Objective:To investigate the ability of 18F-fibroblast activation protein inhibitor (FAPI) PET/CT imaging to identify involved myocardium in patients with hypertrophic cardiomyopathy (HCM) compared with cardiac MRI. Methods:A prospective study was conducted on 50 patients (32 males, 18 females, age (43±13) years) with HCM confirmed by ultrasound or cardiac MRI in Beijing Chaoyang Hospital from July 2021 to January 2022. All patients underwent both cardiac 18F-FAPI PET/CT and MRI. The SUV max and maximum target-to-background ratio (TBR max) of the left ventricular myocardium were obtained using post-processing software. Regions with 18F-FAPI uptake not less than predefined thresholds (SUV max 40%, 50%, 60%) were defined as myocardium with positive uptake. The FAPI amount was defined as the product of TBR max and the extent of FAPI-positive uptake (FAPI%). Cardiac MRI post-processing software was used to measure the extent of left ventricular myocardial late gadolinium enhancement (LGE) (expressed as LGE%), native T 1 value, extracellular volume fraction (ECV), and myocardial deformation characteristics. Spearman rank correlation analysis was employed to assess the correlation between 18F-FAPI imaging parameters and cardiac MRI parameters, as well as the correlation between FAPI amount and the 5-year risk score for sudden cardiac death (SCD). Linear regression analysis was utilized to identify factors associated with FAPI amount. Results:When the threshold for 18F-FAPI-positive uptake in the left ventricular myocardium was set at 60%, the correlations between FAPI amount, FAPI%, and MRI parameters were optimal ( rs values: from -0.465 to 0.460, all P<0.05). Multivariate linear regression analysis revealed that HCM duration ( β=0.128, 95% CI: 0.022-0.233, P=0.008), serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels ( β=0.190, 95% CI: 0.099-0.280, P<0.001), and left ventricular ejection fraction ( β=-0.005, 95% CI: -0.011 to 0.000, P=0.041) were independent predictors of FAPI amount. FAPI amount was positively correlated with the 5-year SCD risk score across different thresholds (40%: rs=0.32, P=0.026; 50%: rs=0.29, P=0.039; 60%: rs=0.29, P=0.040). Conclusions:When the threshold for 18F-FAPI-positive uptake is set at 60%, 18F-FAPI PET/CT imaging can more effectively identify the involved myocardium in HCM. FAPI amount is correlated with the 5-year SCD risk score in patients with HCM.

Myocardial fibrosis(MF)represents a core pathological basis for cardiovascular disease progression,strongly associated with poor prognosis.The clinical evaluation techniques were invasive,lacking specificity and unable to diagnose early MF.Targeted on activated fibroblasts,radionuclide imaging emerged as a transformative solution,leveraging molecular-level specificity for noninvasive early diagnosis,dynamicly monitoring disease progression and evaluation on treatment response of MF.The scientific foundation,evidences of early diagnostic efficacy,and potential of fibroblast-targeted radionuclide imaging applicated in cardiovascular diseases,as well as its role in risk stratification,prognostic assessment and therapeutic decision support of MF were systematically reviewed in this article.

Epicardial adipose tissue(EAT)is a type of fat tissue that is closely adjacent to the coronary arteries and myocardium,and it caused physiological and pathological changes to the body through the secretion of autocrine and paracrine active factors.EAT is regarded as a diagnostic marker and a potential therapeutic target for cardiovascular diseases,and it is of great significance to segment and quantify EAT.This article introduced the evolution of the EAT segmentation and quantification methods from the aspects of traditional imaging,atlas,and artificial intelligence.Furthermore,it reviewed the research progresses on automatically quantified EAT indices in the diagnosis and treatment of cardiovascular diseases.

Epicardial adipose tissue(EAT)is a type of fat tissue that is closely adjacent to the coronary arteries and myocardium,and it caused physiological and pathological changes to the body through the secretion of autocrine and paracrine active factors.EAT is regarded as a diagnostic marker and a potential therapeutic target for cardiovascular diseases,and it is of great significance to segment and quantify EAT.This article introduced the evolution of the EAT segmentation and quantification methods from the aspects of traditional imaging,atlas,and artificial intelligence.Furthermore,it reviewed the research progresses on automatically quantified EAT indices in the diagnosis and treatment of cardiovascular diseases.

