Late Gadolinium Enhancement MRI Research Articles

Late iodine enhancement cardiac computed tomography for detection of myocardial scars: impact of experience in the clinical practice.

Cardiac CT with late iodine enhancement (LIE-CT) may characterize the scarred myocardium, but the role of readers' experience and scar pattern on LIE-CT diagnostic performance is unknown. Aim was to assess the diagnostic performance of LIE-CT according to readers' experience, scar pattern and contrast-to-noise ratio (CNR) using late gadolinium enhancement MRI (LGE-MRI) as reference. LIE-CT and LGE-MRI images of 40 consecutive patients were analyzed. Two readers with different experience (8 and 2years) independently analyzed LIE-CT images defining the presence/absence of scar and scar CNR, segmental involvement, transmural pattern and scar etiology. The same parameters were extracted from LGE-MRI by two expert readers in consensus, blinded to the LIE-CT results. Scars were identified at LGE-MRI in 29/40 patients and 141/680 segments. Scar burden at LIE-CT versus LGE-MRI correlated better for the most experienced reader than for the least experienced one (ρ = 0.954 and ρ = 0.797, p < 0.001). The most experienced reader missed scars in 2 patients and in 21/141 segments; the least experienced in 5 patients and 53/141 segments. The most experienced reader showed higher accuracy and sensitivity compared to the least experienced in per-patient (accuracy: 95% vs. 88%; sensitivity: 93% vs. 83%) and per-segment analysis (accuracy: 96% vs. 92%; sensitivity: 85% vs. 62%). Specificity was excellent (100% per-patient, 99% per-segment,) regardless of readers' experience. Missed scars had non-ischemic pattern, low scar burden (< 6%) and lower CNR compared to ischemic scars (2.33 vs. 3.54, p = 0.005). LIE-CT represents an alternative to LGE-MRI, although the impact of readers' experience on sensitivity for small non-ischemic scars should be considered.

The Effective Contact Force to Minimize Edema Relative to Chronic Lesion Formation During Radiofrequency Ablation in Ventricular Wall.

Radiofrequency (RF) ablation results in creation of acute edema which can lead to temporary disruption of electrical propagation.The goal of this study was to find the effective contact force (CF) to minimize edema formation in comparison to the lesion size.Ventricular RF lesions (n = 49) were created by a CF-sensing catheter in a canine model (n = 10) with varying force for 30 seconds. Animals underwent T2-weighted (T2w) and late gadolinium enhancement MRI (LGE-MRI) immediately after ablation and at 12 weeks. Acute LGE lesion volume, acute edema, and chronic LGE lesion volume were measured. Acute edema/acute LGE lesion volume ratio was used to divide the lesions into two groups.Mean edema/lesion volume ratio was 5.0 ± 2.8. The lesions were divided into greater edema group (n = 8) and smaller edema group (n = 41) based on a cutoff edema/lesion volume ratio. When comparing the two groups, the CF and force time integral (FTI) were significantly lower in the greater edema group. There was no difference in catheter power setting, tip temperature change, impedance drop, and bipolar electrogram voltage change. Acute LGE volume and chronic lesion depth were significantly smaller in the greater edema group. Moreover, receiver-operator characteristic curve for the smaller edema lesion group showed that the most discriminant cutoff values for CF and FTI were 12.4 g and 584 gs, respectively.To minimize edema size while still forming permanent lesions, ablation should be performed with FTI > 584 gs or CF > 12.4 g.

Three-dimensional Deep Convolutional Neural Networks for Automated Myocardial Scar Quantification in Hypertrophic Cardiomyopathy: A Multicenter Multivendor Study.

