T2-weighted cardiovascular magnetic resonance in acute cardiac disease

Myocardial Injury by COVID-19 Infection Assessed by Cardiovascular Magnetic Resonance Imaging - A Prospective Multicenter Study

BACKGROUND

This prospective multicenter study assessed the prevalence of myocardial injury in patients with COVID-19 using cardiac magnetic resonance imaging (CMR).Methods and Results: We prospectively screened 505 patients with moderate to severe COVID-19 disease from 7 hospitals in Japan. Of these patients, 31 (mean [±SD] age 63.5±10.4 years, 23 [74%] male) suspected of myocardial injury, based on elevated serum troponin or B-type natriuretic peptide concentrations either upon admission or 3 months after discharge, underwent CMR 3 months after discharge. The primary endpoint was the presence of myocardial injury, defined by any of the following: (1) contrast enhancement in the left or right ventricle myocardium on late gadolinium enhancement CMR; (2) left or right ventricular dysfunction (defined as <50% and <45%, respectively); and (3) pericardial thickening on contrast enhancement. The mean (±SD) duration between diagnosis and CMR was 117±16 days. The primary endpoint was observed in 13 of 31 individuals (42%), with 8 (26%) satisfying the modified Lake Louise Criteria for the diagnosis of acute myocarditis.

CONCLUSIONS

This study revealed a high incidence of myocardial injury identified by CMR in patients with moderate to severe COVID-19 and abnormal findings for cardiac biomarkers.

Reliable Off-Resonance Correction in High-Field Cardiac MRI Using Autonomous Cardiac B0 Segmentation with Dual-Modality Deep Neural Networks

B0 field inhomogeneity is a long-lasting issue for Cardiac MRI (CMR) in high-field (3T and above) scanners. The inhomogeneous B0 fields can lead to corrupted image quality, prolonged scan time, and false diagnosis. B0 shimming is the most straightforward way to improve the B0 homogeneity. However, today's standard cardiac shimming protocol requires manual selection of a shim volume, which often falsely includes regions with large B0 deviation (e.g., liver, fat, and chest wall). The flawed shim field compromises the reliability of high-field CMR protocols, which significantly reduces the scan efficiency and hinders its wider clinical adoption. This study aims to develop a dual-channel deep learning model that can reliably contour the cardiac region for B0 shim without human interaction and under variable imaging protocols. By utilizing both the magnitude and phase information, the model achieved a high segmentation accuracy in the B0 field maps compared to the conventional single-channel methods (Dice score: 2D-mag = 0.866, 3D-mag = 0.907, and 3D-mag-phase = 0.938, all p < 0.05). Furthermore, it shows better generalizability against the common variations in MRI imaging parameters and enables significantly improved B0 shim compared to the standard method (SD(B0Shim): Proposed = 15 ± 11% vs. Standard = 6 ± 12%, p < 0.05). The proposed autonomous model can boost the reliability of cardiac shimming at 3T and serve as the foundation for more reliable and efficient high-field CMR imaging in clinical routines.

Resorbable conductive materials for optimally interfacing medical devices with the living

Implantable and wearable bioelectronic systems are arising growing interest in the medical field. Linking the microelectronic (electronic conductivity) and biological (ionic conductivity) worlds, the biocompatible conductive materials at the electrode/tissue interface are key components in these systems. We herein focus more particularly on resorbable bioelectronic systems, which can safely degrade in the biological environment once they have completed their purpose, namely, stimulating or sensing biological activity in the tissues. Resorbable conductive materials are also explored in the fields of tissue engineering and 3D cell culture. After a short description of polymer-based substrates and scaffolds, and resorbable electrical conductors, we review how they can be combined to design resorbable conductive materials. Although these materials are still emerging, various medical and biomedical applications are already taking shape that can profoundly modify post-operative and wound healing follow-up. Future challenges and perspectives in the field are proposed.

Mechanisms of Myocardial Edema Development in CVD Pathophysiology

Myocardial edema is the excess accumulation of fluid in the myocardial interstitium or cardiac cells that develops due to changes in capillary permeability, loss of glycocalyx charge, imbalance in lymphatic drainage, or a combination of these factors. Today it is believed that this condition is not only a complication of cardiovascular diseases, but in itself causes aggravation of the disease and increases the risks of adverse outcomes. The study of molecular, genetic, and mechanical changes in the myocardium during edema may contribute to the development of new approaches to the diagnosis and treatment of this condition. This review was conducted to describe the main mechanisms of myocardial edema development at the molecular and cellular levels and to identify promising targets for the regulation of this condition based on articles cited in Pubmed up to January 2024.

Cardiac Magnetic Resonance Studies in a Large Animal Model that Simulates the Cardiac Abnormalities of Human Septic Shock

Background

Septic shock, in humans and in our well-established animal model, is associated with increases in biventricular end diastolic volume (EDV) and decreases in ejection fraction (EF). These abnormalities occur over 2 days and reverse within 10 days. Septic non-survivors do not develop an increase in EDV. The mechanism for this cardiac dysfunction and EDV differences is unknown.

Methods

Purpose-bred beagles randomized to receive intrabronchial Staphylococcus aureus (n=27) or saline (n=6) were provided standard ICU care including sedation, mechanical ventilation, and fluid resuscitation to a pulmonary arterial occlusion pressure of over 10mmHg. No catecholamines were administered. Over 96h, cardiac magnetic resonance imaging, echocardiograms, and invasive hemodynamics were serially performed, and laboratory data was collected. Tissue was obtained at 66h from six septic animals.

Results

From 0-96h after bacterial challenge, septic animals vs. controls had significantly increased left ventricular wall edema (6%) and wall thinning with loss of mass (15%) which was more pronounced at 48h in non-survivors than survivors. On histology, edema was located predominantly in myocytes, the interstitium, and endothelial cells. Edema was associated with significantly worse biventricular function (lower EFs), ventricular-arterial coupling, and circumferential strain. In septic animals, from 0-24h, the EDV decreased from baseline and, despite cardiac filling pressures being similar, decreased significantly more in non-survivors. From 24-48h, all septic animals had increases in biventricular chamber sizes. Survivors biventricular EDVs were significantly greater than baseline and in non-survivors, where biventricular EDVs were not different from baseline. Preload, afterload, or HR differences did not explain these differential serial changes in chamber size.

Conclusion

Systolic and diastolic cardiac dysfunction during sepsis is associated with ventricular wall edema. Rather than differences in preload, afterload, or heart rate, structural alterations to the ventricular wall best account for the volume changes associated with outcome during sepsis. In non-survivors, from 0-24h, sepsis induces a more severe diastolic dysfunction, further decreasing chamber size. The loss of left ventricular mass with wall thinning in septic survivors may, in part explain, the EDV increases from 24-48h. However, these changes continued and even accelerated into the recovery phase consistent with a reparative process rather than ongoing injury.

Clinical Perspective

What is new?: Utilizing multimodal imaging and hemodynamics, we demonstrate the cardiac changes of sepsis have injury and reparative phases.The injury phase (0-24h) has EDV decreases more profound in non-survivors and is associated with worse ventricular compliance, myocardial edema, and diastolic dysfunction.The recovery phase has left ventricular mass loss with wall thinning in survivors that explains the EDV increases (24-96h). These progressed into the EF recovery phase consistent with a reparative process removing damaged tissue.This is the first controlled CMR sepsis study supporting ventricular wall edema is a fundamental aspect of sepsis pathophysiology and dry mass loss a reparative mechanism.What are the clinical implications?: Despite optimizing filling pressures, the cardiac changes in ventricular wall structure and function associated with survival and non-survival in sepsis still occurred, thereby discounting fluid resuscitation as the major factor of therapeutic importance for cardiac function and survival.The changes reported here have potential implications for sepsis treatment especially in the field of fluid resuscitation. These findings yield new understanding into the pathophysiology of sepsis cardiac dysfunction and allow for novel phenotyping and prognosticating of the syndrome with ventricular compliance and EDVs. This also offers potentially high yielding targets for research for new therapeutic approaches for sepsis and heart failure.

MRI Quantification of Cardiac Structure and Function in Cardiomyopathy Patients

Cardiac Magnetic Resonance Imaging (CMRI) is a quantitative technique that enables non-invasive assessment of heart structure and contractile function as well as the mechanisms underlying cardiovascular disease. Here we provide step-by-step instructions and imaging protocols for conducting cardiac MRI exam on the patients with cardiomyopathies. Our imaging protocols are specific to the 3 Tesla magnetic field strength.

