Objective To evaluate the dynamic changes of left ventricular mechanical synchrony in the early period after acute myocardial infarction (AMI) by two-dimensional speckle tracking imaging (2D-STI) and real time three-dimensional echocardiography (RT-3DE),and analyze the correlation with phase analysis of single photo emission computed tomography gated myocardial perfusion imaging (SPECT GMPI) in porcine models,and further to investigate the clinical significance of left ventricular mechanical dyssynchrony in patients with AMI.Methods Bama minipigs(n =11) were subjected to left anterior descending (LAD) occlusion by balloon to introduce AMI porcine models.All animals underwent 2D-STI and RT-3DE at the baseline (before AMI),1 day,1 week and 4 weeks after LAD occlusion,respectively.In addition,SPECT GMPI was measured at baseline and 1 day after AMI.Data was analyzed and compared the dynamic changes of left ventricular mechanical synchrony before and after AMI.Then the correlation between echocardiography and SPECT GMPI in evaluating left ventricular mechanical synchrony before and after AMI were calculated.Results Eight pigs were successfully established as AMI models and complete the study.SPECT GMPI,2D-STI and RT-3DE showed that the left ventricular mechanical synchrony indexes were significantly higher at 1 day after AMI than those before AMI,which means the appearance of left ventricular mechanical dyssynchrony.Compared with those 1 day after AMI,GLS,Time SD,Tmsv16-SD％ and Tmsv16-Dif％ did not change significantly at 1 week after AMI,but they significantly increased at4 weeks after AMI (all P ＜0.05).At baseline and 1 day after AMI,the GLS measured by 2D-STI and the SPECT GMPI parameter phase bandwidth (BW) showed good correlation(r =0.708-0.719,P ＜0.05),Time SD was significantly correlated with the SPECT GMPI parameter phase standard deviation (SD)(r =0.717-0.830,P ＜0.05),while Tmsv16-Dif％ derived from RT-3DE had a better positive correlation with BW (r =0.713-0.857,P ＜0.05),as similar as Tmsv16-SD％ with SD(r =0.803-0.957,P ＜0.05).Conclusions Left ventricular mechanical dyssynchrony is present 1 day after AMI.Compared with that 1 day after AMI,left ventricular mechanical dyssynchrony doesn't change significantly at 1week after AMI,but further aggravates at 4 weeks after AMI.The parameters of 2D-STI and RT-3DE have good correlation with the mechanical synchrony parameters measured by SPECT GMPI.2D-STI and RT-3DE can be used as reliable methods to evaluate left ventricle mechanical dyssynchrony early after AMI.

Objective To assess left ventricular remodeling (LVRM) after acute myocardial in-farction (AMI) quantitatively by SPECT gated myocardial perfusion imaging (GMPI), and further explore its influencing factors. Methods Twelve Ba-Ma miniature swine were used to establish AMI model. GMPI was performed at the baseline (before AMI), 24 h, 1 and 4 weeks after AMI. Infarct expansion index, left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), left ventricular ejection fraction ( LVEF) and myocardial perfusion defect were measured. Meanwhile, creatine kinase isozyme MB (CK-MB) and hypersensitive cardiac troponin I (hs-cTn I) were detected. The changes of LVEDV and LVESV before and after AMI (ΔLVEDV and ΔLVESV) were calculated. Repeated measurement analy-sis of variance, the least significant difference t test and Pearson correlation analysis were performed. Re?sults Nine AMI swine were successfully created. LVRM was present 24 h after AMI. LVEDV and LVESV were significantly greater than those before AMI and aggravated within 1 week after AMI, then were down-wards at 4 weeks after AMI. Before AMI, 24 h, 1 and 4 weeks after AMI, the LVEDV was (34.44±7. 90), (47.56±22.66), (71.89±14.90) and (70.33±19.47) ml (F = 28.836, P<0.001), and the LVESV was (10.11±5.49), (25.33±11.62), (40.89±15.88) and (35.44±17.11) ml (F = 22.450, P<0. 001). In-farct expansion index increased progressively within 4 weeks after AMI (F= 16.054, P<0.001). LVEF was significantly lower after AMI than that before AMI (F = 18.267, P<0.001) and improved at 4 weeks after AMI compared to that at 1 week ((52.56±14.96)％ vs (45.11±15.80)％; t= 2.440, P<0. 05). There was a significant correlation between the change in perfusion defect and the ΔLVEDV or ΔLVESV (r values:0. 731 and 0.700, both P<0.05) at 1 week after AMI. In addition, hs-cTn I at 24 h was correlated withΔLVEDV at 24 h and 4 weeks after AMI, respectively (r values: 0.669 and 0.693, both P<0.05). Conclu?sions LVRM and cardiac dysfunction occur in the early period after AMI. LVRM and cardiac dysfunction are most severe at 1 week after AMI, and recover at 4 weeks after AMI, whereas infarct expansion is aggra-vated within 4 weeks. Infarct size and hs-cTn I are closely related to the degree of LVRM.

