Filip Zemrak

Late Gadolinium Enhancement CMR Predicts Adverse Cardiovascular Outcomes and Mortality in Patients With Coronary Artery Disease: Systematic Review and Meta-Analysis

Cardiovascular magnetic resonance (CMR) has a recognized role in diagnosing and monitoring coronary artery disease (CAD). Multiple studies have shown that CMR can predict adverse outcomes. We reviewed contemporary available literature to establish the role of CMR with late gadolinium enhancement (LGE) in predicting mortality and major adverse cardiac events (MACEs) in patients with CAD. Meta-analysis of available prospective studies showed that the presence of LGE increases the hazards of death by more than 4 times and of MACE by almost 4 times. The size of LGE (per gram or percent) increases the hazards of death and MACE by 4% and 5%, respectively. The presence and size of LGE predict mortality and MACE in CAD. Various parameters derived from LGE images enhance the predictive value. Large randomized controlled trials are needed to establish the actual value of LGE and other derived parameters in the wider population.

UK Biobank’s cardiovascular magnetic resonance protocol

BackgroundUK Biobank’s ambitious aim is to perform cardiovascular magnetic resonance (CMR) in 100,000 people previously recruited into this prospective cohort study of half a million 40-69 year-olds.Methods/designWe describe the CMR protocol applied in UK Biobank’s pilot phase, which will be extended into the main phase with three centres using the same equipment and protocols. The CMR protocol includes white blood CMR (sagittal anatomy, coronary and transverse anatomy), cine CMR (long axis cines, short axis cines of the ventricles, coronal LVOT cine), strain CMR (tagging), flow CMR (aortic valve flow) and parametric CMR (native T1 map).DiscussionThis report will serve as a reference to researchers intending to use the UK Biobank resource or to replicate the UK Biobank cardiovascular magnetic resonance protocol in different settings.

Fractal Analysis of Myocardial Trabeculations in 2547 Study Participants: Multi-Ethnic Study of Atherosclerosis.

PURPOSE To quantitatively determine the population variation and relationship of left ventricular (LV) trabeculation to LV function, structure, and clinical variables. MATERIALS AND METHODS This HIPAA-compliant multicenter study was approved by institutional review boards of participating centers. All participants provided written informed consent. Participants from the Multi-Ethnic Study of Atherosclerosis with cardiac magnetic resonance (MR) data were evaluated to quantify LV trabeculation as a fractal dimension (FD). Entire cohort participants free of cardiac disease, hypertrophy, hypertension, and diabetes were stratified by body mass index (BMI) into three reference groups (BMI <25 kg/m(2); BMI ≥25 kg/m(2) to <30 kg/m(2); and BMI ≥30 kg/m(2)) to explore maximal apical FD (FDMaxApical). Multivariable linear regression models determined the relationship between FD and other parameters. RESULTS Included were 2547 participants (mean age, 68.7 years ± 9.1 [standard deviation]; 1211 men). FDMaxApical are in arbitrary units. FDMaxApical reference ranges for BMI 30 kg/m(2) or greater (n = 163), 25 kg/m(2) or greater to less than 30 kg/m(2) (n = 206), and less than 25 kg/m(2) (n = 235) were 1.203 ± 0.06 (95% confidence interval: 1.194, 1.212), 1.194 ± 0.06 (95% confidence interval: 1.186, 1.202), and 1.169 ± 0.05 (95% confidence interval: 1.162, 1.176), respectively. In the entire cohort, adjusted for anthropometrics, trabeculation was higher in African American participants (standardized β [sβ] = 0.09; P ≤ .001) and Hispanic participants (sβ = 0.05; P = .013) compared with white participants and was also higher in African American participants compared with Chinese American participants (sβ = 0.08; P = .01), and this persisted after adjustment for hypertension and LV size. Hypertension (sβ = 0.07; P < .001), LV mass (sβ = 0.22; P < .001), and wall thickness (sβ = 0.27; P < .001) were positively associated with FDMaxApical even after adjustment. In the group with BMIs less than 25 kg/m(2), Chinese American participants had less trabeculation than white participants (sβ = -0.15; P = .032). CONCLUSION Fractal analysis of cardiac MR imaging data measures endocardial complexity, which helps to differentiate normal from abnormal trabecular patterns in healthy versus diseased hearts. Trabeculation is influenced by race and/or ethnicity and, more importantly, by cardiac loading conditions and comorbidities. Clinicians who interpret cine MR imaging data should expect slightly less endocardial complexity in Chinese American patients and more in African American patients, Hispanic patients, hypertensive patients, and those with hypertrophy.