Sarcoid heart disease and imaging

Cardiac sarcoidosis (CS) can mimic any cardiomyopathy due to its ability to manifest with a variety of clinical presentations. The exact prevalence of CS remains unknown but has been reported ranging from 2.3% to as high as 29.9% among patients presenting with new onset cardiomyopathy and/or atrioventricular block. Early and accurate diagnosis of CS is often challenging due to the nature of disease progression and lack of diagnostic reference standard. The current diagnostic criteria for CS are lacking in sensitivity and specificity. Here, we review the contemporary role of advanced imaging modalities such as cardiac magnetic resonance imaging and positron emission tomography/computed tomography imaging in diagnosing and prognosticating patients with CS.

Aligning Multi-Sequence CMR Towards Fully Automated Myocardial Pathology Segmentation

Myocardial pathology segmentation (MyoPS) is critical for the risk stratification and treatment planning of myocardial infarction (MI). Multi-sequence cardiac magnetic resonance (MS-CMR) images can provide valuable information. For instance, balanced steady-state free precession cine sequences present clear anatomical boundaries, while late gadolinium enhancement and T2-weighted CMR sequences visualize myocardial scar and edema of MI, respectively. Existing methods usually fuse anatomical and pathological information from different CMR sequences for MyoPS, but assume that these images have been spatially aligned. However, MS-CMR images are usually unaligned due to the respiratory motions in clinical practices, which poses additional challenges for MyoPS. This work presents an automatic MyoPS framework for unaligned MS-CMR images. Specifically, we design a combined computing model for simultaneous image registration and information fusion, which aggregates multi-sequence features into a common space to extract anatomical structures (i.e., myocardium). Consequently, we can highlight the informative regions in the common space via the extracted myocardium to improve MyoPS performance, considering the spatial relationship between myocardial pathologies and myocardium. Experiments on a private MS-CMR dataset and a public dataset from the MYOPS2020 challenge show that our framework could achieve promising performance for fully automatic MyoPS.

Abnormal release of cardiac biomarkers in the presence of myocardial oedema evaluated by cardiac magnetic resonance after uncomplicated revascularization procedures

AIMS

To analyse the association of myocardial oedema (ME), observed as high T2 signal intensity (HT2) in cardiac magnetic resonance imaging, with the release of cardiac biomarkers, ventricular ejection, and clinical outcomes after revascularization.

METHODS AND RESULTS

Patients with stable coronary artery disease with the indication for revascularization were included. Biomarker levels [troponin I (cTnI) and creatine kinase MB (CK-MB)] and T2-weighted and late gadolinium enhancement (LGE) images were obtained before and after the percutaneous or surgical revascularization procedures. The association of HT2 with the levels of biomarkers, with and without LGE, evolution of left ventricular ejection fraction (LVEF), and 5-year clinical outcomes were assessed. A total of 196 patients were divided into 2 groups: Group 1 (HT2, 40) and Group 2 (no HT2, 156). Both peak cTnI (8.9 and 1.6 ng/mL) and peak CK-MB values (44.7 and 12.1 ng/mL) were significantly higher in Group 1. Based on the presence of new LGE, patients were stratified into Groups A (no HT2/LGE, 149), B (HT2, 9), C (LGE, 7), and D (both HT2/LGE, 31). The peak cTnI and CK-MB values were 1.5 and 12.0, 5.4 and 44.7, 5.0 and 18.3, and 9.8 and 42.8 ng/mL in Groups A, B, C, and D, respectively, and were significantly different. The average LVEF decreased by 4.4% in Group 1 and increased by 2.2% in Group 2 (P = 0.057).

CONCLUSION

ME after revascularization procedures was associated with increased release of cardiac necrosis biomarkers, and a trend towards a difference in LVEF, indicating a role of ME in cardiac injury after interventions.

Myocardial Tissue Characterization in Patients with Hypertensive Crisis, Positive Troponin, and Unobstructed Coronary Arteries: A Cardiovascular Magnetic Resonance-Based Study

Hypertensive crisis can present with cardiac troponin elevation and unobstructed coronary arteries. We used cardiac magnetic resonance (CMR) imaging to characterize the myocardial tissue in patients with hypertensive crisis, elevated cardiac troponin, and unobstructed coronary arteries. Patients with hypertensive crisis and elevated cardiac troponin with coronary artery stenosis <50% were enrolled. Patients with troponin-negative hypertensive crisis served as controls. All participants underwent CMR imaging at 1.5 Tesla. Imaging biomarkers and tissue characteristics were compared between the groups. There were 19 patients (63% male) with elevated troponin and 24 (33% male) troponin-negative controls. The troponin-positive group was older (57 ± 11 years vs. 47 ± 14 years, p = 0.015). The groups had similar T2-weighted signal intensity ratios and native T1 times. T2 relaxation times were longer in the troponin-positive group, and the difference remained significant after excluding infarct-pattern late gadolinium enhancement (LGE) from the analysis. Extracellular volume (ECV) was higher in the troponin-positive group (25 ± 4 ms vs. 22 ± 3 ms, p = 0.008) and correlated strongly with T2 relaxation time (rs = 0.701, p = 0.022). Late gadolinium enhancement was 32% more prevalent in the troponin-positive group (82% vs. 50%, p = 0.050), with 29% having infarct-pattern LGE. T2 relaxation time was independently associated with troponin positivity (OR 2.1, p = 0.043), and both T2 relaxation time and ECV predicted troponin positivity (C-statistics: 0.71, p = 0.009; and 0.77, p = 0.006). Left ventricular end-diastolic and left atrial volumes were the strongest predictors of troponin positivity (C-statistics: 0.80, p = 0.001; and 0.82, p < 0.001). The increased T2 relaxation time and ECV and their significant correlation in the troponin-positive group suggest myocardial injury with oedema, while the non-ischaemic LGE could be due to myocardial fibrosis or acute necrosis. These CMR imaging biomarkers provide important clinical indices for risk stratification and prognostication in patients with hypertensive crisis.

Differentiation of acute non-ST elevation myocardial infarction and acute infarct-like myocarditis by visual pattern analysis: a head-to-head comparison of different cardiac MR techniques

OBJECTIVES

Parametric cardiac magnetic resonance (CMR) techniques have improved the diagnosis of pathologies. However, the primary tool for differentiating non-ST elevation myocardial infarction (NSTEMI) from myocarditis is still a visual assessment of conventional signal-intensity-based images. This study aimed at analyzing the ability of parametric compared to conventional techniques to visually differentiate ischemic from non-ischemic myocardial injury patterns.

METHODS

Twenty NSTEMI patients, twenty infarct-like myocarditis patients, and twenty controls were examined using cine, T2-weighted CMR (T2w) and late gadolinium enhancement (LGE) imaging and T1/T2 mapping on a 1.5 T scanner. CMR images were presented in random order to two experienced fully blinded observers, who had to assign them to three categories by a visual analysis: NSTEMI, myocarditis, or healthy.

RESULTS

The conventional approach (cine, T2w and LGE combined) had the best diagnostic accuracy with 92% (95%CI: 81-97) for NSTEMI and 86% (95%CI: 71-94) for myocarditis. The diagnostic accuracies using T1 maps were 88% (95%CI: 74-95) and 80% (95%CI: 62-91), 84% (95%CI: 67-93) and 74% (95%CI: 54-87) for LGE, and 83% (95%CI: 66-92) and 73% (95%CI: 53-87) for T2w. The accuracies for cine (72% (95%CI: 52-86) and 60% (95%CI: 38-78)) and T2 maps (62% (95%CI: 40-79) and 47% (95%CI: 28-68)) were significantly lower compared to the conventional approach (p < 0.001 and p < 0.0001).

CONCLUSIONS

The conventional approach provided a reliable visual discrimination between NSTEMI, myocarditis, and controls. The diagnostic accuracy of a visual pattern analysis of T1 maps was not significantly inferior, whereas the diagnostic accuracy of T2 maps was not sufficient in this context.

CLINICAL RELEVANCE STATEMENT

The ability of parametric compared to conventional CMR techniques to visually differentiate ischemic from non-ischemic myocardial injury patterns can avoid potentially unnecessary invasive coronary angiography and help to shorten CMR protocols and to reduce the need of gadolinium contrast agents.

KEY POINTS

• A visual differentiation of ischemic from non-ischemic patterns of myocardial injury is reliably achieved by a combination of conventional CMR techniques (cine, T2-weighted and LGE imaging). • There is no significant difference in accuracies between visual pattern analysis on native T1 maps without providing quantitative values and a conventional combined approach for differentiating non-ST elevation myocardial infarction, infarct-like myocarditis, and controls. • T2 maps do not provide a sufficient diagnostic accuracy for visual pattern analysis for differentiating non-ST elevation myocardial infarction, infarct-like myocarditis, and controls.

