Delayed Enhancement Magnetic Resonance Imaging Research Articles

Selective infarct zone imaging with intravenous acoustically activated droplets.

BackgroundMicrobubbles (MB) can be compressed to nanometer-sized droplets and reactivated with diagnostic ultrasound; these reactivated MB possess unique imaging characteristics.ObjectiveWe hypothesized that droplets formed from compressing Definity MB may be used for infarct-enhancement imaging.MethodsFourteen rats underwent ligation of their left anterior descending (LAD) artery, and five pigs underwent 90 minute balloon occlusions of their mid LAD. At 48 hours in rats, transthoracic ultrasound was performed at two and four minutes following 200 μL intravenous injections (IVI) of Definity droplets (DD), at which point the MI was increased from 0.5 to 1.5 to assess for a transient contrast enhancement zone (TEZ) within akinetic segments. In pigs, 1.0 mL injections of DD were administered and low frame rate (triggered end systolic or 10 Hz) imaging 2–4 minutes post iVI to selectively activate and image the infarct zone (IZ). Infarct size was defined by delayed enhancement magnetic resonance imaging (DE-MRI) and post-mortem staining (TTC).ResultsIncreasing MI to 1.5 (at two or four minutes after IVI) resulted in a TEZ in rats, which correlated with infarct size (r = 0.94, p<0.001). A TEZ was not seen at 2–4 minutes in any rat (n = 8) following Definity MB injections. Fluorescent staining confirmed DD presence within the infarct zone 10 minutes after intravenous injection. In pigs, selective enhancement within the IZ was achieved by using a low frame rate single pulse harmonic mode; IZ size matched the location seen with DE-MRI and correlated with TTC defect size (r = 0.90, p<0.05).ConclusionDD formulated from commercially available MB can be acoustically activated for selective infarct enhancement imaging.

Ablation of persistent atrial fibrillation and beyond.

Percutaneous catheter ablation is an effective treatment for atrial fibrillation. However, catheter ablation for the treatment of persistent atrial fibrillation or long-standing persistent atrial fibrillation is associated with unsatisfying success rates. This review aims to summarize the recent literature on the progress of catheter ablation among patients with persistent atrial fibrillation RECENT FINDINGS: In this review, we outline the potential future therapeutic techniques of catheter ablation of persistent atrial fibrillation. We highlight the innovative techniques (rotor mapping, substrate mapping, delayed enhancement MRI, and high-resolution mapping catheter) of current approaches and optimal procedural endpoint for persistent atrial fibrillation. In summary, the optimal catheter ablation strategy for persistent atrial fibrillation remains unknown. Current data highlight the need for a better understanding of the substrate and mechanisms of arrhythmia maintenance in this population. Current mapping technologies offer additional tools (improved automatic algorithm for annotation, multiple electrode mapping, high-resolution mapping, and application of different processing techniques) for identifying the putative mechanism underlying atrial fibrillation. Further prospective studies are needed for the optimal procedural endpoint and the recent innovative techniques and their clinical benefits in ablation strategies.

Diffuse myocardial fibrosis in adolescents operated with arterial switch for transposition of the great arteries - A CMR study

Diffuse myocardial fibrosis in adolescents operated with arterial switch for transposition of the great arteries - A CMR study

Manganese-Enhanced T1 Mapping in the Myocardium of Normal and Infarcted Hearts.

