Impact of Field Strength in Clinical Cardiac Magnetic Resonance Imaging

Cardiac magnetic resonance imaging (MRI) is widely applied fur the noninvasive assessment of cardiac structure and function, and for tissue characterization. For more than 2 decades, 1.5 T has been considered the field strength of choice for cardiac MRI. Although the number of 3-T systems significantly increased in the past 10 years and numerous new developments were made, challenges seem to remain that hamper a widespread clinical use of 3-T MR systems for cardiac applications. As the number of clinical cardiac applications is increasing, with each having their own benefits at both field strengths, no "holy grail" field strength exists fur cardiac MRI that one should ideally use. This review describes the physical differences between 1.5 and 3 T, as well as the effect of these differences on major (routine) cardiac MRI applications, including functional imaging, edema imaging. late gadolinium enhancement. first-pass stress perfusion, myocardial mapping, and phase contrast flow imaging. For each application, the advantages and limitations at both 1.5 and 3 Tare discussed. Solutions and alternatives are provided to overcome potential limitations. Finally, we briefly elaborate on the potential use of alternative field strengths (ie, below 1.5 T and above 3 T) for cardiac MRI and conclude with field strength recommendations for the future of cardiac MRI

Impact of Field Strength in Clinical Cardiac Magnetic Resonance Imaging

Cardiac magnetic resonance imaging (MRI) is widely applied fur the noninvasive assessment of cardiac structure and function, and for tissue characterization. For more than 2 decades, 1.5 T has been considered the field strength of choice for cardiac MRI. Although the number of 3-T systems significantly increased in the past 10 years and numerous new developments were made, challenges seem to remain that hamper a widespread clinical use of 3-T MR systems for cardiac applications. As the number of clinical cardiac applications is increasing, with each having their own benefits at both field strengths, no "holy grail" field strength exists fur cardiac MRI that one should ideally use. This review describes the physical differences between 1.5 and 3 T, as well as the effect of these differences on major (routine) cardiac MRI applications, including functional imaging, edema imaging. late gadolinium enhancement. first-pass stress perfusion, myocardial mapping, and phase contrast flow imaging. For each application, the advantages and limitations at both 1.5 and 3 Tare discussed. Solutions and alternatives are provided to overcome potential limitations. Finally, we briefly elaborate on the potential use of alternative field strengths (ie, below 1.5 T and above 3 T) for cardiac MRI and conclude with field strength recommendations for the future of cardiac MRI

Persistent microvascular obstruction-like lesion after ventricular tachycardia ablation detected by novel dark-blood late gadolinium enhancement

Microvascular obstruction is a transient phenomenon of "no reflow" after myocardial infarction or radiofrequency ablation, diagnosed using late gadolinium enhancement cardiac MRI. We present a patient with a persistent microvascular obstruction-like lesion following radiofrequency ventricular tachycardia ablation post-myocardial infarction, which was best characterized by a novel dark-blood late gadolinium enhancement technique

A case report of a myocardial ischaemic attack: a novel hyperenhancement pattern on cardiac magnetic resonance in focal ischaemic injury

Background Delayed enhancement cardiac magnetic resonance (DE-CMR) is the reference standard for the non-invasive assessment of myocardial fibrosis. DE-CMR is able to distinguish ischaemic from non-ischaemic aetiologies based on differences in hyperenhancement distribution patterns. Hyperenhancement caused by ischaemic injury typically involves the endocardium, while hyperenhancement confined to the mid- and epicardial layers of the myocardium suggests a non-ischaemic aetiology. Case summary This is a case of a 20-year-old male with an unremarkable medical history with an acute ST-elevation myocardial infarction. DE-CMR revealed two distinct patterns of hyperenhancement: (i) a 'normal' wavefront-ischaemic pattern, and (ii) multiple atypical mid-wall and epicardial areas of focal hyperenhancement. Invasive coronary angiography (ICA) and coronary computed tomographic angiography (CCTA) showed multiple intracoronary thrombi and distal emboli in the left anterior descending, ramus circumflexus, and in smaller branches of the LCA. All hyperenhancement patterns observed on DE-CMR perfectly matched the distribution territories of the affected coronary arteries. Discussion This case with an acute myocardial infarction showed intracoronary thrombi and emboli on ICA and CCTA. Interestingly, DE-CMR showed two different patterns of hyperenhancement in the same territories of the coronary thrombi. This observation may challenge the concept that these non-endocardial areas of hyperenhancement on DE-CMR are always of non-ischaemic aetiology. It is hypothesized that occlusion of smaller distal branches of the coronary arteries may result in mid-wall or epicardial fibrosis as opposed to subendocardial fibrosis commonly found in patients with a large epicardial coronary occlusion. Clinicians should be aware of these atypical patterns to be able to initiate adequate medical therapy

