Minjie Lu

Magnetic Resonance Imaging with Superparamagnetic Iron Oxide Fails to Track the Long-term Fate of Mesenchymal Stem Cells Transplanted into Heart

MRI for in vivo stem cell tracking remains controversial. Here we tested the hypothesis that MRI can track the long-term fate of the superparamagnetic iron oxide (SPIO) nanoparticles labelled mesenchymal stem cells (MSCs) following intramyocardially injection in AMI rats. MSCs (1 × 106) from male rats doubly labeled with SPIO and DAPI were injected 2 weeks after myocardial infarction. The control group received cell-free media injection. In vivo serial MRI was performed at 24 hours before cell delivery (baseline), 3 days, 1, 2, and 4 weeks after cell delivery, respectively. Serial follow-up MRI demonstrated large persistent intramyocardial signal-voids representing SPIO during the follow-up of 4 weeks, and MSCs did not moderate the left ventricular dysfunction. The TUNEL analysis confirmed that MSCs engrafted underwent apoptosis. The histopathological studies revealed that the site of cell injection was infiltrated by inflammatory cells progressively and the iron-positive cells were macrophages identified by CD68 staining, but very few or no DAPI-positive stem cells at 4 weeks after cells transplantation. The presence of engrafted cells was confirmed by real-time PCR, which showed that the amount of Y-chromosome-specific SRY gene was consistent with the results. MRI may not reliably track the long-term fate of SPIO-labeled MSCs engraftment in heart.

Comparison of cardiac magnetic resonance imaging features of isolated left ventricular non-compaction in adults versus dilated cardiomyopathy in adults

AIM To compare cardiac magnetic resonance imaging (MRI) features between isolated left ventricular non-compaction (IVNC) and dilated cardiomyopathy (DCM) in adults. MATERIALS AND METHODS A consecutive series of 50 patients with IVNC from a single institution were reviewed. During the same period, 50 patients with DCM who had prominent trabeculations, who were matched for age, gender, and body surface area, were prospectively included. Left ventricular (LV) morphology and function were assessed using cardiac MRI. RESULTS Compared with patients with DCM, patients with IVNC had a significantly lower LV sphericity index and end-diastolic volume index (LVEDVI) and a greater LV ejection fraction (LVEF), number of trabeculated segments, and ratio of non-compacted to compacted myocardium (NC/C ratio). There were no significant differences in stroke volume index, cardiac output, and cardiac index between the two patient groups. In patients with IVNC, the number of trabeculated segments and the NC/C ratio correlated positively with LVEDVI (r=0.626 and r=0.559, respectively) and negatively with LVEF (r=-0.647 and r=-0.521, respectively, p<0.001 for all). In patients with DCM, the number of non-compacted segments and the NC/C ratio had no correlation with either the LVEDVI (r=-0.082 and r=-0.135, respectively) or the LVEF (r=0.097 and r=0.205, respectively). CONCLUSION There are demonstrable morphological and functional differences between IVNC and DCM at LV assessment using cardiac MRI. The occurrence of trabeculated myocardium might be due to a different pathophysiological mechanism.

Myocardial extracellular volume fraction quantified by cardiovascular magnetic resonance is increased in hypertension and associated with left ventricular remodeling