Background Cardiac MRI late gadolinium enhancement (LGE) scar volume is an important marker for outcome prediction in patients with hypertrophic cardiomyopathy (HCM); however, its clinical application is hindered by a lack of measurement standardization. Purpose To develop and evaluate a three-dimensional (3D) convolutional neural network (CNN)-based method for automated LGE scar quantification in patients with HCM. Materials and Methods We retrospectively identified LGE MRI data in a multicenter (n = 7) and multivendor (n = 3) HCM study obtained between November 2001 and November 2011. A deep 3D CNN based on U-Net architecture was used for LGE scar quantification. Independent CNN training and testing data sets were maintained with a 4:1 ratio. Stacks of short-axis MRI slices were split into overlapping substacks that were segmented and then merged into one volume. The 3D CNN per-site and per-vendor performances were evaluated with respect to manual scar quantification performed in a core laboratory setting using Dice similarity coefficient (DSC), Pearson correlation, and Bland-Altman analyses. Furthermore, the performance of 3D CNN was compared with that of two-dimensional (2D) CNN. Results This study included 1073 patients with HCM (733 men; mean age, 49 years ± 17 [standard deviation]). The 3D CNN-based quantification was fast (0.15 second per image) and demonstrated excellent correlation with manual scar volume quantification (r = 0.88, P < .001) and ratio of scar volume to total left ventricle myocardial volume (%LGE) (r = 0.91, P < .001). The 3D CNN-based quantification strongly correlated with manual quantification of scar volume (r = 0.82-0.99, P < .001) and %LGE (r = 0.90-0.97, P < .001) for all sites and vendors. The 3D CNN identified patients with a large scar burden (>15%) with 98% accuracy (202 of 207) (95% confidence interval [CI]: 95%, 99%). When compared with 3D CNN, 2D CNN underestimated scar volume (r = 0.85, P < .001) and %LGE (r = 0.83, P < .001). The DSC of 3D CNN segmentation was comparable among different vendors (P = .07) and higher than that of 2D CNN (DSC, 0.54 ± 0.26 vs 0.48 ± 0.29; P = .02). Conclusion In the hypertrophic cardiomyopathy population, a three-dimensional convolutional neural network enables fast and accurate quantification of myocardial scar volume, outperforms a two-dimensional convolutional neural network, and demonstrates comparable performance across different vendors. © RSNA, 2019 Online supplemental material is available for this article.

P2272Determinants of left ventricular ATP availability measured in vivo and ex vivo in patients with severe aortic stenosis: correlation of creatine kinase activity with LVEF and ATP diffusion distance

Abstract Introduction The transition to systolic failure in severe aortic stenosis (AS) increases mortality. There are currently no reliable markers of transition, and the guideline LVEF &lt;50% threshold for intervention in asymptomatic severe AS does not capture all subjects at increased risk. In animal models, reduced ATP delivery capacity through creatine kinase (CK) is important, with modest increases in CK capacity conferring cardioprotection. ATP may also diffuse (independent of CK) from mitochondria to the contractile site. We have performed the first human study to test whether ATP diffusion distance relates to CK activity and whether CK activity is reduced in low LVEF severe AS. Methods 19 patients with severe AS, LVEF ≥55% (AS-pEF, mean±SD LVEF 63±5%, mean gradient 48±14 mmHg) and 10 with severe AS, LVEF &lt;55% (AS-rEF, LVEF 42±8%, mean gradient 32±11) underwent 31P-MRS for CK rate constant (kf) and phosphocreatine/ATP (PCr/ATP) ratio, and MRI for LV volumes. LV biopsies were taken during AVR and analysed for CK total activity, CK isoforms, total creatine, and citrate synthase (CS) activity. 9 biopsies also underwent serial block face scanning electron microscopy and mitochondria-sarcomere 3D distance distributions were plotted. Results were compared to 24 controls (LVEF 61±4%), of which 4 had LV biopsy (3 severe MS, 1 LA myxoma, MS-pEF). Surgical patients had flow-limiting atheroma excluded with invasive angiography and prior myocardial infarction excluded with late gadolinium enhancement MRI. Results When compared to controls, both CK total activity and CS activity were lower in AS-pEF (by 27% and 23% respectively, both p&lt;0.05, Panels A-B). Although PCr/ATP reduced in AS-pEF (by 20%, p&lt;0.001, panel C), kf (panel D) and CK flux estimated by kf × total creatine were not different. CK-MB expression reduced in AS-pEF (19 vs 27% of total CK, p=0.003), reflecting compensatory increases in CK-MM (p=0.26) and CK-BB (p=0.18) in the face of reduced CK activity. AS-rEF was associated with further reduction in both CK and CS activities (by 32% and 22% respectively, both p&lt;0.05, Panels A-B), but no differences in PCr/ATP, CK kf or relative CK isozyme expression were seen. There were no significant between-group differences in total creatine (Panel E). Overall this suggests that CK reserve and oxidative capacity potentially reduce in pressure overload, with further falls commensurate with systolic dysfunction. When median mitochondria-sarcomere ATP diffusion distances were plotted against CK total activity a strong positive correlation was observed (r=0.86, p=0.003, Panel F). This suggests a compensatory reduction in diffusion distance develops when CK activity falls. Conclusions Transition to failure in severe AS is associated with lower oxidative capacity and maximal ATP delivery capacity through CK. Despite compensatory falls in ATP diffusion distance and altered CK isozyme expression, these changes may underlie susceptibility to EF decline in AS. Acknowledgement/Funding British Heart Foundation Clinical Research Training Fellowship (FS/15/80/31803) and Programme Grant (RG/18/12/34040).