Background Manganese-enhanced MRI (MEMRI) has the potential to identify viable myocardium and quantify calcium influx and handling. Two distinct manganese contrast media have been developed for clinical application, mangafodipir and EVP1001-1, employing different strategies to mitigate against adverse effects resulting from calcium-channel agonism. Mangafodipir delivers manganese ions as a chelate, and EVP1001-1 coadministers calcium gluconate. Using myocardial T1 mapping, we aimed to explore chelated and nonchelated manganese contrast agents, their mechanism of myocardial uptake, and their application to infarcted hearts. Methods T1 mapping was performed in healthy adult male Sprague-Dawley rats using a 7T MRI scanner before and after nonchelated (EVP1001-1 or MnCl2 (22 μmol/kg)) or chelated (mangafodipir (22–44 μmol/kg)) manganese-based contrast media in the presence of calcium channel blockade (diltiazem (100–200 μmol/kg/min)) or sodium chloride (0.9%). A second cohort of rats underwent surgery to induce anterior myocardial infarction by permanent coronary artery ligation or sham surgery. Infarcted rats were imaged with standard gadolinium delayed enhancement MRI (DEMRI) with inversion recovery techniques (DEMRI inversion recovery) as well as DEMRI T1 mapping. A subsequent MEMRI scan was performed 48 h later using either nonchelated or chelated manganese and T1 mapping. Finally, animals were culled at 12 weeks, and infarct size was quantified histologically with Masson's trichrome (MTC). Results Both manganese agents induced concentration-dependent shortening of myocardial T1 values. This was greatest with nonchelated manganese, and could be inhibited by 30–43% with calcium-channel blockade. Manganese imaging successfully delineated the area of myocardial infarction. Indeed, irrespective of the manganese agent, there was good agreement between infarct size on MEMRI T1 mapping and histology (bias 1.4%, 95% CI −14.8 to 17.1 P>0.05). In contrast, DEMRI inversion recovery overestimated infarct size (bias 11.4%, 95% CI −9.1 to 31.8 P=0.002), as did DEMRI T1 mapping (bias 8.2%, 95% CI −10.7 to 27.2 P=0.008). Increased manganese uptake was also observed in the remote myocardium, with remote myocardial ∆T1 inversely correlating with left ventricular ejection fraction after myocardial infarction (r=−0.61, P=0.022). Conclusions MEMRI causes concentration and calcium channel-dependent myocardial T1 shortening. MEMRI with T1 mapping provides an accurate assessment of infarct size and can also identify changes in calcium handling in the remote myocardium. This technique has potential applications for the assessment of myocardial viability, remodelling, and regeneration.

Evaluation of myocardial viability in myocardial infarction patients by magnetic resonance perfusion and delayed enhancement imaging.

Cardiovascular magnetic resonance imaging (CMR) has been established as amodality to detect myocardial viability. The aim of this study was to evaluate myocardial viability by observing transmural extent of infraction and microvascular perfusion level. We performed CMR in 30myocardial infarction (MI) patients within 7-10days. At the 6‑month follow-up, CMR was used to evaluate the impact of abnormal reperfusion and observe the transmural extent of infraction on recovery of function. The left ventricle was divided into 16segments using the American Heart Association classification. Infarcts were detected in 202 of the 480 segments (42%) by delayed enhancement magnetic resonance imaging (DE-MRI). According to first-pass myocardial perfusion, abnormal perfusion was detected in 278 of 480 segments (60%), reduced perfusion was identified in 173 of 278 (62%), and perfusion defects in 105 of 278 segments (38%). The results showed that the segments with abnormal perfusion were larger than in DE-MRI (P < 0.05), indicating that the area of abnormal perfusion segments extend significantly beyond the region of infarction. Microvascular perfusion with an infarcted region was lower compared to non-infarcted segments (P < 0.05). The extent of myocardial hyperenhancement correlated inversely with microvascular perfusion (P < 0.05). Segments with severe microvascular perfusion and >75% transmural infarction on the 7‑ to 10-day scan had markedly increased at the 6‑month follow-up (P < 0.01), indicating alack of recovery of cardiac function. DE-MRI combined with microvascular perfusion may be effective to detect viable myocardium in patients with MI and may provide ameans of predicting whether revascularization will be effective.

Myocardium segmentation from DE MRI with guided random walks and sparse shape representation.