Objective:To investigate the ability of 18F-fibroblast activation protein inhibitor (FAPI) PET/CT imaging to identify involved myocardium in patients with hypertrophic cardiomyopathy (HCM) compared with cardiac MRI. Methods:A prospective study was conducted on 50 patients (32 males, 18 females, age (43±13) years) with HCM confirmed by ultrasound or cardiac MRI in Beijing Chaoyang Hospital from July 2021 to January 2022. All patients underwent both cardiac 18F-FAPI PET/CT and MRI. The SUV max and maximum target-to-background ratio (TBR max) of the left ventricular myocardium were obtained using post-processing software. Regions with 18F-FAPI uptake not less than predefined thresholds (SUV max 40%, 50%, 60%) were defined as myocardium with positive uptake. The FAPI amount was defined as the product of TBR max and the extent of FAPI-positive uptake (FAPI%). Cardiac MRI post-processing software was used to measure the extent of left ventricular myocardial late gadolinium enhancement (LGE) (expressed as LGE%), native T 1 value, extracellular volume fraction (ECV), and myocardial deformation characteristics. Spearman rank correlation analysis was employed to assess the correlation between 18F-FAPI imaging parameters and cardiac MRI parameters, as well as the correlation between FAPI amount and the 5-year risk score for sudden cardiac death (SCD). Linear regression analysis was utilized to identify factors associated with FAPI amount. Results:When the threshold for 18F-FAPI-positive uptake in the left ventricular myocardium was set at 60%, the correlations between FAPI amount, FAPI%, and MRI parameters were optimal ( rs values: from -0.465 to 0.460, all P<0.05). Multivariate linear regression analysis revealed that HCM duration ( β=0.128, 95% CI: 0.022-0.233, P=0.008), serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels ( β=0.190, 95% CI: 0.099-0.280, P<0.001), and left ventricular ejection fraction ( β=-0.005, 95% CI: -0.011 to 0.000, P=0.041) were independent predictors of FAPI amount. FAPI amount was positively correlated with the 5-year SCD risk score across different thresholds (40%: rs=0.32, P=0.026; 50%: rs=0.29, P=0.039; 60%: rs=0.29, P=0.040). Conclusions:When the threshold for 18F-FAPI-positive uptake is set at 60%, 18F-FAPI PET/CT imaging can more effectively identify the involved myocardium in HCM. FAPI amount is correlated with the 5-year SCD risk score in patients with HCM.

Myocardial fibrosis(MF)represents a core pathological basis for cardiovascular disease progression,strongly associated with poor prognosis.The clinical evaluation techniques were invasive,lacking specificity and unable to diagnose early MF.Targeted on activated fibroblasts,radionuclide imaging emerged as a transformative solution,leveraging molecular-level specificity for noninvasive early diagnosis,dynamicly monitoring disease progression and evaluation on treatment response of MF.The scientific foundation,evidences of early diagnostic efficacy,and potential of fibroblast-targeted radionuclide imaging applicated in cardiovascular diseases,as well as its role in risk stratification,prognostic assessment and therapeutic decision support of MF were systematically reviewed in this article.

Objective:To investigate the clinical value of left ventricular shape index (SI) and eccentricity index (EI) in evaluating left ventricular remodeling.Methods:A retrospective analysis was performed on 324 patients (264 males, 60 females, age (62.5±11.8) years) diagnosed with myocardial infarction (MI) and 113 healthy controls (HC; 47 males, 66 females, age (57.8±10.7) years) who received gated myocardial perfusion imaging (GMPI) in First Hospital of Shanxi Medical University from January 2016 to September 2020. SI (end-diastolic SI (EDSI), end-systolic SI (ESSI)), EI and left ventricular function parameters (end-diastolic volume (EDV), end-systolic volume (ESV), left ventricular ejection fraction (LVEF), summed motion score (SMS), summed thickening score (STS), peak ejection rate (PER) and peak filling rate (PFR)) were obtained by quantitative gated SPECT (QGS) software. Propensity score (PS) inverse probability of treatment weighting (IPTW) was used to balance the intergroup covariates. The differences and correlations of EDSI, ESSI, EI and left ventricular function parameters between patients in MI group and HC group were analyzed. ROC curve analysis was used to evaluate the values of EDV, EDSI, ESSI and EI alone and in combination in the assessment of left ventricular systolic function impairment. Data were analyzed by independent-sample t test, Pearson correlation and Spearman rank correlation analyses, and Delong test. Results:After IPTW, EDSI and ESSI in MI group ( n=319) were higher than those in HC group ( n=133; EDSI: 0.66±0.09 vs 0.60±0.06; ESSI: 0.59±0.11 vs 0.47±0.07; t values: 8.05, 14.67, both P<0.001), and EI was lower than that in HC group (0.81±0.06 vs 0.85±0.03; t=-8.93, P<0.001). In both groups, there were significant correlations between EDSI and ESSI ( r values: 0.928, 0.873), between EDSI, ESSI and EI ( r values: from -0.831 to -0.641), between EDSI, ESSI and LVEF ( r values: from -0.627 to -0.201), between ESSI and EDV, ESV and SMS ( rs values: 0.336-0.584), between ESSI and -PER, PFR ( rs values: from -0.406 to -0.402, r values: from -0.352 to -0.325) (all P<0.01). ROC curve analysis showed that EDV (AUC: 0.895) and ESSI (AUC: 0.839) had the highest efficacy in evaluating left ventricular systolic function impairment in MI group and HC group, respectively. EDV-EDSI-ESSI-(1-EI) had higher efficacy in the assessment of impaired left ventricular systolic function in MI group (AUC: 0.956), which was higher than that of EDV or EDV-EDSI or EDV-ESSI or EDV-(1-EI) ( z values: from -2.64 to -2.18, P values: 0.008-0.029); EDV-EDSI-ESSI-(1-EI) also had high efficacy in HC group (AUC: 0.911), which was higher than that of EDV or EDV-EDSI or EDV-(1-EI) ( z values: from -2.60 to -2.43, P values: 0.009-0.015). Conclusions:In MI patients, the increase of SI and the decrease of EI indicate the increase of left ventricular sphericity and the aggravation of left ventricular remodeling. SI and EI have certain clinical application values in evaluating left ventricular morphology, predicting left ventricular remodeling and left ventricular systolic function impairment.

