Delayed-enhancement Magnetic Resonance Research Articles

A 3-hour time interval may not be sufficient for delayed enhancement magnetic resonance imaging with intravenous gadoteridol injection based on 3d-real IR sequence of the inner ear in Meniere’s disease patient

Background Magnetic resonance imaging (MRI) can be applied to visualize endolymphatic hydrops (EH). Aims/Objectives To explore whether a 3-h time interval was feasible for clinical practice. Materials and methods We prospectively enrolled 15 patients with unilateral Meniere’s disease, each of whom underwent delayed enhancement MRI scan of the inner ear after intravenous gadoteridol injection at a 3-h interval. The ears of these patients were divided into two groups (group A: the affected ears; group B: the unaffected ears). Among the two groups, the signal intensity in perilymphatic area of the basal turn of cochlea, the results of visual evaluations in the vestibule, cochlea and semicircular canal and the detection results of EH were compared. Results Regarding the signal intensity, a difference was found between group A and group B (p = .016). Besides, no difference was found between the visual evaluations in the vestibule, cochlea and semicircular canal of the two groups. Regarding the detection results of EH, group A (6 vestibules were undiagnosable; 8 cochleae were undiagnosable); group B (9 vestibules were undiagnosable; 10 cochleae were undiagnosable). Conclusions and significance In the clinical application of gadoteridol for the inner ear, 3-h delayed MR imaging may not be sufficient.

Pixel-wise statistical analysis of myocardial injury in STEMI patients with delayed enhancement MRI.

Myocardial injury assessment from delayed enhancement magnetic resonance images is routinely limited to global descriptors such as size and transmurality. Statistical tools from computational anatomy can drastically improve this characterization, and refine the assessment of therapeutic procedures aiming at infarct size reduction. Based on these techniques, we propose a new characterization of myocardial injury up to the pixel resolution. We demonstrate it on the imaging data from the Minimalist Immediate Mechanical Intervention randomized clinical trial (MIMI: NCT01360242), which aimed at comparing immediate and delayed stenting in acute ST-Elevation Myocardial Infarction (STEMI) patients. We analyzed 123 patients from the MIMI trial (62 ± 12 years, 98 male, 65 immediate 58 delayed stenting). Early and late enhancement images were transported onto a common geometry using techniques inspired by statistical atlases, allowing pixel-wise comparisons across population subgroups. A practical visualization of lesion patterns against specific clinical and therapeutic characteristics was also proposed using state-of-the-art dimensionality reduction. Infarct patterns were roughly comparable between the two treatments across the whole myocardium. Subtle but significant local differences were observed for the LCX and RCA territories with higher transmurality for delayed stenting at lateral and inferior/inferoseptal locations, respectively (15% and 23% of myocardial locations with a p-value <0.05, mainly in these regions). In contrast, global measurements were comparable for all territories (no statistically significant differences for all-except-one measurements before standardization / for all after standardization), although immediate stenting resulted in more subjects without reperfusion injury. Our approach substantially empowers the analysis of lesion patterns with standardized comparisons up to the pixel resolution, and may reveal subtle differences not accessible with global observations. On the MIMI trial data as illustrative case, it confirmed its general conclusions regarding the lack of benefit of delayed stenting, but revealed subgroups differences thanks to the standardized and finer analysis scale.

Abstract 15179: Histology-Validated Delayed Enhancement Magnetic Resonance Imaging of Atrial Fibrillation Driver Substrate