For patients with myocardial infarction (MI), delayed enhancement (DE) cardiovascular magnetic resonance imaging (MRI) is a sensitive and well-validated technique for the detection and visualization of MI. The myocardium viability assessment with DE MRI is important in diagnosis and treatment management, where myocardium segmentation is a prerequisite. However, few academic works have focused on automated myocardium segmentation from DE images. In this study, we aim to develop an automatic myocardium segmentation algorithm that targets DE images. We propose a segmentation framework based on both prior shape knowledge and image intensity. Instead of the strong request of the pre-segmentation of cine MRI in the same session, we use the sparse representation method to model the myocardium shape. Data from the Cardiac MR Left Ventricle Segmentation Challenge (2009) are used to build the shape template repository. The method of guided random walks is used to integrate the shape model and intensity information. An iterative approach is used to gradually improve the results. The proposed method was tested on the DE MRI data from 30 MI patients. The proposed method achieved Dice similarity coefficients (DSC) of 74.60 ± 7.79% with 201 shape templates and 73.56 ± 6.32% with 56 shape templates, which were close to the inter-observer difference (73.94 ± 5.12%). To test the generalization of the proposed method to routine clinical images, the DE images of 10 successive new patients were collected, which were unseen during the method development and parameter tuning, and a DSC of 76.02 ± 7.43% was achieved. The authors propose a novel approach for the segmentation of myocardium from DE MRI by using the sparse representation-based shape model and guided random walks. The sparse representation method effectively models the prior shape with a small number of shape templates, and the proposed method has the potential to achieve clinically relevant results.

Delayed Enhancement Cardiac MRI In Ischemic and Non-Ischemic Heart Failure

Background: In patients with left ventricular systolic dysfunction, the primary diagnostic issue is to differentiate the underlying cause whether related to coronary artery disease or dilated cardiomyopathy, for which coronary angiography was often used. Aim of the Work: Using Delayed enhancement-magnetic resonance imaging (DE-MRI) to identify myocardial tissue characteristics through retention of gadolinium in areas with reduced density of viable myocytes so appear enhancing (bright). So, we can differentiate dilated from ischemic cardiomyopathy. Patient and Method: Our study included 34 patients with left ventricular systolic dysfunction (ejection fraction less than 40% by echocardiography). All of them were submitted to DE-MRI using achieva 1.5 Tesla MRI machine. Results: 15 patients (44%) showed infarct pattern of DE (presumed ischemic cardiomyopathy) while 19 patients (56%) showed no DE or non-infarct pattern of DE (presumed dilated cardiomyopathy). Conclusion: DE-MRI could be considered as an effective non-invasive tool to differentiate ischemic from non-ischemic cardiomyopathy.

Model-Based Feature Augmentation for Cardiac Ablation Target Learning From Images.

We present a model-based feature augmentation scheme to improve the performance of a learning algorithm for the detection of cardiac radio-frequency ablation (RFA) targets with respect to learning from images alone. Initially, we compute image features from delayed-enhanced magnetic resonance imaging (DE-MRI) to describe local tissue heterogeneities and feed them into a machine learning framework with uncertainty assessment for the identification of potential ablation targets. Next, we introduce the use of a patient-specific image-based model derived from DE-MRI coupled with the Mitchell-Schaeffer electrophysiology model and a dipole formulation for the simulation of intracardiac electrograms. Relevant features are extracted from these simulated signals which serve as a feature augmentation scheme for the learning algorithm. We assess the classifier's performance when using only image features and with model-based feature augmentation. We obtained average classification scores of 97.2 % accuracy, 82.4 % sensitivity, and 95.0 % positive predictive value by using a model-based feature augmentation scheme. Preliminary results also show that training the algorithm on the closest patient from the database, instead of using all the patients, improves the classification results. We presented a feature augmentation scheme based on biophysical cardiac electrophysiology modeling to increase the prediction scores of a machine learning framework for the RFA target prediction. The results derived from this study are a proof of concept that the use of model-based feature augmentation strengthens the performance of a purely image driven learning scheme for the prediction of cardiac ablation targets.

