Myocardial T1 mapping in pediatric and congenital heart disease

Cardiac manifestations and outcomes of COVID-19 vaccine-associated myocarditis in the young in the USA: longitudinal results from the Myocarditis After COVID Vaccination (MACiV) multicenter study

Background

We aimed to study the clinical characteristics, myocardial injury, and longitudinal outcomes of COVID-19 vaccine-associated myocarditis (C-VAM).

Methods

In this longitudinal retrospective observational cohort multicenter study across 38 hospitals in the United States, 333 patients with C-VAM were compared with 100 patients with multisystem inflammatory syndrome in children (MIS-C). We included patients ≤30 years of age with a clinical diagnosis of acute myocarditis after COVID-19 vaccination based on clinical presentation, abnormal biomarkers and/or cardiovascular imaging findings. Demographics, past medical history, hospital course, biochemistry results, cardiovascular imaging, and follow-up information from April 2021 to November 2022 were collected. The primary outcome was presence of myocardial injury as evidenced by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging.

Findings

Patients with C-VAM were predominantly white (67%) adolescent males (91%, 15.7 ± 2.8 years). Their initial clinical course was more likely to be mild (80% vs. 23%, p < 0.001) and cardiac dysfunction was less common (17% vs. 68%, p < 0.0001), compared to MIS-C. In contrast, LGE on CMR was more prevalent in C-VAM (82% vs. 16%, p < 0.001). The probability of LGE was higher in males (OR 3.28 [95% CI: 0.99, 10.6, p = 0.052]), in older patients (>15 years, OR 2.74 [95% CI: 1.28, 5.83, p = 0.009]) and when C-VAM occurred after the first or second dose as compared to the third dose of mRNA vaccine. Mid-term clinical outcomes of C-VAM at a median follow-up of 178 days (IQR 114-285 days) were reassuring. No cardiac deaths or heart transplantations were reported until the time of submission of this report. LGE persisted in 60% of the patients at follow up.

Interpretation

Myocardial injury at initial presentation and its persistence at follow up, despite a mild initial course and favorable mid-term clinical outcome, warrants continued clinical surveillance and long-term studies in affected patients with C-VAM.

Funding

The U.S. Food and Drug Administration.

Recommendations for cardiovascular magnetic resonance and computed tomography in congenital heart disease: a consensus paper from the CMR/CCT Working Group of the Italian Society of Pediatric Cardiology and the Italian College of Cardiac Radiology endorsed by the Italian Society of Medical and Interventional Radiology (Part II)

Cardiovascular magnetic resonance (CMR) and computed tomography (CCT) are advanced imaging modalities that recently revolutionized the conventional diagnostic approach to congenital heart diseases (CHD), supporting echocardiography and often replacing cardiac catheterization. This is the second of two complementary documents, endorsed by experts from the Working Group of the Italian Society of Pediatric Cardiology and the Italian College of Cardiac Radiology of the Italian Society of Medical and Interventional Radiology, aimed at giving updated indications on the appropriate use of CMR and CCT in different clinical CHD settings, in both pediatrics and adults. In this article, support is also given to radiologists, pediatricians, cardiologists, and cardiac surgeons for indications and appropriateness criteria for CMR and CCT in the most referred CHD, following the proposed new criteria presented and discussed in the first document. This second document also examines the impact of devices and prostheses for CMR and CCT in CHD and additionally presents some indications for CMR and CCT exams when sedation or narcosis is needed.

Right ventricular fibrosis in adults with uncorrected secundum atrial septal defect and pulmonary hypertension: a cardiovascular magnetic resonance study with late gadolinium enhancement, native T1 and extracellular volume

Introduction

Right ventricular (RV) fibrosis represents both adaptive and maladaptive responses to the overloaded RV condition. Its role in pulmonary hypertension (PH) associated with secundum atrial septal defect (ASD), which is the most common adult congenital heart disease (CHD), remains poorly understood.

Methods

We enrolled 65 participants aged ≥18 years old with uncorrected secundum ASD who had undergone clinically indicated right heart catheterization (RHC), divided into the non-PH group (n = 7), PH group (n = 42), and Eisenmenger syndrome (ES) group (n = 16). We conducted cardiovascular magnetic resonance (CMR) studies with late gadolinium enhancement (LGE) imaging, native T1 mapping, and extracellular volume (ECV) measurement to evaluate the extent and clinical correlates of RV fibrosis.

Results

LGE was present in 94% of the population and 86% of the non-PH group, mostly located at the right ventricular insertion point (RVIP) regions. LGE in the septal and inferior RV region was predominantly observed in the ES group compared to the other groups (p = 0.031 and p < 0.001, respectively). The mean LGE scores in the ES and PH groups were significantly higher than those in the non-PH group (3.38 ± 0.96 vs. 2.74 ± 1.04 vs. 1.57 ± 0.79; p = 0.001). The ES and PH groups had significantly higher degrees of interstitial RV fibrosis compared to those in the non-PH group, indicated by native T1 (1,199.9 ± 68.9 ms vs. 1,131.4 ± 47.8 ms vs. 1,105.4 ± 44.0 ms; p < 0.001) and ECV (43.6 ± 6.6% vs. 39.5 ± 4.9% vs. 39.4 ± 5.8%; p = 0.037). Additionally, native T1 significantly correlated with pulmonary vascular resistance (r = 0.708, p < 0.001), RV ejection fraction (r = -0.468, p < 0.001) and peripheral oxygen saturation (r = -0.410, p = 0.001).

Conclusion

In patients with uncorrected secundum ASD, RV fibrosis may occur before the development of PH and progressively intensify alongside the progression of PH severity. A higher degree of RV fibrosis, derived from CMR imaging, correlates with worse hemodynamics, RV dysfunction, and poorer clinical conditions.

Right ventricular myocardial fibrosis evaluated by extracellular volume fraction by magnetic resonance imaging in patients with repaired tetralogy of Fallot: a meta-analysis

OBJECTIVE

The objective of this meta-analysis was to assess the clinical utility of anomalous discoveries on cardiac magnetic resonance, particularly the right ventricular extracellular volume (RV-ECV), among individuals who underwent surgical repair for Tetralogy of Fallot (rTOF).

METHODS

We conducted a systematic search of electronic databases including PubMed, Web of Science Core Collection, Cochrane advanced search, and EMBASE. Our analysis involved a comparison of ECV levels between rTOF patients and controls, as well as an evaluation of the predictive value of ECV for future adverse events.

RESULTS

We identified 16 eligible studies that encompassed 856 rTOF patients and 283 controls. Our meta-analysis showed a significant increase in LV-ECV among rTOF patients compared to control subjects (MD = 2.63, 95%CI: 1.35 to 3.90, p < 0.0001, I2 = 86%, p for heterogeneity < 0.00001). Moreover, RV-ECV was found to be substantially higher in patients compared to LV-ECV. Our meta-analysis also revealed a significant association between RV-ECV and adverse events (HR = 1.15, 95% CI: 1.04 to 1.27, p = 0.005, I2 = 0%, p for heterogeneity = 0.62), while LV-ECV did not show any significant association with adverse events (HR = 1.12, 95% CI: 0.92 to 1.36, p = 0.16, I2 = 0%, p for heterogeneity = 0.46).

CONCLUSION

The results of this meta-analysis on RV-ECV confirmed the presence of RV fibrosis as one of the prognostic factors in rTOF patients.

Cardiovascular remodelling in response to exercise training in patients after the Fontan procedure: a pilot study

BACKGROUND

The cardiovascular adaptations associated with structured exercise training in Fontan patients remain unknown. We hypothesised that short-term training causes cardiac remodelling and parallel improvement in maximal exercise capacity (VO2 max) in these patients.