Introduction: Persistent (per) AF may be maintained by localized extra-PV drivers (DRs). Regional fibrosis can serve as a substrate for AF DRs, but its visualization by delayed enhancement (DE)-MRI lacks proper validation for driver substrates. The objective of this study is to evaluate if histology-validated normalized (HVN) DE-MRI thresholds can define arrhythmogenic fibrotic content in multielectrode mapping (MEM)-defined DRs from perAF patients’ (Pts) DE-MRI. Methods: PerAF Pts (n=14, 71% male; 63±10 y/o) had DE-MRI at 3T (0.63x0.63x0.63mm 3 , 0.2mmol/kg Gd) before their perAF ablation procedure. Chamber-specific DE-MRI intensity was normalized to the healthy atria (mean lowest 5% intensity, 0 AU) and mitral (LA) or tricuspid (RA) valve (100 AU). 3 control and 5 perAF canines had DE-MRI and regional histology to validate DE-MRI fibrotic thresholds for the LA and RA, which were defined as standard deviations (SD) above 40% of the mean healthy atrial tissue intensity (LA: 3.7 SD, RA: 2.7 SD). Fibrosis-enhancement of segmented MEM-defined DRs (LA: n=25, RA: n=11) were analyzed using conventional, non-normalized 3 SD and HVN thresholds and compared to 5 random regions (non-DRs) within the same anatomical region(s). Results: Only our HVN approach could reveal arrhythmogenic fibrotic substrates in LA DR regions, but not the conventional approach. Both approaches could not provide significant differences for RA DR vs non-DR fibrosis regions. The cut-off of 33.6% of LA DE-MRI fibrotic enhancement using the HVN approach allowed to distinguish LA DR vs. non-DR regions with 56% sensitivity and 70% specificity. At 12 months follow-up, 10 Pts remained free of AF. Conclusion: MEM-defined DRs within fibrotic regions, identified by HVN DE-MRI, may represent efficient targets for ablation of LA arrhythmogenic perAF substrates. Integration of MEM and MRI may lead to improved targeted ablation and long-term AF freedom.

Agreement between real-time elastography and delayed enhancement magnetic resonance enterography on quantifying bowel wall fibrosis in Crohn's disease

Backgroundthe assessment of fibrosis in Crohn's disease (CD) bowel lesions helps to guide therapeutic decisions. Real-time elastography (RTE) and delayed-enhancement magnetic resonance enterography (DE-MRE) have demonstrated good accuracy in quantifying CD-related ileal fibrosis as compared with histological examination. To date no study has compared DE-MRE and RTE. Aimswe aimed to evaluate the agreement between RTE and DE-MRE on quantifying CD-related ileal fibrosis. Methodsconsecutive patients with ileal or ileocolonic CD underwent RTE and DE-MRE. Ileal fibrosis was quantified by calculating the strain ratio (SR) at RTE and the 70s-7 min percentage of enhancement gain (%EG) of both mucosa and submucosa at DE-MRE. A SR ≥2 was applied to define severe fibrosis. Clinically relevant outcomes occurring at follow-up were recorded. Results40 CD patients were enrolled. A significant linear correlation was observed between SR and submucosal %EG (r = 0.594, p < 0.001). Patients with severe fibrosis (SR ≥2) had significantly higher submucosal %EG values than patients with low/moderate fibrosis (median values 26.4% vs. 9.5%, p < 0.001). During a median 43.8-month follow-up relevant disease outcomes occurred more frequently in the severe-fibrosis group (75% vs. 36%, HR 5.4, 95% CI 1.2–24.6, p = 0.029). Conclusionsthe study demonstrates an excellent agreement between RTE and DE-MRE in assessing ileal fibrosis in CD.

DE-MR simulation imaging for prone radiotherapy after breast-conserving surgery: assessing its application in lumpectomy cavity delineation based on deformable image registration