ObjectivesTo determine whether extracellular volume fraction (ECV) quantification by cardiac magnetic resonance (CMR) can demonstrate left ventricle (LV) abnormalities and relationship between ECV and LV remodeling in hypertension (HTN) patientsMethodsECV quantification was prospectively performed in 134 consecutive HTN patients and 97 healthy subjects. Individual and regional ECV were compared to the regions on late gadolinium enhancement (LGE) images. Statistical analysis of the relationship between LV global functional parameters and ECV was carried out using Pearson’s correlation, Student’s t test and multiple regressions.ResultsIn the HTN group, 70.1% (94/134) were LGE negative and 29.9% (40/134) LGE positive. The mean ECV after adjusting for age, sex, BMI, diabetes, smoking and dyslipidaemia in healthy controls and LGE-negative patients were 26.9 ± 2.67% and 28.5 ± 2.9% (p < 0.001), respectively. The differences in ECV reached statistical significance among the regions of LGE, LGE-Peri, LGE remote and the normal area between the control and LGE-positive subgroup (all p < 0.05). Global ECV significantly correlated with LVEF (r = −0.466, p < 0 .001) and LV hypertrophy (r = 0.667, p < 0.001).ConclusionsECV can identify LV abnormalities at an early stage in HTN patients without LGE. These abnormalities may reflect an increase in diffuse myocardial fibrosis and are associated with LV remodeling.Key points• Diffuse myocardial fibrosis may develop in hypertensive cardiomyopathy before conventional MRI detectable LGE.• ECV can identify myocardial fibrosis at an early stage in hypertensive patients.• Elevated ECV is associated with decreased LV global function and LV remodeling in hypertension.

Detection of Recent Myocardial Infarction Using Native T1 Mapping in a Swine Model: A Validation Study

Late gadolinium enhancement (LGE) imaging is the currently the gold standard for in-vivo detection of myocardial infarction. However, gadolinium contrast administration is contraindicated in patients with renal insufficiency. We aim to evaluate the diagnostic sensitivity and specificity of this contrast-free MRI technique, native T1 mapping, in detecting recent myocardial infarction versus a reference histological gold standard. Ten pigs underwent CMR at 2 weeks after induced MI. The infarct size and transmural extent of MI was calculated using native T1 maps and LGE images. Histological validation was performed using triphenyl tetrazolium chloride (TTC) staining in the corresponding ex-vivo slices. The infarct size and transmural extent of myocardial infarction assessed by T1 mapping correlated well with that assessed by LGE and TTC images. Using TTC staining as the reference, T1 mapping demonstrated underestimation of infarct size and transmural extent of infarction. Additionally, there was a slight but not significant difference found in the diagnostic performance between the native T1 maps and LGE images for the location of MI. Our study shows that native T1 mapping is feasible alternative method to the LGE technique for the assessment of the size, transmural extent, and location of MI in patients who cannot receive gadolinium contrast.

Dynamic stress computed tomography myocardial perfusion for detecting myocardial ischemia: A systematic review and meta-analysis

BACKGROUND Comparing to SPECT and MRI, with higher temporal and spatial resolution and development of radiation dose reduction, myocardial computed tomography perfusion has emerged as a potential method for evaluation of hemodynamic myocardial ischemia. This meta-analysis systematically analyzed the performance of dynamic CT myocardial perfusion (DCTMP) to diagnose myocardial ischemia (MI) with clinically established reference methods [MR/SPECT/PET perfusion and fractional flow reserve (FFR)] as the reference standard. METHODS We searched PubMed, Embase and web of science databases for all published studies that evaluated the accuracy of DCTMP to diagnose MI met our inclusion criteria. An exact binomial rendition of the bivariate mixed-effects regression model with test type as a random-effects covariate was performed to synthesize the available data. RESULTS The search revealed 13 eligible studies including 482 patients. The pooled sensitivity and specificity of myocardial blood flow (MBF) were 0.83 (95% CI: 0.80 to 0.86) and 0.90 (95% CI: 0.88 to 0.91) at the segment level, 0.85 (95% CI: 0.80 to 0.88) and 0.81 (95% CI: 0.78 to 0.84) at the artery level, and 0.93 (95% CI: 0.82 to 0.98) and 0.82 (95% CI: 0.70 to 0.91), at the patient level, respectively. The high area under the sROC curves of MBF were 0.944 at segment level, 0.911 at vessel level and 0.949 at patient level, respectively. CONCLUSIONS DCTMP has a high diagnostic accuracy in detecting myocardial ischemia and it may increase significantly at segment level in combined use of coronary CTA.