Objective:To investigate whether patients with pulmonary hypertension (PH) develop abnormal fibroblast activation protein (FAP) inhibitor (FAPI) uptake in the left ventricular free wall and to analyze its characteristics and significance.Methods:Al 18F-1, 4, 7-triazacyclononane-1, 4, 7-triacetic acid (NOTA)-FAPI-04 PET/CT images of 51 patients diagnosed with PH (24 males, 27 females; age: (48±21) years) and 10 healthy volunteers (4 males, 6 females; age: (59±12) years) from Beijing Chaoyang Hospital of Capital Medical University between February 2021 and January 2024 were retrospectively analyzed. Higher FAPI uptake in the left ventricular free wall than that in blood pool was defined as abnormal and SUV max, SUV mean, and total lesion FAP activity were quantitatively measured. Associated factors with FAPI uptake in the left ventricle were analyzed, and differences of clinical parameters between patients with and without abnormal left ventricular uptake were compared. Independent-sample t test and Mann-Whitney U test were used to compare differences between groups. Spearman rank correlation analysis was used for correlation analysis. Results:Abnormal FAPI uptake that was diffusely distributed in the left ventricular free wall was observed in 19 patients with PH. Total lesion FAP activity was positively correlated with peak mitral late-diastolic inflow velocity ( A) ( rs=0.696, P=0.001) and negatively correlated with peak mitral early-diastolic inflow velocity ( E)/ A and pulmonary vascular resistance (PVR) ( rs values: -0.629, -0.540, P values: 0.004, 0.017). Significant differences in E/ A (0.8(0.6, 1.1) vs 0.9(0.8, 1.4); z=-2.33, P=0.020), left ventricular end-systolic internal diameter ((25.7±2.6) vs (27.8±4.2) mm; t=-2.22, P=0.031), and left ventricular end-systolic volume ((26.7±7.3) vs (32.5±9.9) ml; t=-2.26, P=0.028) were found between patients with and without abnormal FAPI uptake in the left ventricle. Conclusion:In patients with PH, the left ventricular free wall develops diffuse abnormal uptake of FAPI, the extent of which is related to impaired left ventricular diastolic function.