METHODS AND RESULTS

Five patients, median age 19.5 (17.6-21.3) years, with a history of Fontan operation meeting inclusion/exclusion criteria, participated in a 3-month training programme designed to improve endurance. Magnetic resonance images for assessment of cardiac function, fibrosis, cardiac output, and liver elastography to assess stiffness were obtained at baseline and after training. Maximal exercise capacity (VO2 max) and cardiac output Qc (effective pulmonary blood flow) at rest and during exercise were measured (C2H2 rebreathing) at the same interval. VO2 max increased from median (IQR) 27.2 (26-28.7) to 29.6 (28.5-32.2) ml/min/kg (p = 0.04). There was an improvement in cardiac output (Qc) during maximal exercise testing from median (IQR) 10.3 (10.1-12.3) to 12.3 (10.9-14.9) l/min, but this change was variable (p = 0.14). Improvement in VO2 max correlated with an increase in ventricular mass (r = 0.95, p = 0.01), and improvement in Quality-of-life inventory (PedsQL) Cardiac scale scores for patient-reported symptoms (r = 0.90, p = 0.03) and cognitive problems (r = 0.89, p = 0.04). The correlation between VO2 max and Qc showed a positive trend but was not significant (r = 0.8, p = 0.08). No adverse cardiac or liver adaptations were noted.

CONCLUSION

Short-term training improved exercise capacity in this Fontan pilot without any adverse cardiac or liver adaptations. These results warrant further study in a larger population and over a longer duration of time.

TRIAL REGISTRATION NUMBER

NCT03263312, Unique Protocol ID: STU 122016-037; Registration Date: 18 January, 2017.

Use of Cardiovascular Magnetic Resonance for Risk Stratification in Repaired Tetralogy of Fallot

The risk of premature death in adult patients with repaired tetralogy of Fallot is real and not inconsiderable. From the third decade of life, the incidence of malignant ventricular arrhythmia (VA) is known to exponentially rise. Progressive adverse mechanoelectrical modelling because of years of volume and/or pressure overload from residual pulmonary valve dysfunction and ventricular scar creates the perfect catalyst for VA. Although potentially lifesaving, implantable cardiac defibrillators are associated with substantial psychological and physical morbidity. Better selection of patients most at risk of VA, so that implantable cardiac defibrillators are not inflicted on patients who will never need them, is therefore crucial and has inspired research on this topic for several decades. Cardiovascular magnetic resonance (CMR) enables noninvasive, radiation-free clinical assessment of anatomy and function, making it ideal for the lifelong surveillance of patients with congenital heart disease. Gold standard measurements of ventricular volumes and systolic function can be derived from CMR. Tissue characterization using CMR can identify a VA substrate and provides insight into myocardial disease. We detail risk factors for VA identified using currently available CMR techniques. We also discuss emerging and advanced CMR techniques that have not all yet translated into routine clinical practice. We review how CMR-defined predictors of VA in repaired tetralogy of Fallot can be incorporated into risk scores with other clinical factors to improve the accuracy of risk prediction and to allow for pragmatic clinical application. Finally, we discuss what the future may hold.

Left ventricular deformation and myocardial fibrosis in pediatric patients with Duchenne muscular dystrophy

BACKGROUND

Left ventricular (LV) strain and rotation are emerging functional markers for early detection of LV dysfunction and have been associated with the burden of myocardial fibrosis in several disease states. This study examined the association between LV deformation (i.e., LV strain and rotation) and extent and location of LV myocardial fibrosis in pediatric patients with Duchenne muscular dystrophy (DMD).

METHODS AND RESULTS

34 pediatric patients with DMD underwent cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE) to assess LV myocardial fibrosis. Offline CMR feature-tracking analysis was used to assess global and segmental longitudinal and circumferential LV strain, and LV rotation. Patients with fibrosis (n = 18, 52.9%) were older than those without fibrosis (14 ± 3 years (yrs) vs 11 ± 2 yrs., p = 0.01). There was no significant difference in LV ejection fraction (LVEF) between subjects with and without fibrosis (54 ± 6% vs 56 ± 4%, p = 0.18). However, lower endocardial global circumferential strain (GCS), but not LV rotation, was associated with presence of fibrosis (adjusted Odds Ratio 1.25 [95% CI 1.01-1.56], p = 0.04). Both GCS and global longitudinal strain correlated with the extent of fibrosis (r = .52, p = 0.03 and r = .75, p < 0.01, respectively). Importantly, segmental strain did not seem to correspond to location of fibrosis.

CONCLUSION

A lower global, but not segmental, strain is associated with presence and extent of LV myocardial fibrosis in pediatric DMD patients. Therefore, strain parameters might detect structural myocardial alterations, however currently more research is needed to evaluate its value (e.g., prognostic) in clinical practice.

Myocardial Fibrosis in Congenital Heart Disease and the Role of MRI

Progress in the field of congenital heart surgery over the last century can only be described as revolutionary. Recent improvements in patient outcomes have been achieved through refinements in perioperative care. In the current and future eras, the preservation and restoration of myocardial health, beginning with the monitoring of tissue remodeling, will be central to improving cardiac outcomes. Visualization and quantification of fibrotic myocardial remodeling is one of the greatest assets that cardiac MRI brings to the field of cardiology, and its clinical use within the field of congenital heart disease (CHD) has been an area of particular interest in the last few decades. This review summarizes the physical underpinnings of myocardial tissue characterization in CHD, with an emphasis on T1 parametric mapping and late gadolinium enhancement. It describes methods and suggestions for obtaining images, extracting quantitative and qualitative data, and interpreting the results for children and adults with CHD. The tissue characterization observed in different lesions is used to examine the causes and pathomechanisms of fibrotic remodeling in this population. Similarly, the clinical consequences of elevated imaging biomarkers of fibrosis on patient health and outcomes are explored. Keywords: Pediatrics, MR Imaging, Cardiac, Heart, Congenital, Tissue Characterization, Congenital Heart Disease, Cardiac MRI, Parametric Mapping, Fibrosis, Late Gadolinium Enhancement © RSNA, 2023.

Ventricular function and tissue characterization by cardiac magnetic resonance imaging following hospitalization for multisystem inflammatory syndrome in children: a prospective study

BACKGROUND

Multisystem inflammatory syndrome in children (MIS-C) is a severe life-threatening manifestation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection that often presents with acute cardiac dysfunction and cardiogenic shock. While recovery from acute illness is excellent, the long-term myocardial impact is unknown.

OBJECTIVE

To compare cardiac MRI findings in children 6-9 months after their hospitalization with MIS-C against MRI findings in healthy controls to assess for residual myocardial disease.

MATERIALS AND METHODS

We prospectively performed cardiac MRI on 13 children 6-9 months following their hospitalization with MIS-C: eight of these children had a history of left ventricle ejection fraction (LVEF) < 50%, persistent symptoms, or electrocardiogram (ECG) abnormalities and underwent clinical MRI; five of these children without cardiac abnormalities during their hospitalization underwent research MRIs. We compared their native T1 and T2 mapping values with those of 20 normal controls.

RESULTS

Cardiac MRI was performed at 13.6 years of age (interquartile range [IQR] 11.9-16.4 years) and 8.2 months (IQR 6.8-9.6 months) following hospitalization. Twelve children displayed normal ejection fraction: left ventricle (LV) 57.2%, IQR 56.1-58.4; right ventricle (RV) 53.1%, IQR 52.0-55.7. One had low-normal LVEF (52%). They had normal extracellular volume (ECV) and normal T2 and native T1 times compared to controls. There was no qualitative evidence of edema. One child had late gadolinium enhancement (LGE) with normal ejection fraction, no edema, and normal T1 and T2 times. When stratifying children who had MIS-C according to history of LVEF <55% on echocardiography, there was no difference in MRI values.

CONCLUSION

Although many children with MIS-C present acutely with cardiac dysfunction, residual myocardial damage 6-9 months afterward appears minimal. Long-term implications warrant further study.

Heart Failure with Preserved Ejection Fraction in Children

Diastolic dysfunction (DD) refers to abnormalities in the mechanical function of the left ventricle (LV) during diastole. Severe LVDD can cause symptoms and the signs of heart failure (HF) in the setting of normal or near normal LV systolic function and is referred to as diastolic HF or HF with preserved ejection fraction (HFpEF). Pediatric cardiologists have long speculated HFpEF in children with congenital heart disease and cardiomyopathy. However, understanding the risk factors, clinical course, and validated biomarkers predictive of the outcome of HFpEF in children is challenging due to heterogeneous etiologies and overlapping pathophysiological mechanisms. The natural history of HFpEF varies depending upon the patient's age, sex, race, geographic location, nutritional status, biochemical risk factors, underlying heart disease, and genetic-environmental interaction, among other factors. Pediatric onset HFpEF is often not the same disease as in adults. Advances in the noninvasive evaluation of the LV diastolic function by strain, and strain rate analysis with speckle-tracking echocardiography, tissue Doppler imaging, and cardiac magnetic resonance imaging have increased our understanding of the HFpEF in children. This review addresses HFpEF in children and identifies knowledge gaps in the underlying etiologies, pathogenesis, diagnosis, and management, especially compared to adults with HFpEF.

