T1 mapping in children and young adults with hypertrophic cardiomyopathy

Cardiac MRI in diagnosis, prognosis, and follow-up of hypertrophic cardiomyopathy in children: current perspectives

Hypertrophic Cardiomyopathy (HCM) is an inherited myocardial disease characterised by left ventricular hypertrophy, which carries an increased risk of life-threatening arrhythmias and sudden cardiac death. The age of presentation and the underlying aetiology have a significant impact on the prognosis and quality of life of children with HCM, as childhood-onset HCM is associated with high mortality risk and poor long-term outcomes. Accurate cardiac assessment and identification of the HCM phenotype are therefore crucial to determine the diagnosis, prognostic stratification, and follow-up. Cardiac magnetic resonance (CMR) is a comprehensive evaluation tool capable of providing information on cardiac morphology and function, flow, perfusion, and tissue characterisation. CMR allows to detect subtle abnormalities in the myocardial composition and characterise the heterogeneous phenotypic expression of HCM. In particular, the detection of the degree and extent of myocardial fibrosis, using late-gadolinium enhanced sequences or parametric mapping, is unique for CMR and is of additional value in the clinical assessment and prognostic stratification of paediatric HCM patients. Additionally, childhood HCM can be progressive over time. The rate, timing, and degree of disease progression vary from one patient to the other, so close cardiac monitoring and serial follow-up throughout the life of the diagnosed patients is of paramount importance. In this review, an update of the use of CMR in childhood HCM is provided, focussing on its clinical role in diagnosis, prognosis, and serial follow-up.

Differentiation of Myocardial Properties in Physiological Athletic Cardiac Remodeling and Mild Hypertrophic Cardiomyopathy

Clinical differentiation between athletes' hearts and those with hypertrophic cardiomyopathy (HCM) can be challenging. We aimed to explore the role of speckle tracking echocardiography (STE) and cardiac magnetic resonance imaging (CMR) in the differentiation between athletes' hearts and those with mild HCM. We compared 30 competitive endurance elite athletes (7% female, age 41 ± 9 years) and 20 mild phenotypic mutation-positive HCM carriers (15% female, age 51 ± 12 years) with left ventricular wall thickness 13 ± 1 mm. Mechanical dispersion (MD) was assessed by means of STE. Native T1-time and extracellular volume (ECV) were assessed by means of CMR. MD was higher in HCM mutation carriers than in athletes (54 ± 16 ms vs. 40 ± 11 ms, p = 0.001). Athletes had a lower native T1-time (1204 (IQR 1191, 1234) ms vs. 1265 (IQR 1255, 1312) ms, p < 0.001) and lower ECV (22.7 ± 3.2% vs. 25.6 ± 4.1%, p = 0.01). MD > 44 ms optimally discriminated between athletes and HCM mutation carriers (AUC 0.78, 95% CI 0.65-0.91). Among the CMR parameters, the native T1-time had the best discriminatory ability, identifying all HCM mutation carriers (100% sensitivity) with a specificity of 75% (AUC 0.83, 95% CI 0.71-0.96) using a native T1-time > 1230 ms as the cutoff. STE and CMR tissue characterization may be tools that can differentiate athletes' hearts from those with mild HCM.

Functional significance of myocardial activity at 18F-FAPI PET/CT in hypertrophic cardiomyopathy identified by cardiac magnetic resonance feature-tracking strain analysis

PURPOSE

This study aimed to evaluate the functional significance of 18F-labeled fibroblast activation protein inhibitor (18F-FAPI) activity in hypertrophic cardiomyopathy (HCM) by comparison with cardiac magnetic resonance feature-tracking (CMR-FT) strain analysis.

METHODS

A total of 49 HCM patients were included in this study. Two independent control groups of healthy participants with a matched age and sex to the HCM patients were also enrolled. Left ventricular (LV) 18F-FAPI activity was analyzed for extent (FAPI%) and intensity (maximum target-to-background ratio, TBRmax). The CMR tissue characterization parameters of the LV included late gadolinium enhancement, native T1 value, and extracellular volume fraction. LV strain analysis was performed in radial, circumferential, and longitudinal peak strains (PS).