New Non-Invasive Imaging Technologies in Cardiac Transplant Follow-Up: Acquired Evidence and Future Options

Heart transplantation (HT) is the established treatment for end-stage heart failure, significantly enhancing patients' survival and quality of life. To ensure optimal outcomes, the routine monitoring of HT recipients is paramount. While existing guidelines offer guidance on a blend of invasive and non-invasive imaging techniques, certain aspects such as the timing of echocardiographic assessments and the role of echocardiography or cardiac magnetic resonance (CMR) as alternatives to serial endomyocardial biopsies (EMBs) for rejection monitoring are not specifically outlined in the guidelines. Furthermore, invasive coronary angiography (ICA) is still recommended as the gold-standard procedure, usually performed one year after surgery and every two years thereafter. This review focuses on recent advancements in non-invasive and contrast-saving imaging techniques that have been investigated for HT patients. The aim of the manuscript is to identify imaging modalities that may potentially replace or reduce the need for invasive procedures such as ICA and EMB, considering their respective advantages and disadvantages. We emphasize the transformative potential of non-invasive techniques in elevating patient care. Advanced echocardiography techniques, including strain imaging and tissue Doppler imaging, offer enhanced insights into cardiac function, while CMR, through its multi-parametric mapping techniques, such as T1 and T2 mapping, allows for the non-invasive assessment of inflammation and tissue characterization. Cardiac computed tomography (CCT), particularly with its ability to evaluate coronary artery disease and assess graft vasculopathy, emerges as an integral tool in the follow-up of HT patients. Recent studies have highlighted the potential of nuclear myocardial perfusion imaging, including myocardial blood flow quantification, as a non-invasive method for diagnosing and prognosticating CAV. These advanced imaging approaches hold promise in mitigating the need for invasive procedures like ICA and EMB when evaluating the benefits and limitations of each modality.

Advanced Cardiac Imaging and Women's Chest Pain: A Question of Gender

Awareness of gender differences in cardiovascular disease (CVD) has increased: both the different impact of traditional cardiovascular risk factors on women and the existence of sex-specific risk factors have been demonstrated. Therefore, it is essential to recognize typical aspects of ischemic heart disease (IHD) in women, who usually show a lower prevalence of obstructive coronary artery disease (CAD) as a cause of acute coronary syndrome (ACS). It is also important to know how to recognize pathologies that can cause acute chest pain with a higher incidence in women, such as spontaneous coronary artery dissection (SCAD) and myocardial infarction with non-obstructive coronary arteries (MINOCA). Coronary computed tomography angiography (CCTA) and cardiac magnetic resonance imaging (CMR) gained a pivotal role in the context of cardiac emergencies. Thus, the aim of our review is to investigate the most frequent scenarios in women with acute chest pain and how advanced cardiac imaging can help in the management and diagnosis of ACS.

Cardiac Magnetic Resonance-Detected Acute Myocardial Edema as Predictor of Favourable Prognosis: A Comprehensive Review

Acute myocardial edema (AME) is increased water content in the myocardium and represents the first and transient pathophysiological response to an acute myocardial injury. In-vivo and non-invasive evaluation is feasible with cardiac magnetic resonance (CMR), which is a powerful imaging technique capable of tissue characterization. In the clinical setting, early demonstration of AME has a recognized diagnostic value for acute coronary syndromes and acute myocarditis, although its prognostic value is not well established. This article provides a comprehensive narrative review on the clinical meaning of AME in heart diseases. In particular, the available evidence of a possible favourable prognostic value in several clinical scenarios is addressed.

The Role of Multimodality Imaging in Pediatric Cardiomyopathies

Cardiomyopathies are a heterogeneous group of myocardial diseases representing the first cause of heart transplantation in children. Diagnosing and classifying the different phenotypes can be challenging, particularly in this age group, where cardiomyopathies are often overlooked until the onset of severe symptoms. Cardiovascular imaging is crucial in the diagnostic pathway, from screening to classification and follow-up assessment. Several imaging modalities have been proven to be helpful in this field, with echocardiography undoubtedly representing the first imaging approach due to its low cost, lack of radiation, and wide availability. However, particularly in this clinical context, echocardiography may not be able to differentiate from cardiomyopathies with similar phenotypes and is often complemented with cardiovascular magnetic resonance. The latter allows a radiation-free differentiation between different phenotypes with unique myocardial tissue characterization, thus identifying the presence and extent of myocardial fibrosis. Nuclear imaging and computed tomography have a complementary role, although they are less used in daily clinical practice due to the concern related to the use of radiation in pediatric patients. However, these modalities may have some advantages in evaluating children with cardiomyopathies. This paper aims to review the strengths and limitations of each imaging modality in evaluating pediatric patients with suspected or known cardiomyopathies.

Multimodality Cardiac Imaging in COVID-19 Infection

COVID-19 infection often produces cardiovascular complications, which can range from mild to severe and influence the overall prognosis. Imaging is the cornerstone for diagnosing initial COVID-19 cardiovascular involvement as well as treatment guidance. In this review, we present the current state of the literature on this subject while also emphasizing possible algorithms for indicating and executing these investigations.

Linear fine-tuning: a linear transformation based transfer strategy for deep MRI reconstruction

Introduction

Fine-tuning (FT) is a generally adopted transfer learning method for deep learning-based magnetic resonance imaging (MRI) reconstruction. In this approach, the reconstruction model is initialized with pre-trained weights derived from a source domain with ample data and subsequently updated with limited data from the target domain. However, the direct full-weight update strategy can pose the risk of "catastrophic forgetting" and overfitting, hindering its effectiveness. The goal of this study is to develop a zero-weight update transfer strategy to preserve pre-trained generic knowledge and reduce overfitting.

Methods

Based on the commonality between the source and target domains, we assume a linear transformation relationship of the optimal model weights from the source domain to the target domain. Accordingly, we propose a novel transfer strategy, linear fine-tuning (LFT), which introduces scaling and shifting (SS) factors into the pre-trained model. In contrast to FT, LFT only updates SS factors in the transfer phase, while the pre-trained weights remain fixed.

Results

To evaluate the proposed LFT, we designed three different transfer scenarios and conducted a comparative analysis of FT, LFT, and other methods at various sampling rates and data volumes. In the transfer scenario between different contrasts, LFT outperforms typical transfer strategies at various sampling rates and considerably reduces artifacts on reconstructed images. In transfer scenarios between different slice directions or anatomical structures, LFT surpasses the FT method, particularly when the target domain contains a decreasing number of training images, with a maximum improvement of up to 2.06 dB (5.89%) in peak signal-to-noise ratio.

Discussion

The LFT strategy shows great potential to address the issues of "catastrophic forgetting" and overfitting in transfer scenarios for MRI reconstruction, while reducing the reliance on the amount of data in the target domain. Linear fine-tuning is expected to shorten the development cycle of reconstruction models for adapting complicated clinical scenarios, thereby enhancing the clinical applicability of deep MRI reconstruction.

Fast and accurate T2 mapping using Bloch simulations and low-rank plus sparse matrix decomposition

PURPOSE

MRI's T2 relaxation time is one of the key contrast mechanisms for clinical diagnosis and prognosis of pathologies. Mapping this relaxation time, however, involves extensive scan times, which are needed to collect quantitative data, thereby impeding its integration into clinical routine. This study employs a low-rank plus sparse (L + S) signal decomposition approach in order to reconstruct accurate T2-maps from highly undersampled multi-echo spin-echo (MESE) MRI data.

METHODS

Two new algorithms are presented: the first uses standard L + S approach, where both L and S are iteratively updated. The second technique, dubbed SPArse and fixed RanK (SPARK), uses a fixed-rank L, under the assumption that most MESE information is found in the L component and that this rank can be pre-calculated. The utility of these new techniques is demonstrated on in vivo brain and calf data at x2 to x6 acceleration factors.

RESULTS

Accelerated T2 maps showed improved accuracy compared to fully sampled ground truth maps, when using L + S and SPARK techniques vis-à-vis standard GRAPPA acceleration.

CONCLUSION

SPARK provides accurate T2 maps with increased robustness to the selection of reconstruction parameters making it suitable to a wide range of applications and facilitating the use of quantitative T2 information in clinical settings.

Dynamic Cardiac Magnetic Resonance Fingerprinting During Vasoactive Breathing Maneuvers: First Results

BACKGROUND

Cardiac magnetic resonance fingerprinting (cMRF) enables simultaneous mapping of myocardial T1 and T2 with very short acquisition times. Breathing maneuvers have been utilized as a vasoactive stress test to dynamically characterize myocardial tissue in vivo. We tested the feasibility of sequential, rapid cMRF acquisitions during breathing maneuvers to quantify myocardial T1 and T2 changes.

METHODS

We measured T1 and T2 values using conventional T1 and T2-mapping techniques (modified look locker inversion [MOLLI] and T2-prepared balanced-steady state free precession), and a 15 heartbeat (15-hb) and rapid 5-hb cMRF sequence in a phantom and in 9 healthy volunteers. The cMRF_5-hb sequence was also used to dynamically assess T1 and T2 changes over the course of a vasoactive combined breathing maneuver.