BackgroundThe application of delayed-enhancement magnetic resonance (DE-MR) simulation imaging in lumpectomy cavity (LC) delineation for prone radiotherapy in patients with an invisible seroma or a low seroma clarity score (SCS) after breast-conserving surgery (BCS) based on deformable image registration (DIR) was assessed.MethodsTwenty-six patients who were suitable for radiotherapy in prone positions after BCS were enrolled, and both computed tomography (CT) and DE-MR simulation scans were acquired. The LC delineated based on titanium surgical clips on CT images was denoted as LCCT. The LC delineated based on the signal of cavity boundaries on fat-suppressed T2-weighted imaging (T2WI) and multiphase delayed-enhancement T1-weighted imaging (DE-T1WI), which was performed at 2 min, 5 min and 10 min postinjection, were denoted as LCT2, LC2T1, LC5T1 and LC10T1, respectively. Afterwards, DIR was performed to compare the volumes and locations of the LCs with MIM software. The generalized conformity index (CIgen) of inter (intra) observer (Inter-CIgen and Intra-CIgen) was also used to explore the inter(intra) observer variation for LC delineation on each image modality.ResultsLCCT–LC10T1 provided the best conformal index (CI) and degree of inclusion (DI), increasing by 2.08% and 4.48% compared to LCCT–LCT2, 11.36% and 2.94% for LCCT–LC2T1, and 8.89% and 7.69% for LC5T1–LCCT, respectively. The center of mass (COM) of LCCT–LC10T1 decreased by 17.86%, 6.12% and 13.21% compared with that of LCCT–LCT2, LCCT–LC2T1 and LCCT–LC5T1, respectively. The agreement of LC delineation was strongest for 10th min DE-TIWI (coefficient of variation, COV = 2.30%, Inter-CIgen = 87.06%, Intra-CIgen = 92.64%).ConclusionFor patients with a low SCS (SCS ≤ 2) after BCS, it is feasible to contour the LC based on prone DE-MR simulation images. Furthermore, the LC derived from prone DE-T1WI at 10 min was found to be most similar to that derived from prone CT simulation scans using titanium surgical clips regardless of the volume and location of the LC. Inter (intra) variability was minimal for the delineation of the LC based on 10th min DE-TIWI.

Delayed Echo Enhancement Imaging to Quantify Myocardial Infarct Size

Perfluoropropane droplets formulated from commercial microbubbles exhibit different acoustic characteristics than their parent microbubbles, most likely from enhanced endothelial permeability. This enhanced permeability may permit delayed echo-enhancement imaging (DEEI) similar to delayed enhancement magnetic resonance imaging (DE-MRI). We hypothesized this would allow detection and quantification of myocardial scar. In 15 pigs undergoing 90minutes of left anterior descending ischemia by either balloon (n=13) or thrombotic occlusion (n=2), DE-MRI was performed at 2-24days postocclusion. Delayed echo-enhancement imaging was performed at 2-4minutes following an intravenous injection of 1mL of 50% Definity (Lantheus Medical) compressed into 180nm droplets; DEEI was attempted in all pigs with single-pulse harmonic imaging at 1.7 transmit/3.4MHz receive. Myocardial defects observed with DEEI were quantified (percentage of infarct area) and compared with DE-MRI as well as postmortem staining. In six pigs, multipulse low-mechanical index (MI) fundamental nonlinear imaging (FNLI) with intermittent high-MI impulses was performed to determine whether droplet activation within the infarct zone was achievable with a longer pulse duration. The range of infarct size area by DE-MRI ranged from 0% to 46% of total left ventricular area. Single-pulse harmonic imaging detected a contrast defect that correlated closely with infarct area by DE-MRI (r=0.81, P=.0001). The FNLI high-MI impulses resulted in droplet activation in both the infarct and normal zones. Harmonic subtraction of the FNLI images resulted in infarct zone enhancement that also correlated closely with infarct size (r=0.83; P=.04). Droplets were observed on postmortem transmission electron microscopy within myocytes of the infarct and remote normal zone. Intravenously Definity nanodroplets can be utilized to detect and quantify infarct zone at the bedside using DEEI techniques.

The influence of scar on the spatio-temporal relationship between electrical and mechanical activation in heart failure patients.

The aim of this study was to determine the relationship between electrical and mechanical activation in heart failure (HF) patients and whether electromechanical coupling is affected by scar. Seventy HF patients referred for cardiac resynchronization therapy or biological therapy underwent endocardial anatomo-electromechanical mapping (AEMM) and delayed-enhancement magnetic resonance (CMR) scans. Area strain and activation times were derived from AEMM data, allowing to correlate mechanical and electrical activation in time and space with unprecedented accuracy. Special attention was paid to the effect of presence of CMR-evidenced scar. Patients were divided into a scar (n = 43) and a non-scar group (n-27). Correlation between time of electrical and mechanical activation was stronger in the non-scar compared to the scar group [R = 0.84 (0.72-0.89) vs. 0.74 (0.52-0.88), respectively; P = 0.01]. The overlap between latest electrical and mechanical activation areas was larger in the absence than in presence of scar [72% (54-81) vs. 56% (36-73), respectively; P = 0.02], with smaller distance between the centroids of the two regions [10.7 (4.9-17.4) vs. 20.3 (6.9-29.4) % of left ventricular radius, P = 0.02]. Scar decreases the association between electrical and mechanical activation, even when scar is remote from late activated regions.