RESULTS

Intense LV myocardial 18F-FAPI uptake was observed in HCM patients, whereas no obvious uptake was detected in healthy participants (median TBRmax, 9.1 vs. 1.2, p < 0.001). The strain parameters of HCM patients, compared with healthy participants, were significantly impaired (mean radial PS, 23.5 vs. 36.0, mean circumferential PS, -14.5 vs. -20.0, and mean longitudinal PS, -9.9 vs. -16.0, all p < 0.001). At segmental levels, there was a moderate correlation between 18F-FAPI activity and strain parameters. The number of positive 18F-FAPI uptake segments (n = 653) was higher than that of hypertrophic segments (n = 190) and positive CMR tissue characterization segments (n = 525) (all p < 0.001). In segments with negative CMR tissue characterization findings, the strain capacity of positive 18F-FAPI uptake segments was lower than that of negative 18F-FAPI uptake segments (median radial PS, 30.5 vs. 36.1, p = 0.026 and median circumferential PS, -18.4 vs. -19.7, p = 0.041).

CONCLUSION

18F-FAPI imaging can partially reflect the potential strain reduction in HCM patients. 18F-FAPI imaging detects more involved myocardium than CMR tissue characterization techniques, and the additionally identified myocardium has impaired strain capacity.

Fabry Disease: More than a Phenocopy of Hypertrophic Cardiomyopathy

Fabry disease (FD) is a genetic lysosomal storage disease with frequent cardiovascular involvement, whose presence is a major determinant of adverse clinical outcomes. As a potentially treatable cause of left ventricular hypertrophy (LVH) and heart failure with preserved ejection fraction, the early recognition of FD is crucial to initiate enzyme replacement therapy and improve long-term prognosis. Multimodality imaging plays a central role in the evaluation of patients with FD and helps in the differential diagnosis of other conditions presenting with LVH. In the present review, we explore the current applications of multimodality cardiac imaging, in particular echocardiography and cardiovascular magnetic resonance, in the diagnosis, prognostic assessment, and follow-up of patients with FD.

Myocardial tissue characterization by cardiovascular magnetic resonance T1 mapping and pericardial fat quantification in adolescents with morbid obesity. Cardiac dimorphism by gender

PURPOSE

Changes in the myocardial extracellular matrix (ECM) identified using T1 mapping cardiovascular magnetic resonance (CMR) have been only reported in obese adults, but with opposite conclusions. The objectives are to assess the composition of the myocardial ECM in an obese pediatric population without type 2 diabetes by quantifying native T1 time, and to quantify the pericardial fat index (PFI) and their relationship with cardiovascular risk factors.

METHODS

Observational case-control research of 25 morbidly obese adolescents and 13 normal-weight adolescents. Native T1 and T2 times (ms), left ventricular (LV) geometry and function, PFI (g/ht³) and hepatic fat fraction (HFF, %) were calculated by 1.5-T CMR.

RESULTS

No differences were noticed in native T1 between obese and non-obese adolescents (1000.0 vs. 990.5 ms, p0.73), despite showing higher LV mass values (28.3 vs. 22.9 g/ht³, p0.01). However, the T1 mapping values were significantly higher in females (1012.7 vs. 980.7 ms, p < 0.01) while in males, native T1 was better correlated with obesity parameters, particularly with triponderal mass index (TMI) (r = 0.51), and inflammatory cells. Similarly, the PFI was correlated with insulin resistance (r = 0.56), highly sensitive C-reactive protein (r = 0.54) and TMI (r = 0.77).

CONCLUSION

Female adolescents possess myocardium peculiarities associated with higher mapping values. In males, who are commonly more exposed to future non-communicable diseases, TMI may serve as a useful predictor of native T1 and pericardial fat increases. Furthermore, HFF and PFI appear to be markers of adipose tissue infiltration closely related with hypertension, insulin resistance and inflammation.

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.

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.

Feasibility of Hepatic T1-Mapping and Extracellular Volume Quantification on Routine Cardiac Magnetic Resonance Imaging in Patients with Infiltrative and Systemic Disorders

RATIONALE AND OBJECTIVES

Cardiac magnetic resonance imaging (CMR) is commonly obtained to evaluate for myocardial infiltrative disorders and fibrosis. Pre- and post-Gadolinium contrast T1-mapping sequences are employed to estimate interstitial expansion using extracellular volume fraction (ECV). Given the proximity of the liver to the heart, T1 and ECV quantification of the liver is feasible on CMR. The purpose of this study was to evaluate for hepatic measures of fibrosis and interstitial expansion in patients with amyloidosis or systemic disease on CMR.