RESULTS

In healthy volunteers, the mean myocardial T1 of the different mapping methodologies were: MOLLI 1,224 ± 81 ms, cMRF_15-hb 1,359 ± 97 ms, and cMRF_5-hb 1,357 ± 76 ms. The mean myocardial T2 measured with the conventional mapping technique was 41.7 ± 6.7 ms, while for cMRF_15-hb 29.6 ± 5.8 ms and cMRF_5-hb 30.5 ± 5.8 ms. T2 was reduced with vasoconstriction (post-hyperventilation compared to a baseline resting state) (30.15 ± 1.53 ms vs. 27.99 ± 2.07 ms, p = 0.02), while T1 did not change with hyperventilation. During the vasodilatory breath-hold, no significant change of myocardial T1 and T2 was observed.

CONCLUSIONS

cMRF_5-hb enables simultaneous mapping of myocardial T1 and T2, and may be used to track dynamic changes of myocardial T1 and T2 during vasoactive combined breathing maneuvers.

Imaging Methods: Magnetic Resonance Imaging

Myocardial inflammation occurs following activation of the cardiac immune system, producing characteristic changes in the myocardial tissue. Cardiovascular magnetic resonance is the non-invasive imaging gold standard for myocardial tissue characterization, and is able to detect image signal changes that may occur resulting from inflammation, including edema, hyperemia, capillary leak, necrosis, and fibrosis. Conventional cardiovascular magnetic resonance for the detection of myocardial inflammation and its sequela include T2-weighted imaging, parametric T1- and T2-mapping, and gadolinium-based contrast-enhanced imaging. Emerging techniques seek to image several parameters simultaneously for myocardial tissue characterization, and to depict subtle immune-mediated changes, such as immune cell activity in the myocardium and cardiac cell metabolism. This review article outlines the underlying principles of current and emerging cardiovascular magnetic resonance methods for imaging myocardial inflammation.

Evolution of myocardial oedema and fibrosis in HIV infected persons after the initiation of antiretroviral therapy: a prospective cardiovascular magnetic resonance study

BACKGROUND

Human immunodeficiency virus (HIV) infected persons on antiretroviral therapy (ART) have been shown to have functionally and structurally altered ventricles and may be related to cardiovascular inflammation. Mounting evidence suggests that the myocardium of HIV infected individuals may be abnormal before ART is initiated and may represent subclinical HIV-associated cardiomyopathy (HIVAC). The influence of ART on subclinical HIVAC is not known.

METHODS

Newly diagnosed, ART naïve persons with HIV infection were enrolled along with HIV uninfected, age- and sex-matched controls. All participants underwent comprehensive cardiovascular assessment, including contrasted cardiovascular magnetic resonance (CMR) with multiparametric mapping on a 1.5T CMR system. The HIV group was started on ART (tenofovir/lamivudine/dolutegravir) and prospectively evaluated 9 months later. Cardiac tissue characterisation was compared in, and between groups using the appropriate statistical tests for the cross sectional data and the paired, prospective data respectively.

RESULTS

Seventy-three ART naïve HIV infected individuals (32 ± 7 years, 45% female) and 22 healthy non-HIV subjects (33 ± 7 years, 50% female) were enrolled. Compared with non-HIV healthy subjects, the global native T1 (1008 ± 31 ms vs 1032 ± 44 ms, p = 0.02), global T2 (46 ± 2 vs 48 ± 3 ms, p = 0.006), and the prevalence of pericardial effusion (18% vs 67%, p < 0.001) were significantly higher in the HIV infected group at diagnosis. Global native T1 (1032 ± 44 to 1014 ± 34 ms, p < 0.001) and extracellular volume (ECV) (26 ± 4% to 25 ± 3%, p = 0.001) decreased significantly after 9 months on ART and were significantly associated with a decrease in the HIV viral load, decreased high sensitivity C-reactive protein, and improvement in the CD4 count (p < 0.001). Replacement fibrosis was significantly higher in the HIV infected group than controls (49% vs 10%, p = 0.02). The prevalence of late gadolinium enhancement did not change significantly over the 9-month study period (49% vs 55%, p = 0.4).

CONCLUSION

Subclinical HIVAC may already be present at the time of HIV diagnosis, as suggested by the combination of subclinical myocardial oedema and fibrosis found to be present before administration of ART. Markers of myocardial oedema on tissue characterization improved on ART in the short term, however, it is unclear if the underlying pathological mechanism is halted, or merely slowed by ART. Mid- to long term prospective studies are needed to evaluate subtle myocardial changes over time and to assess the significance of subclinical myocardial fibrosis.

Exercise-induced myocardial edema in master triathletes: Insights from cardiovascular magnetic resonance imaging

Background

Strenuous exercise has been associated with functional and structural cardiac changes due to local and systemic inflammatory responses, reflecting oxidative, metabolic, hormonal, and thermal stress, even in healthy individuals. We aimed to assess changes in myocardial structure and function using cardiovascular magnetic resonance (CMR) imaging in master triathletes early after a full-distance Ironman Triathlon race.

Materials and methods

Ten master triathletes (age 45 ± 8 years) underwent CMR within 3 h after a full-distance Ironman Triathlon race (3.8 km swimming, 180 km cycling, and 42.2 km running) completed with a mean time of 12 ± 1 h. All the triathletes had a 30-day follow-up CMR. Cine balanced steady-state free precession, T2-short tau inversion recovery (STIR), tagging, and late gadolinium enhancement (LGE) imaging sequences were performed on a 1.5-T MR scanner. Myocardial edema was defined as a region with increased T2 signal intensity (SI) of at least two SDs above the mean of the normal myocardium. The extent of myocardial edema was expressed as the percentage of left ventricular (LV) mass. Analysis of LV strain and torsion by tissue tagging included the assessment of radial, longitudinal, and circumferential peak systolic strain, rotation, and twist.

Results

Compared with postrace, biventricular volumes, ejection fraction, and LV mass index remained unchanged at 30-day follow-up. Global T2 SI was significantly higher in the postrace CMR (postrace 10.5 ± 6% vs. follow-up 3.9 ± 3.8%, P = 0.004) and presented with a relative apical sparing distribution (P < 0.001) matched by reduction of radial peak systolic strain of basal segments (P = 0.003). Apical rotation and twist were significantly higher immediately after the competition compared with follow-up (P < 0.05).

Conclusion

Strenuous exercise in master triathletes is associated with a reversible regional increase in myocardial edema and reduction of radial peak systolic strain, both presenting with a relative apical sparing pattern.

The utility of cardiac magnetic resonance imaging in the diagnosis of adult patients with acute myocarditis: A systematic review and meta-analysis

BACKGROUND

The presence of myocardial late gadolinium enhancement (LGE) indicates myocyte necrosis, and assists with the diagnosis of acute myocarditis (AM). Cardiac magnetic resonance (CMR) measures other than LGE i.e. tissue characterization and myocardial structural and functional parameters, play an important diagnostic role in assessment for inflammation, as seen in AM. The aim of this systematic review was to appraise the evidence for the use of quantitative CMR measures to identify myocardial inflammation in order to diagnose of AM in adult patients.

METHODS

A systematic literature search of medical databases was performed using PRISMA principles to identify relevant CMR studies on AM in adults (2005-2020; English; PROSPERO registration CRD42020180605). Data for a range of quantitative CMR measures were extracted. Continuous variables with low heterogeneity were meta-analyzed using a random-effects model for overall effect size measured as the standard mean difference (SMD).

RESULTS

Available data from 25 studies reporting continuous quantitative 1.5 T CMR measures revealed that AM is most reliably differentiated from healthy controls using T1 mapping (SMD 1.80, p < 0.01) and T2 mapping (SMD 1.63, p < 0.01), respectively. All other measures examined including T2-weighted ratio, extracellular volume, early gadolinium enhancement ratio, right ventricular ejection fraction, and LV end-diastolic volume, mass, ejection fraction, longitudinal strain, circumferential strain, and radial strain also had discriminatory ability although with smaller standard mean difference values (|SMD| 0.32-0.96, p < 0.01 for all).

CONCLUSIONS

Meta-analysis shows that myocardial tissue characterization (T1 mapping>T2 mapping) followed by measures of left ventricular structure and function demonstrate diagnostic discriminatory ability in AM.

Correcting for imaging gradients-related bias of T2 relaxation times at high-resolution MRI

Purpose

High‐resolution animal imaging is an integral part of preclinical drug development and the investigation of diseases' pathophysiology. Quantitative mapping of T₂ relaxation times (qT₂) is a valuable tool for both preclinical and research applications, providing high sensitivity to subtle tissue pathologies. High‐resolution T₂ mapping, however, suffers from severe underestimation of T₂ values due to molecular diffusion. This affects both single‐echo and multi‐echo spin echo (SSE and MESE), on top of the well‐known contamination of MESE signals by stimulated echoes, and especially on high‐field and preclinical scanners in which high imaging gradients are used in comparison to clinical scanners.