P1808Routine screening practices for cardiac involvement in patients with sarcoidosis

Abstract Introduction Sarcoidosis is a multi-systemic granulomatous disease of unknown etiology. Cardiac sarcoidosis (CS) has proven to be a clinically significant cause of unexplained ventricular dysfunction, atrioventricular block (AVB) and ventricular tachyarrhythmias (VT). Studies have suggested that clinically manifest cardiac involvement occurs in only 5% of patients with sarcoidosis. However, recent imaging studies have shown that cardiac involvement can be observed in up to 54.9% of patients with extracardiac sarcoidosis, mostly clinically silent, but that can eventually manifest into life-threatening arrhythmias. Purpose The purpose of this study was to evaluate the routine use of cardiac testing in patients with sarcoidosis. We aimed to evaluate the frequency with which clinical evaluation and cardiac testing are routinely utilized, the results of these tests, and how these results impacted downstream management. Methods This study was carried out in a tertiary hospital, assessing referred patients with suspected cardiac sarcoidosis. Clinically manifest CS was defined as the presence of ventricular systolic dysfunction, AVB or sustained VT. The cardiac involvement was evaluated with Late gadolinium-enhanced MRI and PET-CT with FDG. The diagnosis of cardiac sarcoidosis was performed using the criteria of the HRS. All patients had a biopsy with a histopathology suggestive of Sarcoidosis. Results Forty-one patients with sarcoidosis were evaluated. CS was confirmed in 46% (N=19), with exclusive cardiac involvement in 10% (N=2). The mean age was 53±9.6 years old and 53% (N=10) were female. Clinically manifest CS was present in 63% (N=12). The most prevalent initial cardiac manifestation was left ventricular dysfunction, in 58% (N=7), usually in the silent form (71%), with VT in 25% (N=3) and AVB in 17% (N=2). All patients with cardiac silent form had PET-CT with FDG or MRI suggestive of CS. The sensitivity of the MRI and PET-CT with FDG was 75% and 82%, respectively, while the concomitant performance of the two methods had a sensitivity of 100%, considering the HRS criteria as gold standard. Conclusion Cardiac involvement in patients with sarcoidosis is high and has important prognostic implications. With the enhancement of imaging tests, diagnosis of CS has significantly increased. PET-CT with FDG and MRI are very useful and effective in the evaluation of patients with CS.

Cardiac MRI and Fibrosis Quantification.

Left atrial fibrosis plays an important role in the pathophysiology of atrial fibrillation. Left atrial ablation is an effective and increasingly used strategy to restore and maintain sinus rhythm in patients with atrial fibrillation. Late gadolinium enhancement (LGE) MRI and custom image analysis software have been used to visualize and quantify preablation atrial fibrosis and postablation scar and new fibrosis formation. This article reviews technical aspects of imaging atrial fibrosis/scar by LGE-MRI; use of atrial fibrosis and scar in predicting outcomes; applications of LGE-MRI to assess ablation lesions and optimize ablation parameters while avoiding collateral damage.

Value of myocardial scar in predicting malignant ventricular arrhythmia in patients with chronic myocardial infarction

To assess the predictive value of myocardial scar mass in malignant ventricular arrhythmia (MVA) after myocardial infarction. Thirty myocardial infarction patients with complete electrophysiology and cardiac MRI data admitted from January 2012 to August 2017 were enrolled in the study. According to the results of intracavitary electrophysiological study, MVA developed in 16 patients (MVA group) and not developed in 14 patients (non-MVA group). The qualitative and quantitative analysis of left ventricular ejection fraction (LVFE) and scar mass was performed with CVI42 post-processing software and predictive value of myocardial scar and LVEF for MVA after myocardial infarction was analyzed using ROC curves. LVEF in MVA group was significantly lower than that in non-MVA group, and scar mass in MVA group was significantly higher than that in non-MVA group (all P<0.05). Regression analysis showed that LVEF (OR=1.580) and scar mass (OR=6.270) were risk factors for MVA after myocardial infarction. For predicting MVA, the area under ROC curve (AUC) of LVEF was 0.696 with a sensitivity of 0.786 and the specificity of 0.685; the AUC of the scar mass was 0.839 with a sensitivity was 0.618 and the specificity of 0.929; the AUC of LVEF combined with scar mass was 0.848 with a sensitivity of 0.688 and specificity of 0.857. Myocardial scar assessed by late gadolinium enhancement MRI is more effective than LVEF in predicting MVA after myocardial infarction.

