High-resolution Cardiac Magnetic Resonance Research Articles

Combining 3D SONAR with High Resolution Imaging to Improve Vision in Atrial Fibrillation Ablation

Real-time, accurate imaging of improperly functioning tissue that causes atrial fibrillation (AF) is essential for successful catheter ablation procedures. Ablation procedures and success rates may be improved by overlaying intracardiac echocardiography with high resolution cardiac imaging. Data extracted from previous research reports that current pharmacological agents do not address the principal cause of AF. Unlike medication, catheter ablation resolves the issue by treating AF’s source. Therefore, catheter ablation is the better alternative. However, while catheter ablation is preferable to medication, the detail and accuracy of anatomical visualizations used to guide the catheter can be inconsistent. While real time guidance technology updates, the visibility quality is limited. However, detailed preliminary imaging does not accurately reflect the latest changes. This paper discusses the current limitations of catheter ablation and proposes real-time three-dimensional Sound Navigation and Ranging (SONAR) imaging paired with high-resolution cardiac Magnetic Resonance Imaging (MRI) as a novel tool to improve live-imaging localizations and resolution for cardiac ablation procedures.

Progressive Feedback Residual Attention Network for Cardiac Magnetic Resonance Imaging Super-Resolution.

Atrial fibrillation (AF) is an increasing medical burden worldwide, and its pathological manifestations are atrial tissue remodeling and low-pressure atrial tissue fibrosis. Due to the inherent defects of medical image data acquisition systems, the acquisition of high-resolution cardiac magnetic resonance imaging (CMRI) faces many problems. In response to these problems, we propose the Progressive Feedback Residual Attention Network (PFRN) for CMRI super-resolution. Specifically, we directly perform feature extraction on low-resolution images, retain feature information to a large extent, and then build multiple independent progressive feedback modules to extract high-frequency details. To accelerate network convergence and improve image reconstruction quality, we implement the MS-SSIM-L1 loss function. Furthermore, we utilize the residual attention stack module to explore the image's internal relevance and extract the low-resolution image's detailed features. Extensive benchmark evaluation shows that PFRN can improve the detailed information of the image SR reconstruction results, and the reconstructed CMRI has a better visual effect.

PO-03-139 HIGH-RESOLUTION CARDIAC MAGNETIC RESONANCE IMAGING FOR LEFT ATRIAL APPENDAGE SIZING AND THROMBUS EXCLUSION PRIOR TO DEVICE CLOSURE

Transesophageal echocardiography and cardiac computed tomography angiography are currently utilized for left atrial appendage closure (LAAC) planning. The advent of high-resolution cardiac magnetic resonance imaging (HR-CMR) now potentially allows for adequate spatial resolution for LAAC planning. This study sought to assess preoperative HR-CMR with software-based sizing vs intraoperative TEE for LAA sizing and thrombus exclusion prior to LAAC. This retrospective study conducted at The Ohio State University Wexner Medical Center included all patients who underwent preoperative HR-CMR and intraoperative TEE for LAAC with Watchman FLX (Boston Scientific, Marlborough, MA) from May to September 2022. For HR-CMR, magnetic resonance angiography (MRA) and late gadolinium enhancement (LGE) sequences were obtained for LAA sizing and thrombus exclusion respectively. A proprietary sizing software (TruPlan, Boston Scientific) was utilized to analyze the MRA sequence to characterize LAA anatomy, predict closure device size, and estimate device compression ratio. HR-CMR was compared to TEE for assessing accuracy of LAA thrombus exclusion, maximum ostial diameter, depth, lobe count, morphology, and accuracy of predicted device size. 16 patients were included, with baseline characteristics notable for 8 (50%) females, age 73 ± 6 years, 30 ± 7 kg/m2 body mass index, 54 ± 8% left ventricular ejection fraction, and 4 ± 2 CHA2DS2-VASc. 15 (94%) cases were successfully completed. There was no significant difference in LAA thrombus exclusion (CMR 14 (88%) vs TEE 16 (100%) cases, p=0.48), maximum ostial diameter (CMR 20.9 ± 4.2 vs TEE 20.6 ± 4.2 mm, p=0.99), depth (CMR 31.1 ± 7.8 vs TEE 26.8 ± 5.6 mm, p=0.09), lobe count (CMR 1.8 ± 0.8 vs TEE 1.4 ± 0.6 lobes, p=0.25), and morphology features (p=0.44). LAA assessments are summarized in Table I. The mean devices deployed per case was 1.1 ± 0.3. In 2 (13%) cases a device downsize was required. 1 case was aborted due to inability to access a very small LAA ostium. On 45-day TEE or CCTA, no peri-device leak ≥5 mm or device-related thrombus were noted. A comparison of standard vs high-resolution contrast-enhanced (CE)-MRA of the LAA is demonstrated in Figure 1. HR-CMR is a viable modality for preoperative LAA sizing and thrombus exclusion with promising results. HR-CMR may provide utility in cases where TEE or CCTA are contraindicated or unavailable.Tabled 1Table IMeasureHR-CMR (N=16)TEE (N=16)P-valueLAA thrombus accurately excluded14 (88%)16 (100%)0.484Minimum LAA ostial diameter (mm)18.0 ± 4.216.6 ± 3.40.335Target LAA ostial diameter (mm)*20.9 ± 4.220.6 ± 4.20.987LAA depth (mm)31.1 ± 7.826.8 ± 5.60.093Number of lobes1.8 ± 0.81.4 ± 0.60.250Morphology0.437Cactus4 (25%)3 (19%)Cauliflower0 (0%)2 (13%)Chicken wing5 (31%)2 (13%)Windsock7 (44%)8 (50%)Other0 (0%)1 (6%)LAA closure device size accurately predicted12 (75%)12 (75%)1.000Values presented as mean ± 1 standard deviation for continuous variables and n (%) for categorical variables. Abbreviations: HR-CMR = high resolution cardiac magnetic resonance imaging, LAA = left atrial appendage, TEE = transesophageal echocardiography. *Based on maximum diameter measured on TEE vs area-derived diameter on HR-CMR. Open table in a new tab