Fractal frontiers in cardiovascular magnetic resonance: towards clinical implementation

Many of the structures and parameters that are detected, measured and reported in cardiovascular magnetic resonance (CMR) have at least some properties that are fractal, meaning complex and self-similar at different scales. To date however, there has been little use of fractal geometry in CMR; by comparison, many more applications of fractal analysis have been published in MR imaging of the brain.This review explains the fundamental principles of fractal geometry, places the fractal dimension into a meaningful context within the realms of Euclidean and topological space, and defines its role in digital image processing. It summarises the basic mathematics, highlights strengths and potential limitations of its application to biomedical imaging, shows key current examples and suggests a simple route for its successful clinical implementation by the CMR community.By simplifying some of the more abstract concepts of deterministic fractals, this review invites CMR scientists (clinicians, technologists, physicists) to experiment with fractal analysis as a means of developing the next generation of intelligent quantitative cardiac imaging tools.

Hypertrabeculated Left Ventricular Myocardium in Relationship to Myocardial Function and Fibrosis: The Multi-Ethnic Study of Atherosclerosis.

Purpose To determine if excess greater left ventricle (LV) trabeculation is associated with decreased average regional myocardial function, diffuse fibrosis, or both. Materials and Methods This was a HIPAA-compliant institutional board approved multicenter study, and all participants provided written informed consent. Participants in the Multi-Ethnic Study of Atherosclerosis (MESA) underwent a comprehensive cardiac magnetic resonance (MR) examination. LV trabeculation was measured with the maximal apical fractal dimension (FD), which is a marker of endocardial complexity. Demographic covariates, cardiovascular risk factors, and cardiac MR measurements were compared across quartiles of FD. Associations between FD and peak regional systolic circumferential strain (Ecc) and T1 time, a surrogate for diffuse myocardial fibrosis, were assessed with multivariable linear regression models. Results A total of 1123 subjects (593 [52.8%] female; mean age, 67.1 years ± 8.7 [standard deviation]) underwent FD and Ecc measurement, and 992 (521 [52.5%] female; mean age, 67.1 years ± 8.7) underwent FD and T1 measurement. Mean FD was 1.2 ± 0.07 in both groups, and mean Ecc was -18.3 ± 2.27 in the subjects who underwent FD and Ecc measurement. Global volumes and ejection fraction showed no differences between FD quartiles. However, with increasing FD quartile, Ecc was greater (indicating worse average regional function) (P < .001). After adjustment, greater trabeculation was associated with 21% worse myocardial strain (relative to the mean) per unit change in FD (regression coefficient = 4.0%; P < .001). There was no association between the degree of trabeculation and diffuse fibrosis measured with T1 mapping. Conclusion Average regional LV function was worse in individuals with greater LV trabeculation, supporting the concept of hypertrabeculation being an epiphenomenon of disease.

Left Ventricular Noncompaction, or Is It? ∗

Left ventricular noncompaction is a heart (cardiac) muscle disorder that occurs when the lower left chamber of the heart (left ventricle), which helps the heart pump blood, does not develop correctly. Instead of the muscle being smooth and firm, the cardiac muscle in the left ventricle is thick and appears spongy. The abnormal cardiac muscle is weak and has an impaired ability to pump blood because it either cannot completely contract or it cannot completely relax. For the heart to pump blood normally, cardiac muscle must contract and relax fully.

Characterisation of myocardial structure and function in adult-onset growth hormone deficiency using cardiac magnetic resonance

Growth hormone (GH) can profoundly influence cardiac function. While GH excess causes well-defined cardiac pathology, fewer data are available regarding the more subtle cardiac changes seen in GH deficiency (GHD). This preliminary study uses cardiac magnetic resonance imaging (CMR) to assess myocardial structure and function in GHD. Ten adult-onset GHD patients underwent CMR, before and after 6 and 12 months of GH replacement. They were compared to 10 age-matched healthy controls and sex-matched healthy controls. Left ventricular (LV) mass index (LVMi) increased with 1 year of GH replacement (53.8 vs. 57.0 vs. 57.3 g/m2, analysis of variance p = 0.0229). Compared to controls, patients showed a trend towards reduced LVMi at baseline (51.4 vs. 60.0 g/m2, p = 0.0615); this difference was lost by 1 year of GH treatment (57.3 vs. 59.9 g/m2, p = 0.666). Significantly reduced aortic area was observed in GHD (13.2 vs. 19.0 cm2/m2, p = 0.001). This did not change with GH treatment. There were no differences in other LV parameters including end-diastolic volume index (EDVi), end-systolic volume index, stroke volume index (SVi), cardiac index and ejection fraction. There was a trend towards reduced baseline right ventricular (RV)SVi (44.1 vs. 49.1 ml/m2, p = 0.0793) and increased RVEDVi over 1 year (70.3 vs. 74.3 vs. 73.8 ml/m2, p = 0.062). Two patients demonstrated interstitial expansion, for example with fibrosis, and three myocardial ischaemia as assessed by late gadolinium enhancement and stress perfusion. The increased sensitivity of CMR to subtle cardiac changes demonstrates that adult-onset GHD patients have reduced aortic area and LVMi increases after 1 year of GH treatment. These early data should be studied in larger studies in the future.