Left Atrial Fibrosis Assessed with Cardiac MRI in Patients with Paroxysmal and Those with Persistent Atrial Fibrillation.

Background Electrophysiology studies have demonstrated that left atrial late gadolinium enhancement (LGE) is associated with the chronicity of atrial fibrillation (AF). To date, cardiac MRI has been used to assess the extent of atrial LGE but not the distribution pattern of LGE in the left atrium. Purpose To determine whether the MRI pattern of left atrial fibrosis is associated with the chronicity of AF. Materials and Methods This retrospective study included patients with AF who underwent LGE MRI between June 2017 and May 2018. The presence of left atrial LGE was assessed at nine left atrial segments; the extent was determined by the number of segments involved. According to the chronicity of AF, patients were separated into paroxysmal AF (PAF) and persistent AF (PeAF) groups. The location and extent of left atrial LGE were compared between PAF and PeAF by using the χ2 test and logistic regression analysis. Results Of the 195 patients (mean age, 55 years ± 10 [standard deviation], 161 men), 74 (38%) had PAF and 121 (62%) had PeAF. Of all patients, 114 (58.4%) had at least one left atrial LGE segment. The mean number of LGE segments was higher (1.4 ± 1.1 vs 0.6 ± 0.7, P = .002) in the PeAF group than in the PAF group. The incidence of LGE at the left inferior pulmonary vein (LIPV) antrum was higher in the PeAF group than in the PAF group (39.2% [29 of 74] vs 7.4% [nine of 121]; P < .001). In multivariable analysis, LGE at the LIPV antrum was independently associated with PeAF (odds ratio = 4.2; 95% confidence interval: 1.7, 10.5; P < .001). Conclusion The presence of fibrosis assessed with late gadolinium enhancement MRI of the left inferior pulmonary vein antrum was associated with persistent atrial fibrillation. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Almeida in this issue.

Metal Artifact Reduction in Cardiovascular MRI for Accurate Myocardial Scar Assessment in Patients With Cardiac Implantable Electronic Devices.

OBJECTIVE. An important application of late gadolinium enhancement (LGE) cardiac MRI is accurate assessment of myocardial scar before ablation. However, this is often limited in patients with cardiac implantable electronic devices (CIEDs) because of metal device-induced artifacts. The purpose of this study was to determine whether a modified wideband inversion recovery (IR) LGE MRI technique decreases artifact volume to allow the assessment of myocardial scar. SUBJECTS AND METHODS. Fifty patients (17 women and 33 men; mean age ± SD, 61 ± 12 years; mean ejection fraction ± SD, 35.9% ± 13.3%) with CIEDs underwent cardiac MRI using conventional and modified wideband IR LGE techniques before ablation. The volume of device-induced artifact was quantified and stratified by tertiles on mild, moderate, and severe. Ordinal logistic regression analysis assessed the association between artifact volume on conventional and wideband images adjusted for patients' demographics. RESULTS. Conventional LGE MRI resulted in device-induced hyperintense artifacts that obscured ventricular segments in 32 of 50 (64%) cases. Wideband LGE MRI significantly reduced severe artifact volume (p < 0.0001) and completely resolved all mild and most moderate artifacts. Overall, wideband techniques resulted in a 56% reduction in total artifact volume for the cohort (p < 0.0001). The wideband LGE MRI sequence minimized artifacts in the most commonly obscured segments on the conventional LGE MRI sequence, with persistent artifacts in seven, eight, and four of 32 cases at the basal anterior, midventricular anterior, and midventricular anteroseptal segments, respectively. CONCLUSION. The modified wideband IR technique completely resolves mild and moderate device-induced hyperintense artifacts and significantly reduces the volume of severe artifact to allow accurate identification of myocardial scar in patients with CIEDs before ablation.