MATERIALS AND METHODS

Myocardial and hepatic native T1 values were measured retrospectively using a cardiac short axis modified Look-Locker inversion recovery sequence. Myocardial and hepatic ECV were calculated using pre- and post-contrast T1 and blood pool values according to the following formula: ECV = (Δ(1/T1) myocardium or liver and/or Δ(1/T1) blood)x(1 - hematocrit). Patients were divided into three cohorts by final diagnosis: amyloidosis, systemic disease (e.g. sarcoid, scleroderma), and controls (EF > 50, no ischemia).

RESULTS

Of the 135 patients who underwent CMR, 22 had cardiac amyloidosis (age 59.9 ± 12.6 yrs, 41% female), 20 had systemic disease (age 50.9 ± 13.4 yrs, 35% female), and 93 were controls (age 49.5 ± 17.3 yrs, 50% female). Myocardial T1 and ECV values were highest for patients with amyloid, second highest for systemic disease, and least for controls (T1: 1169 ± 92 vs 1101 ± 53 vs 1027 ± 73 ms, p < 0.0001; ECV: 0.47 ± 0.11 vs 0.31 ± 0.05 vs 0.27 ± 0.04, p < 0.0001). Hepatic T1 and ECV were similarly higher in patients with amyloid and systemic disease compared to controls (T1: 646 ± 101 vs 660 ± 93 vs 595 ± 58 ms, p < 0.0001; ECV: 0.38 ± 0.08 vs 0.37 ± 0.05 vs 0.31 ± 0.03, p < 0.0001). There was a positive correlation between hepatic T1 and ECV (R² = 0.282, p < 0.0001). No patients had abnormal liver function tests or clinical liver disease.

CONCLUSION

Hepatic ECV quantification on CMR in patients with amyloidosis and systemic disorders is feasible. Further longitudinal investigation regarding detection of early or subclinical liver disease is warranted.

Pediatric Hypertrophic Cardiomyopathy: Exploring the Genotype-Phenotype Association

Pediatric hypertrophic cardiomyopathy (HCM) is the most common form of cardiomyopathy in children and a leading cause of sudden cardiac death. Yet, the association between genotype variation, phenotype expression, and adverse events in pediatric HCM has not been fully elucidated. Although the literature on this topic is evolving in adult HCM, the evidence in children is lacking. Solidifying our understanding of this relationship could improve risk stratification as well as improve our comprehension of the underlying pathophysiological characteristics of pediatric HCM. In this state‐of‐the‐art review, we examine the current literature on genetic variations in HCM and their association with outcomes in children, discuss the current approaches to identifying cardiovascular phenotypes in pediatric HCM, and explore possible avenues that could improve sudden cardiac death risk assessment.

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.

Cardiovascular magnetic resonance imaging in children after recovery from symptomatic COVID-19 or MIS-C: a prospective study

BACKGROUND

Cardiac evaluations, including cardiovascular magnetic resonance (CMR) imaging and biomarker results, are needed in children during mid-term recovery after infection with SARS-CoV-2. The incidence of CMR abnormalities 1-3 months after recovery is over 50% in older adults and has ranged between 1 and 15% in college athletes. Abnormal cardiac biomarkers are common in adults, even during recovery.

METHODS

We performed CMR imaging in a prospectively-recruited pediatric cohort recovered from COVID-19 and multisystem inflammatory syndrome in children (MIS-C). We obtained CMR data and serum biomarkers. We compared these results to age-matched control patients, imaged prior to the SARS-CoV-2 pandemic.

RESULTS

CMR was performed in 17 children (13.9 years, all ≤ 18 years) and 29 age-matched control patients without SARS-CoV-2 infection. Cases were recruited with symptomatic COVID-19 (11/17, 65%) or MIS-C (6/17, 35%) and studied an average of 2 months after diagnosis. All COVID-19 patients had been symptomatic with fever (73%), vomiting/diarrhea (64%), or breathing difficulty (55%) during infection. Left ventricular and right ventricular ejection fractions were indistinguishable between cases and controls (p = 0.66 and 0.70, respectively). Mean native global T1, global T2 values and segmental T2 maximum values were also not statistically different from control patients (p ≥ 0.06 for each). NT-proBNP and troponin levels were normal in all children.