Native T1 mapping detects both acute clinical rejection and graft dysfunction in pediatric heart transplant patients

BACKGROUND

Cardiovascular magnetic resonance (CMR) is emerging as an important tool for cardiac allograft assessment. Native T1 mapping may add value in identifying rejection and in assessing graft dysfunction and myocardial fibrosis burden. We hypothesized that CMR native T1 values and features of textural analysis of T1 maps would identify acute rejection, and in a secondary analysis, correlate with markers of graft dysfunction, and with fibrosis percentage from endomyocardial biopsy (EMB).

METHODS

Fifty cases with simultaneous EMB, right heart catheterization, and 1.5 T CMR with breath-held T1 mapping via modified Look-Locker inversion recovery (MOLLI) in 8 short-axis slices and subsequent quantification of mean and peak native T1 values, were performed on 24 pediatric subjects. A single mid-ventricular slice was used for image texture analysis using nine gray-level co-occurrence matrix features. Digital quantification of Masson trichrome stained EMB samples established degree of fibrosis. Markers of graft dysfunction, including serum brain natriuretic peptide levels and hemodynamic measurements from echocardiography, catheterization, and CMR were collated. Subjects were divided into three groups based on degree of rejection: acute rejection requiring new therapy, mild rejection requiring increased ongoing therapy, and no rejection with no change in treatment. Statistical analysis included student's t-test and linear regression.

RESULTS

Peak and mean T1 values were significantly associated with acute rejection, with a monotonic trend observed with increased grade of rejection. Texture analysis demonstrated greater spatial heterogeneity in T1 values, as demonstrated by energy, entropy, and variance, in cases requiring treatment. Interestingly, 2 subjects who required increased therapy despite low grade EMB results had abnormal peak T1 values. Peak T1 values also correlated with increased BNP, right-sided filling pressures, and capillary wedge pressures. There was no difference in histopathological fibrosis percentage among the 3 groups; histopathological fibrosis did not correlate with T1 values or markers of graft dysfunction.

CONCLUSION

In pediatric heart transplant patients, native T1 values identify acute rejection requiring treatment and may identify graft dysfunction. CMR shows promise as an important tool for evaluation of cardiac grafts in children, with T1 imaging outperforming biopsy findings in the assessment of rejection.

Cardiac magnetic resonance diastolic indices correlate with ventricular filling pressures in pediatric heart transplant recipients

BACKGROUND

Atrial and ventricular filling pressures are routinely used in pediatric heart transplant (PHTx) recipients to assess graft function. We hypothesized that cardiac magnetic resonance (CMR) diastolic indices correlate with filling pressures, providing a noninvasive method of hemodynamic assessment.

METHODS

Pediatric heart transplant recipients were prospectively enrolled at the time of cardiac catheterization. Pulmonary capillary wedge pressure (PCWP) and right atrial pressure (RAP) were measured. CMR included standard volumetric analysis. Filling curves were calculated by contouring every phase in the short-axis stack. Global longitudinal and circumferential strain (GLS, GCS) were calculated using feature tracking. Atrial volumes and ejection fraction were calculated from 4-chamber and 2-chamber cine images. Correlations were analyzed using Spearman's Rho; modeling was performed with multivariable logistic regression.

RESULTS

A total of 35 patients with a mean age of 15.5 years were included, 12 with acute rejection. The median time post-transplant was 6.2 years. Peak filling rate (PFR) and peak LV ejection rate/end-diastolic volume (PER/EDV) correlated with PCWP (rho = 0.48 p = .005, and rho = -0.35 p = .046, respectively) as did GLS and GCS (rho = 0.52 p = .002, and 0.40 p = .01). Indexed maximum and minimum left atrial (LA) volume correlated with PCWP (rho = 0.41, p = .01, rho = 0.41 p = .01), and LA ejection fraction inversely correlated with PCWP (rho = -0.40, p = .02). GLS and GCS correlated with RAP (rho = 0.55, p = .001 and rho = 0.43, p = .01). A model including LV GLS and PFR estimated PCWP ≥12 mmHg with an area under the curve of 0.84.

CONCLUSIONS

Cardiac magnetic resonance can be a useful noninvasive modality to assess for signs of diastolic dysfunction after PHTx.

SCMR expert consensus statement for cardiovascular magnetic resonance of acquired and non-structural pediatric heart disease

Cardiovascular magnetic resonance (CMR) is widely used for diagnostic imaging in the pediatric population. In addition to structural congenital heart disease (CHD), for which published guidelines are available, CMR is also performed for non-structural pediatric heart disease, for which guidelines are not available. This article provides guidelines for the performance and reporting of CMR in the pediatric population for non-structural ("non-congenital") heart disease, including cardiomyopathies, myocarditis, Kawasaki disease and systemic vasculitides, cardiac tumors, pericardial disease, pulmonary hypertension, heart transplant, and aortopathies. Given important differences in disease pathophysiology and clinical manifestations as well as unique technical challenges related to body size, heart rate, and sedation needs, these guidelines focus on optimization of the CMR examination in infants and children compared to adults. Disease states are discussed, including the goals of CMR examination, disease-specific protocols, and limitations and pitfalls, as well as newer techniques that remain under development.

Society for Cardiovascular Magnetic Resonance/European Society of Cardiovascular Imaging/American Society of Echocardiography/Society for Pediatric Radiology/North American Society for Cardiovascular Imaging Guidelines for the use of cardiovascular magnetic resonance in pediatric congenital and acquired heart disease : Endorsed by The American Heart Association

Cardiovascular magnetic resonance (CMR) has been utilized in the management and care of pediatric patients for nearly 40 years. It has evolved to become an invaluable tool in the assessment of the littlest of hearts for diagnosis, pre-interventional management and follow-up care. Although mentioned in a number of consensus and guidelines documents, an up-to-date, large, stand-alone guidance work for the use of CMR in pediatric congenital 36 and acquired 35 heart disease endorsed by numerous Societies involved in the care of these children is lacking. This guidelines document outlines the use of CMR in this patient population for a significant number of heart lesions in this age group and although admittedly, is not an exhaustive treatment, it does deal with an expansive list of many common clinical issues encountered in daily practice.

Society for Cardiovascular Magnetic Resonance/European Society of Cardiovascular Imaging/American Society of Echocardiography/Society for Pediatric Radiology/North American Society for Cardiovascular Imaging Guidelines for the Use of Cardiac Magnetic Resonance in Pediatric Congenital and Acquired Heart Disease: Endorsed by The American Heart Association

Cardiovascular magnetic resonance has been utilized in the management and care of pediatric patients for nearly 40 years. It has evolved to become an invaluable tool in the assessment of the littlest of hearts for diagnosis, pre-interventional management and follow-up care. Although mentioned in a number of consensus and guidelines documents, an up-to-date, large, stand-alone guidance work for the use of cardiovascular magnetic resonance in pediatric congenital 36 and acquired 35 heart disease endorsed by numerous Societies involved in the care of these children is lacking. This guidelines document outlines the use of cardiovascular magnetic resonance in this patient population for a significant number of heart lesions in this age group and although admittedly, is not an exhaustive treatment, it does deal with an expansive list of many common clinical issues encountered in daily practice.

Recommendations for cardiovascular magnetic resonance and computed tomography in congenital heart disease: a consensus paper from the CMR/CCT working group of the Italian Society of Pediatric Cardiology (SICP) and the Italian College of Cardiac Radiology endorsed by the Italian Society of Medical and Interventional Radiology (SIRM) Part I

Cardiovascular magnetic resonance (CMR) and computed tomography (CCT) are advanced imaging modalities that recently revolutionized the conventional diagnostic approach to congenital heart diseases (CHD), supporting echocardiography and often replacing cardiac catheterization. Nevertheless, correct execution and interpretation require in-depth knowledge of all technical and clinical aspects of CHD, a careful assessment of risks and benefits before each exam, proper imaging protocols to maximize diagnostic information, minimizing harm. This position paper, written by experts from the Working Group of the Italian Society of Pediatric Cardiology and from the Italian College of Cardiac Radiology of the Italian Society of Medical and Interventional Radiology, is intended as a practical guide for applying CCT and CMR in children and adults with CHD, wishing to support Radiologists, Pediatricians, Cardiologists and Cardiac Surgeons in the multimodality diagnostic approach to these patients. The first part provides a review of the most relevant literature in the field, describes each modality's advantage and drawback, making considerations on the main applications, image quality, and safety issues. The second part focuses on clinical indications and appropriateness criteria for CMR and CCT, considering the level of CHD complexity, the clinical and logistic setting and the operator expertise.