Atrial Fibrosis: Translational Considerations for the Management of AF Patients.

Fibrosis plays a fundamental role in the initiation and maintenance of AF, mainly due to enhanced automaticity and anisotropy-related re-entry. The identification and quantification of atrial fibrosis is achieved either preprocedurally by late gadolinium enhancement MRI or intraprocedurally using electroanatomic voltage mapping. The presence and extent of left atrial fibrosis among AF patients may influence relevant decision making regarding the need for anticoagulation, the adoption of rate versus rhythm control and mainly the type of ablation strategy that will be followed during interventional treatment. Several types of individualised substrate modifications targeting atrial fibrotic areas have been proposed, although their impact on patient outcome needs to be further investigated in adequately powered prospective randomised controlled clinical trials.

Prognostic value of new imaging parameters in patients with hypertrophic cardiomyopathy: A prospective study

Hypertrophic cardiomyopathy (HCM) is a frequent hereditary cardiac disease and a major cause of sudden cardiac death (SCD). Although very useful, ESC risk score's predictive value has been interrogated since it was retrospective and did not include MRI parameters and new echocardiographic markers. To assess the additional value of new echocardiographic and MRI parameters in predicting SCD and outcome in patients with HCM. Between 2007 and 2017, 307 patients with HCM were prospectively included and followed for 1.63 years. In addition to conventional prognostic factors, all patients underwent cardiac MRI evaluation of late gadolinium enhancement (LGE), and echocardiographic measurements of LV and LA volumes and strains, including left atrial peak longitudinal strain (PALS) and left atrial peak contraction strain (PACS). Primary end-point was SCD or appropriate defibrillator therapy. Secondary end-point was a composite end-point including death, hospitalization for heart failure, new-onset of atrial fibrillation, need for septal ablation, myomectomy, or heart transplantation. Among the 307 patients, 6 patients (2%) died and the secondary end-point occurred in 65 (21%). Factors associated with SCD by univariate analysis were low LVEF [HR 0.91 (0.93–0.99)] impaired PALS [HR 0.86 (0.72–0.97)], and moderate mitral regurgitation (MR). Factors associated with the secondary end-point were impaired LV GLS [HR 1.23 (1.13; 1.35)], impaired LA 4-chamber PALS [HR 0.94 (0.91; 0.97)] and PACS [HR 0.91 (0.86; 95)], LA 2 chamber PALS [HR 0.93 (0.89; 0.96)] and PACS [HR 0.86 (0.83;0. 94)], as well as TTE and MRI MR, and presence of MRI LGE. Impaired LA 4-chamber PALS remained as an independent predictor for the composite end-point [HR 0.92 (0.87; 0.97)] after adjustment. This study suggests an additive prognostic value of an impaired LV and LA TTE strain, the presence of MR, and MRI LGE, to the classical ESC 7 recommended risk factors.

Virtual electrophysiological study as a tool for evaluating efficacy of MRI techniques in predicting adverse arrhythmic events in ischemic patients

Myocardial infarct (MI) related indices determined by late gadolinium enhancement (LGE) MRI have been widely investigated in determining patients suitable for implantable cardiovascular-defibrillator (ICD) therapy to complement left ventricular ejection fraction (LV EF). In comparison to LGE-MRI using inversion-recovery fast-gradient-echo (IR-FGRE), T1 mapping techniques, such as multi contrast late enhancement (MCLE), have been shown to provide more quantitative and reproducible estimates of infarct regions. The objective of this study is to use individualized heart computer models in determining the efficacy of IR-FGRE and MCLE techniques in predicting the occurrence of post-MI ventricular tachycardia (VT). Twenty-seven patients with MI underwent LGE-MRI using IR-FGRE and MCLE prior to ICD implantation and were followed up for 6–46 months. Individualized image-based computational models were built separately for each imaging technique; simulations of propensity to VT were conducted with each model. The imaging methods were evaluated by comparing simulated inducibility of VT to clinical outcome (appropriate ICD therapy) in patients. Twelve patients had at least one appropriate ICD therapy for VT at follow-up. For both MCLE and IR-FGRE, the outcomes of the simulations of VT were significantly associated with the events of appropriate ICD therapy. This indicates that, as compared to conventional measurements such as LV EF, the simulations of VT corresponding to both MCLE and IR-FGRE were more sensitive in predicting appropriate ICD therapy in post-MI patients.