Pericardial fat is adversely related to cardio-mechanical interaction in heart failure with preserved ejection fraction: implications for exercise intolerance

Abstract Background Exercise intolerance is the primary manifestation in heart failure with preserved ejection fraction (HFpEF); however, the pathophysiologic mechanism(s) remains incompletely understood. Excess cardiac adiposity may physically constrain the myocardium, resulting in adverse Cardio-Mechanical Interaction (i.e., greater left ventricular eccentricity); a phenomenon only expected to worsen during exercise, with increased respiratory excursion and hemodynamic load. Evidence for this hypothesis, however, remains limited to a small number of observations, from a single group, made only under resting conditions using transthoracic echocardiography. Purpose To evaluate the relationship between pericardial fat and cardio-mechanical interaction in HFpEF at rest and during exercise using high resolution cardiac magnetic resonance imaging (cMRI). Methods We performed real-time (ungated), free-breathing cinematic imaging of the left ventricular (LV) short axis in 11 individuals with HFpEF (4M/7F, BMI: 36±6, age: 69±4 years). Imaging was performed at rest and during dynamic leg exercise (30 Watts) using an MRI-compatible ergometer (Ergospect, Austria). Epicardial and paracardial fat area were measured using high resolution cine images in the horizontal long axis imaging plane, with epicardial fat defined as the adipose tissue within the pericardium and paracardial fat defined as the adipose tissue outside of the pericardium (Figure 1A); the sum of which defined pericardial fat area. The LV eccentricity index was calculated as the ratio of LV short axis diameter parallel to the septum (anteroposterior dimension, AP) to the LV short axis diameter perpendicular to the septum (septolateral dimension, SL, Figure 1A) at mid-ventricular level, during inspiration at end-diastole. Results At rest, adverse cardio-mechanical interaction (i.e., AP/SL >1.0) was observed in 5 of the 11 cases. In those with adverse cardio-mechanical interaction both epicardial and paracardial fat area were significantly higher, resulting in greater pericardial fat area (Figure 1B). While epicardial fat area was not related to LV eccentricity index (R2=0.19, P=0.18), we observed a strong correlation between paracardial fat area and LV eccentricity index (R2=0.93, P<0.01), and pericardial fat area and LV eccentricity index (R2=0.86, P<0.01, Figure 1C). In contrast to our hypothesis, however, supine exercise did not exacerbate cardio-mechanical interaction, with LV eccentricity index remaining elevated in 4 of the 5 original cases, improving the fifth case (1.1 to 0.9, rest to exercise). Conclusions Taken together, these data extend prior reports of adverse cardio-mechanical interaction in HFpEF, showing greater contribution from paracardial fat versus epicardial fat. Future studies are needed to examine cardio-mechanical interaction during upright exercise in HFpEF patients. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): National Institutes of Health

50 Years Ago in TheJournalofPediatrics: Rescuing Infants with Critical Congenital Heart Disease

Engle MA. The salvage of babies and children with congenital heart disease. J Pediatr 1972;81:203-4. Fifty years ago in The Journal, Dr Engle reported early recognition of cyanosis in newborns and prompt highly skilled transport to a cardiac center as cornerstones of rescuing infants with critical congenital heart disease (CCHD). Initial stabilization, followed by a precise diagnosis using cardiac catheterization, allowed for optimal medical or surgical management. A holistic approach to care included long-term psychological well-being and a life as free of disabilities as possible. These core principles continue to form the basis for current management of CCHD. The implementation of a CCHD screen using simple pulse oximetry in the right hand and either foot before hospital discharge has significantly improved the early identification of CCHD and decreased mortality. The screen was adopted by all US states and the District of Columbia by 2018 and is supported by the federal Newborn Screens Save Lives Act of 2008. Significant innovations in ultrasound technology have revolutionized diagnosis by producing real-time images of the congenitally malformed heart. Portable echocardiogram machines can now render highly precise postnatal diagnoses within minutes, without the need for invasive catheterization. Cardiac-gated computed tomography scans or high-resolution cardiac magnetic resonance imaging can add further finer anatomic and functional details. Advances in maternal ultrasound also allow effective screening for major disease with subsequent fetal echocardiography yielding highly precise diagnoses. Delivery at a cardiac center with immediate stabilization of the newborn can be arranged prenatally for complex CCHD. The commercial availability of prostaglandin allows mothers to choose delivery closer to home with subsequent stabilization of infants with known CCHD before transfer to the cardiac center. Prostaglandin can effectively rescue infants missed at hospital discharge who present in the emergency room with shock. With improved survival of patients with CCHD into adulthood, there is increased awareness of neurodevelopmental outcomes with the need for early childhood interventions. Despite significant advances, many challenges remain. CCHD screen is not adopted globally, especially in resource-limited countries where many infants are born at home and with limited transport capabilities. High-quality CCHD imaging, the availability of prostaglandin, in-house pediatric echocardiograms, and prompt transport remain challenging even for high- and middle-income countries. Even with these advances, 97% of infants with non-CCHD but only 75% of those with CCHD will survive to 1 year of age.1Oster M.E. Lee K.A. Honein M.A. Riehle-Colarusso T. Shin M. Correa A. Temporal trends in survival among infants with critical congenital heart defects.Pediatrics. 2013; 131: e1502-e1508Crossref PubMed Scopus (317) Google Scholar We have come far, but there is surely a long road still ahead.