Study of the Distribution of Epicardial Vagal Ganglion and the Relationship Between Delayed Enhancement Magnetic Resonance Imaging and Radiofrequency Ablation in Patients with Atrial Fibrillation

This article presents a retrospective study of patients undergoing radiofrequency ablation of atrial fibrillation (AF); analyzes the characteristics of heart rate variability (HRV) in patients; and explores the role of delayed enhancement magnetic resonance imaging and autonomic nervous system function, changes in autonomic nervous system function, and recurrence of AF after radiofrequency ablation to understand the effect of denervation of the autonomic nervous system on the efficacy of radiofrequency ablation of AF. The study found that there were no significant differences in clinical baseline characteristics, mean heart rate, and HRV indicators between patients without relapse and patients with relapse (P > 0.05). The overall HRV index was significantly reduced after surgery as well as before surgery. In the relapse-free group, the high-frequency power that responded to vagal tone was more significant, the low-frequency/high-frequency power ratio increased, and other HRV indicators were significantly reduced; in the relapse group, mean heart rate increased, sympathetic response to the low-frequency power of nerve tension was significantly reduced, and the low-frequency/high-frequency power ratio was decreased. The difference was statistically significant (P < 0.05). Therefore, sympathetic and parasympathetic nerve function were significantly reduced after radiofrequency ablation of the pulmonary veins in patients with AF. Reducing vagus nerve tension may inhibit early recurrence of paroxysmal AF in patients after left atrial ring pulmonary vein ablation.

ADDITIONAL VALUE OF QUANTIFICATION OF MYOCARDIAL FIBROSIS BY CONTRAST-ENHANCED MRI TO IDENTIFY SUBJECTS WITH HYPERTROPHIC CARDIOMYOPATHY AND SUDDEN CARDIAC DEATH RISK

Background. A 5-year sudden cardiac death risk model in line with ESC-2014 (HCM Risk-SCD score) Guidelines assesses the risk of sudden cardiac death in individuals with hypertrophic cardiomyopathy using clinical parameters without taking into account magnetic resonance imaging indices including myocardial fibrosis.Aim. To compare subjects with low, moderate, and high sudden cardiac death risks, identified based on HCM Risk-SCD score, with delayed enhancement magnetic resonance imaging-evidenced fibrosis and to assess the role of fibrosis in identification of patients with sudden cardiac death risk.Material and Methods. A total of 98 patients with hypertrophic cardiomyopathy underwent an integrative examination including cardiac echocardiography, 24-h electrocardiography monitoring, delayed gadolinium-enhanced magnetic resonance imaging, and an assessment of a 5-year sudden cardiac death risk by HCM Risk-SCD score.Results and Discussion. Out of 98 patients, 45 (46%) patients had low risk of sudden cardiac death, 26 (26%) patients had intermediate risk, and 27 (28%) patients had high sudden cardiac death risk by HCM Risk-SCD score. During the follow-up period, (mean 41 months; 25 to 58 months), 16 adverse events were registered: sudden cardiac death occurred in 9 patients while 7 patients had been successfully resuscitated and implanted with implantable cardioverter defibrillator for secondary prevention of sudden cardiac death. The risk assessment using HCM Risk-SCD score showed high risk in 8 out of 16 (50%) patients; 2 (12.5%) patients had moderate risk, while 6 (37.5%) patients had low risk. High-risk patients demonstrated significantly (p&lt;0.001) larger fibrosis (mean 28.5%; quartiles 21.9%; 44.1%) compared to those with moderate risk (mean 17.6%; quartiles 8.0%; 22.5%) and low risk of sudden cardiac death (mean 11.7%; quartiles 5.8%; 17.6%). The volume of fibrosis by delayed contrast-enhanced magnetic resonance imaging was associated with the adverse outcomes rate, which was 15%. A Log rank test in the KaplanMeier survival analysis showed statistically significant differences (p=0,002) in groups with fibrosis &lt;15% and≥15%. The regression analysis showed that myocardial fibrosis was more significant factor associated with sudden cardiac death (OR 12; 95% CI 1.6–91) compared to SCD ESC-2014 score (OR 2.8 95% CI 1.1–7.5).Conclusion. Therefore, based on regression analysis, patients with hypertrophic cardiomyopathy who had myocardial fibrosis volume ≥15% were identified as a group with risk of sudden cardiac death and adverse arrhythmic events.