Role of Cardiac Magnetic Resonance Imaging in the Assessment of Myocardial Viability in Patients with Coronary Artery Disease

AbstractBackground: The principal goal of the assessment of myocardial viability is to identify patients whose symptoms, exercise capacity, and long-term prognosis may improve after revascularization. Contrast enhanced cardiac MRI has devel-oped as a promising imaging modality for the assessment of myocardial viability which provides direct imaging of necrotic tissue with high contrast and high spatial resolution. Aim of the work was to assess role of cardiac MRI as a non-invasive tool in the evaluation of myocardial viability in patients with coronary artery disease.Aim of Study: To assess the role of cardiac MRI as a non-invasive tool in the evaluation of myocardial viability in patients with coronary artery disease.Material and Methods: The study included 25 patients diagnosed as having Coronary Artery Disease (CAD), (age range, 28-68 years ±11.29). All selected patients were subjected to cardiac MRI examination using 1.5-T MR system for studying myocardial function and viability. Comparison was made between echocardiography and cardiac MRI regarding segmental wall motion using the 17-segment model of the American Heart Association for assessment of myocardial function. Delayed-enhancement MRI was performed to deter-mine myocardial viability and scarring while black blood T2W sequence with fat suppression was done to detect cases with acute infarction. Microvascular occlusion was diagnosed using early Gadolinium enhancement sequence.Results: Good agreement between cardiac MRI and echocardiography regarding segmental wall motion with p-value of 0.065. Sensitivity and specificity of cardiac MRI for detecting SWMA were 93.6%, and 44.4% respectively. Myo-cardial viability was evaluated by cardiac MRI with the use of end-diastolic wall thickness, imaging of early and late enhancement after contrast administration. Late gadolinium enhancement allowed assessing state of myocardium and visualizing myocardial scar with its quantification. Two segments showed 1-25% transmural extent of myocardial wall infarction, while 120 segments showed 71-100% extent and 261 segments showed no enhancing scar.Conclusion: Cardiac MR imaging is an effective and reliable method for the evaluation of myocardial function as compared to echocardiography. Also it is effective and reliable method for the evaluation of myocardial viability being able to assess both the infarct size and trans-murality and accord-ingly helps to predict functional recovery after revasculariza-tion.

Relationship Between Ventricular Arrhythmias, Conduction Disorders, and Myocardial Fibrosis in Patients With Systemic Sclerosis.

Delayed-enhancement magnetic resonance imaging (DE-MRI) is a noninvasive diagnostic tool able to identify myocardial fibrosis. In patients with scleroderma, its relationship with arrhythmias and conduction disorders has not been fully explored. The aim of this study was to evaluate the possible correlations between ventricular arrhythmias, conduction disorders, and myocardial fibrosis in patients with systemic sclerosis. Thirty-six patients with diffuse or limited cutaneous scleroderma underwent 12-lead electrocardiogram (ECG), 24-hour Holter ECG monitoring, transthoracic echocardiography, and cardiac DE-MRI, with gadolinium administration in 33 patients. High-quality DE-MRI scans were obtained in 30 patients. Myocardial fibrosis was detected in 25 patients (83.3%). Eighteen patients (60%) had ventricular arrhythmias or conduction disorders. There was no significant difference in ventricular arrhythmia burden (the total number of premature ventricular contractions [PVCs]/24 hours) (48 ± 304 vs. 69 ± 236, P = 0.97), ventricular arrhythmia severity (couplets, triplets, runs) on Holter ECG, or in the presence of conduction disorders (36% vs. 40%, P = 0.86) between patients with and without myocardial fibrosis. In univariate analysis, diffuse fibrosis was weakly associated with the number of PVCs/24 hours (R = 0.157, P = 0.03). A number of at least 597 PVCs/24 hours had a sensitivity of 60% and a specificity of 92% in predicting the presence of diffuse fibrosis on DE-MRI (area under the curve = 0.640). Delayed-enhancement magnetic resonance imaging can identify myocardial fibrosis in a high percentage of scleroderma patients. Its presence does not seem to influence the ventricular arrhythmia burden and severity or the presence of conduction disorders, with the exception of diffuse myocardial fibrosis, which modestly influences the total number of PVCs/24 hours.