Heart Failure Risk Predictions and Prognostic Factors in Adults With Congenital Heart Diseases

In recent decades the number of adults with congenital heart diseases (ACHD) has increased significantly. This entails the need for scrupulous evaluation of the current condition of these patients. The ACHD population is one of the most challenging in contemporary medicine, especially as well-known scales such as the NYHA classification have very limited application. At the moment, there is a lack of universal parameters or scales on the basis of which we can easily capture the moment of deterioration of our ACHD patients' condition. Hence it is crucial to identify factors that are widely available, cheap and easy to use. There are studies showing more and more potential prognostic factors that may be of use in clinical practice: thorough assessment with echocardiography and magnetic resonance imaging (e.g., anatomy, ventricular function, longitudinal strain, shunt lesions, valvular defects, pericardial effusion, and pulmonary hypertension), cardiopulmonary exercise testing (e.g., peak oxygen uptake, ventilatory efficiency, chronotropic incompetence, and saturation) and biomarkers (e.g., N-terminal pro-brain type natriuretic peptide, growth-differentiation factor 15, high-sensitivity troponin T, red cell distribution width, galectin-3, angiopoietin-2, asymmetrical dimethylarginine, and high-sensitivity C-reactive protein). Some of them are very promising, but more research is needed to create a specific panel on the basis of which we will be able to assess patients with specific congenital heart diseases.

Native cardiac magnetic resonance T1 mapping and cardiac mechanics as assessed by speckle tracking echocardiography in patients with beta-thalassaemia major

BACKGROUND

We hypothesize that cardiac magnetic resonance (CMR) native T1 is associated with myocardial deformation in thalassaemia patients. The present study aimed to compare CMR native T1 values to conventional T2* values in patients with beta-thalassaemia and to explore relationships between these CMR parameters of myocardial iron overload and left ventricular (LV) and left atrial (LA) myocardial deformation.

METHODS

Thirty-four (16 males) patients aged 35.5 ± 9.2 years were studied. Myocardial T2* and T1 mapping were performed to assess the cardiac iron overload, while two-dimensional speckle-tracking echocardiography was performed in determine LV and LA myocardial deformation.

RESULTS

T2* was 36.4 ± 8.7 ms with 3 patients having myocardial iron load (T2*<20 ms). The native T1 was 947.1 ± 84.8 ms, which was significantly lower than the reported normal values in the literature. There was a significant correlation between T1 and T2* values (r = 0.68, p < 0.001). There were no significant correlations between T1 and T2* values and conventional and tissue Doppler parameters of left ventricular systolic and diastolic function. On the other hand, T1, but not T2*, values were found to correlate negatively with maximum LA area indexed by body surface area (r = -0.34, p = 0.047) and positively with LA strain rate at atrial contraction (r = 0.36, p = 0.04). There were no associations between either of these CMR parameters with indices of ventricular deformation.

CONCLUSIONS

In patients with beta-thalassaemia major, native T1 values are decreased, associated with T2* values, and correlated with maximum LA area and LA strain rate at atrial contraction.

Myocardial fibrosis in congenital heart disease

Myocardial fibrosis resulting from the excessive deposition of collagen fibers through the myocardium is a common histopathologic finding in a wide range of cardiovascular diseases, including congenital anomalies. Interstitial fibrosis has been identified as a major cause of myocardial dysfunction since it distorts the normal architecture of the myocardium and impairs the biological function and properties of the interstitium. This review summarizes current knowledge on the mechanisms and detrimental consequences of myocardial fibrosis in heart failure and arrhythmias, discusses the usefulness of available imaging techniques and circulating biomarkers to assess this entity and reviews the current body of evidence regarding myocardial fibrosis in the different subsets of congenital heart diseases with implications in research and treatment.

Myocardial Parametric Mapping by Cardiac Magnetic Resonance Imaging in Pediatric Cardiology and Congenital Heart Disease

Parametric mapping, that is, a pixel-wise map of magnetic relaxation parameters, expands the diagnostic potential of cardiac magnetic resonance by enabling quantification of myocardial tissue-specific magnetic relaxation on an absolute scale. Parametric mapping includes T₁ mapping (native and postcontrast), T₂ and T₂* mapping, and extracellular volume measurements. The myocardial composition is altered in various disease states affecting its inherent magnetic properties and thus the myocardial relaxation times that can be directly quantified using parametric mapping. Parametric mapping helps in the diagnosis of nonfocal disease states and allows for longitudinal disease monitoring, evaluating therapeutic response (as in Thalassemia patients with iron overload undergoing chelation), and risk-stratification of certain diseases. In this review article, we describe various mapping techniques and their clinical utility in congenital heart disease. We will also review the available literature on normative values in children, the strengths, and weaknesses of these techniques. This review provides a starting point for pediatric cardiologists to understand and implement parametric mapping in their practice.

Patients with repaired tetralogy of Fallot and the HIF1A1744C/T variant have increased imaging markers of diffuse myocardial fibrosis

BACKGROUND

Right ventricular fibrotic remodeling has been identified pre- and postoperatively in patients with tetralogy of Fallot (ToF) and linked to adverse outcomes. Polymorphisms of hypoxia inducible factor-1-alpha (HIF1A) have been associated with the fibrotic burden by cardiac magnetic resonance (CMR) late gadolinium enhancement imaging. Their association with diffuse fibrotic myocardial remodeling is unknown. We sought to determine whether polymorphisms in HIF1A are related to CMR markers of diffuse myocardial fibrosis.

METHODS

Patients with repaired ToF who had undergone CMR with T1 mapping as well as whole genome sequencing were included. Myocardial native T1 was quantified using a modified Look-Locker inversion recovery sequence and measured in the left ventricular free wall, the interventricular septum, and the right ventricular free wall. Patients who had at least one functioning allele of HIF1A were compared to those who did not using the Mann Whitney U test for continuous variables and chi-square or the Fischer test for discrete variables.

RESULTS

46 patients had both CMR and whole genome sequencing. Only one HIF1A variant was identified in the cohort and present in 13 patients. There were no significant differences in demographics, surgical variables, right or left ventricular volumes or function between patients with and without the variant. Despite a trend towards a lower age at the time of CMR (11.3 vs 13.7 years; p = 0.07), patients with HIF1A variants had higher native T1 values (1094 vs. 1050; p = 0.027) in the right ventricular outflow tract myocardium, reflecting increased diffuse interstitial ventricular fibrosis in them.

CONCLUSION

Hypoxia-inducible factor is associated with imaging markers of increased diffuse right ventricular fibrosis late after repair of tetralogy of Fallot.

Adverse fibrosis remodeling and aortopulmonary collateral flow are associated with poor Fontan outcomes

BACKGROUND

The extent and significance in of cardiac remodeling in Fontan patients are unclear and were the subject of this study.

METHODS

This retrospective cohort study compared cardiovascular magnetic resonance (CMR) imaging markers of cardiac function, myocardial fibrosis, and hemodynamics in young Fontan patients to controls.