Methods

Diffusion bias due to imaging gradients was analyzed by quantifying the effective b‐value for each coherence pathway in SSE and MESE protocols, and incorporating this information in a joint T₂‐diffusion reconstruction algorithm. Validation was done on phantoms and in vivo mouse brain using a 9.4T and a 7T MRI scanner.

Results

Underestimation of T₂ values due to strong imaging gradients can reach up to 70%, depending on scan parameters and on the sample's diffusion coefficient. The algorithm presented here produced T₂ values that agreed with reference spectroscopic measurements, were reproducible across scan settings, and reduced the average bias of T₂ values from −33.5 ± 20.5% to −0.1 ± 3.6%.

Conclusions

A new joint T₂‐diffusion reconstruction algorithm is able to negate imaging gradient–related underestimation of T₂ values, leading to reliable mapping of T₂ values at high resolutions.

Click here for author‐reader discussions

Could CMR Tissue-Tracking and Parametric Mapping Distinguish Between Takotsubo Syndrome and Acute Myocarditis? A Pilot Study

RATIONALE AND OBJECTIVE

Takotsubo syndrome (TS) is a transient and often misdiagnosed form of left ventricular dysfunction. Acute myocarditis (AM) is usually included in TS differential diagnosis. The aim of this study is to assess the role of cardiac magnetic resonance imaging coupled with tissue-tracking technique (CMR-TT) and parametric mappings analysis in discriminating between TS and AM.

MATERIALS AND METHODS

We retrospectively enrolled three groups: patients with TS (n = 12), patients with AM (n = 14), and 10 healthy controls. All the patients had a comprehensive CMR examination, including the assessment of global and segmental longitudinal strain, circumferential strain, radial strain (RS), and parametric mapping.

RESULTS

The analysis of variance was used to compare the different groups. In TS patients, basal RS, global T1 mapping, global T2 mapping, mid T2 mapping, apical T1 and T2 mapping were statistically significantly different compared with the other groups. MANCOVA analysis confirmed that the association between myocardial strain data and parametric mapping was independent on age and sex. Apical T1 and T2 mapping proved to have a good performance in differentiating TS from AM (area under the curves of 0.908 and 0.879, respectively).

CONCLUSION

Basal RS and apical tissue mapping analysis are the most advanced CMR-derived parameters in making a differential diagnosis between TS and AM.

The role of cardiovascular magnetic resonance in the evaluation of acute myocarditis and inflammatory cardiomyopathies in clinical practice - a comprehensive review

Inflammatory cardiomyopathy (I-CMP) is defined as myocarditis in association with cardiac dysfunction and/or ventricular remodelling. It is characterized by inflammatory cell infiltration into the myocardium and has heterogeneous infectious and non-infectious aetiologies. A complex interplay of genetic, autoimmune, and environmental factors contributes to the substantial risk of deteriorating cardiac function, acute heart failure, and arrhythmia as well as chronic dilated cardiomyopathy and its sequelae. Multi-parametric cardiovascular magnetic resonance (CMR) imaging is sensitive to many tissue changes that occur during myocardial inflammation, regardless of its aetiology. In this review, we summarize the various aetiologies of I-CMP and illustrate how CMR contributes to non-invasive diagnosis.

Cardiac MR: From Theory to Practice

Cardiovascular disease (CVD) is the leading single cause of morbidity and mortality, causing over 17. 9 million deaths worldwide per year with associated costs of over $800 billion. Improving prevention, diagnosis, and treatment of CVD is therefore a global priority. Cardiovascular magnetic resonance (CMR) has emerged as a clinically important technique for the assessment of cardiovascular anatomy, function, perfusion, and viability. However, diversity and complexity of imaging, reconstruction and analysis methods pose some limitations to the widespread use of CMR. Especially in view of recent developments in the field of machine learning that provide novel solutions to address existing problems, it is necessary to bridge the gap between the clinical and scientific communities. This review covers five essential aspects of CMR to provide a comprehensive overview ranging from CVDs to CMR pulse sequence design, acquisition protocols, motion handling, image reconstruction and quantitative analysis of the obtained data. (1) The basic MR physics of CMR is introduced. Basic pulse sequence building blocks that are commonly used in CMR imaging are presented. Sequences containing these building blocks are formed for parametric mapping and functional imaging techniques. Commonly perceived artifacts and potential countermeasures are discussed for these methods. (2) CMR methods for identifying CVDs are illustrated. Basic anatomy and functional processes are described to understand the cardiac pathologies and how they can be captured by CMR imaging. (3) The planning and conduct of a complete CMR exam which is targeted for the respective pathology is shown. Building blocks are illustrated to create an efficient and patient-centered workflow. Further strategies to cope with challenging patients are discussed. (4) Imaging acceleration and reconstruction techniques are presented that enable acquisition of spatial, temporal, and parametric dynamics of the cardiac cycle. The handling of respiratory and cardiac motion strategies as well as their integration into the reconstruction processes is showcased. (5) Recent advances on deep learning-based reconstructions for this purpose are summarized. Furthermore, an overview of novel deep learning image segmentation and analysis methods is provided with a focus on automatic, fast and reliable extraction of biomarkers and parameters of clinical relevance.

Cardiovascular Imaging in Stress Cardiomyopathy (Takotsubo Syndrome)

Stress cardiomyopathy (Takotsubo syndrome) is a reversible syndrome stemming from myocardial injury leading to systolic dysfunction and is usually noted in the setting of a stressful event, be it an emotional or physical trigger. While the exact pathophysiology behind stress cardiomyopathy is yet unknown, there is ample evidence suggesting that neurocardiogenic mechanisms may play an important role. Although historically stress cardiomyopathy was generally thought to be a relatively benign condition, there is growing recognition of the cardiovascular complications associated with it despite its reversibility. Our review aims to shed light onto key cardiovascular imaging modalities used to diagnose stress cardiomyopathy while highlighting the role that imaging plays in assessing disease severity, identifying complications, dictating treatment approaches, and in short-term and long-term prognosis.

Reconstruction of cardiovascular black-blood T2-weighted image by deep learning algorithm: A comparison with intensity filter

Background

Deep learning-based methods have been used to denoise magnetic resonance imaging.

Purpose

The purpose of this study was to evaluate a deep learning reconstruction (DL Recon) in cardiovascular black-blood T2-weighted images and compare with intensity filtered images.

Material and Methods

Forty-five DL Recon images were compared with intensity filtered and the original images. For quantitative image analysis, the signal to noise ratio (SNR) of the septum, contrast ratio (CR) of the septum to lumen, and sharpness of the endocardial border were calculated in each image. For qualitative image quality assessment, a 4-point subjective scale was assigned to each image (1 = poor, 2 = fair, 3 = good, 4 = excellent).

Results

The SNR and CR were significantly higher in the DL Recon images than in the intensity filtered and the original images (p < .05 in each). Sharpness of the endocardial border was significantly higher in the DL Recon and intensity filtered images than in the original images (p < .05 in each). The image quality of the DL Recon images was significantly better than that of intensity filtered and original images (p < .001 in each).

Conclusions

DL Recon reduced image noise while improving image contrast and sharpness in the cardiovascular black-blood T2-weight sequence.

Takotsubo Syndrome-Is There a Need for CMR?

PURPOSE OF REVIEW

Takotsubo syndrome (TTS) is a transient but severe myocardial dysfunction that has been known for decades and is still to be fully understood regarding its clinical presentations and pathophysiological mechanisms. Cardiac magnetic resonance (CMR) imaging plays a key role in the comprehensive analysis of patients with TTS in acute and follow-up examinations. In this review, we focus on the major advantages and latest evolutions of CMR in diagnosis and prognostication of TTS and discuss future perspectives and needs in the field of research and cardiovascular imaging in TTS.

RECENT FINDINGS

Specific CMR criteria for TTS diagnosis at the time of acute presentation are established. In addition to identifying the typical regional wall motion abnormalities, CMR allows for precise quantification of right ventricular and left ventricular (LV) function, the assessment of additional abnormalities/complications (e.g. pericardial and/or pleural effusion, LV thrombi), and most importantly myocardial tissue characterization (myocardial oedema, inflammation, necrosis/fibrosis). CMR enables a comprehensive assessment of the entire spectrum of functional and structural changes that occur in patients with TTS and may have also a prognostic impact. CMR can distinguish between TTS and other important differential diagnoses (myocarditis, myocardial infarction) with direct consequences on medical therapy.