CONCLUSIONS

Children prospectively recruited following SARS-CoV-2 infection had normal CMR and cardiac biomarker evaluations during mid-term recovery. Trial Registration Not applicable.

Diffuse myocardial fibrosis by T1 mapping is associated with heart failure in pediatric primary dilated cardiomyopathy

BACKGROUND

In adult cardiomyopathy (CM), diffuse myocardial fibrosis is associated with adverse clinical outcome. However, its relevance in pediatric patients remains relatively unknown. The study aimed to evaluate myocardial extracellular volume (ECV) reflecting diffuse myocardial fibrosis with cardiovascular magnetic resonance (CMR) T1 mapping, and to analyze correlations with clinical and functional data in children and adolescents with different CM phenotypes.

METHODS

Patients with primary dilated (DCM), hypertrophic (HCM) or left ventricular non-compaction CM (LVNC) were prospectively enrolled and compared with healthy controls. Study participants underwent standardized CMR with modified Look-Locker Inversion recovery (MOLLI) T1 mapping.

RESULTS

In total, 33 patients (median age 12.0 years; DCM: n = 10, HCM: n = 13; LVNC: n = 10) and 7 controls (14.5 years) were included. DCM: ECV was higher than in controls (38.1 ± 7.5% vs. 27.2 ± 3.6%; p = 0.014). Patients with elevated ECV were younger than those with normal values (p = 0.044). ECV correlated with N-terminal pro brain natriuretic peptide (r = 0.66, p = 0.038), left ventricular ejection fraction (r = -0.63, p = 0.053), and stroke volume of left (r = -0.75, p = 0.013) and right ventricle (r = -0.67, p = 0.033). During a median follow-up of 25.3 months, 3 patients underwent heart transplantation (HTx), and 2 were listed for HTx. All 5 patients had elevated ECV.

HCM/LVNC

ECV was within normal range in HCM (25.5 ± 4.5%) and LVNC (29.6 ± 4.2), and was not related with clinical and/or functional parameters.

CONCLUSIONS

Our results indicate an increased burden of diffuse myocardial fibrosis in relation with younger age in pediatric DCM. ECV was associated with clinical and biventricular functional markers of heart failure in DCM.

Normative Data for Myocardial Native T1 and Extracellular Volume Fraction in Children

Purpose

To establish normative data for myocardial T1, including extracellular volume (ECV) fraction, in healthy children.

Materials and Methods

In this retrospective, single-center study, T1 mapping data were collected from 48 healthy pediatric patients (14 years ± 3 [standard deviation]; range, 9-18 years; 27 of 48 [56%] male) referred for cardiac screening 1.5-T MRI between 2014 and 2017. T1 relaxometry was performed using a 5(number of heartbeats [nHB])3 modified Look-Locker inversion recovery (MOLLI) sequence, where nHB was three to five heartbeats depending on the heart rate, and was repeated 15 minutes following the administration of 0.2 mmol per kilogram of body weight of gadobenate dimeglumine, with 19 patients receiving contrast material. T1 values were calculated using a curve-fitting algorithm on average region-of-interest signal and corrected for imperfect inversion pulse efficiency. Comparisons within patients were performed with paired Student t test, between groups with unpaired Student t test or Mann-Whitney U test, and linear regression was performed to examine for associations with other variables.

Results

Average native T1 was 1008 msec ± 31, with a nonsignificant increase in females (1017 msec ± 27 vs 1001 msec ± 33, P = .066). Average ECV was 20.8% ± 2.4, with a nonsignificant increase in values in females (21.7% ± 1.9 vs 20.0% ± 2.6, P = .123). T1 and ECV values were increased in the septum versus the free wall.

Conclusion

Normative data are presented for myocardial native T1 and ECV using the MOLLI T1 mapping sequence at 1.5 T.Supplemental material is available for this article.© RSNA, 2020.

Diagnostic value of the novel CMR parameter "myocardial transit-time" (MyoTT) for the assessment of microvascular changes in cardiac amyloidosis and hypertrophic cardiomyopathy

BACKGROUND

Coronary microvascular dysfunction (CMD) is present in various non-ischemic cardiomyopathies and in particular in those with left-ventricular hypertrophy. This study evaluated the diagnostic value of the novel cardiovascular magnetic resonance (CMR) parameter "myocardial transit-time" (MyoTT) in distinguishing cardiac amyloidosis from other hypertrophic cardiomyopathies.