Assessing the field of view of multisize electrodes in ischemic cardiomyopathy by validating against ex-vivo high resolution cardiac magnetic resonance

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Leiden University Medical Centre Background Substrate identification after myocardial infarction (MI) relies on voltage mapping. Early reperfusion results in non-transmural scar (NTS). Narrow-spaced microelectrodes (ME) are thought to have a limited field of view (FOV). The role of ME for delineation of NTS is unclear. Purpose To evaluate mapping with multi-size electrodes for identifying NTS, validated against high-resolution ex-vivo cardiac magnetic resonance imaging (HR-LGE-CMR). Methods Nine swine with early reperfusion MI underwent endocardial electroanatomical voltage mapping (EAVM) with the QDOT catheter which incorporates three ME in the 3.5mm tip electrode. HR-LGE-CMR (0.3mm slices) were obtained and merged with EAVM. At each EAVM point a transmural cylinder (5mm radius) was projected on the CMR and the volume of viable myocardium (VM) in the cylinder quantified (Otsu method). Unipolar (UV) and bipolar (BV) voltages from conventional (c) and microelectrodes (µ) were related to VM. Cut-off values for normal myocardium were based on 5th percentiles of areas without fibrosis. Results In each swine 220 (IQR 216-260) mapping points were collected (total 2322 points). Cut-off for normal myocardium were 3.18 mV, 0.85 mV, 3.28mV and 1.93 mV for UVc, BVc, UVµ and BVµ, respectively. Wall thickness (WT) was reduced in areas with fibrosis vs. no fibrosis (5.4mm, IQR 3.2- 6.9 vs. 7.4mm, IQR 5.3 - 9.6). All voltages were reduced at sites with fibrosis vs. no fibrosis (UVs 4.4mV vs. 6.8mV; BVc 1.2mV vs. 2.1mV; UVµ 2.5mV vs. 5.5mV, and BVµ 2.9mV vs. 5.4mV, all p<0.001). For areas with any fibrosis, all voltages increased with increasing WT up to the maximal WT of 13mm (fig. 1). Similarly, all voltages increased with an increase in VM volumes from >200mm3 to >600 mm3 (equivalent to a cylinder with h=7.64mm) (fig. 2) with the strongest correlation for UVµ (r=0.47). Below a volume of 200mm3 VM voltages did not correlate significantly with VM. Conclusion In NTS, UVc, BVc, and, notably, BVµ and UVµ increase with increasing WT and increasing transmural volume of VM, with the biggest role perhaps laid out for UVµ to estimate transmural VM. EAVM cannot accurately delineate areas with the lowest amount of VM, potentially due to insufficient far field cancellation in NTS. Both these findings argue against a limited FOV of ME.

High-Resolution Cardiac Magnetic Resonance Imaging Techniques for the Identification of Coronary Microvascular Dysfunction

ObjectivesThis study assessed the ability to identify coronary microvascular dysfunction (CMD) in patients with angina and nonobstructive coronary artery disease (NOCAD) using high-resolution cardiac magnetic resonance (CMR) and hypothesized that quantitative perfusion techniques would have greater accuracy than visual analysis. BackgroundHalf of all patients with angina are found to have NOCAD, while the presence of CMD portends greater morbidity and mortality, it now represents a modifiable therapeutic target. Diagnosis currently requires invasive assessment of coronary blood flow during angiography. With greater reliance on computed tomography coronary angiography as a first-line tool to investigate angina, noninvasive tests for diagnosing CMD warrant validation. MethodsConsecutive patients with angina and NOCAD were enrolled. Intracoronary pressure and flow measurements were acquired during rest and vasodilator-mediated hyperemia. CMR (3-T) was performed and analyzed by visual and quantitative techniques, including calculation of myocardial blood flow (MBF) during hyperemia (stress MBF), transmural myocardial perfusion reserve (MPR: MBFHYPEREMIA / MBFREST), and subendocardial MPR (MPRENDO). CMD was defined dichotomously as an invasive coronary flow reserve <2.5, with CMR readers blinded to this classification. ResultsA total of 75 patients were enrolled (57 ± 10 years of age, 81% women). Among the quantitative perfusion indices, MPRENDO and MPR had the highest accuracy (area under the curve [AUC]: 0.90 and 0.88) with high sensitivity and specificity, respectively, both superior to visual assessment (both p < 0.001). Visual assessment identified CMD with 58% accuracy (41% sensitivity and 83% specificity). Quantitative stress MBF performed similarly to visual analysis (AUC: 0.64 vs. 0.60; p = 0.69). ConclusionsHigh-resolution CMR has good accuracy at detecting CMD but only when analyzed quantitatively. Although omission of rest imaging and stress-only protocols make for quicker scans, this is at the cost of accuracy compared with integrating rest and stress perfusion. Quantitative perfusion CMR has an increasingly important role in the management of patients frequently encountered with angina and NOCAD.