Cardiovascular Magnetic Resonance Reveals Cardiac Pathophysiology in Autoimmune Rheumatic Diseases

Background/Aims

The high incidence of cardiovascular disease (CVD) in patients with autoimmune rheumatic diseases (ARDs) is the main driver towards increased mortality in this patient group. Cardiovascular magnetic resonance (CMR) can non-invasively and robustly detect CVD in ARD patients at an early stage of development. The review summarises the diagnostic information provided by CMR in ARD patients.

Summary

CMR uses a strong magnetic field combined with radio-frequency pulses (pulse sequences) to generate images. Firstly, balanced steady-state free precession (bSSFP) can be used for evaluating cardiac anatomy, mass, wall motion, atrial/ventricular function. Secondly, T2-weighted imaging (T2-W) can be used for oedema detection, which appears as a high signal intensity area on STIR (short tau inversion recovery) images. T2 mapping is a newer T2-W technique that can provide more optimal identification of myocardial oedema. Lastly, late gadolinium enhanced (LGE) T1-W images, taken 15 min. after injection of contrast agent, allow the detection of myocardial replacement fibrosis, which appears as a bright area in a background of black myocardium. However, LGE has inherent disadvantages for the assessment of diffuse myocardial fibrosis. Therefore, T1 mapping and extracellular volume fraction (ECV) have been developed to quantify diffuse myocardial fibrosis.

Results

Although multicentre studies are still missing, the CMR parameters have been extensively applied for the identification of oedema/fibrosis and treatment decision making in ARDs.

Conclusions

Tissue characterisation with CMR allows early and robust identification of CVD in ARD patients and contributes to personalized management in the patients.

CMR for myocardial characterization in ischemic heart disease: state-of-the-art and future developments

Ischemic heart disease and its sequelae are one of the major contributors to morbidity and mortality worldwide. Over the last decades, technological developments have strengthened the role of noninvasive imaging for detection, risk stratification, and management of patients with ischemic heart disease. Cardiac magnetic resonance (CMR) imaging incorporates both functional and morphological characterization of the heart to determine presence, acuteness, and severity of ischemic heart disease by evaluating myocardial wall motion and function, the presence and extent of myocardial edema, ischemia, and scarring. Currently established clinical protocols have already demonstrated their diagnostic and prognostic value. Nevertheless, there are emerging imaging technologies that provide additional information based on advanced quantification of imaging biomarkers and improved diagnostic accuracy, therefore potentially allowing reduction or avoidance of contrast and/or stressor agents. The aim of this review is to summarize the current state of the art of CMR imaging for ischemic heart disease and to provide insights into promising future developments.

Current Knowledge and Future Challenges in Takotsubo Syndrome: Part 1-Pathophysiology and Diagnosis

First recognized in 1990, takotsubo syndrome (TTS) constitutes an acute cardiac condition that mimics acute myocardial infarction commonly in the absence of obstructive coronary artery disease; it is characterized by temporary left ventricular dysfunction, regularly in a circumferential apical, midventricular, or basal distribution. Considering its acute clinical presentation, coronary angiography with left ventriculography constitutes the gold standard diagnostic tool to exclude or confirm TTS. Frequently, TTS is related to severe emotional or physical stress and a subsequent increased adrenergic stimulation affecting cardiac function. Beyond clinical presentation, epidemiology, and novel diagnostic biomarkers, this review draws attention to potential pathophysiological mechanisms for the observed reversible myocardial dysfunction such as sympathetic overdrive-mediated multi-vessel epicardial spasms, microvascular dysfunction, the direct toxicity of catecholamines, lipotoxicity, and inflammation. Considering the long-term prognosis, further experimental and clinical research is indispensable to elucidate further pathophysiological mechanisms underlying TTS before randomized control trials with evidence-based therapeutic management can be performed.

Cardiovascular Magnetic Resonance as Pathophysiologic Tool in Diabetes Mellitus

Diabetes mellitus can independently contribute to cardiovascular disease and represents a severe risk factor for premature development of cardiovascular disease. A three-fold higher mortality than the general population has been observed in type 1 diabetes mellitus whereas a two- to four-fold increased probability to develop cardiovascular disease has been observed in type 2 diabetes mellitus. Cardiovascular magnetic resonance, a non-radiative modality, is superior to all other modalities in detecting myocardial infarction. The main cardiovascular magnetic resonance sequences used include a) balanced steady-state free precession (bSSFP) for function evaluation; b) T2-W for oedema detection; c) T1 W for ischemia detection during adenosine stress; and d) late gadolinium enhanced T1-W images (LGE), evaluated 15 min after injection of paramagnetic contrast agent gadolinium, which permit the diagnosis of replacement fibrosis, which appears white in the middle of suppressed, nulled myocardium. Although LGE is the technique of choice for diagnosis of replacement fibrosis, it cannot assess diffuse myocardial fibrosis. The application of T1 mapping (native or pre contrast and post contrast) allows identification of diffuse myocardial fibrosis, which is not detectable my other means. Native T1 and Contrast-enhanced T1 mapping are involved in the extracellular volume fraction (ECV) calculation. Recently, 1H-cardiovascular magnetic resonance spectroscopy has been applied to calculate the amount of myocardial triglycerides, but at the moment it is not part of the routine assessment of diabetes mellitus. The multifaceted nature of cardiovascular magnetic resonance has the great potential of concurrent evaluation of function and myocardial ischemia/fibrosis in the same examination and represents an indispensable tool for accurate diagnosis of cardiovascular disease in diabetes mellitus.

Multimodality imaging in takotsubo syndrome: a joint consensus document of the European Association of Cardiovascular Imaging (EACVI) and the Japanese Society of Echocardiography (JSE)

Takotsubo syndrome (TTS) is a complex and still poorly recognized heart disease with a wide spectrum of possible clinical presentations. Despite its reversibility, it is associated with serious adverse in-hospital events and high complication rates during follow-up. Multimodality imaging is helpful for establishing the diagnosis, guiding therapy, and stratifying prognosis of TTS patients in both the acute and post-acute phase. Echocardiography plays a key role, particularly in the acute care setting, allowing for the assessment of left ventricular (LV) systolic and diastolic function and the identification of the typical apical-midventricular ballooning pattern, as well as the circumferential pattern of wall motion abnormalities. It is also useful in the early detection of complications (i.e. LV outflow tract obstruction, mitral regurgitation, right ventricular involvement, LV thrombi, and pericardial effusion) and monitoring of systolic function recovery. Left ventriculography allows the evaluation of LV function and morphology, identifying the typical TTS patterns when echocardiography is not available or wall motion abnormalities cannot be properly assessed with ultrasound. Cardiac magnetic resonance provides a more comprehensive depiction of cardiac morphology and function and tissue characterization and offers additional value to other imaging modalities for differential diagnosis (myocardial infarction and myocarditis). Coronary computed tomography angiography has a substantial role in the diagnostic workup of patients with acute chest pain and a doubtful TTS diagnosis to rule out other medical conditions. It can be considered as a non-invasive appropriate alternative to coronary angiography in several clinical scenarios. Although the role of nuclear imaging in TTS has not yet been well established, the combination of perfusion and metabolic imaging may provide useful information on myocardial function in both the acute and post-acute phase.

Black-Blood Contrast in Cardiovascular MRI

MRI is a versatile technique that offers many different options for tissue contrast, including suppressing the blood signal, so‐called black‐blood contrast. This contrast mechanism is extremely useful to visualize the vessel wall with high conspicuity or for characterization of tissue adjacent to the blood pool. In this review we cover the physics of black‐blood contrast and different techniques to achieve blood suppression, from methods intrinsic to the imaging readout to magnetization preparation pulses that can be combined with arbitrary readouts, including flow‐dependent and flow‐independent techniques. We emphasize the technical challenges of black‐blood contrast that can depend on flow and motion conditions, additional contrast weighting mechanisms (T₁, T₂, etc.), magnetic properties of the tissue, and spatial coverage. Finally, we describe specific implementations of black‐blood contrast for different vascular beds.

Multimodality imaging in takotsubo syndrome: a joint consensus document of the European Association of Cardiovascular Imaging (EACVI) and the Japanese Society of Echocardiography (JSE)

Takotsubo syndrome (TTS) is a complex and still poorly recognized heart disease with a wide spectrum of possible clinical presentations. Despite its reversibility, it is associated with serious adverse in-hospital events and high complication rates during follow-up. Multimodality imaging is helpful for establishing the diagnosis, guiding therapy, and stratifying prognosis of TTS patients in both the acute and post-acute phase. Echocardiography plays a key role, particularly in the acute care setting, allowing for the assessment of left ventricular (LV) systolic and diastolic function and the identification of the typical apical-midventricular ballooning pattern, as well as the circumferential pattern of wall motion abnormalities. It is also useful in the early detection of complications (i.e. LV outflow tract obstruction, mitral regurgitation, right ventricular involvement, LV thrombi, and pericardial effusion) and monitoring of systolic function recovery. Left ventriculography allows the evaluation of LV function and morphology, identifying the typical TTS patterns when echocardiography is not available or wall motion abnormalities cannot be properly assessed with ultrasound. Cardiac magnetic resonance provides a more comprehensive depiction of cardiac morphology and function and tissue characterization and offers additional value to other imaging modalities for differential diagnosis (myocardial infarction and myocarditis). Coronary computed tomography angiography has a substantial role in the diagnostic workup of patients with acute chest pain and a doubtful TTS diagnosis to rule out other medical conditions. It can be considered as a non-invasive appropriate alternative to coronary angiography in several clinical scenarios. Although the role of nuclear imaging in TTS has not yet been well established, the combination of perfusion and metabolic imaging may provide useful information on myocardial function in both the acute and post-acute phase.