Mechanisms of Atrial Fibrillation and Their Impact on Strategies for Catheter Ablation

Atrial fibrillation (AF) is the most common sustained arrhythmia, and is ubiquitous in clinical practice. The underlying mechanisms of initiation and maintenance of AF are complex and not completely understood. This knowledge, however, is fundamental for the development of treatment strategies for AF. Within the last 20 years, catheter ablation has played an increasing role as a rhythm control therapy. Based on diverse models for the initiation and maintenance of AF, various ablation strategies have been proposed. The cornerstone of AF ablation has been pulmonary vein isolation (PVI). In persistent AF, however, PVI alone is often not sufficient. This may be because of the structural remodelling of the atria leading to dilation and fibrosis amongst other factors. The optimal strategy for substrate modification, however, is still a matter of investigation. Current studies are concentrating on the ablation of fibrotic areas, especially in the left atrium, either detected by delayed enhancement magnetic resonance imaging or by identification of low-voltage areas as a surrogate marker. The second intensely evaluated strategy is the localisation and ablation of rotational activity. Many further randomised controlled trials will likely be needed to determine the optimal ablation strategy for individual patients.

Imaging-derived Biomarkers Associated with Atrial FIBROsis, Structural Remodeling and the Risk of Cardioembolic Events in Patients with Atrial Fibrillation – the FIBROS Study

Abstract Recent studies demonstrated that despite restoration of the sinus rhythm, patients with a positive history of atrial fibrillation (AF) are still at risk of thromboembolic events. The primary objective of this study is to identify new imaging-derived biomarkers provided by modern imaging technologies, such as cardiac computed tomography angiography, delayed enhancement magnetic resonance imaging, or speckle tracking echocardiography, as well as hematological biomarkers, associated with the risk of intracavitary thrombosis in patients with AF, in order to identify the imaging-derived characteristics associated with an increased risk of cardioembolic events. Imaging data collected will be post-processed using advanced techniques of computational modeling, in order to fully characterize the degree of structural remodeling and the amount of atrial fibrosis. The primary endpoint of the study is represented by the rate of thromboembolic events. The rate of cardiovascular death, the rate of major adverse cardiovascular events, and the rate of AF recurrence will also be determined in relation to the degree of structural remodeling and atrial fibrosis.

Myocardium Segmentation From DE MRI Using Multicomponent Gaussian Mixture Model and Coupled Level Set.