Bipolar ablation with contact force‐sensing of swine ventricles shows improved acute lesion features compared to sequential unipolar ablation

Despite technical progress, ventricular tachycardia (VT) recurrence after unipolar ablation remains relatively high (12%-47%). Bipolar ablation has been proposed as an appealing solution that may overcome limitations associated with unipolar ablation settings. We designed an animal study to compare bipolar (BPA) vs sequential unipolar ablation (UPA) using contact force-sensing technology on both ablation catheters. Twenty large white female pigs (6-months-old, 50-60 kg) underwent multiple RF ablations (30 W, 60 seconds, 30 mL/min irrigation) on the ventricular myocardium from the epicardial and endocardial sides. The hearts were fixed and scanned with high-resolution cardiac magnetic resonance imaging. Thermal lesions were located and characterized in volume, depth, width, and transmurality. Lesion volume was calculated as the sum of epicardial or endocardial conjoined/isolated lesions at one location. Linear dimensions (width and depth) were measured twice for each location, on the endocardial and epicardial side. We evaluated 35 lesions across the intraventricular septum (UPA, N = 17 vs BPA, N = 18). No difference in volume, linear dimensions or impedance drop was observed in this area between UPA and BPA. However, BPA required half RF time and showed an increased transmurality trend. We then analyzed 73 lesions from the endocardial side (UPA, N = 35 vs BPA, N = 38) and 50 from the epicardial side (UPA, N = 11 vs BPA N = 39) of the ventricular free walls. Lesion transmurality was markedly improved by BPA (P = .030, odds ratio, 23.73 [4.71,31.96]). Ventricular BPA lesions were significantly deeper on the epicardial side (P < .0001) and endocardial side (P = .015). Bipolar ablation is more likely to create transmural and epicardial lesions in the ventricle wall. Half the time is needed for the creation of comparably deep and large lesions.

MR imaging of the fetal heart.

In the last decade, technological advances have enabled the acquisition of high spatial and temporal resolution cardiac magnetic resonance imaging (MRI) in the fetus. Fetal cardiac MRI has emerged as an alternative to ultrasound, which may be helpful to confirm a diagnosis of congenital heart disease when ultrasound assessment is hampered, for example in late gestation or in the setting of oligohydramnios. MRI also provides unique physiologic information, including vessel blood flow, oxygen saturation and hematocrit, which may be helpful to investigate cardiac and placental diseases. In this review, we summarize some of the main techniques and significant advances in the field to date. Level of Evidence: 5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2020;51:1030-1044.

Cardiac Magnetic Resonance Imaging of Mechanical Cavopulmonary Assistance

Mechanical circulatory support (MCS) options are limited for patients with dysfunctional single ventricle physiology. To address this unmet clinical need, we are developing an axial-flow blood pump to provide mechanical assistance to the cavopulmonary circulation. In this study, we investigate the use of high-resolution cardiac magnetic resonance imaging (MRI) to visualize the complex fluid flow conditions of mechanical circulatory assist in two patient-specific Fontan anatomies. A three-bladed axial-flow impeller coupled to a supportive cage with a four-bladed diffuser was positioned in the inferior vena cava (IVC) of each Fontan anatomy. Cardiac magnetic resonance (CMR) imaging and power efficiency studies were conducted at physiologic relevant parameters with cardiac outputs of 2, 3, and 4 L/min with impeller rotational speeds of 2000 and 4000 rpm. The axial-flow impeller was able to generate improved flow in the total cavopulmonary connection (TCPC). The higher rotational speed was able to redistribute flow in the TCPC anastomosis aiding in removing stagnant blood. No retrograde flow was observed or measured in the superior vena cava (SVC). As an extension of the CMR data, a scalar stress analysis was performed on both models and found a maximum scalar stress of approximately 42 Pa for both patient anatomies. The power efficiency experiments demonstrated a maximum energy gain of 8.6 mW for TCPC Anatomy 1 and 12.58 mW for TCPC Anatomy 2 for a flow rate of 4 L/min and at 4000 rpm. These findings support the continued development of axial blood pumps for mechanical cavopulmonary assist.

