Practice Patterns of Cardiovascular Magnetic Resonance Use in the Diagnosis of Pediatric Myocarditis: A Survey-Based Study.

BACKGROUND: Cardiovascular magnetic resonance (CMR) is used to diagnose myocarditis in adults and children based on the original Lake Louise Criteria (LLC) and more recently the revised LLC. The major change included in the revised LLC was the incorporation of parametric mapping, which significantly increases the sensitivity and specificity of diagnosis. Subsequently, scientific statements have recommended the use of parametric mapping in the diagnosis of myocarditis in children. However, there are some challenges to parametric mapping that are unique to the pediatric population. Our goal is to characterize clinical CMR and parametric mapping practice patterns for diagnosis of myocarditis in pediatric centers. METHODS: The Cardiovascular Magnetic Resonance Evaluation in Return to Athletes for Myocarditis in COVID-19 and Immunization Consortium created a REDCap survey to evaluate clinical practice patterns for diagnosis of myocarditis in pediatrics. This survey was distributed to the Society for Cardiovascular Magnetic Resonance community. RESULTS: 59 responses from 51 centers were received, with only one response from each center being utilized. Only 35% of centers (37% of North America, 31% of international) reported using CMR routinely in all patients with a suspicion for myocarditis. Diagnostic uncertainty was noted as the most important reason for CMR, while cost was noted as the least important consideration. The majority of centers reported using the revised LLC (37/51, 72%) compared to original LLC (7/51, 14%) or a hybrid criteria (6/51, 12%). When looking at the use of parametric mapping, only 5/47 (11%) for T1 mapping and 11/49 (22%) for T2 mapping reported having scanner-specific pediatric normative data. CONCLUSION: Routine CMR imaging for diagnosis of myocarditis in pediatrics is infrequently performed at surveyed centers despite the focus on a group of non-invasive cardiac imagers. While the majority reported using parametric mapping, few centers reporting having pediatric scanner-specific normative data. This highlights an important gap in the utilization of CMR that may aid in the diagnosis of myocardial disease.

Echocardiographic measured shunt velocity does not predict pulmonary blood flow in patients with Blalock-Thomas-Taussig shunt.

INTRODUCTION: Catheterisation is the gold standard used to evaluate pulmonary blood flow in patients with a Blalock-Thomas-Taussig shunt. It involves risk and cannot be performed frequently. This study aimed to evaluate if echocardiographic measurements obtained in a clinical setting correlate with catheterisation-derived pulmonary blood flow in patients with a Blalock-Thomas-Taussig shunt as the sole source of pulmonary blood flow. METHODS: Chart review was performed retrospectively on consecutive patients referred to the catheterisation lab with a Blalock-Thomas-Taussig shunt. Echocardiographic parameters included peak, mean, and diastolic gradients across the Blalock-Thomas-Taussig shunt and forward and reverse velocity time integral across the distal transverse aorta. In addition to direct correlations, we tested a previously published formula for pulmonary blood flow calculated as velocity time integral across the shunt × heart rate × Blalock-Thomas-Taussig shunt area. Catheterisation parameters included pulmonary and systemic blood flow as calculated by the Fick principle. RESULTS: 18 patients were included. The echocardiography parameters and oxygen saturation did not correlate with catheterisation-derived pulmonary blood flow, systemic blood flow, or the ratio of pulmonary to systemic blood flow. As the ratio of reverse to forward velocity time integral across the transverse aorta increased, the probability of shunt stenosis decreased. CONCLUSION: Echocardiographic measurements obtained outside the catheterisation lab do not correlate with catheterisation-derived pulmonary blood flow. The ratio of reverse to forward velocity time integral across the transverse aortic arch may be predictive of Blalock-Thomas-Taussig shunt narrowing; this finding should be investigated further.

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.

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.

Flagellin stimulates protective lung mucosal immunity: role of cathelicidin-related antimicrobial peptide.