Complementing sparse vascular imaging data by physiological adaptation rules

Mathematical modeling of pressure and flow waveforms in blood vessels using pulse wave propagation (PWP) models has tremendous potential to support clinical decision making. For a personalized model outcome, measurements of all modeled vessel radii and wall thicknesses are required. In clinical practice, however, data sets are often incomplete. To overcome this problem, we hypothesized that the adaptive capacity of vessels in response to mechanical load could be utilized to fill in the gaps of incomplete patient-specific data sets. We implemented homeostatic feedback loops in a validated PWP model to allow adaptation of vessel geometry to maintain physiological values of wall stress and wall shear stress. To evaluate our approach, we gathered vascular MRI and ultrasound data sets of wall thicknesses and radii of central and arm arterial segments of 10 healthy subjects. Reference models (i.e., termed RefModel, n = 10) were simulated using complete data, whereas adapted models (AdaptModel, n = 10) used data of one carotid artery segment only, and the remaining geometries in this model were estimated using adaptation. We evaluated agreement between RefModel and AdaptModel geometries, as well as that between pressure and flow waveforms of both models. Limits of agreement (bias +/- 2 SD of difference) between AdaptModel and RefModel radii and wall thicknesses were 0.2 +/- 2.6 mm and -140 +/- 557 mu m, respectively. Pressure and flow waveform characteristics of the AdaptModel better resembled those of the RefModels as compared with the model in which the vessels were not adapted. Our adaptation-based PWP model enables personalization of vascular geometries even when not all required data are available.NEW & NOTEWORTHY To benefit personalized pulse wave propagation (PWP) modeling, we propose a novel method that, instead of relying on extensive data sets on vascular geometries, incorporates physiological adaptation rules. The developed vascular adaptation model adequately predicted arterial radius and wall thickness compared with ultrasound and MRI estimates, obtained in humans. Our approach could be used as a tool to facilitate personalized modeling, notably in case of missing data, as routinely found in clinical settings

Symptomatic Carotid Plaques Demonstrate Less Leaky Plaque Microvasculature Compared With the Contralateral Side: A Dynamic Contrast-Enhanced Magnetic Resonance Imaging Study

Contains fulltext : 207086.pdf (publisher's version ) (Open Access)Background Rupture of a vulnerable carotid atherosclerotic plaque is an important underlying cause of ischemic stroke. Increased leaky plaque microvasculature may contribute to plaque vulnerability. These immature microvessels may facilitate entrance of inflammatory cells into the plaque. The objective of the present study is to investigate whether there is a difference in plaque microvasculature (the volume transfer coefficient K(trans)) between the ipsilateral symptomatic and contralateral asymptomatic carotid plaque using noninvasive dynamic contrast-enhanced magnetic resonance imaging. Methods and Results Eighty-eight patients with recent transient ischemic attack or ischemic stroke and ipsilateral >2 mm carotid plaque underwent 3 T magnetic resonance imaging to identify plaque components and to determine characteristics of plaque microvasculature. The volume transfer coefficient K(trans), indicative for microvascular density, flow, and permeability, was calculated for the ipsilateral and asymptomatic plaque, using a pharmacokinetic model (Patlak). Presence of a lipid-rich necrotic core, intraplaque hemorrhage, and a thin and/or ruptured fibrous cap was assessed on multisequence magnetic resonance imaging . We found significantly lower K(trans) in the symptomatic carotid plaque compared with the asymptomatic side (0.057+/-0.002 min(-1) versus 0.062+/-0.002 min(-1); P=0.033). There was an increased number of slices with intraplaque hemorrhage (0.9+/-1.6 versus 0.3+/-0.8, P=0.002) and lipid-rich necrotic core (1.4+/-1.9 versus 0.8+/-1.4, P=0.016) and a higher prevalence of plaques with a thin and/or ruptured fibrous cap (32% versus 17%, P=0.023) at the symptomatic side. Conclusions K(trans) was significantly lower in symptomatic carotid plaques, indicative for a decrease of plaque microvasculature in symptomatic plaques. This could be related to a larger amount of necrotic tissue in symptomatic plaques. Clinical Trial Registration URL : http://www.clinicaltrials.gov.uk . Unique identifier: NCT 01208025

High-resolution structural-functional substrate-trigger characterization: Future roadmap for catheter ablation of ventricular tachycardia