RESULTS

Fifty-five Fontan patients and 44 healthy controls were included (median age 14 years (range 7-17 years) vs 13 years (range 4-14 years), p = 0.057). Fontan patients had a higher indexed end-diastolic ventricular volume (EDVI 129 ml/m2 vs 93 ml/m2, p < 0.001), and lower ejection fraction (EF 45% vs 58%, p < 0.001), circumferential (CS - 23.5% vs - 30.8%, p < 0.001), radial (6.4% vs 8.2%, p < 0.001), and longitudinal strain (- 13.3% vs - 24.8%, p < 0.001). Compared to healthy controls, Fontan patients had higher extracellular volume fraction (ECV) (26.3% vs 20.6%, p < 0.001) and native T1 (1041 ms vs 986 ms, p < 0.001). Patients with a dominant right ventricle demonstrated larger ventricles (EDVI 146 ml/m2 vs 120 ml/m2, p = 0.03), lower EF (41% vs 47%, p = 0.008), worse CS (- 20.1% vs - 25.6%, p = 0.003), and a trend towards higher ECV (28.3% versus 24.1%, p = 0.09). Worse EF and CS correlated with longer cumulative bypass (R = - 0.36, p = 0.003 and R = 0.46, p < 0.001), cross-clamp (R = - 0.41, p = 0.001 and R = 0.40, p = 0.003) and circulatory arrest times (R = - 0.42, p < 0.001 and R = 0.27, p = 0.03). T1 correlated with aortopulmonary collateral (APC) flow (R = 0.36, p = 0.009) which, in the linear regression model, was independent of ventricular morphology (p = 0.9) and EDVI (p = 0.2). The composite outcome (cardiac readmission, cardiac reintervention, Fontan failure or any clinically significant arrhythmia) was associated with increased native T1 (1063 ms vs 1026 ms, p = 0.029) and EDVI (146 ml/m2 vs 118 ml/m2, p = 0.013), as well as decreased EF (42% vs 46%, p = 0.045) and worse CS (- 22% vs - 25%, p = 0.029). APC flow (HR 5.5 CI 1.9-16.2, p = 0.002) was independently associated with the composite outcome, independent of ventricular morphology (HR 0.71 CI 0.30-1.69 p = 0.44) and T1 (HR1.006 CI 1.0-1.13, p = 0.07).

CONCLUSIONS

Pediatric Fontan patients have ventricular dysfunction, altered myocardial mechanics and increased fibrotic remodeling. Cumulative exposure to cardiopulmonary bypass and increased aortopulmonary collateral flow are associated with myocardial dysfunction and fibrosis. Cardiac dysfunction, fibrosis, and collateral flow are associated with adverse outcomes.

Improving the robustness of MOLLI T1 maps with a dedicated motion correction algorithm

Myocardial tissue T1 constitutes a reliable indicator of several heart diseases related to extracellular changes (e.g. edema, fibrosis) as well as fat, iron and amyloid content. Magnetic resonance (MR) T1-mapping is typically achieved by pixel-wise exponential fitting of a series of inversion or saturation recovery measurements. Good anatomical alignment between these measurements is essential for accurate T1 estimation. Motion correction is recommended to improve alignment. However, in the case of inversion recovery sequences, this correction is compromised by the intrinsic contrast variation between frames. A model-based, non-rigid motion correction method for MOLLI series was implemented and validated on a large database of cardiac clinical cases (n = 186). The method relies on a dedicated similarity metric that accounts for the intensity changes caused by T1 magnetization relaxation. The results were compared to uncorrected series and to the standard motion correction included in the scanner. To automate the quantitative analysis of results, a custom data alignment metric was defined. Qualitative evaluation was performed on a subset of cases to confirm the validity of the new metric. Motion correction caused noticeable (i.e. > 5%) performance degradation in 12% of cases with the standard method, compared to 0.3% with the new dedicated method. The average alignment quality was 85% ± 9% with the default correction and 90% ± 7% with the new method. The results of the qualitative evaluation were found to correlate with the quantitative metric. In conclusion, a dedicated motion correction method for T1 mapping MOLLI series has been evaluated on a large database of clinical cardiac MR cases, confirming its increased robustness with respect to the standard method implemented in the scanner.

Right Ventricular Function and T1-Mapping in Boys With Duchenne Muscular Dystrophy

BACKGROUND

Clinical management of boys with Duchenne muscular dystrophy (DMD) relies on in-depth understanding of cardiac involvement, but right ventricular (RV) structural and functional remodeling remains understudied.

PURPOSE

To evaluate several analysis methods and identify the most reliable one to measure RV pre- and postcontrast T1 (RV-T1) and to characterize myocardial remodeling in the RV of boys with DMD.

STUDY TYPE

Prospective.

POPULATION

Boys with DMD (N = 27) and age-/sex-matched healthy controls (N = 17) from two sites.

FIELD STRENGTH/SEQUENCE

3.0 T using balanced steady state free precession, motion-corrected phase sensitive inversion recovery and modified Look-Locker inversion recovery sequences.

ASSESSMENT

Biventricular mass (Mi), end-diastolic volume (EDVi) and ejection fraction (EF) assessment, tricuspid annular excursion (TAE), late gadolinium enhancement (LGE), pre- and postcontrast myocardial T1 maps. The RV-T1 reliability was assessed by three observers in four different RV regions of interest (ROI) using intraclass correlation (ICC).

STATISTICAL TESTS

The Wilcoxon rank sum test was used to compare RV-T1 differences between DMD boys with negative LGE(-) or positive LGE(+) and healthy controls. Additionally, correlation of precontrast RV-T1 with functional measures was performed. A P-value <0.05 was considered statistically significant.

RESULTS

A 1-pixel thick RV circumferential ROI proved most reliable (ICC > 0.91) for assessing RV-T1. Precontrast RV-T1 was significantly higher in boys with DMD compared to controls. Both LGE(-) and LGE(+) boys had significantly elevated precontrast RV-T1 compared to controls (1543 [1489-1597] msec and 1550 [1402-1699] msec vs. 1436 [1399-1473] msec, respectively). Compared to healthy controls, boys with DMD had preserved RVEF (51.8 [9.9]% vs. 54.2 [7.2]%, P = 0.31) and significantly reduced RVMi (29.8 [9.7] g vs. 48.0 [15.7] g), RVEDVi (69.8 [29.7] mL/m² vs. 89.1 [21.9] mL/m² ), and TAE (22.0 [3.2] cm vs. 26.0 [4.7] cm). Significant correlations were found between precontrast RV-T1 and RVEF (β = -0.48%/msec) and between LV-T1 and LVEF (β = -0.51%/msec).

DATA CONCLUSION

Precontrast RV-T1 is elevated in boys with DMD compared to healthy controls and is negatively correlated with RVEF.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 2.

Effect of anthracycline therapy on myocardial function and markers of fibrotic remodelling in childhood cancer survivors

AIMS

Anthracyclines are a cornerstone of paediatric cancer treatment. We aimed to quantify myocardial cardiac magnetic resonance (CMR) native T1 (NT1) and extracellular volume fraction (ECV) as markers of fibrosis in a cohort of childhood cancer survivors (CCS).

METHODS AND RESULTS

A cohort of CCS in remission underwent CMR T1 mapping. Diastolic function was assessed by echocardiography. Results were compared to a cohort of normal controls of similar age and gender. Fifty-five CCS and 46 controls were included. Both groups had similar mean left ventricular (LV) NT1 values (999 ± 36 vs. 1007 ± 32 ms, P = 0.27); ECV was higher (25.6 ± 6.9 vs. 20.7 ± 2.4%, P = 0.003) and intracellular mass was lower (37.5 ± 8.4 vs. 43.3 ± 9.9g/m2, P = 0.02) in CCS. The CCS group had lower LV ejection fraction (EF) and LV mass index with otherwise normal diastolic function in all but one patient. The proportion of subjects with elevated ECV compared to controls did not differ between subgroups with normal or reduced LV EF (22% vs. 28%; P = 0.13) and no correlations were found between LVEF and ECV. While average values remained within normal range, mitral E/E' (6.6 ± 1.6 vs. 5.9 ± 0.9, P = 0.02) was higher in CCS. Neither NT1 nor ECV correlated with diastolic function indices or cumulative anthracycline dose.

CONCLUSIONS

There is evidence for mild diffuse extracellular volume expansion in some asymptomatic CCS; myocyte loss could be part of the mechanism, accompanied by subtle changes in systolic and diastolic function. These findings suggest mild myocardial damage and remodelling after anthracycline treatment in some CCS which requires continued monitoring.

Myocardial Fibrosis in Pediatric Patients With Ebstein's Anomaly

BACKGROUND

Left ventricular dysfunction in Ebstein's anomaly (EA) is associated with higher mortality. The health of the left ventricular myocardium in children and adolescents with EA has not been investigated in detail.

METHODS

Patients with unrepaired EA who had undergone cardiac magnetic resonance imaging including T1 mapping were retrospectively reviewed. Patients were compared with age- and sex-matched controls. EA severity index was calculated using volumetric measurements at end diastole ([right atrial+atrialized right ventricular volumes]/[functional right ventricular+left atrial+left ventricular volumes]). Global circumferential and radial strain and as well as strain rate were examined using cardiac magnetic resonance feature tracking.