ADDITIONAL VALUE OF QUANTIFICATION OF MYOCARDIAL FIBROSIS BY CONTRAST-ENHANCED MRI TO IDENTIFY SUBJECTS WITH HYPERTROPHIC CARDIOMYOPATHY AND SUDDEN CARDIAC DEATH RISK

Background. A 5-year sudden cardiac death risk model in line with ESC-2014 (HCM Risk-SCD score) Guidelines assesses the risk of sudden cardiac death in individuals with hypertrophic cardiomyopathy using clinical parameters without taking into account magnetic resonance imaging indices including myocardial fibrosis.Aim. To compare subjects with low, moderate, and high sudden cardiac death risks, identified based on HCM Risk-SCD score, with delayed enhancement magnetic resonance imaging-evidenced fibrosis and to assess the role of fibrosis in identification of patients with sudden cardiac death risk.Material and Methods. A total of 98 patients with hypertrophic cardiomyopathy underwent an integrative examination including cardiac echocardiography, 24-h electrocardiography monitoring, delayed gadolinium-enhanced magnetic resonance imaging, and an assessment of a 5-year sudden cardiac death risk by HCM Risk-SCD score.Results and Discussion. Out of 98 patients, 45 (46%) patients had low risk of sudden cardiac death, 26 (26%) patients had intermediate risk, and 27 (28%) patients had high sudden cardiac death risk by HCM Risk-SCD score. During the follow-up period, (mean 41 months; 25 to 58 months), 16 adverse events were registered: sudden cardiac death occurred in 9 patients while 7 patients had been successfully resuscitated and implanted with implantable cardioverter defibrillator for secondary prevention of sudden cardiac death. The risk assessment using HCM Risk-SCD score showed high risk in 8 out of 16 (50%) patients; 2 (12.5%) patients had moderate risk, while 6 (37.5%) patients had low risk. High-risk patients demonstrated significantly (p&lt;0.001) larger fibrosis (mean 28.5%; quartiles 21.9%; 44.1%) compared to those with moderate risk (mean 17.6%; quartiles 8.0%; 22.5%) and low risk of sudden cardiac death (mean 11.7%; quartiles 5.8%; 17.6%). The volume of fibrosis by delayed contrast-enhanced magnetic resonance imaging was associated with the adverse outcomes rate, which was 15%. A Log rank test in the KaplanMeier survival analysis showed statistically significant differences (p=0,002) in groups with fibrosis &lt;15% and≥15%. The regression analysis showed that myocardial fibrosis was more significant factor associated with sudden cardiac death (OR 12; 95% CI 1.6–91) compared to SCD ESC-2014 score (OR 2.8 95% CI 1.1–7.5).Conclusion. Therefore, based on regression analysis, patients with hypertrophic cardiomyopathy who had myocardial fibrosis volume ≥15% were identified as a group with risk of sudden cardiac death and adverse arrhythmic events.

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.

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.

Clinical value of 4-hour delayed gadolinium-Enhanced 3D FLAIR MR Images in Acute Vestibular Neuritis.