Cardiac Dual-Energy CT with Late Iodine Enhancement as an Alternative to Late Gadolinium Enhancement MRI

Cardiac Dual-Energy CT with Late Iodine Enhancement as an Alternative to Late Gadolinium Enhancement MRI

Multiview Sequential Learning and Dilated Residual Learning for a Fully Automatic Delineation of the Left Atrium and Pulmonary Veins from Late Gadolinium-Enhanced Cardiac MRI Images.

Accurate delineation of heart substructures is a prerequisite for abnormality detection, for making quantitative and functional measurements, and for computer-aided diagnosis and treatment planning. Late Gadolinium-Enhanced Cardiac MRI (LGE-CMRI) is an emerging imaging technology for myocardial infarction or scar detection based on the differences in the volume of residual gadolinium distribution between scar and healthy tissues. While LGE-CMRI is a well-established non-invasive tool for detecting myocardial scar tissues in the ventricles, its application to left atrium (LA) imaging is more challenging due to its very thin wall of the LA and poor quality images, which may be produced because of motion artefacts and low signal-to-noise ratio. As the LGE-CMRI scan is designed to highlight scar tissues by altering the gadolinium kinetics, the anatomy among different heart substructures has less distinguishable boundaries. An accurate, robust and reproducible method for LA segmentation is highly in demand because it can not only provide valuable information of the heart function but also be helpful for the further delineation of scar tissue and measuring the scar percentage. In this study, we proposed a novel deep learning framework working on LGE-CMRI images directly by combining sequential learning and dilated residual learning to delineate LA and pulmonary veins fully automatically. The achieved results showed accurate segmentation results compared to the state-of-the-art methods. The proposed framework leads to an automatic generation of a patient-specific model that can potentially enable an objective atrial scarring assessment for the atrial fibrillation patients.

Image Data Analysis for Quantifying Scar Transmurality in MRI phantoms for Cardiac Resynchronisation Therapy.

The use of implantable cardiac devices has increased in the last 30 years. Cardiac resynchronisation therapy (CRT) is a procedure which involves implanting a coin sized pacemaker for reversing heart failure. The pacemaker electrode leads are implanted into cardiac myocardial tissue. The optimal site for implantation is highly patient-specific. Most implanters use empirical placement of the lead. One region identified to have a poor response rate are myocardial tissue with transmural scar. Studies that precisely measure transmurality of scar tissue in the left ventricle (LV) are few. Most studies lack proper validation of their transmurality measurement technique. This study presents an image analysis technique for computing scar transmurality from late-gadolinium enhancement MRI. The technique is validated using phantoms under a CRT image guidance system. The study concludes that scar transmurality can be accurately measured in certain situations and validation with phantoms is important.

Improved Diagnosis of Detection of Late Enhancement in Left Ventricular Myocardium Using 2nd Generation 320-Slice CT Reconstructed with FIRST in Non-Ischemic Cardiomyopathy.

Forward Projected Model-based Iterative Reconstruction SoluTion (FIRST) is a new reconstruction technique using CT, which provides successful reconstruction of high-quality CT images, especially in low contrast imaging. To evaluate improvements in the diagnostic accuracy of the detection of abnormal late enhancement (LE) in left-ventricular myocardium (LVM) using 320-slice CT with FIRST, we compared this modality with previous CT methods in patients with non-ischemic cardiomyopathy or a cardiac tumor.This was a retrospective study of 88 patients (56 males; 57 ± 15 years) suspected of having non-ischemic myocardial disease or a cardiac tumor. The first 52 consecutive patients (Group 1) underwent 16-slice CT at 140 kV tube voltage and an average tube current of 337 ± 20 mA, and 1.5 T MRI. The next 18 patients (Group 2) underwent 1st generation 320-slice CT at 120 kV tube voltage and an average tube current of 255 ± 106 mA, and 1.5T MRI; the remaining 18 patients (Group 3) underwent 2nd generation 320-slice CT with FIRST, at 80 kV tube voltage and a tube current of 800 mA, and 1.5T or 3T MRI.On patient-based analysis, no significant differences were observed between the 3 groups. For segment-based analysis, the specificity and overall accuracy were significantly higher (both P < 0.05) in Group 3 than in Group 1. Positive predictive value (PPV) was significantly higher in Group 3 than in Groups 1 and 2.The diagnostic accuracy of LE on CT for detecting myocardial fibrosis determined by late gadolinium-enhanced MRI was improved with the use of 2nd generation 320-slice CT with FIRST, in particular regarding specificity, PPV, and overall accuracy.