RESULTS

Twelve EA patients and an equal number of controls were included. Functional and atrialized right ventricular end-diastolic volumes were 84±15 and 21±13 mL/m², respectively. Late gadolinium enhancement, confined to the right ventricle, was found in 2 patients (16%). Left ventricular native T1 values and extracellular volume fractions were higher in patients compared with controls (1026±47 versus 956±40 ms, P=0.0004 and 28.5±3.4% versus 22.5±2.6%, P<0.001, respectively). Native T1 times correlated inversely with patients' age, body surface area, and O₂ saturations (r=-0.63, -0.62, and -0.91, respectively; P=0.02, P=0.02, and P<0.0001, respectively). EA severity index ranged between 0.15 and 0.94 and correlated with T1 values (r=0.76, P=0.003). Native T1 correlated with global circumferential strain (r=0.58, P=0.04) but not ejection fraction (EF). EA patients had reduced maximum oxygen uptake (Vo₂max). Vo₂max correlated inversely with T1 values (r=-0.79, P=0.01).

CONCLUSIONS

Children and adolescents with EA experience an abnormal degree of diffuse myocardial fibrosis. Its association with O₂ saturation points toward a role of hypoxemia in the pathogenesis of fibrosis. Larger and prospective studies are needed to evaluate the value of T1 mapping for risk stratification and monitoring in EA.

Diagnosis, Prevention, Treatment and Surveillance of Anthracycline-Induced Cardiovascular Toxicity in Pediatric Cancer Survivors

Advances in pediatric cancer therapies have dramatically improved the likelihood of survival. As survivors are aging, however, we are now understanding that treatment carries a significant risk of cardiovascular toxicity, which can develop immediately, or even many years after completing therapy. Anthracycline derivates are some of the most commonly used agents in pediatric oncology treatment protocols, which have a dose-dependent correlation with the development of cardiac toxicity. As we learn more about the mechanisms of toxicity, we are developing prevention strategies, including improvements in surveillance, to improve early diagnosis of heart disease. Current survivorship surveillance protocols often include screening echocardiograms to evaluate systolic function by measuring the ejection fraction or fractional shortening. However, these measurements alone are not enough to capture early myocardial changes. The use of additional imaging biomarkers, serum biomarkers, electrocardiograms, as well as cholesterol and blood pressure screening, are key to the early detection of cardiomyopathy and cardiovascular disease. Medical treatment strategies are the same as those used for heart failure from other causes, but earlier recognition and implementation can lead to improved long term outcomes.

Left atrial dysfunction in sickle cell anemia is associated with diffuse myocardial fibrosis, increased right ventricular pressure and reduced exercise capacity

Increased extracellular volume (ECV) by CMR is a marker of interstitial myocardial fibrosis and is associated with diastolic dysfunction in sickle cell anemia (SCA). Left atrial (LA) dysfunction and stiffness contribute to the development of diastolic heart failure in other settings. We aimed to evaluate LA function and stiffness associations with ECV, tricuspid regurgitation jet velocity (TRV) and exercise abnormalities in SCA. In a prospective study, individuals with SCA underwent CMR, echocardiography and exercise test. ECV was measured using MOLLI sequence. Atrial strain was studied in the 4- and 2-chamber views. LA stiffness was calculated as the ratio of echocardiographic E/e’-to-LA reservoir strain. Twenty-four participants with SCA were included (median age 20 years). ECV was increased in participant with SCA compared to our lab normal values (mean 0.44 ± 0.08 vs 0.26 ± 0.02, P < 0.0001). Six (25%) had LA LGE. ECV positively correlated with LA stiffness (r = 0.45, p = 0.04). There was a negative correlation between LA stiffness and %predicted VO2 (r = −0.50, p = 0.04). LA stiffness was moderately associated with increased TRV (r = 0.55, p < 0.005). LA stiffness is associated with ECV, exercise impairment and increased TRV. This study sheds insights on the interaction between LA function, RV hypertension, and myocardial fibrosis in SCA.

Potential Value of Native T1 Mapping in Symptomatic Adults with Congenital Heart Disease: A Preliminary Study of 3.0 Tesla Cardiac Magnetic Resonance Imaging

The native T1 value at 3.0 Tesla is a sensitive marker of diffuse myocardial damage. We evaluated the clinical usefulness of native T1 mapping in symptomatic adults with congenital heart disease (CHD), particularly in the systemic right ventricle (RV). Prospectively, 45 consecutive symptomatic adults with CHD were enrolled: 20 with systemic RV and 25 with tetralogy of Fallot underwent cardiac magnetic resonance (CMR) imaging at 3.0 Tesla. The Modified Look-Locker Inversion recovery sequence was used for T1 mapping. Cardiovascular events in the systemic RV were defined as heart failure and tachyarrhythmia. Brain natriuretic peptide (BNP) and indexed systemic ventricular end-diastolic volume were significantly higher in the systemic RV group. The native T1 value and extracellular volume (ECV) of the septal and lateral walls were higher in the systemic RV group, suggesting high impairment of the myocardium in the systemic RV group. There was a strong correlation between the native T1 value and ECV of the septum (r = 0.58, P = 0.03) and lateral wall (r = 0.56, P = 0.046) in the systemic RV group. Seven patients with systemic RV had cardiovascular events. In univariate logistic regression analysis, BNP and native T1 values of the insertion point were important for predicting cardiovascular events. The native T1 value at 3.0 Tesla may be a sensitive, contrast-free, and non-invasive adjunct marker of myocardial damage in CHD and predictive of cardiovascular events in the systemic RV.

Cardiac Abnormalities in Patients With Hutchinson-Gilford Progeria Syndrome

Importance

Hutchinson-Gilford progeria syndrome (HGPS) is an ultrarare disorder associated with premature death due to cardiovascular events during the second decade of life. However, because of its rarity (107 identified living patients), the natural history of cardiac disease remains uncharacterized. Therefore, meaningful cardiac end points for clinical trials have been difficult to establish.

Objective

To examine the course of appearance of cardiac abnormalities in patients with HGPS to identify meaningful cardiac end points for use in future clinical trials.

Design, Setting, and Participants

In this prospective, cross-sectional, observational study, 27 consecutive patients with clinically and genetically confirmed classic HGPS were evaluated at a single center for 1 visit from July 1, 2014, through February 29, 2016, before initiation of treatment.

Exposure

Classic HGPS.

Main Outcomes and Measures

Echocardiography was used to assess ventricular and valve function using standard techniques. Diastolic left ventricular (LV) function was assessed using tissue Doppler imaging. Previously published normative data were used to adjust findings to age and body size.

Results

This study included 27 patients (median age, 5.6 years; age range, 2-17 years; 15 [56%] male). Among echocardiographic indicators, LV diastolic dysfunction, defined as a tissue Doppler septal or lateral early velocity z score less than -2, was the most prevalent abnormality, seen in 16 patients (59%). Diastolic dysfunction was seen in all age groups, and its prevalence increased with age, mirroring findings seen during normal aging. Indicators of LV diastolic function were more abnormal in older patients. The z scores for lateral and septal early velocities were lower (r = -0.77, P < .001; and r = -0.66, P < .001, respectively), whereas those for the ratio of early mitral inflow velocity to early diastolic tissue Doppler myocardial velocity were higher (r = 0.80, P < .001; and r = 0.72, P < .001, respectively) in older patients. Other echocardiographic findings, including LV hypertrophy, LV systolic dysfunction, and valve disease, were less prevalent in the first decade and were seen more frequently in the second decade.

Conclusions and Relevance

In this largest-to-date cohort of patients with HGPS, LV diastolic dysfunction was the most prevalent echocardiographic abnormality and its prevalence increased with aging. Echocardiographic indicators of LV diastolic function may be useful end points in future clinical trials in this patient population.

Mapping versus source methods for quantifying myocardial T1 in controls and in repaired tetralogy of Fallot: interchangeability and reproducibility in children

BACKGROUND

Myocardial T1 relaxometry can be performed by contouring on individual T1-weighted source images (source method) or on a single T1 map (mapping method).

OBJECTIVE

This study compares (a) agreement between native T1 and extracellular volume results of the two methods and (b) interobserver reproducibility of the two methods in children without heart disease and those with tetralogy of Fallot (TOF).