METHODS

N = 20 patients with biopsy-proven cardiac amyloidosis (CA), N = 20 patients with known hypertrophic cardiomyopathy (HCM), and N = 20 control patients without relevant cardiac disease underwent dedicated CMR studies on a 1.5-T MR scanner. The CMR protocol comprised cine and late-gadolinium-enhancement (LGE) imaging as well as first-pass perfusion acquisitions at rest for MyoTT measurement. MyoTT was defined as the blood circulation time from the orifice of the coronary arteries to the pooling in the coronary sinus (CS) reflecting the transit-time of gadolinium in the myocardial microvasculature.

RESULTS

MyoTT was significantly prolonged in patients with CA compared to both groups: 14.8 ± 4.1 s in CA vs. 12.2 ± 2.5 s in HCM (p = 0.043) vs. 7.2 ± 2.6 s in controls (p < 0.001). Native T1 and extracellular volume (ECV) were significantly higher in CA compared to HCM and controls (p < 0.001). Both parameters were associated with a higher diagnostic accuracy in predicting the presence of CA compared to MyoTT: area under the curve (AUC) for native T1 = 0.93 (95% confidence interval (CI) = 0.83-1.00; p < 0.001) and AUC for ECV = 0.95 (95% CI = 0.88-1.00; p < 0.001)-compared to the AUC for MyoTT = 0.76 (95% CI = 0.60-0.92; p = 0.008). In contrast, MyoTT performed better than all other CMR parameters in differentiating HCM from controls (AUC for MyoTT = 0.93; 95% CI = 0.81-1.00; p = 0.003 vs. AUC for native T1 = 0.69; 95% CI = 0.44-0.93; p = 0.20 vs. AUC for ECV = 0.85; 95% CI = 0.66-1.00; p = 0.017).

CONCLUSION

The relative severity of CMD (measured by MyoTT) in relationship to extracellular changes (measured by native T1 and/or ECV) is more pronounced in HCM compared to CA-in spite of a higher absolute MyoTT value in CA patients. Hence, MyoTT may improve our understanding of the interplay between extracellular/intracellular and intravasal changes that occur in the myocardium during the disease course of different cardiomyopathies.

Altered regional myocardial velocities by tissue phase mapping and feature tracking in pediatric patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is associated with heart failure, atrial fibrillation and sudden death. Reduced myocardial function has been reported in HCM despite normal left ventricular (LV) ejection fraction. Additionally, LV fibrosis is associated with elevated T1 and might be an outcome predictor.

OBJECTIVE

To systematically compare tissue phase mapping and feature tracking for assessing regional LV function in children and young adults with HCM and pediatric controls, and to evaluate structure-function relationships among myocardial velocities, LV wall thickness and myocardial T1.

MATERIALS AND METHODS

Seventeen pediatric patients with HCM and 21 age-matched controls underwent cardiac MRI including standard cine imaging, tissue phase mapping (two-dimensional cine phase contrast with three-directional velocity encoding), and modified Look-Locker inversion recovery to calculate native global LV T1. Maximum LV wall thickness was measured on cine images. LV radial, circumferential and long-axis myocardial velocity time courses, as well as global and segmental systolic and diastolic peak velocities, were quantified from tissue phase mapping and feature tracking.

RESULTS

Both tissue phase mapping and feature tracking detected significantly decreased global and segmental diastolic radial and long-axis peak velocities (by 12-51%, P<0.001-0.05) in pediatric patients with HCM vs. controls. Feature tracking peak velocities were lower than directly measured tissue phase mapping velocities (mean bias = 0.3-2.9 cm/s). Diastolic global peak velocities correlated moderately with global T1 (r = -0.57 to -0.72, P<0.01) and maximum wall thickness (r = -0.37 to -0.61, P<0.05).

CONCLUSION

Both tissue phase mapping and feature tracking detected myocardial velocity changes in children and young adults with HCM vs. controls. Associations between impaired diastolic LV velocities and elevated T1 indicate structure-function relationships in HCM.

Tissue characterisation and myocardial mechanics using cardiac MRI in children with hypertrophic cardiomyopathy

INTRODUCTION

Distinguishing between hypertrophic cardiomyopathy and other causes ofleft ventricular hypertrophy can be difficult in children. We hypothesised that cardiac MRI T1 mapping could improve diagnosis of paediatric hypertrophic cardiomyopathy and that measures of myocardial function would correlate with T1 times and extracellular volume fraction.