Objective: In this paper, we propose a fully automatic framework for myocardium segmentation of delayed-enhancement (DE) MRI images without relying on prior patient-specific information. Methods: We employ a multicomponent Gaussian mixture model to deal with the intensity heterogeneity of myocardium caused by the infarcts. To differentiate the myocardium from other tissues with similar intensities, while at the same time maintain spatial continuity, we introduce a coupled level set (CLS) to regularize the posterior probability. The CLS, as a spatial regularization, can be adapted to the image characteristics dynamically. We also introduce an image intensity gradient based term into the CLS, adding an extra force to the posterior probability based framework, to improve the accuracy of myocardium boundary delineation. The prebuilt atlases are propagated to the target image to initialize the framework. Results: The proposed method was tested on datasets of 22 clinical cases, and achieved Dice similarity coefficients of 87.43 ± 5.62% (endocardium), 90.53 ± 3.20% (epicardium) and 73.58 ± 5.58% (myocardium), which have outperformed three variants of the classic segmentation methods. Conclusion: The results can provide a benchmark for the myocardial segmentation in the literature. Significance: DE MRI provides an important tool to assess the viability of myocardium. The accurate segmentation of myocardium, which is a prerequisite for further quantitative analysis of myocardial infarction (MI) region, can provide important support for the diagnosis and treatment management for MI patients.Objective: In this paper, we propose a fully automatic framework for myocardium segmentation of delayed-enhancement (DE) MRI images without relying on prior patient-specific information. Methods: We employ a multicomponent Gaussian mixture model to deal with the intensity heterogeneity of myocardium caused by the infarcts. To differentiate the myocardium from other tissues with similar intensities, while at the same time maintain spatial continuity, we introduce a coupled level set (CLS) to regularize the posterior probability. The CLS, as a spatial regularization, can be adapted to the image characteristics dynamically. We also introduce an image intensity gradient based term into the CLS, adding an extra force to the posterior probability based framework, to improve the accuracy of myocardium boundary delineation. The prebuilt atlases are propagated to the target image to initialize the framework. Results: The proposed method was tested on datasets of 22 clinical cases, and achieved Dice similarity coefficients of 87.43 ± 5.62% (endocardium), 90.53 ± 3.20% (epicardium) and 73.58 ± 5.58% (myocardium), which have outperformed three variants of the classic segmentation methods. Conclusion: The results can provide a benchmark for the myocardial segmentation in the literature. Significance: DE MRI provides an important tool to assess the viability of myocardium. The accurate segmentation of myocardium, which is a prerequisite for further quantitative analysis of myocardial infarction (MI) region, can provide important support for the diagnosis and treatment management for MI patients.

GW28-e0555 Telmisartan in the diabetic murine model of acute myocardial infarction evaluated by dual contrast manganese-enhanced and delayed enhancement MRI

GW28-e0555 Telmisartan in the diabetic murine model of acute myocardial infarction evaluated by dual contrast manganese-enhanced and delayed enhancement MRI

Ablation of long-standing persistent atrial fibrillation.

Atrial fibrillation (AF) is the most commonly encountered arrhythmia in the clinical setting affecting nearly 6 million people in United States and the numbers are only expected to rise as the population continues to age. Broadly it is classified into paroxysmal, persistent and longstanding persistent AF. Electrical, structural and autonomic remodeling are some of the diverse pathophysiological mechanisms that contribute to the persistence of AF. Our review article emphasizes particularly on long standing persistent atrial fibrillation (LSPAF) aspect of the disease which poses a great challenge for electrophysiologists. While pulmonary vein isolation (PVI) has been established as a successful ablation strategy for paroxysmal AF, same cannot be said for LSPAF owing to its long duration, complexity of mechanisms, multiple triggers and substrate sites that are responsible for its perpetuation. The article explains different approaches currently being adopted to achieve freedom from atrial arrhythmias. These mainly include ablation techniques chiefly targeting complex fractionated atrial electrograms (CFAE), rotors, linear lesions, scars and even considering hybrid approaches in a few cases while exploring the role of delayed enhancement magnetic resonance imaging (deMRI) in the pre-procedural planning to improve the overall short and long term outcomes of catheter ablation.

Assessment of Left Atrial Fibrosis by LateGadolinium Enhancement Magnetic Resonance Imaging: Methodology and Clinical Implications.

Recently, studies using late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) to identify structural changes of atrial tissue have contributed significantly to understanding the pathophysiology and progression of atrial fibrillation (AF). Moreover, imaging of atrial fibrosis using MRI has evolved to be a tool to improve clinical outcome of AF ablation procedures by allowing a patient-specific individualized management approach. LGE-MRI has been shown to predict AF ablation outcome based on pre-procedural imaging to define the extent of atrial fibrosis. The results of the ongoing DECAAF II (Delayed-Enhancement MRI Determinant of Successful Radiofrequency Catheter Ablation of Atrial Fibrillation) trial might extend ablation strategies from pulmonary vein isolation alone to a substrate-based approach. Furthermore, an improved understanding of the underlying mechanisms of atrial structural remodeling is crucial in order to reduce the occurrence of AF-associated complications (e.g., ischemic stroke and heart failure). This review article provides current methodology of atrial fibrosis imaging using LGE-MRI and delineates actual clinical implications and future directions for this imaging approach.