Cardiac Intravoxel Incoherent Motion Diffusion-Weighted Magnetic Resonance Imaging With T1 Mapping to Assess Myocardial Perfusion and Fibrosis in Systemic Sclerosis: Association With Cardiac Events From a Prospective Cohort Study

OBJECTIVE

Myocardial involvement may occur during systemic sclerosis (SSc) and can lead to impaired myocardial contraction and/or arrhythmia. Cardiac magnetic resonance imaging (MRI) is used for noninvasive characterization of the myocardium. The aim of this study was to evaluate the utility of cardiac MRI with intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) and longitudinal relaxation time (T1) sequence mapping for assessment of myocardial microvascular and interstitium impairment in SSc.

METHODS

In this single-center prospective cohort study, 40 consecutive patients with SSc and 20 healthy controls were assessed by cardiac MRI with IVIM DWI and T1 mapping sequences on a 3T scanning system. Images were analyzed independently by 2 assessors, and Bland-Altman plots were used to assess interreader concordance and reproducibility. Characteristics of the patients were compared according to quartiles of T1 and perfusion fraction (f-coefficient) values, using exact Cochran-Ermitage trend tests for qualitative variables and analysis of variance for quantitative variables. Kaplan-Meier cardiac events-free survival curves were plotted and compared with a log-rank test for trend.

RESULTS

T1 values were higher in SSc patients than in healthy controls, and were higher in the diffuse cutaneous SSc (dcSSc) subset (P = 0.02). Higher T1 values were associated with the immunologic pattern seen in patients with the dcSSc form (P = 0.0001), a higher modified Rodnan skin thickness score (MRSS) (P = 0.003), and a higher frequency of interstitial lung disease (P = 0.03). Moreover, higher T1 values were correlated with higher MRSS scores (r = +0.32, P = 0.04) and reduced forced vital capacity (r = -0.34, P = 0.048), and tended to be correlated with reduced total lung capacity (r = -0.30, P = 0.07). Lower f-coefficient values, as a measure of decreased tissue perfusion, were associated with less frequent use of vasodilators (P = 0.02 for angiotensin-converting enzyme inhibitors and P = 0.06 for calcium-channel blockers) and more frequent use of glucocorticoids (P = 0.02). The f-coefficients were inversely correlated with the T1 values (r = -0.31, P = 0.02). Furthermore, higher T1 values were associated with higher incidence of cardiac events (log-rank test for trend P = 0.03).

CONCLUSION

Increased T1 values, potentially suggesting microscopic fibrosis, were observed more frequently in patients with dcSSc, and higher T1 values were associated with interstitial lung disease and more frequent cardiac events during follow-up. The results of this study show that cardiac MRI with T1 mapping sequences and IVIM DWI may be useful in assessing myocardial involvement in patients with SSc.

Cardiovascular magnetic resonance imaging for structural heart disease

Cardiovascular magnetic resonance (CMR) has increasingly become a powerful imaging technique over the past few decades due to increasing knowledge about clinical applications, operator experience and technological advances, including the introduction of high field strength magnets, leading to improved signal-to-noise ratio. Its success is attributed to the free choice of imaging planes, the wide variety of imaging techniques, and the lack of harmful radiation. Developments in CMR have led to the accurate evaluation of cardiac structure, function and tissues characterisation, so this non-invasive technique has become a powerful tool for a broad range of cardiac pathologies. This review will provide an introduction of magnetic resonance imaging (MRI) physics, an overview of the current techniques and clinical application of CMR in structural heart disease, and illustrated examples of its use in clinical practice.

Clinical and Advanced MRI Techniques for Detection of Checkpoint Inhibitor Associated Myocarditis

Purpose of Review

With the advent of immune checkpoint inhibitors (ICIs), cancer treatment has been revolutionized; however, these agents are associated with immune-related adverse events, including myocarditis, which ranges from mild to fulminant in severity. Currently, there are no established guidelines in diagnosing ICI-associated myocarditis, and the gold standard test for diagnosis of myocarditis in general is invasive endomyocardial biopsy (EMB). Cardiac magnetic resonance (CMR) imaging is a noninvasive test with the advantage of providing structural, functional and tissue characterization information. Additionally, it provides high spatial and temporal resolution without exposure to ionizing radiation, iodinated contrast, or radioactive isotopes.

Recent Findings

With an increasing number of reported cases of ICI associated myocarditis, understanding of the disease process and associated CMR findings is growing. Diagnostic testing with cardiac biomarkers, electrocardiogram, and echocardiogram can be nonspecific and EMB can have sampling errors. CMR as a diagnostic tool can provide functional assessment of biventricular ejection fraction, myocardial strain, tissue characterization of myocardial edema and inflammation as well as fibrosis. Furthermore, with advanced parametric mapping techniques, CMR provides even more sensitive and quantitative information about myocardial inflammation and fibrosis, including measurements of extracellular volume.

Summary

ICI-associated myocarditis is a serious immune adverse event, and CMR plays a vital role in establishing its diagnosis, providing prognostic information, and has the potential for use as a tool for screening and serial monitoring in patients exposed to ICIs.

Ferumoxytol-enhanced cardiovascular magnetic resonance detection of early stage acute myocarditis

BACKGROUND

The diagnostic utility of cardiovascular magnetic resonance (CMR) is limited during the early stages of myocarditis. This study examined whether ferumoxytol-enhanced CMR (FE-CMR) could detect an earlier stage of acute myocarditis compared to gadolinium-enhanced CMR.

METHODS

Lewis rats were induced to develop autoimmune myocarditis. CMR (3 T, GE Signa) was performed at the early- (day 14, n = 7) and the peak-phase (day 21, n = 8) of myocardial inflammation. FE-CMR was evaluated as % myocardial dephasing signal loss on gradient echo images at 6 and 24 h (6 h- & 24 h-FE-CMR) following the administration of ferumoxytol (300μmolFe/kg). Pre- and post-contrast T2* mapping was also performed. Early (EGE) and late (LGE) gadolinium enhancement was obtained after the administration of gadolinium-DTPA (0.5 mmol/kg) on day 14 and 21. Healthy rats were used as control (n = 6).

RESULTS

Left ventricular ejection fraction (LVEF) was preserved at day 14 with inflammatory cells but no fibrosis seen on histology. EGE and LGE at day 14 both showed limited myocardial enhancement (EGE: 11.7 ± 15.5%; LGE: 8.7 ± 8.7%; both p = ns vs. controls). In contrast, 6 h-FE-CMR detected extensive myocardial signal loss (33.2 ± 15.0%, p = 0.02 vs. EGE and p < 0.01 vs. LGE). At day 21, LVEF became significantly decreased (47.4 ± 16.4% vs control: 66.2 ± 6.1%, p < 0.01) with now extensive myocardial involvement detected on EGE, LGE, and 6 h-FE-CMR (41.6 ± 18.2% of LV). T2* mapping also detected myocardial uptake of ferumoxytol both at day 14 (6 h R2* = 299 ± 112 s- 1vs control: 125 ± 26 s- 1, p < 0.01) and day 21 (564 ± 562 s- 1, p < 0.01 vs control). Notably, the myocardium at peak-phase myocarditis also showed significantly higher pre-contrast T2* (27 ± 5 ms vs control: 16 ± 1 ms, p < 0.001), and the extent of myocardial necrosis had a strong positive correlation with T2* (r = 0.86, p < 0.001).

CONCLUSIONS

FE-CMR acquired at 6 h enhance detection of early stages of myocarditis before development of necrosis or fibrosis, which could potentially enable appropriate therapeutic intervention.

A personalized computational model of edema formation in myocarditis based on long-axis biventricular MRI images

Background

Myocarditis is defined as the inflammation of the myocardium, i.e. the cardiac muscle. Among the reasons that lead to this disease, we may include infections caused by a virus, bacteria, protozoa, fungus, and others. One of the signs of the inflammation is the formation of edema, which may be a consequence of the interaction between interstitial fluid dynamics and immune response. This complex physiological process was mathematically modeled using a nonlinear system of partial differential equations (PDE) based on porous media approach. By combing a model based on Biot’s poroelasticity theory with a model for the immune response we developed a new hydro-mechanical model for inflammatory edema. To verify this new computational model, T2 parametric mapping obtained by Magnetic Resonance (MR) imaging was used to identify the region of edema in a patient diagnosed with unspecific myocarditis.