Motion-corrected whole-heart PET-MR for the simultaneous visualisation of coronary artery integrity and myocardial viability: an initial clinical validation

PurposeCardiac PET-MR has shown potential for the comprehensive assessment of coronary heart disease. However, image degradation due to physiological motion remains a challenge that could hinder the adoption of this technology in clinical practice. The purpose of this study was to validate a recently proposed respiratory motion-corrected PET-MR framework for the simultaneous visualisation of myocardial viability (18F-FDG PET) and coronary artery anatomy (coronary MR angiography, CMRA) in patients with chronic total occlusion (CTO).MethodsA cohort of 14 patients was scanned with the proposed PET-CMRA framework. PET and CMRA images were reconstructed with and without the proposed motion correction approach for comparison purposes. Metrics of image quality including visible vessel length and sharpness were obtained for CMRA for both the right and left anterior descending coronary arteries (RCA, LAD), and relative increase in 18F-FDG PET signal after motion correction for standard 17-segment polar maps was computed. Resulting coronary anatomy by CMRA and myocardial integrity by PET were visually compared against X-ray angiography and conventional Late Gadolinium Enhancement (LGE) MRI, respectively.ResultsMotion correction increased CMRA visible vessel length by 49.9% and 32.6% (RCA, LAD) and vessel sharpness by 12.3% and 18.9% (RCA, LAD) on average compared to uncorrected images. Coronary lumen delineation on motion-corrected CMRA images was in good agreement with X-ray angiography findings. For PET, motion correction resulted in an average 8% increase in 18F-FDG signal in the inferior and inferolateral segments of the myocardial wall. An improved delineation of myocardial viability defects and reduced noise in the 18F-FDG PET images was observed, improving correspondence to subendocardial LGE-MRI findings compared to uncorrected images.ConclusionThe feasibility of the PET-CMRA framework for simultaneous cardiac PET-MR imaging in a short and predictable scan time (~11 min) has been demonstrated in 14 patients with CTO. Motion correction increased visible length and sharpness of the coronary arteries by CMRA, and improved delineation of the myocardium by 18F-FDG PET, resulting in good agreement with X-ray angiography and LGE-MRI.

The assessment of the left atrial myocardial fibrosis of atrial fibrillation with late Gadolinium enhancement MRI

Objective To investigate the clinical value of 2 dimension late Gadolinium enhancement MRI (LGE-MRI) technique for the evaluation of atrial myocardial fibrosis in patients with atrial fibrillation. Methods Forty-nine cases of atrial fibrillation in our hospital from March 2015 to December 2016 were retrospectively collected. The LGE-MR was acquired by the Siemens 3.0 T MR machine before the catheter ablation. The findings of LGE-MR were evaluated by two experienced doctors. The left atrium (LA) were manually segmented into 8 regions in axial view. All patients were classified into 4 stages based on the extent of enhancement, stage 0: absence of enhancement, stage Ⅰ: enhancement appeared in minimal two consecutive slices in single region, stage Ⅱ: enhancement in two regions, stage Ⅲ: enhancement in three or more regions. All electroanatomic maps were obtained after electrical conversion during catheter ablation. The Kappa test was used to assess the consistency of LGE-MRI left atrial myocardial fibrosis and CARTO system of the left atrial endocardial voltage reconstruction. Results Forty-nine cases of atrial fibrillation with LGE-MRI and CARTO were included. There were 17 cases of atrial fibrosis stage 0, 10 cases of stage Ⅰ, 11 cases of stage Ⅱ, 11 cases of stage Ⅲ according to LGE-MRI findings;There were 17 cases of atrial fibrosis stage 0, 19 cases of stage Ⅰ, 12 cases of stage Ⅱ, 11 cases of stage Ⅲ with reference to CARTO findings. The diagnostic accuracy of the LGE-MRI atrial fibrosis was 81.6% (40/49), of which the correlation was good (Kappa= 0.751, P<0.001). Conclusions LGE-MRI can accurately assess the degree of left atrial myocardial fibrosis in patients with atrial fibrillation, help to select the proper candidate and strategy in catheter ablation. Key words: Atrial fibrillation; Magnetic resonance imaging; Comparative study

Single-Dose Gadoterate Meglumine for 3T Late Gadolinium Enhancement MRI for the Assessment of Chronic Myocardial Infarction: Intra-Individual Comparison with Conventional Double-Dose 1.5T MRI.