Association of left atrial low-voltage area and thromboembolic risk in patients with atrial fibrillation.

Atrial fibrillation (AF) is associated with thromboembolic events. Currently, the CHA2DS2-VASc score is recommended for thromboembolic risk stratification in non-valvular AF patients. However, recent data suggested a potential role of atrial remodelling on thromboembolism. This study aimed to assess the association between left atrial low-voltage area (LVA) and history of clinical manifest as well as subclinical silent cerebral ischaemia (SCI) in AF patients. Two-hundred patients [64 ± 10.5 years, 75 women (37.5%)] with symptomatic paroxysmal (n = 88, 44%) or persistent AF undergoing pulmonary vein isolation (PVI) were prospectively enrolled. Left atrial LVA (bipolar voltage < 0.5mV) was evaluated by intra-procedural mapping (>300 points per patient) during sinus rhythm. Cerebral delayed-enhancement magnetic resonance imaging was performed after PVI for detection of pre-existing procedural-independent SCI. Over all, 17 patients (8.5%) had previous history of stroke. Pre-existing SCIs were detected in 135 patients (67.5%). Patients with previous stroke (4.0 ± 1.5 vs. 2.1 ± 1.3, P < 0.0001) and pre-existing SCI (2.7 ± 1.3 vs. 1.5 ± 1.4, P < 0.0001) had a significantly higher CHA2DS2-VASc score. LVA was significantly larger in patients with previous stroke (12.5 ± 8.5% vs. 3.4 ± 5.4%, P < 0.0001) as well as pre-existing SCI (5.8 ± 6.9% vs. 0.8 ± 1.7%, P < 0.0001). Multivariate regression analysis revealed that LVA was independently associated with the presence of SCI [hazard ratio (HR) per 1% LVA 1.13 (1.06-1.22), P = 0.0003] and history of stroke [HR per 1% LVA 1.36 (1.19-1.60), P < 0.0001] after adjustment of CHA2DS2-VASc score. Left atrial LVA is associated with history of stroke and SCI in patients with non-valvular AF and might improve thromboembolic risk stratification after confirmation of its predictive value in future studies.

Abstract 8: Effectiveness of Combination Allogeneic Stem Cells in a Novel Large Animal Model of Chronic Kidney Disease-induced Heart Failure With Preserved Ejection Fraction (HFpEF)

Background: Chronic Kidney Disease (CKD) is an independent risk factor for cardiovascular morbidity and mortality. Left ventricular (LV) hypertrophy and heart failure with preserved ejection fraction (HFpEF) are the primary manifestations of the cardiorenal syndrome in 60 to 80% of CKD patients. Therapies that improve morbidity and mortality in HFpEF are lacking. Stem cell therapy reduces fibrosis, increases neovascularization, and promotes cardiac repair in ischemic and non-ischemic cardiomyopathies. We hypothesized that stem cell treatment ameliorates HFpEF in a CKD model. Methods: Yorkshires pigs (n=27) underwent 5/6 nephrectomy via renal artery embolization and 4-weeks later received either: allogeneic (allo-) MSC (10х10 6 ), allo-kidney c-kit + cells (c-kit; 10х10 6 ), combination (MSC+c-kit; 1:1 ratio [5х10 6 each]), or placebo (each n=5). Cell therapy was delivered via the patent renal artery. Kidney function, renal and cardiac MRI, and PV loops were measured at baseline, and at 4- and 12-weeks (euthanasia) post-embolization. Results: The CKD model was confirmed by increased creatinine and BUN and decreased GFR. Mean arterial pressure (MAP) was not different between groups from baseline to 4 weeks (p=0.7). HFpEF was demonstrated at 4 weeks by increased LV mass (20.3%; p= 0.0001), wall thickening (p&lt;0.008), EDP (p=0.01), EDPVR (p=0.005), and arterial elastance (p=0.03), with no change in EF. Diffuse intramyocardial fibrosis was evident in histological analysis and delayed enhancement MRI imaging. After 12 weeks, there was a significant difference in MAP between groups (p=0.04), with an increase in the placebo group (19.97± 8.65 mmHg, p=0.08). GFR significantly improved in the combination group (p=0.033). EDV increased in the placebo (p=0.009) and c-kit (p=0.004) groups. ESV increased most in the placebo group (7.14±1.62ml; p=0.022). EF, wall thickness, and LV mass did not differ between groups at 12 weeks. Conclusion: A CKD large animal model manifests the characteristics of HFpEF. Intra-renal artery allogeneic cell therapy was safe. A beneficial effect of cell therapy was observed in the combination and MSC groups. These findings have important implications on the use of cell therapy for HFpEF and cardiorenal syndrome.