Daily exercise prevents diastolic dysfunction and oxidative stress in a female mouse model of western diet induced obesity by maintaining cardiac heme oxygenase-1 levels

ObjectiveObesity is a global epidemic with profound cardiovascular disease (CVD) complications. Obese women are particularly vulnerable to CVD, suffering higher rates of CVD compared to non-obese females. Diastolic dysfunction is the earliest manifestation of CVD in obese women but remains poorly understood with no evidence-based therapies. We have shown early diastolic dysfunction in obesity is associated with oxidative stress and myocardial fibrosis. Recent evidence suggests exercise may increase levels of the antioxidant heme oxygenase-1 (HO-1). Accordingly, we hypothesized that diastolic dysfunction in female mice consuming a western diet (WD) could be prevented by daily volitional exercise with reductions in oxidative stress, myocardial fibrosis and maintenance of myocardial HO-1 levels. Materials/MethodsFour-week-old female C57BL/6J mice were fed a high-fat/high-fructose WD for 16weeks (N=8) alongside control diet fed mice (N=8). A separate cohort of WD fed females was allowed a running wheel for the entire study (N=7). Cardiac function was assessed at 20weeks by high-resolution cardiac magnetic resonance imaging (MRI). Functional assessment was followed by immunohistochemistry, transmission electron microscopy (TEM) and Western blotting to identify pathologic mechanisms and assess HO-1 protein levels. ResultsThere was no significant body weight decrease in exercising mice, normalized body weight 14.3g/mm, compared to sedentary mice, normalized body weight 13.6g/mm (p=0.38). Total body fat was also unchanged in exercising, fat mass of 6.6g, compared to sedentary mice, fat mass 7.4g (p=0.55). Exercise prevented diastolic dysfunction with a significant reduction in left ventricular relaxation time to 23.8ms for exercising group compared to 33.0ms in sedentary group (p<0.01). Exercise markedly reduced oxidative stress and myocardial fibrosis with improved mitochondrial architecture. HO-1 protein levels were increased in the hearts of exercising mice compared to sedentary WD fed females. ConclusionsThis study provides seminal evidence that exercise can prevent diastolic dysfunction in WD-induced obesity in females even without changes in body weight. Furthermore, the reduction in myocardial oxidative stress and fibrosis and improved HO-1 levels in exercising mice suggests a novel mechanism for the antioxidant effect of exercise.

Abstract 10335: Systolic Motion of the Basal Right Ventricular Freewall is the Strongest Predictor of Global Function: A High Resolution 3D Cardiac Magnetic Resonance Study

Background: Right ventricular (RV) function has prognostic value in disease cohorts and the general population although its complex geometry and motion make rapid assessment difficult. Several two-dimensional regional measures are used to estimate global RV function, however the optimal measure is not known. Methods: High-resolution 3-dimensional cardiac magnetic resonance (3D-CMR) cine imaging of the whole heart was acquired in 300 healthy volunteers and a computational model of RV motion created. From this model, points where regional function was significantly associated with global function were identified, and a two-dimensional, Optimized Single-Point Marker (SPM-O) of global function developed. This marker was prospectively compared with tricuspid annular plane systolic excursion (TAPSE), septum-freewall displacement (SFD) and their fractional derivatives (TAPSE-F, SFD-F) in a test cohort (n=300). Performance in predicting RVEF was compared by correlation, bootstrapped linear regression and mean absolute error. Results: Three-dimensional imaging suggested that RVEF was significantly associated with systolic function in a contiguous 7.3cm 2 patch of the basal RV freewall which combined components of transverse (38%), longitudinal (35%) and circumferential (27%) contraction. SPM-O was identified where this patch coincided with the four-chamber view and combined longitudinal and transverse contraction. In the test cohort, all single-point surrogates correlated with RVEF (p&lt;0.01), but correlation was significantly higher for SPM-O (R = 0.44) than TAPSE (R = 0.24, p&lt;0.002) and SFD (R = 0.22, p&lt;0.001), and non-significantly higher than TAPSE-F (R = 0.40, p=0.50) and SFD-F (R = 0.43, p=0.86). SPM-O explained more of the observed variance in RVEF (19%) and predicted RVEF more accurately than any other 2D marker (median error 2.8 vs 3.6%, p&lt;0.001). Conclusions: Systolic motion of the basal RV freewall in the four-chamber plane is a more accurate surrogate of global function than other two-dimensional estimators. However, the performance of two-dimensional estimators is fundamentally limited by a failure to adequately summarize three-dimensional contractile patterns, such as those found in the right ventricle.

Quantitative assessment of myocardial fibrosis in an age-related rat model by ex vivo late gadolinium enhancement magnetic resonance imaging with histopathological correlation

Late gadolinium enhanced (LGE) cardiac magnetic resonance (CMR) imaging can detect the presence of myocardial infarction from ischemic cardiomyopathies (ICM). However, it is more challenging to detect diffuse myocardial fibrosis from non-ischemic cardiomyopathy (NICM) with this technique due to more subtle and heterogeneous enhancement of the myocardium. This study investigates whether high-resolution LGE CMR can detect age-related myocardial fibrosis using quantitative texture analysis with histological validation. LGE CMR of twenty-four rat hearts (twelve 6-week-old and twelve 2-year-old) was performed using a 7T MRI scanner. Picrosirius red was used as the histopathology reference for collagen staining. Fibrosis in the myocardium was quantified with standard deviation (SD) threshold methods from the LGE CMR images and 3D contrast texture maps that were computed from gray level co-occurrence matrix of the CMR images. There was a significant increase of collagen fibers in the aged compared to the young rat histology slices (2.60±0.27 %LV vs. 1.24±0.29 %LV, p<0.01). Both LGE CMR and texture images showed a significant increase of myocardial fibrosis in the elderly compared to the young rats. Fibrosis in the LGE CMR images correlated strongly with histology with the 3 SD threshold (r=0.84, y=0.99x+0.00). Similarly, fibrosis in the contrast texture maps correlated with the histology using the 4 SD threshold (r=0.89, y=1.01x+0.00). High resolution ex-vivo LGE CMR can detect the presence of diffuse fibrosis that naturally developed in elderly rat hearts. Our results suggest that texture analysis may improve the assessment of myocardial fibrosis in LGE CMR images.