ObjectiveTo intra-individually compare 3T magnetic resonance (MR) images obtained with one dose gadoterate meglumine to 1.5T MR using conventional double dose for assessment of chronic myocardial infarction.Materials and MethodsSixteen patients diagnosed with chronic myocardial infarctions were examined on single-dose 3T MR within two weeks after undergoing double-dose 1.5T MR. Representative short-axis images were acquired at three points after administration of gadoterate meglumine. Contrast-to-noise ratios between infarcted and normal myocardium (CNRinfarct-normal) and between infarct and left ventricular cavity (CNRinfarct-LVC) were calculated and compared intra-individually at each temporal scan. Additionally, two independent readers assessed relative infarct size semi-automatically and inter-observer reproducibility was evaluated using intraclass correlation coefficient.ResultsWhile higher CNRinfarct-normal was revealed at single-dose 3T at only 10 minutes scan (p = 0.047), the CNRinfarct-LVC was higher at single-dose 3T MR at each temporal scan (all, p < 0.05). Measurement of relative infarct size was not significantly different between both examinations for both observers (all, p > 0.05). However, inter-observer reproducibility was higher at single-dose 3T MR (all, p < 0.05).ConclusionSingle-dose 3T MR is as effective as double-dose 1.5T MR for delineation of infarcted myocardium while being superior in detection of infarcted myocardium from the blood cavity, and provides better reproducibility for infarct size quantification.

Termination of re-entrant atrial tachycardia via optogenetic stimulation with optimized spatial targeting: insights from computational models.

Optogenetics has emerged as a potential alternative to electrotherapy for treating heart rhythm disorders, but its applicability for terminating atrial arrhythmias remains largely unexplored. We used computational models reconstructed from clinical MRI scans of fibrotic patient atria to explore the feasibility of optogenetic termination of atrial tachycardia (AT), comparing two different illumination strategies: distributed vs. targeted. We show that targeted optogenetic stimulation based on automated, non-invasive flow-network analysis of patient-specific re-entry morphology may be a reliable approach for identifying the optimal illumination target in each individual (i.e. the critical AT isthmus). The above-described approach yields very high success rates (up to 100%) and requires dramatically less input power than distributed illumination We conclude that simulations in patient-specific models show that targeted light pulses lasting longer than the AT cycle length can efficiently and reliably terminate AT if the human atria can be successfully light-sensitized via gene delivery of ChR2. Optogenetics has emerged as a potential alternative to electrotherapy for treating arrhythmia, but feasibility studies have been limited to ventricular defibrillation via epicardial light application. Here, we assess the efficacy of optogenetic atrial tachycardia (AT) termination in human hearts using a strategy that targets for illumination specific regions identified in an automated manner. In three patient-specific models reconstructed from late gadolinium-enhanced MRI scans, we simulated channelrhodopsin-2 (ChR2) expression via gene delivery. In all three models, we attempted to terminate re-entrant AT (induced via rapid pacing) via optogenetic stimulation. We compared two strategies: (1) distributed illumination of the endocardium by multi-optrode grids (number of optrodes, Nopt =64, 128, 256) and (2) targeted illumination of the critical isthmus, which was identified via analysis of simulated activation patterns using an algorithm based on flow networks. The illuminated area and input power were smaller for the targeted approach (19-57.8mm2 ; 0.6-1.8W) compared to the sparsest distributed arrays (Nopt =64; 124.9±6.3mm2 ; 3.9±0.2W). AT termination rates for distributed illumination were low, ranging from <5% for short pulses (1/10ms long) to ∼20% for longer stimuli (100/1000ms). When we attempted to terminate the same AT episodes with targeted illumination, outcomes were similar for short pulses (1/10ms long: 0% success) but improved for longer stimuli (100ms: 54% success; 1000ms: 90% success). We conclude that simulations in patient-specific models show that light pulses lasting longer than the AT cycle length can efficiently and reliably terminate AT in atria light-sensitized via gene delivery. We show that targeted optogenetic stimulation based on analysis of AT morphology may be a reliable approach for defibrillation and requires less power than distributed illumination.