Introduction Patients with ventricular tachyarrhythmias (VT) are at high risk of sudden cardiac death. When appropriate, catheter ablation is modestly effective, with relatively high VT recurrence and complication rates. Personalized models that incorporate imaging and computational approaches have advanced VT management. However, 3D patient-specific functional electrical information is typically not considered. We hypothesize that incorporating non-invasive 3D electrical and structural characterization in a patient-specific model improves VT-substrate recognition and ablation targeting.Materials and methods In a 53-year-old male with ischemic cardiomyopathy and recurrent monomorphic VT, we built a structural-functional model based on high-resolution 3D late-gadolinium enhancement (LGE) cardiac magnetic resonance imaging (3D-LGE CMR), multi-detector computed tomography (CT), and electrocardiographic imaging (ECGI). Invasive data from high-density contact and pace mapping obtained during endocardial VT-substrate modification were also incorporated. The integrated 3D electro-anatomic model was analyzed off-line.Results Merging the invasive voltage maps and 3D-LGE CMR endocardial geometry led to a mean Euclidean node-to-node distance of 5 & PLUSMN; 2 mm. Inferolateral and apical areas of low bipolar voltage ( 0.4) and with higher transmurality of fibrosis. Areas of functional conduction delay or block (evoked delayed potentials, EDPs) were in close proximity to 3D-LGE CMR-derived heterogeneous tissue corridors. ECGI pinpointed the epicardial VT exit at & SIM;10 mm from the endocardial site of origin, both juxtaposed to the distal ends of two heterogeneous tissue corridors in the inferobasal left ventricle. Radiofrequency ablation at the entrances of these corridors, eliminating all EDPs, and at the VT site of origin rendered the patient non-inducible and arrhythmia-free until the present day (20 months follow-up). Off-line analysis in our model uncovered dynamic electrical instability of the LV inferolateral heterogeneous scar region which set the stage for an evolving VT circuit.Discussion and conclusion We developed a personalized 3D model that integrates high-resolution structural and electrical information and allows the investigation of their dynamic interaction during arrhythmia formation. This model enhances our mechanistic understanding of scar-related VT and provides an advanced, non-invasive roadmap for catheter ablation

Evaluation of miCRovascular rarefaction in vascUlar Cognitive Impairment and heArt faiLure (CRUCIAL): Study protocol for an observational study

Introduction: Microvascular rarefaction, the functional reduction in perfused microvessels and structural reduction of microvascular density, seems to be an important mechanism in the pathophysiology of small blood vessel related disorders including vascular cognitive impairment (VCI) due to cerebral small vessel disease and heart failure with preserved ejection fraction (HFpEF). Both diseases share common risk factors including hypertension, diabetes mellitus, obesity, and ageing; in turn, these co-morbidities are associated with microvascular rarefaction. Our consortium aims to investigate novel non-invasive tools to quantify microvascular health and rarefaction in both organs, as well as surrogate biomarkers for cerebral and/or cardiac rarefaction (via sublingual capillary health, vascular density of the retina, and RNA content of circulating extracellular vesicles), and to determine whether microvascular density relates to disease severity.Methods/design: The clinical research program of CRUCIAL consists of four observational cohort studies. We aim to recruit 75 VCI patients, 60 HFpEF patients, 60 patients with severe aortic stenosis (AS) undergoing surgical aortic valve replacement as a pressure overload HFpEF model, and 200 elderly participants with mixed comorbidities to serve as controls. Data collected will include medical history, physical examination, cognitive testing, advanced brain and cardiac MRI, ECG, echocardiography, sublingual capillary health, optical coherence tomography angiography (OCTa), extracellular vesicles RNA analysis and myocardial remodelling-related serum biomarkers. The AS cohort undergoing surgery will also have myocardial biopsy for histological microvascular assessment. Discussion: CRUCIAL will examine the pathophysiological role of microvascular rarefaction in VCI and HFpEF using advanced brain and cardiac MRI techniques. Furthermore, we will investigate surrogate biomarkers for non-invasive, faster, easier, and cheaper assessment of microvascular density since these are more likely to be disseminated into widespread clinical practice. If microvascular rarefaction is an early marker of developing small vessel diseases, then measuring rarefaction may allow pre-clinical diagnosis, with implications for screening, risk stratification, and prevention. Further knowledge of the relevance of microvascular rarefaction and its underlying mechanisms may provide new avenues for research and therapeutic targets

Rationale and Design of the ISOLATION Study:: A Multicenter Prospective Cohort Study Identifying Predictors for Successful Atrial Fibrillation Ablation in an Integrated Clinical Care and Research Pathway

Introduction: Continuous progress in atrial fibrillation (AF) ablation techniques has led to an increasing number of procedures with improved outcome. However, about 30-50% of patients still experience recurrences within 1 year after their ablation. Comprehensive translational research approaches integrated in clinical care pathways may improve our understanding of the complex pathophysiology of AF and improve patient selection for AF ablation. Objectives: Within the "IntenSive mOlecular and eLectropathological chAracterization of patienTs undergoIng atrial fibrillatiOn ablatioN " (ISOLATION) study, we aim to identify predictors of successful AF ablation in the following domains: (1) clinical factors, (2) AF patterns, (3) anatomical characteristics, (4) electrophysiological characteristics, (5) circulating biomarkers, and (6) genetic background. Herein, the design of the ISOLATION study and the integration of all study procedures into a standardized pathway for patients undergoing AF ablation are described. Methods: ISOLATION (NCT04342312) is a two-center prospective cohort study including 650 patients undergoing AF ablation. Clinical characteristics and routine clinical test results will be collected, as well as results from the following additional diagnostics: determination of body composition, pre-procedural rhythm monitoring, extended surface electrocardiogram, biomarker testing, genetic analysis, and questionnaires. A multimodality model including a combination of established predictors and novel techniques will be developed to predict ablation success. Discussion: In this study, several domains will be examined to identify predictors of successful AF ablation. The results may be used to improve patient selection for invasive AF management and to tailor treatment decisions to individual patient