259 ASYMMETRICAL SEPTAL HYPERTROPHY IS ASSOCIATED WITH MEAN ARTERIAL BLOOD PRESSURE IN HEALTHY ADULTS: DATA FROM HIGH RESOLUTION 3D CARDIAC MRI

Background Left ventricular hypertrophy (LVH) is the result of complex interactions between genes and environmental factors, and an independent risk factor for all-cause mortality. Clinically, it is important to differentiate ‘physiological’ LVH, such as in hypertension, from pathological LVH as found in hypertrophic cardiomyopathy. Standard methods of cardiac phenotyping such as echocardiography or 2D cardiac magnetic resonance (CMR) provide only macroscopic descriptors of LV mass (LVM) and function. These methods are underpowered for population wide study of regional wall thickness variability. Methods and Results 187 healthy multi-ethnic volunteers (105 female, age range 18–72, mean age 40) were recruited into a sub-study of the UK GenScan project. Exclusion criteria included established history of cardiovascular disease, hypertension, diabetes or hypercholesterolemia. Subjects were phenotyped by CMR using a 1.5T Philips Achieva system with a 32 element cardiac phased-array coil. High resolution 3D cine imaging of the LV was obtained with a voxel size of 2x2x4 mm and 20 cardiac phases. Three blood pressure (BP) measurements were taken and averaged (in mmHg): Mean systolic BP 123 (range 90–186), mean diastolic BP 80.4 (range 47–109). The high resolution 3D images were automatically segmented using training data from 10 healthy volunteers in which the myocardium had been manually labelled at end-diastole and end-systole (Figure 1). The 187 3D segmentations were exactly co-registered with each other so that corresponding points within the myocardium could be accurately compared within the cohort. Mean wall thickness was calculated at each point as the distance between the endocardial and epicardial surfaces. Automated measurements were validated against manual readings using standard clinical software (Philips Extended Workspace). LV end-diastolic volumes and LVM measurements were highly correlated (R 2 =.98 and R 2 =0.93 respectively). Mass univariate analysis was performed on the co-registered 3D models with wall thickness as the dependent variable. Pooling data from all the subjects, we plotted wall thickness at each 3D coordinate as a linear function of Mean Arterial Pressures (MAP) with gender and age held constant. The 3D models showed that blood pressure associated LVH begins asymmetrically within the mid-septum and progressively extends towards the base and apex with rising MAP (Figure 2). The lateral wall and apex are relatively spared. Conclusions Whole-heart high-resolution 3D CMR provides new opportunities for quantitative phenotyping of the heart and understanding the genetic and environmental determinants of heart disease. In this study we used these techniques to show the pattern of progressive asymmetrical septal hypertrophy that is associated with increasing blood pressure even within the general population.

1337 CARDIAC FUNCTION IMPROVES FOLLOWING HIGH INTENSITY INTERMITTENT EXERCISE THERAPY IN NON-ALCOHOLIC FATTY LIVER DISEASE

associated with a twofold greater risk of developing cardiovascular disease than those without. Recent research has shown that there are alterations in cardiac structure and function in NAFLD in the absence of overt cardiac disease. This study aimed to investigate exercise as a therapeutic tool to decrease cardiac risk in NAFLD. Patients and Methods: Twenty adults with NAFLD were randomised to 12 weeks of high intensity intermittent training or continue standard care. Cardiac structure and function were assessed using high resolution cardiac magnetic resonance imaging and tagging at 3.0T. High energy phosphate metabolism was assessed using 31 P-spectroscopy to measure PCr/ATP ratio. People with a history of discrete cardiac events or potential cardiac symptoms were excluded from the study. Liver fat was assessed using 1 H-magnetic resonance spectroscopy. The intervention group undertook exercise 3 times per week. Results: Exercise improved diastolic function in adults with NAFLD. E/A ratio increased with exercise (1.16±0.47 to 1.49±0.62; p = 0.022) but not in control (1.48± 0.98 to 1.17 ±0.46; p = 0.346) as did the early diastolic filling rate (exercise: 261.2±70.8 to 315.3±93.6 ml/s; p = 0.008, control: 276.2±86.2 to 281.9±75.3 ml/s; p = 0.757). Exercise also decreased peak cardiac torsion (exercise: 7.78±2.49 to 6.34±1.84deg; p = 0.048. control: 5.48±0.96 to 6.50±2.16deg; p = 0.300) but had no effect on cardiac structure, systolic function, or cardiac energetics. Conclusions: A 12-week high intensity intermittent exercise programme improves cardiac diastolic function and torsion in adults with NAFLD. Clinical care teams should consider high intensity intermittent exercise as part of their therapeutic regimen to modify the excess risk of cardiovascular disease associated with NAFLD.