Objective:To evaluate the efficacy of balloon pulmonary angioplasty (BPA) in chronic thromboembolic pulmonary hypertension (CTEPH) using 99Tc m-macroaggregated albumin (MAA) pulmonary perfusion tomography imaging. Methods:Twenty-five patients (4 males, 21 females; age (56.5±12.3) years) with CTEPH who underwent BPA from January 2017 to April 2020 in Beijing Chaoyang Hospital, Capital Medical University were enrolled retrospectively. Effect of BPA on the improvement of pulmonary lobe/pulmonary segment perfusion was analyzed, and the proportions of improved and unimproved pulmonary lobe/pulmonary segment perfusion by BPA were calculated. The percentages of perfusion defect scores (PPDs%) of lung perfusion tomography imaging before BPA and after 4-6 times BPA were compared and analyzed (paired t test). The correlations between PPDs% and mean pulmonary artery pressure (mPAP) before BPA and after BPA were analyzed respectively, and the correlation between decreased percentage of PPDs% and decreased percentage of mPAP after BPA were also analyzed (Pearson correlation analysis). Results:Among 150 lobes of 25 patients, 96.00%(144/150) lobes showed perfusion abnormalities before BPA. After BPA, 11.11%(16/144) showed complete improvement, 57.64%(83/144) showed partial improvement, and 31.25%(45/144) showed no improvement. Among 450 pulmonary segments of 25 patients, 62.44%(281/450) showed perfusion abnormalities before BPA. After BPA, 30.60%(86/281), 37.37%(105/281), 32.03%(90/281) showed complete, partial and no improvement, respectively. The post-BPA PPDs% was significantly lower than that of pre-BPA ((39.08±10.88)% vs (57.88±10.46)%; t=10.40, P<0.001). The post-BPA mPAP was significantly lower than that of pre-BPA ((32.36±10.57) vs (49.08±10.23) mmHg; 1 mmHg=0.133 kPa; t=10.25, P<0.001). There was no significant correlation between PPDs% and mPAP either before BPA ( r=0.01, P=0.953) or after BPA ( r=0.27, P=0.199), but there was a positive correlation between the changes of PPDs% and mPAP ( r=0.40, P=0.045). Conclusions:BPA can significantly improve the pulmonary perfusion and reduce mPAP in CTEPH patients. Pulmonary perfusion tomography imaging can be used to evaluate the efficacy of BPA in CTEPH.

Objective:To explore suitable strategies for atrial 18F-FDG PET/CT imaging and analyze the characteristics of abnormal atrial uptake in patients with atrial fibrillation(AF). Methods:From August 2017 to August 2018, 69 AF patients (43 males, 26 females, age (64±11) years) in Beijing Chaoyang Hospital were prospectively enrolled and underwent dual-phase 18F-FDG PET/CT imaging (60 and 120 min postinjection). Additionally, 10 healthy controls (3 males, 7 females, age (66±4) years) were prospectively enrolled and underwent 18F-FDG PET/CT imaging (60 min postinjection). A comprehensive strategy recommended by the Society of Nuclear Medicine and Molecular Imaging/American Society of Nuclear Cardiology/Society of Cardiovascular Computed Tomography (SNMMI/ASNC/SCCT) guideline was followed to suppress myocardial uptake. Image analysis: (1) 18F-FDG uptake of left ventricle was qualitatively analyzed and classified into 3 levels: grade 0, the activity of blood pool exceeded or was equal to myocardial activity; grade 1, myocardial activity was mildly higher than blood pool activity; grade 2, myocardial activity was obviously higher than blood pool activity. 18F-FDG uptake in the left atrium(LA), left atrial appendage (LAA) and right atrium (RA) higher than that in blood pool were defined as abnormal. Paired χ2 test was used to compare the rates of abnormal uptake in atrial structures between two phases. (2) Quantitative analysis: 18F-FDG uptake in all atrial structures were quantitatively analyzed by measuring SUV max, and left atrial cavity and right atrial cavity were quantitatively analyzed by measuring SUV mean. The target to background ratio (TBR) was calculated. Differences of TBR between two phases were analyzed by Wilcoxon signed rank test. Differences of 18F-FDG uptake in atrial structures between patients with AF and healthy controls were analyzed by Mann-Whitney U test and χ2 test. Results:Most subjects (84.8%, 67/79) achieved sufficient myocardial suppression. In one patient, the interpretation of LAA was affected by left ventricle uptake. The incidence of abnormal uptake of LA, LAA and RA in delayed phase were higher than those in early phase, but only the difference of LAA was significantly different (27.9%(19/68) vs 42.6%(29/68); χ2=8.10, P=0.020). TBR of LA, LAA and RA in delayed phase were all significantly higher than those in early phase (LA: 1.1 (1.0, 1.3) vs 1.1 (1.0, 1.2); LAA: 1.2 (1.0, 1.5) vs 1.0 (0.9, 1.2); RA: 1.4 (1.1, 1.9) vs 1.3 (1.0, 1.5); z values: from -6.81 to -3.42, all P<0.05). There were 87.0%(60/69) of AF patients with abnormal atrial FDG accumulation, which was significantly higher than that of the control group (0/10; χ2=31.50, P<0.001). In LAA and RA, the incidences of abnormal accumulation were significantly higher in AF than those in the control group (LAA: 30.4%(21/69) vs 0 (0/10); χ2=4.10, P=0.042; RA: 53.6%(37/69) and 0 (0/10); χ2=8.00, P=0.001). Conclusions:Using the method recommended by the SNMMI/ASNC/SCCT guideline to suppress the physiological uptake of the left ventricle and appropriately extending the interval is conducive to observing the abnormal 18F-FDG uptake in the atrium. The uptake of 18F-FDG in the atrium of patients with AF is increased.