.The mean values of each segment were defined as Amyocardium and βmyocardium,respectively.The maximal intensity value of cardiac cavity was recorded and corrected Amyocardium and corrected Aβmyocardium were obtained.Patients were followed up for cardiac events,and all patients were divided into non-occurrence group(NCE group)and occurrence group(CE group).Results:(1)All patients were followed up for an average of 3(2)months,49(76.56%)patients were in NCE group,and 15(23.44%)patients were in CE group.(2)The proportion of patients with ultra-Tn I≥50 ng/ml in the CE group was significantly higher than that in the NCE group(P<0.05),and there were no statistical differences in the remaining baseline data and coronary angiography indexes(all P>0.05).(3)Compared with the NCE group,the LVESV,WMSI and MPSI in the CE group significantly increased,while the GLS,βmyocardium and corrected Aβmyocardium in the CE group significantly decreased(all P<0.05).(4)The areas under the curves(AUC)of each index to predict cardiac events were MPSI>βmyocardium>corrected Aβmyocardium>WMSI>GLS>LVESV>ultra-Tn I≥50 ng/ml(0.854,0.808,0.789,0.779,0.724,0.697 and 0.645,respectively).The cut-off value of MPSI was 1.38(sensitivity 86.70%,specificity 69.40%),and the cut-off value of βmyocardium was 1.17 s-1(sensitivity 80.00%,specificity 81.60%),the cut-off value of corrected Aβmyocardium was 0.22 d B/s(sensitivity 73.30%,specificity 75.50%).(5)Combined with MPSI≥1.38,βmyocardium≤ 1.17 s-1,and corrected Aβmyocardium≤0.22 d B/s,the AUC,sensitivity and specificity for predicting cardiac events were increased to 0.944,100%,and 81.60%,respectively.Kaplan-Meier survival curve confirmed that patients with MPSI<1.38,βmyocardium>1.17 s-1,or corrected Aβmyocardium>0.22 d B/s were more likely free from cardiac events(all Log Rank P≤0.001).Conclusions: Qualitative and quantitative parameters of myocardial contrast echocardiography can accurately predict cardiac events in STEMI patients with TIMI flow grade 3 following e PCI,and their combined predictive value is higher,which is expected to provide an effective method for early clinical risk stratification of STEMI patients after e PCI. |
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