Segmentation Integrating Watershed and Shape Priors Applied to Cardiac Delayed Enhancement MR Images

Background: In recent years, there has been a rapid rise in the use of shape priors applied to segmentation process of medical images. Previous approaches on left ventricle segmentation from Delayed-Enhancement Magnetic Resonance Imaging (DE-MRI) have focused on the extraction of myocardium or just diseased region in short axis orientation. However these studies did not take into account the segmentation of non-diseased myocardium from DE-MRI. The segmentation of non-diseased myocardium from DE-MRI, has some useful applications. For instance it can simplify the PET-MR registration process.Methods: This paper presents a novel semi-automatic segmentation method of non-diseased myocardium contours from DE-MRI based on watershed algorithm with shape priors application. The segmentation process was performed on long and short axis DE-MR images, acquired from patients with different cardiac diseases.Results: Segmented images were compared with gold standard contours performed by an experienced user. To assess our results the Dice Coefficient (DC) and Root Mean Square Distance (RMSD) were computed. The best value of these parameters was obtained for four cavity images (RMSD = 1.68 ± 0.47 mm, DC = 0.78), and the computed value for two cavity images (RMSD = 1.93 ± 0.38 mm, DC = 0.73) and short axis images (RMSD = 1.89 ± 0.47 mm, DC = 0.71) were slightly lower.Conclusion: In conclusion, we have proposed a novel solution for non-diseased myocardium segmentation from DE-MRI, which brought very promising results.

Myocardial delayed-enhancement CT: initial experience in children and young adults.

Clinical utility of myocardial delayed enhancement CT has not been reported in children and young adults. To describe initial experience of myocardial delayed enhancement CT regarding image quality, radiation dose and identification of myocardial lesions in children and young adults. Between August 2013 and November 2016, 29 consecutive children and young adults (median age 16months) with suspected coronary artery or myocardial abnormality underwent arterial- and delayed-phase cardiac CT at our institution. We measured CT densities in normal myocardium, left ventricular cavity, and arterial and delayed hypo-enhancing and delayed hyperenhancing myocardial lesions. We then compared the extent of delayed hyperenhancing lesions with delayed-enhancement MRI or thallium single-photon emission CT. Normal myocardium and left ventricular cavity showed significantly higher CT numbers on arterial-phase CT than on delayed-phase CT (t-test, P<0.0001). Contrast-to-noise ratios of the arterial and delayed hypo-enhancing and delayed hyperenhancing lesions on CT were 26.7, 17.6 and 18.7, respectively. Delayed-phase CT findings were equivalent to those of delayed-enhancement MRI in all cases (7/7) and to those of thallium single-photon emission CT in 70% (7/10). Myocardial delayed-enhancement CT can be added to evaluate myocardial lesions in select children and young adults with suspected coronary artery or myocardial abnormality.