MATERIALS AND METHODS

We retrospectively analyzed pediatric patients (controls and those with repaired TOF) with cardiac magnetic resonance examinations including extracellular volume quantification using the modified Look-Locker inversion recovery (MOLLI) sequence. We compared native T1 and extracellular volume of the entire left ventricle and interventricular septum derived using the source and the mapping approaches.

RESULTS

In the control group (n=25, median age 14.0 years, interquartile range [IQR] 11.5-16.5 years), the mapping method produced lower native T1 values than the source method in the interventricular septum (mean difference ± standard deviation [SD] = 12±15 ms, P<0.001). In the TOF group (n=50, median age 13.3 years, IQR 9.9-15.0 years), the mapping method produced lower values for native T1 and extracellular volume in the interventricular septum (mean difference 9±14 ms and 0.6±1.1%, P<0.001). In 6-12% of the children, differences were >3 standard deviations from the mean difference. Interobserver reproducibility between the two methods by intraclass correlation coefficients were clinically equivalent.

CONCLUSION

T1 and extracellular volume values generated by the source and mapping methods show systematic differences and can vary significantly in an individual child, and thus cannot be used interchangeably in clinical practice. The source method might allow for easier detection and, in some cases, mitigation of artifacts that are not infrequent in children and can be difficult to appreciate on the T1 map.

Increased extracellular volume in the liver of pediatric Fontan patients

BACKGROUND

Patients with single ventricle physiology are at increased risk for developing liver fibrosis. Its extent and prevalence in children with bidirectional cavopulmonary connection (BCPC) and Fontan circulation are unclear. Extracellular volume fraction (ECV), derived from cardiovascular magnetic resonance (CMR) and T1 relaxometry, reflect fibrotic remodeling and/or congestion in the liver. The aim of this study was to investigate whether pediatric patients with single ventricle physiology experience increased native T1 and ECV as markers of liver fibrosis/congestion.

METHODS

Hepatic native T1 times and ECV, using a cardiac short axis modified Look-Locker inversion recovery sequence displaying the liver, were measured retrospectively in children with BCPC- and Fontan circulations and compared to pediatric controls.

RESULTS

Hepatic native T1 time were increased in Fontan patients (n = 62, 11.4 ± 4.4 years, T1 762 ± 64 ms) versus BCPC patients (n = 20, 2.8 ± 0.9 years, T1 645 ± 43 ms, p = 0.04). Both cohorts had higher T1 than controls (n = 44, 13.7 ± 2.9 years, T1 604 ± 54 ms, p < 0.001 for both). ECV was 41.4 ± 4.8% in Fontan and 36.4 ± 4.8% in BCPC patients, respectively (p = 0.02). In Fontan patients, T1 values correlated with exposure to cardiopulmonary bypass time (R = 0.3, p = 0.02), systolic and end diastolic volumes (R = 0.3, p = 0.04 for both) and inversely with oxygen saturations and body surface area (R = -0.3, p = 0.04 for both). There were no demonstrable associations of T1 or ECV with central venous pressure or age after Fontan.

CONCLUSION

Fontan and BCPC patients have elevated CMR markers suggestive of hepatic fibrosis and/or congestion, even at a young age. The tissue changes do not appear to be related to central venous pressures.

TRIAL REGISTRATION

Retrospectively registered data.

Left ventricular remodelling in long-term survivors after the arterial switch operation for transposition of the great arteries

Aims

The objective of this study was to quantify imaging markers of myocardial fibrosis and assess myocardial function in long-term transposition of the great arteries survivors after the arterial switch operation (ASO).

Methods and results

Paediatric ASO patients were prospectively studied by cardiac magnetic resonance imaging, including first-pass myocardial perfusion, late gadolinium enhancement, and T1 relaxometry, as well as echocardiography for left ventricular (LV) systolic and diastolic function including strain analysis, with comparison to healthy controls. Thirty ASO patients (mean age 15.4 ± 2.9 years vs. 14.1 ± 2.6 years in 28 controls, P = 0.04) were included. Patients had normal LV ejection fraction (EF) (57 ± 5% vs. 59 ± 5%, P = 0.07), but end-diastolic and end-systolic volumes were increased (104 ± 20 mL/m2 vs. 89 ± 10 mL/m2, P < 0.01 and 46 ± 13 mL/m2 vs. 36 ± 7 mL/m2, P < 0.01, respectively). Longitudinal strain at two-, three-, and four-chamber levels of the LV were lower in ASO patients (-19.0 ± 2.6% vs. -20.9 ± 2.3%, P = 0.006, -17.7 ± 2.0% vs. -19.1 ± 2.4%, P = 0.02, and -18.9 ± 1.9% vs. -20.1 ± 1.7%, P = 0.01, respectively), while circumferential strain was higher at all short-axis levels (-24.6 ± 2.3% vs. -19.3 ± 1.6%, P < 0.001 at the mid-ventricular level). LV native T1 times were higher in ASO patients (1042 ± 27 ms vs. 1011 ± 27 ms, P < 0.01) and correlated with LV mass/volume ratio (R = 0.60, P < 0.001). Myocardial scarring or myocardial perfusion defects were not observed in our cohort.

Conclusion

Children and adolescents after ASO have normal LV systolic function, in line with their overall good clinical health. At a myocardial level however, imaging markers of diffuse myocardial fibrosis are elevated, along with an altered LV contraction pattern. Whether these abnormalities will progress into future clinically significant dysfunction and whether they are harbingers of adverse outcomes remains to be studied.

Myocardial fibrosis and its relation to adverse outcome in transposition of the great arteries with a systemic right ventricle

BACKGROUND

Myocardial dysfunction has been implicated in gradual heart failure in transposition of the great arteries (TGA) with a systemic right ventricle (RV). Fibrosis can be assessed using the extracellular volume fraction (ECV). Our aim was to measure ECV and determine its associations with clinical findings and outcomes.

METHODS

We prospectively measured ECV in systemic RV subjects (either D-loop after atrial switch or L-loop) and healthy controls. T₁ measurements for a single mid-ventricular short-axis plane before and 3, 7, and 15 min after gadolinium contrast were used to quantify systemic ventricular ECV. Individuals with elevated ECV were compared to those without.

RESULTS

In 53 TGA subjects (age 34.6 ± 10.3 years, 41% female) the mean ECV for the systemic RV (28.7 ± 4.4%) was significantly higher than the left ventricle in 22 controls (26.1 ± 2.8%, P = 0.0104). Those with an elevated ECV (n = 15, 28.3%) had a higher b-type natriuretic peptide (BNP) (P < 0.011) and a longer 6-min walk distance (P = 0.021), but did not differ by age, arrhythmia history, ventricular volume, function, or circulating collagen byproducts. At follow-up (median 4.4 years), those experiencing major cardiovascular endpoints (new arrhythmia, arrhythmia device, heart failure hospitalization, listing for transplantation, mechanical support, or cardiovascular death, n = 14) had a higher ECV. ECV, age, and BNP were independent predictors of cardiac events in Cox-proportional hazard models.

CONCLUSIONS

Myocardial fibrosis is common in the systemic RV and associated with a higher BNP. Elevated CMR-derived ECV was associated with adverse clinical outcome. The findings suggest a role of diffuse myocardial fibrosis in clinical deterioration of the systemic RV.

Pediatric Cardiac MR Imaging:: Practical Preoperative Assessment

Prevalence of patients with congenital heart disease (CHD) is rapidly increasing due to continuous advancements in diagnostic techniques and medical or surgical treatment approaches. Along with cardiac computed tomography angiography, cardiac magnetic resonance (CMR) serves as a fundamental imaging modality for pre-surgical planning in patients with CHD, as CMR allows for the evaluation of cardiac and great vessel anatomy, biventricular function, flow dynamics, and tissue characterization. This information is essential for risk-assessment and optimal timing of surgical interventions. This article discusses the current role of pediatric cardiac MR imaging as a practical preoperative assessment tool in the pediatric population.

Diastolic dysfunction is associated with exercise impairment in patients with sickle cell anemia

BACKGROUND

Left ventricular diastolic dysfunction (DD) is an independent risk factor for mortality in sickle cell anemia (SCA) and is associated with increased extracellular volume (ECV) on cardiac MRI (CMR). Exercise impairment is common in SCA, but its causes and prognostic value are not well understood.