Excessive left ventricular trabeculation does not promote cardiac dysfunction in asymptomatic middle aged and older individuals with preserved cardiac function: an analysis from the Multi-Ethnic Study of Atherosclerosis

Background Left ventricular (LV) trabeculation is highly variable between individuals, and prominent trabeculation, or non-compaction, has been considered to be evidence of abnormal cardiac development. The significance of increased trabeculation in asymptomatic healthy individuals with preserved LV systolic function is unknown. The aim of this study was to determine if excessive LV trabeculation in middle aged and older subjects without LV dysfunction or advanced cardiac disease was associated with changes in cardiac volumes and function over the ensuing 10 years.

A comparison of cardiac motion analysis software packages: application to left ventricular deformation analysis in hypertensive patients

Background Although myocardial function is clinically assessed with global measurements (ventricular volumes, ejection fraction), recent research has shown that regional measurements, such as wall-thickening, strain, and torsion, could provide earlier sub-clinical markers to examine left ventricular (LV) dysfunction and myocardial diseases. Cardiovascular Magnetic Resonance myocardial feature tracking (CMR-FT) technique is used to post-process cine CMR images to provide a quantitative assessment of LV motion deformation parameters. It derives myocardial motion deformation from image features such as myocardium-blood cavity boundary and pixel intensities, and relies only on standard cine images to extract motion deformation. The main objective of this study is to compare two current feature tracking software packages in hypertensive patients. Methods 29 hypertensive subjects were prospectively recruited from a tertiary hypertension clinic and enrolled to undergo CMR examinations. All images were acquired using a 1.5T scanner (Siemens Medical Imaging, Germany), and a cardiac surface coil. LV function was assessed with cine acquisitions in the following planes: 2-chamber, 4-chamber and short-axis slices (basal, mid and apical levels). LV deformation was analysed using: 2D Cardiac Performance Analysis, MR (TomTec Imaging Systems, Munich, Germany) and CVI42 (Circle Cardiovascular Imaging Inc. Calgary, Canada). Endocardial and epicardial LV contours were drawn manually at the end diastolic phase in order to achieve best tracking results; the software packages then allow semi-automated analysis to provide quantitative measurement of global and regional deformation parameters. Results Results of circumferential, radial, and longitudinal strains are given in table 1. Statistical analysis was performed using the student’s paired t-test for dependent sample in order to assess the difference between the two software packages.All radial strain mean values obtained with CVI42 were higher than with Tomtec and the difference was statistically significant for all short-axis circumferential strains. This was also the case for shortaxis apical and 4-chamber radial strains. In total five parameters (short-axis apical and 4-chamber radial strains, all 3 short-axis slices circumferential strains) were statistically different and 5 were not. Conclusions From our results, there is a trend in circumferential strain in short-axis (apical, mid, and basal) where there is a significant difference in the values obtained by the two software packages, whereas radial and longitudinal strain values showed no clear trend. Therefore, there is a clear need for a gold standard validation to assess the accuracy of cardiac motion analysis software packages.

Automated cardiovascular magnetic resonance image analysis with fully convolutional networks

BackgroundCardiovascular resonance (CMR) imaging is a standard imaging modality for assessing cardiovascular diseases (CVDs), the leading cause of death globally. CMR enables accurate quantification of the cardiac chamber volume, ejection fraction and myocardial mass, providing information for diagnosis and monitoring of CVDs. However, for years, clinicians have been relying on manual approaches for CMR image analysis, which is time consuming and prone to subjective errors. It is a major clinical challenge to automatically derive quantitative and clinically relevant information from CMR images.MethodsDeep neural networks have shown a great potential in image pattern recognition and segmentation for a variety of tasks. Here we demonstrate an automated analysis method for CMR images, which is based on a fully convolutional network (FCN). The network is trained and evaluated on a large-scale dataset from the UK Biobank, consisting of 4,875 subjects with 93,500 pixelwise annotated images. The performance of the method has been evaluated using a number of technical metrics, including the Dice metric, mean contour distance and Hausdorff distance, as well as clinically relevant measures, including left ventricle (LV) end-diastolic volume (LVEDV) and end-systolic volume (LVESV), LV mass (LVM); right ventricle (RV) end-diastolic volume (RVEDV) and end-systolic volume (RVESV).ResultsBy combining FCN with a large-scale annotated dataset, the proposed automated method achieves a high performance in segmenting the LV and RV on short-axis CMR images and the left atrium (LA) and right atrium (RA) on long-axis CMR images. On a short-axis image test set of 600 subjects, it achieves an average Dice metric of 0.94 for the LV cavity, 0.88 for the LV myocardium and 0.90 for the RV cavity. The mean absolute difference between automated measurement and manual measurement is 6.1 mL for LVEDV, 5.3 mL for LVESV, 6.9 gram for LVM, 8.5 mL for RVEDV and 7.2 mL for RVESV. On long-axis image test sets, the average Dice metric is 0.93 for the LA cavity (2-chamber view), 0.95 for the LA cavity (4-chamber view) and 0.96 for the RA cavity (4-chamber view). The performance is comparable to human inter-observer variability.ConclusionsWe show that an automated method achieves a performance on par with human experts in analysing CMR images and deriving clinically relevant measures.