Objective:To evaluate the left ventricular diastolic dyssynchrony (LVDD) and its influencing factors early after acute myocardial infarction (AMI) using phase analysis of SPECT gated myocardial perfusion imaging (GMPI).Methods:Bama miniature swines ( n=16) were subjected to establish AMI models. GMPI was performed before and 1 d after AMI to obtain the extent of myocardial perfusion defect (Extent, %) and left ventricular systolic dyssynchrony (LVSD)/LVDD parameters, namely the phase histogram bandwidth (PBW) and phase standard deviation (PSD). Meanwhile, left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), left ventricular ejection fraction (LVEF), and the ratio of early to late peak mitral diastolic flow (E/A) were obtained by echocardiography. Independent-sample t test, paired t test and Pearson correlation analysis were used to analyze the data. Results:Sixteen AMI swines were successfully created. Compared to baseline, Extent, LVEDV and LVESV significantly increased on 1 d after AMI ( t values: -11.14, -4.55, -6.12, all P<0.001), while LVEF and E/A significantly decreased ( t values: 10.16, 2.18, P<0.001, P=0.046). GMPI showed that the LVDD parameters PBW and PSD increased significantly on 1 d after AMI when compared to those at baseline((142.25±72.06)° vs (33.06±8.98)°, (56.15±26.71)° vs (12.51±5.13)°; t values: -6.11, -6.60, both P<0.001). There were significant differences between LVSD parameters and LVDD parameters (PBW: (109.06±62.40)° vs (142.25±72.06)°, PSD: (44.40±25.61)° vs (56.15±26.71)°; t values: -2.73, -2.20, P values: 0.016, 0.044). LVDD parameters PBW, PSD were negatively correlated with E/A after AMI ( r values: -0.569, -0.566, P values: 0.021, 0.022), and positively correlated with the Extent ( r values: 0.717, 0.634, P values: 0.002, 0.008). The phase analysis of SPECT GMPI to evaluate LVDD showed good intra-observer and inter-observe reproducibility (intraclass correlation coefficient (ICC): 0.953-0.984, all P<0.001). Conclusions:LVDD occurs early on 1 d after AMI, and can reflect left ventricular diastolic dysfunction. The Extent is correlated with LVDD significantly. Phase analysis of SPECT GMPI is an accurate method to evaluate LVDD and left ventricular diastolic function.

Objective:To evaluate inflammation early in the infarct zone and its dynamic changes after acute myocardial infarction (AMI) using 18F-FDG PET imaging, and analyze its relationship with left ventricular remodeling progression (LVRP). Methods:Sixteen Bama miniature pigs (4-6 months old, 8 females) were selected. AMI models were established by balloon occlusion of the left anterior descending artery. 18F-FDG PET imaging was performed before AMI and at days 1, 5, 8, and 14 post-AMI to evaluate the regional inflammation response. 18F-FDG SUV ratio (SUVR) and the percentage of uptake area of left ventricle (F-extent) in the infarct zone, and the SUVRs of the spleen and bone marrow, were measured. Echocardiography and 99Tc m-methoxyisobutylisonitrile(MIBI) SPECT myocardial perfusion imaging (MPI) were performed at the above time points and on day 28 post-AMI to assess left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), left ventricular ejection fraction (LVEF), and myocardial perfusion defect extent. The degree of LVRP at day 28 post-AMI was defined as ΔLVESV(%)=(LVESV AMI 28 d-LVESV AMI 1 d)/LVESV AMI 1 d×100%. Data were analyzed using repeated measures analysis of variance, Kruskal-Wallis rank sum test and Pearson correlation analysis. Results:Twelve pigs were successfully modeled and completed the study. Inflammation in the infarct zone persisted until day 14 post-AMI. The SUVR of the infarct zone pre-AMI and at days 1, 5, 8, and 14 post-AMI were 1.03±0.08, 3.49±1.06, 2.93±0.90, 2.38±0.76, and 1.63±0.62, respectively ( F=49.31, P<0.001). The F-extent values in the infarct zone pre-AMI and at days 1, 5, 8, and 14 post-AMI were 0, (40.08±12.46)%, (40.00±12.76)%, (31.08±12.82)%, and 16.50%(7.25%, 22.00%), respectively ( H=37.61, P=0.001). There were no significant differences in the SUVRs of bone marrow and spleen before and after AMI ( F values: 0.69 and 0.77, both P>0.05). At day 1 post-AMI, both SUVR and F-extent in the infarct zone were significantly correlated with LVRP ( r values: 0.82 and 0.70, P values: 0.001 and 0.035). Conclusions:18F-FDG PET imaging can be used to evaluate inflammation in the infarct area and its dynamic changes after AMI. Inflammation in the infarct area is severe at day 1, and then gradually decreases. The extent and severity of inflammation visible on 18F-FDG PET imaging 1 d after AMI are closely related to LVRP.