OBJECTIVE

To study the effects of DD and ECV on cardiopulmonary exercise test (CPET) in patients with SCA.

METHODS AND RESULTS

As part of a prospective study to characterize the cardiomyopathy of SCA (NCT02410811), 20 children and adults with SCA underwent CMR, echocardiography, and cycle ergometer CPET (age range 8-43 years). Maximum exercise was reached in 18 patients and 17 (94%) had reduced exercise capacity (%predicted VO₂ less than 80%). Six patients had DD and none had systolic dysfunction. Patients with DD had lower exercise capacity compared to patients with normal diastolic function (%predicted VO₂ 48.2 ± 9.1% vs. 61.2 ± 11.7%; P = 0.01). The z-score of left ventricular lateral E/e' ratio, which is a marker of DD, was negatively associated with %predicted VO₂ (r = -0.61, P = 0.01). All patients with moderate-to-severe exercise impairment (%predicted VO₂  < 60%) had lateral E/e' z-score > 2. In a multivariate analysis, lateral E/e' z-score was independently associated with %predicted VO₂ (P = 0.02). All participants had elevated ECV but the degree of elevation was not associated with exercise parameters.

CONCLUSION

Left ventricular DD is associated with decreased exercise capacity in SCA. Interventions to prevent or delay DD could improve exercise capacity, quality of life, and long-term outcomes in SCA.

Long-Standing Cyanosis in Congenital Heart Disease Does not Cause Diffuse Myocardial Fibrosis

The assumption of the presence of diffuse myocardial fibrosis in long-standing cyanotic congenital heart disease (CHD) inspired us to noninvasively determine the myocardial extracellular volume (ECV) using contrast CMR. T1 maps were measured pre and 10 min after the injection of 0.15 mmol/kg of gadolinium in 25 subjects. Seven patients with long-standing cyanotic CHD and no previous cardiac surgery (aged 16-53 years and oxygen saturations of 69-90%), nine normal subjects (aged 14-49 years), and nine patients with previously cyanotic CHD, who had been corrected by open heart surgery (aged 2 months-58 years, mean 9 years). Late gadolinium enhancement was performed to exclude scar areas. The T1 values were measured in the interventricular septum and in the left lateral or inferior ventricular wall, such that same areas were assessed in every patient in the pre- and post-contrast T1 scan. ECV was calculated according to ΔR1myocardium/ΔR1blood * (1 - hematocrit). Cyanotic patients had significantly lower ECV percentage than the previous cyanotic patients (septum: 22 ± 2.7% vs 35 ± 4.6%, p = 0.002; LV wall: 22 ± 2.2% vs 30 ± 3.7%, p = 0.01, respectively). No significant differences were found between cyanotic patients and normal controls (septum: 22 ± 2.7% vs 24 ± 1.4%, p = 0.44; LV wall: 22 ± 2.2% vs 24 ± 2%, p = 0.57, respectively). Long-standing cyanosis in CHD without cardiac surgery does not cause diffuse myocardial fibrosis or expansion of the myocardial ECV.

Clinical recommendations for cardiovascular magnetic resonance mapping of T1, T2, T2* and extracellular volume: A consensus statement by the Society for Cardiovascular Magnetic Resonance (SCMR) endorsed by the European Association for Cardiovascular Imaging (EACVI)

Parametric mapping techniques provide a non-invasive tool for quantifying tissue alterations in myocardial disease in those eligible for cardiovascular magnetic resonance (CMR). Parametric mapping with CMR now permits the routine spatial visualization and quantification of changes in myocardial composition based on changes in T1, T2, and T2*(star) relaxation times and extracellular volume (ECV). These changes include specific disease pathways related to mainly intracellular disturbances of the cardiomyocyte (e.g., iron overload, or glycosphingolipid accumulation in Anderson-Fabry disease); extracellular disturbances in the myocardial interstitium (e.g., myocardial fibrosis or cardiac amyloidosis from accumulation of collagen or amyloid proteins, respectively); or both (myocardial edema with increased intracellular and/or extracellular water). Parametric mapping promises improvements in patient care through advances in quantitative diagnostics, inter- and intra-patient comparability, and relatedly improvements in treatment. There is a multitude of technical approaches and potential applications. This document provides a summary of the existing evidence for the clinical value of parametric mapping in the heart as of mid 2017, and gives recommendations for practical use in different clinical scenarios for scientists, clinicians, and CMR manufacturers.

Magnetic Resonance Characterization of Cardiac Adaptation and Myocardial Fibrosis in Pulmonary Hypertension Secondary to Systemic-To-Pulmonary Shunt

BACKGROUND

Pulmonary hypertension (PH) and right ventricular (RV) dysfunction are strong predictors of morbidity and mortality among patients with congenital heart disease. Early detection of RV involvement may be useful in the management of these patients. We aimed to assess progressive cardiac adaptation and quantify myocardial extracellular volume in an experimental porcine model of PH because of aorto-pulmonary shunt using cardiac magnetic resonance (CMR).

METHODS AND RESULTS

To characterize serial cardiac adaptation, 12 pigs (aorto-pulmonary shunt [n=6] or sham operation [n=6]) were evaluated monthly with right heart catheterization, CMR, and computed tomography during 4 months, followed by pathology analysis. Extracellular volume by CMR in different myocardial regions was studied in 20 animals (aorto-pulmonary shunt [n=10] or sham operation [n=10]) 3 months after the intervention. All shunted animals developed PH. CMR evidenced progressive RV hypertrophy and dysfunction secondary to increased afterload and left ventricular dilatation secondary to volume overload. Shunt flow by CMR strongly correlated with PH severity, left ventricular end-diastolic pressure, and left ventricular dilatation. T1-mapping sequences demonstrated increased extracellular volume at the RV insertion points, the interventricular septum, and the left ventricular lateral wall, reproducing the pattern of fibrosis found on pathology. Extracellular volume at the RV insertion points strongly correlated with pulmonary hemodynamics and RV dysfunction.

CONCLUSIONS

Prolonged systemic-to-pulmonary shunting in growing piglets induces PH with biventricular remodeling and myocardial fibrosis that can be detected and monitored using CMR. These results may be useful for the diagnosis and management of congenital heart disease patients with pulmonary overcirculation.

Update on the Role of Cardiac Magnetic Resonance Imaging in Congenital Heart Disease

OPINION STATEMENT

Cardiac magnetic resonance imaging (CMR) is an important imaging modality in the evaluation of congenital heart diseases (CHD). CMR has several strengths including good spatial and temporal resolutions, wide field-of-view, and multi-planar imaging capabilities. CMR provides significant advantages for imaging in CHD through its ability to measure function, flow and vessel sizes, create three-dimensional reconstructions, and perform tissue characterization, all in a single imaging study. Thus, CMR is the most comprehensive imaging modality available today for the evaluation of CHD. Newer MRI sequences and post-processing tools will allow further development of quantitative methods of analysis, and opens the door for risk stratification in CHD. CMR also can interface with computer modeling, 3D printing, and other methods of understanding the complex anatomic and physiologic relationships in CHD.

Magnetic resonance imaging of the transplanted pediatric heart as a potential predictor of rejection

AIM

To evaluate cardiac magnetic resonance imaging (CMR) as a non-invasive tool to detect acute cellular rejection (ACR) in children after heart transplant (HT).

METHODS

Thirty pediatric HT recipients underwent CMR at the time of surveillance endomyocardial biopsy (EMB) and results were compared to 14 non-transplant controls. Biventricular volumes, ejection fractions (EFs), T2-weighted signal intensities, native T1 times, extracellular volumes (ECVs) and presence of late gadolinium enhancement (LGE) were compared between patients and controls and between patients with International Society of Heart and Lung Transplantation (ISHLT) grade ≥ 2R rejection and those with grade 0/1R. Heart rate (HR) and brain natriuretic peptide (BNP) were assessed as potential biomarkers.

RESULTS

Significant ACR (ISHLT grade ≥ 2R) was an infrequent event in our population (5/30, 17%). Ventricular volumes, EFs, LGE prevalence, ECVs, native T1 times, T2 signal intensity ratios, HR and BNP were not associated with the presence of ≥ 2R ACR.

CONCLUSION

In this pilot study CMR did not reliably identify ACR-related changes in pediatric HT patients.