METHODS

Thirty patients with hypertrophic cardiomyopathy completed MRI with tissue tagging, T1-mapping, and late gadolinium enhancement. Left ventricular circumferential strain was calculated from tagged images. T1, partition coefficient, and synthetic extracellular volume were measured at base, mid, apex, and thickest area of myocardial hypertrophy. MRI measures compared to cohort of 19 healthy children and young adults. Mann-Whitney U, Spearman's rho, and multivariable logistic regression were used for statistical analysis.

RESULTS

Hypertrophic cardiomyopathy patients had increased left ventricular ejection fraction and indexed mass. Hypertrophic cardiomyopathy patients had decreased global strain and increased native T1 (-14.3% interquartile range [-16.0, -12.1] versus -17.3% [-19.0, -15.7], p < 0.001 and 1015 ms [991, 1026] versus 990 ms [972, 1001], p = 0.019). Partition coefficient and synthetic extracellular volume were not increased in hypertrophic cardiomyopathy. Global native T1 correlated inversely with ejection fraction (ρ = -0.63, p = 0.002) and directly with global strain (ρ = 0.51, p = 0.019). A logistic regression model using ejection fraction and native T1 distinguished between hypertrophic cardiomyopathy and control with an area under the receiver operating characteristic curve of 0.91.

CONCLUSION

In this cohort of paediatric hypertrophic cardiomyopathy, strain was decreased and native T1 was increased compared with controls. Native T1 correlated with both ejection fraction and strain, and a model using native T1 and ejection fraction differentiated patients with and without hypertrophic cardiomyopathy.

Normal myocardial native T1 values in children using single-point saturation recovery and modified look-locker inversion recovery (MOLLI)

BACKGROUND

T₁ mapping is useful to quantify diffuse myocardial processes such as fibrosis, edema, storage disorders, or hemochromatosis. Normal pediatric myocardial T₁ values are scarce using modified Look-Locker inversion recovery (MOLLI) sequences and unavailable using Smart1Map, a single-point saturation recovery sequence that measures true T₁ .

PURPOSE/HYPOTHESIS

To establish normal pediatric myocardial T₁ values by Smart1Map and to compare them with T₁ by MOLLI.

STUDY TYPE

Prospective cohort study.

SUBJECTS

Thirty-four children and adolescents aged 8-18 years (14 males) without cardiovascular or inflammatory diseases.

FIELD STRENGTH/SEQUENCES

1.5T, MOLLI, Smart1Map.

ASSESSMENT

Mean T₁ values of the left ventricular myocardium, the interventricular septum, and the blood pool were measured with MOLLI and Smart1Map in basal, mid-ventricular, and apical short axis slices.

STATISTICAL TESTS

T₁ values were compared between locations and methods by paired samples t-tests, Wilcoxon signed ranks test, repeated-measures analysis of variance (ANOVA), or Friedman's test. Pearson's correlation coefficient was calculated. For interobserver variability, intraclass correlation coefficients and coefficients of variation were calculated, and Bland-Altman analyses were performed.

RESULTS

T₁ values were longer by Smart1Map than by MOLLI in all measured locations (myocardium: 1191-1221 vs. 990-1042 msec; all P < 0.001). T₁ in basal vs. mid-ventricular slices differed both by MOLLI and by Smart1Map for myocardium and for blood (all P < 0.001). Myocardial T₁ did not correlate with age, heart rate, right or left ventricular ejection fraction (all P > 0.05) by either method. Septal vs. total myocardial T₁ values in each slice did not differ by MOLLI (basal P = 0.371; mid-ventricular P = 0.08; apical P = 0.378) nor by Smart1Map (basal P = 0.056; mid-ventricular P = 0.918; apical P = 0. 392), after artifacts had been carefully excluded.

DATA CONCLUSION

We established pediatric normal native T₁ values using the Smart1Map sequence and compared the results with T₁ mapping with MOLLI. Septal T₁ values did not differ from total myocardial T₁ values in each of the myocardial slices.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:897-903.