To investigate the clinical significance of 4-hour delayed-enhanced 3.0 Tesla three-dimensional (3D) fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging in acute vestibular neuritis. A prospective observational study. Twenty-nine vestibular neuritis patients were enrolled between January 2017 and June 2017. Vestibular function tests, comprising the caloric and video head impulse tests and vestibular-evoked myogenic potential measurements, were performed. Precontrast, 10-minute, and 4-hour delayed-enhanced 3D-FLAIR MR images using double-dose IV gadolinium were obtained. After laterality and extent of inner ear enhancement were defined, the patients were divided into groups based on the patterns of enhancement, and clinical parameters were analyzed according to the groups. Twenty patients (20 of 29, 69.0%) had obviously asymmetric enhancement of the affected inner ear structures on 4-hour delayed images, whereas only three patients (10.3%) had marked enhancement on 10-minute delayed images. The duration of spontaneous nystagmus (DurSN) was significantly longer in the patients with enhancement, especially with enhancement of the whole inner ear, including the vestibule and semicircular canals (P < 0.033). Spontaneous nystagmus resolved within 12 days in patients without laterality of enhancement, and within 16 days in ipsilesional enhancement confined to the inner auditory canal and fundus. Other results of vestibular function tests did not reveal any significant associations with MR enhancement. Contrast enhancement of the vestibular nerve and inner ear structures can be identified on 4-hour delayed-enhanced 3T 3D-FLAIR MR images in acute vestibular neuritis. The extent of inner ear enhancement may be associated with the DurSN. 4. Laryngoscope, 1946-1951, 2018.

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.

66Comparison of gaps detected by delayed-enhancement cardiac magnetic resonance after radiofrequency and cryoballon ablation of paroxysmal atrial fibrillation: a case-control study

66Comparison of gaps detected by delayed-enhancement cardiac magnetic resonance after radiofrequency and cryoballon ablation of paroxysmal atrial fibrillation: a case-control study

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.

P345Comparison of cryoballoon versus radiofrequency gaps detected by delayed-enhancement cardiac magnetic resonance after ablation of paroxysmal atrial fibrillation: a case-control study

P345Comparison of cryoballoon versus radiofrequency gaps detected by delayed-enhancement cardiac magnetic resonance after ablation of paroxysmal atrial fibrillation: a case-control study

Assessment of myocardial viability with delayed-enhancement MRI in coronary artery disease: A correlative study with coronary artery stenosis using digital subtraction angiography.

The aim of the present study was to investigate the correlation between the degree of coronary artery stenosis determined by digital subtraction angiography (DSA) and infarcted segments detected by delayed enhancement magnetic resonance imaging (DE-MRI). DE-MRI and DSA were performed in 40 patients with coronary artery disease. The number of myocardial segments with infarction, the transmural extent of myocardial infarction, score of myocardial infarction by MRI, degree of coronary artery stenosis and Gensini score of the coronary artery were assessed. The correlation was analyzed using Spearman's rank correlation test. Among the 40 patients, 126 infarcted myocardial segments with a total score of 307 were found by DE-MRI; the total Gensini score for coronary artery stenosis was 587. It was observed that 81.74% of the infarcted segments were at sites with >50% coronary artery stenosis. The correlation coefficient between the Gensini score and myocardial infarction score was 0.786 (P<0.001), indicating a good correlation. However, 18.26% of myocardial infarction segments were found in patients with slight coronary artery stenosis (≤25%). A correlation was identified between DSA detected coronary artery stenosis and infarcted segments detected by DE-MRI; a higher transmural extent of myocardial infarction correlated with more severe stenosis of the coronary artery. The combined use of the two tools may facilitate accurate diagnosis.

MANGANESE CHELATE-ENHANCED MAGNETIC RESONANCE IMAGING OF MYOCARDIAL INFARCTION IN A RABBIT ISCHEMIA MODEL: COMPARISON WITH GADOLINIUM-ENHANCED MAGNETIC RESONANCE IMAGING

Gadolinium-based delayed enhancement magnetic resonance imaging (DEMRI) quantitatively identifies myocardial infarction (MI) but is nonspecific. Manganese (Mn)-enhanced MRI (MEMRI) can specifically detect cardiomyocyte viability. We developed a rigid Mn(II) chelate as MRI contrast agent to