Classification of Coronary Atherosclerotic Plaques Ex Vivo With T1, T2, and Ultrashort Echo Time CMR

This study sought to determine whether the classification of human coronary atherosclerotic plaques with T1, T2, and ultrashort echo time (UTE) cardiac magnetic resonance (CMR) would correlate well with atherosclerotic plaque classification by histology. CMR has been extensively used to classify carotid plaque, but its ability to characterize coronary plaque remains unknown. In addition, the detection of plaque calcification by CMR remains challenging. Here, we used T1, T2, and UTE CMR to evaluate atherosclerotic plaques in fixed post-mortem human coronary arteries. We hypothesized that the combination of T1, T2, and UTE CMR would allow both calcified and lipid-rich coronary plaques to be accurately detected. Twenty-eight plaques from human donor hearts with proven coronary artery disease were imaged at 9.4-T with a T1-weighted 3-dimensional fast low-angle shot (FLASH) sequence (250-μm resolution), a T2-weighted rapid acquisition with refocused echoes (RARE) sequence (in-plane resolution 0.156 mm), and an UTE sequence (300-μm resolution). Plaques showing selective hypointensity on T2-weighted CMR were classified as lipid-rich. Areas of hypointensity on the T1-weighted images, but not the UTE images, were classified as calcified. Hyperintensity on the T1-weighted and UTE images was classified as hemorrhage. Following CMR, histological characterization of the plaques was performed with a pentachrome stain and established American Heart Association criteria. CMR showed high sensitivity and specificity for the detection of calcification (100% and 90%, respectively) and lipid-rich necrotic cores (90% and 75%, respectively). Only 2 lipid-rich foci were missed by CMR, both of which were extremely small. Overall, CMR-based classification of plaque was in complete agreement with the histological classification in 22 of 28 cases (weighted κ = 0.6945, p < 0.0001). The utilization of UTE CMR allows plaque calcification in the coronary arteries to be robustly detected. High-resolution CMR with T1, T2, and UTE contrast enables accurate classification of human coronary atherosclerotic plaque.

Paradoxical changes in lumen size during progression and regression of carotid atherosclerosis

Summary Atherosclerotic changes regarding the lipid pool and frbrous cap are related to the lumen and show countgerintuitive changes; a discourse on Glagov’s Hypothesis. Background Relative changes in arterial lumen size during progression and regression of atherosclerosis particularly in response to lipid modulating therapy are largely unknown. This study was designed to investigate the effects of statin therapy on human carotid atherosclerotic lesions as measured by high-resolution Cardiac Magnetic Resonance (CMR). Methods Via CMR (1.5T GE, WI), 35 carotid arteries of 18 asymptomatic, ‘statin naive’ patients with maximum carotid stenosis >50% (mean 64±21), were imaged at baseline and following 12 months of randomized, blinded statin therapy (simvastatin 40mg or Vytorin (Ezetimibe 10mg/ simvastatin 40mg)). The effects of statins on these lesions were evaluated as changes in carotid outer wall area (OWA), lumen area (LuA), vessel wall area (VWA), lipid area (LpA) and lipid percentage (Lp%). The percentage of stenosis of each slice was determined in reference to a normal or near normal sl. Results A total of 707-2mm slices of interpretable quality were available representing 39 in vivo plaques. Among these as followed over time, 378 (53.5%) demonstrated progression while 329 (46.5%) showed regression. Among ‘Progressors’, OWA, VWA, Lp% and LuA increased (P< .001 for OWA, VWA and Lp% and 0.14 for LuA), while among ‘Regressors’, all the above parameters decreased significantly (P<.001 for all). There was no statistically significant change in any of the parameters when all contiguous slices of all carotid plaques were analyzed in a 3D fashion. Conclusions Changes in carotid plaque after lipid lowering therapy, as measured by high-resolution CMR depict a counterintuitive effect on lumen size: as VWA and LpA decrease so does the LuA. Similarly, as VWA and LpA increase so does LuA. The measurement of luminal area may not be ar eliable measure of response of carotid plaque to statin therapy, as progression of carotid atherosclerosis is associated with a paradoxical increase and regression of atherosclerosis with a paradoxical decrease in luminal area. Funding Internal.

A Quantitative Pixel-Wise Measurement of Myocardial Blood Flow by Contrast-Enhanced First-Pass CMR Perfusion Imaging: Microsphere Validation in Dogs and Feasibility Study in Humans