Results

A patient-specific geometrical model was created using MRI images from the patient with myocarditis. With this model, edema formation was simulated using the proposed hydro-mechanical mathematical model in a two-dimensional domain. The computer simulations allowed us to correlate spatiotemporal dynamics of representative cells of the immune systems, such as leucocytes and the pathogen, with fluid accumulation and cardiac tissue deformation.

Conclusions

This study demonstrates that the proposed mathematical model is a very promising tool to better understand edema formation in myocarditis. Simulations obtained from a patient-specific model reproduced important aspects related to the formation of cardiac edema, its area, position, and shape, and how these features are related to immune response.

T2STIR preparation for single-shot cardiovascular magnetic resonance myocardial edema imaging

BACKGROUND

Myocardial edema in acute myocardial infarction (AMI) is commonly imaged using dark-blood short tau inversion recovery turbo spin echo (STIR-TSE) cardiovascular magnetic resonance (CMR). The technique is sensitive to cardiac motion and coil sensitivity variation, leading to myocardial signal nonuniformity and impeding reliable depiction of edematous tissues. T2-prepared balanced steady state free precession (T2p-bSSFP) imaging has been proposed, but its contrast is low, and averaging is commonly needed. T2 mapping is useful but requires a long scan time and breathholding. We propose here a single-shot magnetization prepared sequence that increases the contrast between edema and normal myocardium and apply it to myocardial edema imaging.

METHODS

A magnetization preparation module (T2STIR) is designed to exploit the simultaneous elevation of T1 and T2 in edema to improve the depiction of edematous myocardium. The module tips magnetization down to the -z axis after T2 preparation. Transverse magnetization is sampled at the fat null point using bSSFP readout and allows for single-shot myocardial edema imaging. The sequence (T2STIR-bSSFP) was studied for its contrast behavior using simulation and phantoms. It was then evaluated on 7 healthy subjects and 7 AMI patients by comparing it to T2p-bSSFP and T2 mapping using the contrast-to-noise ratio (CNR) and the contrast ratio as performance indices.

RESULTS

In simulation and phantom studies, T2STIR-bSSFP had improved contrast between edema and normal myocardium compared with the other two edema imaging techniques. In patients, the CNR of T2STIR-bSSFP was higher than T2p-bSSFP (5.9 ± 2.6 vs. 2.8 ± 2.0, P < 0.05) but had no significant difference compared with that of the T2 map (T2 map: 6.6 ± 3.3 vs. 5.9 ± 2.6, P = 0.62). The contrast ratio of T2STIR-bSSFP (2.4 ± 0.8) was higher than that of the T2 map (1.3 ± 0.1, P < 0.01) and T2p-bSSFP (1.4 ± 0.5, P < 0.05).

CONCLUSION

T2STIR-bSSFP has improved contrast between edematous and normal myocardium compared with commonly used bSSFP-based edema imaging techniques. T2STIR-bSSFP also differentiates between fat that was robustly suppressed and fluids around the heart. The technique is useful for single-shot edema imaging in AMI patients.

Anthracycline Therapy Is Associated With Cardiomyocyte Atrophy and Preclinical Manifestations of Heart Disease

OBJECTIVES

The goal of this study was to demonstrate that cardiac magnetic resonance could reveal anthracycline-induced early tissue remodeling and its relation to cardiac dysfunction and left ventricular (LV) atrophy.

BACKGROUND

Serum biomarkers of cardiac dysfunction, although elevated after chemotherapy, lack specificity for the mechanism of myocardial tissue alterations.

METHODS

A total of 27 women with breast cancer (mean age 51.8 ± 8.9 years, mean body mass index 26.9 ± 3.6 kg/m²), underwent cardiac magnetic resonance before and up to 3 times after anthracycline therapy. Cardiac magnetic resonance variables were LV ejection fraction, normalized T2-weighted signal intensity for myocardial edema, extracellular volume (ECV), LV cardiomyocyte mass, intracellular water lifetime (τ_ic; a marker of cardiomyocyte size), and late gadolinium enhancement.

RESULTS

At baseline, patients had a relatively low (10-year) Framingham cardiovascular event risk (median 5%), normal LV ejection fractions (mean 69.4 ± 3.6%), and normal LV mass index (51.4 ± 8.0 g/m²), a mean ECV of 0.32 ± 0.038, mean τ_ic of 169 ± 69 ms, and no late gadolinium enhancement. At 351 to 700 days after anthracycline therapy (240 mg/m²), mean LV ejection fraction had declined by 12% to 58 ± 6% (p < 0.001) and mean LV mass index by 19 g/m² to 36 ± 6 g/m² (p < 0.001), and mean ECV had increased by 0.037 to 0.36 ± 0.04 (p = 0.004), while mean τ_ic had decreased by 62 ms to 119 ± 54 ms (p = 0.004). Myocardial edema peaked at about 146 to 231 days (p < 0.001). LV mass index was associated with τ_ic (β = 4.1 ± 1.5 g/m² per 100-ms increase in τ_ic, p = 0.007) but not with ECV. Cardiac troponin T (mean 4.6 ± 1.4 pg/ml at baseline) increased significantly after anthracycline treatment (p < 0.001). Total LV cardiomyocyte mass, estimated as: (1 - ECV) × LV mass, declined more rapidly after anthracycline therapy, with peak cardiac troponin T >10 pg/ml. There was no evidence for any significant interaction between 10-year cardiovascular event risk and the effect of anthracycline therapy.

CONCLUSIONS

A decrease in LV mass after anthracycline therapy may result from cardiomyocyte atrophy, demonstrating that mechanisms other than interstitial fibrosis and edema can raise ECV. The loss of LV cardiomyocyte mass increased with the degree of cardiomyocyte injury, assessed by peak cardiac troponin T after anthracycline treatment. (Doxorubicin-Associated Cardiac Remodeling Followed by CMR in Breast Cancer Patients; NCT03000036).

Quantitative cardiac MRI

Cardiac MRI has become an indispensable imaging modality in the investigation of patients with suspected heart disease. It has emerged as the gold standard test for cardiac function, volumes, and mass and allows noninvasive tissue characterization and the assessment of myocardial perfusion. Quantitative MRI already has a key role in the development and incorporation of machine learning in clinical imaging, potentially offering major improvements in both workflow efficiency and diagnostic accuracy. As the clinical applications of a wide range of quantitative cardiac MRI techniques are being explored and validated, we are expanding our capabilities for earlier detection, monitoring, and risk stratification of disease, potentially guiding personalized management decisions in various cardiac disease models. In this article we review established and emerging quantitative techniques, their clinical applications, highlight novel advances, and appraise their clinical diagnostic potential. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:693-711.

Clinical impact of native T1 mapping for detecting myocardial impairment in takotsubo cardiomyopathy

Aims

To investigate the clinical impact of T1 mapping for detecting myocardial impairment in takotsubo cardiomyopathy (TTC) over time.

Methods and results

In 23 patients with the apical ballooning type of TTC, the following 3T magnetic resonance (MR) examinations were performed at baseline and 3 months after TTC onset: T2-weighted imaging, T2 mapping, native T1 mapping, extracellular volume fraction (ECV), and late gadolinium enhancement. Eight healthy controls underwent the same MR examinations. Serial echocardiography was performed daily for ≥7 days and monthly until 3 months after onset. The median time from onset to MR examination was 7 days. During the acute phase, patients had, relative to controls, higher native T1 (1438 ± 162 vs. 1251 ± 90 ms, P < 0.001), ECV (35 ± 5% vs. 29 ± 4%, P < 0.001), and T2 (90 ± 34 vs. 68 ± 12 ms, P < 0.001) for the entire heart. Per-region analysis showed that higher native T1 and T2 in the basal region were correlated with lower left ventricular ejection fraction (r = −0.599, P = 0.004 and r = −0.598, P = 0.003, respectively). Receiver operator characteristic analysis showed that the area under the curve for native T1 (0.96) was significantly larger than that for T2 (0.86; P = 0.005) but similar to that for ECV (0.92; P = 0.104). At 3-month follow-up, native T1, ECV, and T2 in the apical region remained significantly elevated in all patients with TTC. The number of left ventricular (LV) segments with elevated native T1 (cut-off value 1339 ms) was significantly correlated with prolonged LV wall motion recovery time (r = 0.494, P = 0.027).

Conclusion

Characterization of myocardium with native T1 mapping is a promising method for predicting LV wall motion restoration in TTC.