Diagnostic performance of cardiovascular magnetic resonance native T1 and T2 mapping in pediatric patients with acute myocarditis

BACKGROUND

Multiple studies in adult patients suggest that tissue mapping performed by cardiovascular magnetic resonance (CMR) has excellent diagnostic accuracy in acute myocarditis, however, these techniques have not been studied in depth in children.

METHODS

CMR data on 23 consecutive pediatric patients from 2014 to 2017 with a clinical diagnosis of acute myocarditis were retrospectively analyzed and compared to 39 healthy controls. The CMR protocol included native T1, T2, and extracellular volume fraction (ECV) in addition to standard Lake Louise Criteria (LLC) parameters on a 1.5 T scanner.

RESULTS

Mean global values for novel mapping parameters were significantly elevated in patients with clinically suspected acute myocarditis compared to controls, with native T1 1098 ± 77 vs 990 ± 34 ms, T2 52.8 ± 4.6 ms vs 46.7 ± 2.6 ms, and ECV 29.8 ± 5.1% vs 23.3 ± 2.6% (all p-values < 0.001). Ideal cutoff values were generated using corresponding ROC curves and were for global T1 1015 ms (AUC 0.936, sensitivity 91%, specificity 86%), for global T2 48.5 ms (AUC 0.908, sensitivity 91%, specificity 74%); and for ECV 25.9% (AUC 0.918, sensitivity 86%, specificity 89%). While the diagnostic yield of the LLC was 57% (13/23) in our patient cohort, 70% (7/10) of patients missed by the LLC demonstrated abnormalities across all three global mapping parameters (native T1, T2, and ECV) and another 20% (2/10) of patients demonstrated at least one abnormal mapping value.

CONCLUSIONS

Similar to findings in adults, pediatric patients with acute myocarditis demonstrate abnormal CMR tissue mapping values compared to controls. Furthermore, we found CMR parametric mapping techniques measurably increased CMR diagnostic yield when compared with conventional LLC alone, providing additional sensitivity and specificity compared to historical references. Routine integration of these techniques into imaging protocols may aid diagnosis in children.

Histogram Analysis of Native T1 Mapping and Its Relationship to Left Ventricular Late Gadolinium Enhancement, Hypertrophy, and Segmental Myocardial Mechanics in Patients With Hypertrophic Cardiomyopathy

BACKGROUND

The use of native T₁ mapping for evaluation of hypertrophic cardiomyopathy (HCM) is being explored, and its combination with histogram analysis may benefit the accuracy of such assessments.

PURPOSE

To investigate the relationship of segmental left ventricular wall thickness (LVWT), myocardial fibrosis, and strain parameters with segmental histogram parameters of native T₁ mapping in HCM patients.

STUDY TYPE

Retrospective.

SUBJECTS

Ninety-three HCM patients without previous cardiovascular diseases were included.

FIELD STRENGTH/SEQUENCE

3.0T cardiac MR. Steady-state free precession cine imaging, modified Look-Locker inversion recovery, phase-sensitive inversion recovery.

ASSESSMENT

Images were assessed by three experienced radiologists.

STATISTICAL TESTS

Mann-Whitney U-tests, area under the curve (AUC), Spearman's rank correlation, intraclass correlation coefficient, and Bland-Altman test were used for statistical analysis.

RESULTS

A higher LVWT value correlated with higher means, minimums, 10^th /25^th /50^th /75^th /90^th percentiles, maximums, kurtosis, entropy, and lower SD and energy of T₁ mapping (P < 0.05 for all), with the correlation being stronger for entropy and energy (Spearman's rho = 0.439 and -0.413, respectively) than other parameters. Late gadolinium enhancement positive (LGE+) segments exhibited higher mean, minimum, 10^th /25^th /50^th /75^th /90^th percentiles, maximum, entropy, and lower energy of T₁ times than late gadolinium enhancement negative (LGE-) segments (P < 0.001 for all). Impaired strain function parameters (peak thickening and thickening rate in radial, circumferential, and longitudinal directions) demonstrated a weak correlation with higher entropy (P < 0.001 for all) and lower energy (P < 0.001 for all).

DATA CONCLUSION

Histogram parameters of native T₁ mapping provide more information than mean T₁ times alone. Among these parameters, entropy and energy may correlate better with LVWT, myocardial late gadolinium enhancement, and strain parameters than mean T₁ times in HCM patients.

LEVEL OF EVIDENCE

2 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;49:668-677.