The aim of this study was to evaluate fully quantitative myocardial blood flow (MBF) at a pixel level based on contrast-enhanced first-pass cardiac magnetic resonance (CMR) imaging in dogs and in patients. Microspheres can quantify MBF in subgram regions of interest, but CMR perfusion imaging may be able to quantify MBF and differentiate blood flow at a much higher resolution. First-pass CMR perfusion imaging was performed in a dog model with local hyperemia induced by intracoronary adenosine. Fluorescent microspheres were the reference standard for MBF validation. CMR perfusion imaging was also performed on patients with significant coronary artery disease (CAD) by invasive coronary angiography. Myocardial time-signal intensity curves of the images were quantified on a pixel-by-pixel basis using a model-constrained deconvolution analysis. Qualitatively, color CMR perfusion pixel maps were comparable to microsphere MBF bull's-eye plots in all animals. Pixel-wise CMR MBF estimates correlated well against subgram (0.49 ± 0.14 g) microsphere measurements (r = 0.87 to 0.90) but showed minor underestimation of MBF. To reduce bias due to misregistration and minimize issues related to repeated measures, 1 hyperemic and 1 remote sector per animal were compared with the microsphere MBF, which improved the correlation (r = 0.97 to 0.98), and the bias was close to zero. Sector-wise and pixel-wise CMR MBF estimates also correlated well (r = 0.97). In patients, color CMR stress perfusion pixel maps showed regional blood flow decreases and transmural perfusion gradients in territories served by stenotic coronary arteries. MBF estimates in endocardial versus epicardial subsectors, and ischemic versus remote sectors, were all significantly different (p < 0.001 and p < 0.01, respectively). Myocardial blood flow can be quantified at the pixel level (∼32 μl of myocardium) on CMR perfusion images, and results compared well with microsphere measurements. High-resolution pixel-wise CMR perfusion maps can quantify transmural perfusion gradients in patients with CAD.

MRI morphological and functional method for clear distinction of patients with left ventricular non-compaction, inflammatory dilated cardiomyopathy and physiological myocardial trabeculation

Background Left ventricular non-compaction (LVNC) cardiomyopathy is characterized by a thin, compacted epimyocardial and a thick non-compacted, trabeculated endomyocardial layer. High-resolution cardiac magnetic resonance imaging (CMR) has been clinically successfully used to establish a Non-compact-to-compact- (NCTC) ratio of 2.3 in a 4-chamber view which is regarded pathological. Clinically, in patients with dilated cardiomyopathy (DCMP) and noticeably even in volunteers with physiological myocardial trabecularisation, up to 28% of verifiably healthy participants demonstrated the NCTC-ratio ≥ 2.3 so that there is a clinical need for a better distinction between patients with LVNC, DCMP and healthy subjects. We hypothesized that MRI is able to clearly distinguish LVNC from DCMP and healthy volunteers by a novel combined MRI and statistical approach of morphological and functional parameters. Methods 31 LVNC patients, defined by an MRI NCTC-ratio >2.3 (in a 4-chamber view plus one additional parameter (fulfilment of echo-criteria, histology, genetic proof, invasive X-ray), 13 patients with histologically proven inflammatory DCMP as well as 117 male/female healthy volunteers were studied employing a vector-ECG gated multislice 2-, 3-, 4-chamber and short axis (SA) standard cine SSFP-sequence covering the entire left ventricle. Functional parameters like end-diastolic, end-systolic volumes and ejection fraction were generated via SA SSFP slices as usual. Compacted and non-compacted

118 High-resolution cardiac magnetic resonance perfusion imaging vs positron emission tomography for the detection and localisation of coronary artery disease

Background Non-invasive imaging has a key role in the detection of coronary artery disease (CAD). Its importance has been affirmed by recent National Institute of Clinical Excellence (NICE) guidelines. Localisation of ischaemia to a coronary territory is also important in patient management. Cardiac Magnetic Resonance (CMR) perfusion imaging is a well-established and radiation-free test for these purposes. However, there are few data comparing perfusion CMR with Positron Emission Tomography (PET), which is widely regarded as the non-invasive gold standard. Furthermore novel CMR methods, including those based on k-t acceleration techniques, allow myocardial perfusion imaging with unprecedented spatial resolution. Methods 31 patients with known or suspected CAD referred for diagnostic x-ray coronary angiography (XCA) underwent both CMR and PET examinations. Both PET and CMR protocols included adenosine stress and rest perfusion imaging. CMR perfusion imaging was performed at 1.5T with a k-t -accelerated steady-state free-precession sequence. PET imaging was performed with 13 N-Ammonia. The Abstract 118 figure 1 shows an example. Experts blinded to the clinical data analysed the imaging data and experts blinded to the imaging results visually analysed the XCA data. A significant coronary artery stenosis was defined as ≥70% reduction in diameter or a fractional flow reserve Results Patient characteristics are shown in the Abstract 118 table 1. Mean age ± SD was 64±9 years. One CMR examination was non-diagnostic. The interval between PET and CMR was 2±6 days (77% same day), between PET and XCA 22±28 days and between CMR and XCA 22±29 days. The prevalence of CAD was 81%. For the detection of CAD PET sensitivity was 80% (95% CI 59% to 92%) and specificity was 67% (24% to 94%). CMR sensitivity was 83% (95% CI 62 to 95%) and specificity was also 83% (36% to 99%). In patients with CAD ischaemia was localised to 63% of the territories supplied by stenotic arteries by PET and 76% by CMR. Remote ischaemia was detected in 24% of territories by PET and 16% by CMR. Conclusions CMR is at least as accurate as PET for the diagnosis of CAD and also for the localisation of ischaemia to coronary territories. Relatively low numbers mean that CIs are wide and further work is required. Using an anatomic test as the reference-standard for functional tests has well-described limitations. Remote ischaemia is likely to occur for several reasons including underestimation of disease severity at XCA, microvascular disease and also false positive results.