TLRs are required for generation of protective lung mucosal immune responses against microbial pathogens. In this study, we evaluated the effect of the TLR5 ligand flagellin on stimulation of antibacterial mucosal immunity in a lethal murine Pseudomonas aeruginosa pneumonia model. The intranasal pretreatment of mice with purified P. aeruginosa flagellin induced strong protection against intratracheal P. aeruginosa-induced lethality, which was attributable to markedly improved bacterial clearance, reduced dissemination, and decreased alveolar permeability. The protective effects of flagellin on survival required TLR5 and were observed even in the absence of neutrophils. Flagellin induced strong induction of innate genes, most notably the antimicrobial peptide cathelicidin-related antimicrobial peptide. Finally, flagellin-induced protection was partially abrogated in cathelicidin-related antimicrobial peptide-deficient mice. Our findings illustrate the profound stimulatory effect of flagellin on lung mucosal innate immunity, a response that might be exploited therapeutically to prevent the development of gram-negative bacterial infection of the respiratory tract.

The Diagnostic Role of Echocardiographic Strain Analysis in Patients Presenting with Chest Pain and Elevated Troponin: A Multicenter Study.

BACKGROUND: Myocarditis presenting as acute chest pain with elevated troponins without significant cardiac compromise is rare in previously healthy children, often referred to as myopericarditis. Diagnosis is challenging, as conventional echocardiographic measures of systolic function can be normal. The aim of this study was to demonstrate the diagnostic utility of strain imaging in this scenario. METHODS: This was a multicenter, retrospective study including patients presenting with chest pain and elevated troponin from 10 institutions who underwent cardiac magnetic resonance imaging and transthoracic echocardiography within 30 days of each other (group 1). Findings were compared with those among 19 control subjects (group 2). Clinical data and conventional echocardiographic and cardiac magnetic resonance imaging data were collected. Echocardiography-derived strain was measured at the core laboratory. Group 1 was divided into subgroups as myocarditis positive (group 1a) or negative (group 1b) on cardiac magnetic resonance imaging on the basis of established criteria. RESULTS: Group 1 included 108 subjects (88 in group 1a, 20 in group 1b). Although all groups had normal mean fractional shortening and mean left ventricular ejection fraction, group 1 had significantly lower ejection fraction (56.8 ± 7.0%) compared with group 2 (62.3 ± 4.9%; P < .005) and fractional shortening (31.2 ± 4.9%) compared with group 2 (34.1 ± 3.5%; P < .05). Additionally, peak global longitudinal strain (GLS) was markedly abnormal in group 1 (-13.9 ± 3.4%) compared with group 2 (-19.8 ± 2.1%; P < .001). In subgroup analysis, GLS was markedly abnormal in group 1a (-13.2 ± 3.0%) compared with group 1b (-17.3 ± 2.6%; P < .001). Fifty-four subjects underwent follow-up echocardiography (46 in group 1a, eight in group 1b), with mean a follow-up time of 10 ± 11 months. At follow-up, whereas ejection fraction and fractional shortening returned to normal in all patients, abnormalities in strain persisted in group 1, with 22% still having abnormal GLS. Moreover, mean GLS was more abnormal in group 1a (-16.1 ± 2.6%) compared with group 1b (-17.4 ± 1.2%; P < .05). CONCLUSIONS: The present study demonstrates that echocardiographic GLS is significantly worse in subjects with myopericarditis presenting with chest pain and elevated troponins compared with control subjects even when conventional measures of systolic function are largely normal and that these abnormalities persisted over time.

Evolution and Current Results of a Unified Strategy for Sinus Venosus Surgery.

BACKGROUND: Given recent reports of percutaneous closure of sinus venosus atrial septal defects, we reviewed our experience with surgical repair. Owing to the high incidence of arrhythmias with the two-patch technique, since 2001 we have used either one-patch repairs or the Warden procedure. METHODS: A retrospective review was performed of pediatric patients undergoing sinus venosus atrial septal defect repair at our institution from January 1, 1990, to July 1, 2018. Standard demographic data such as echocardiographic and cross-sectional imaging along with operative details and clinical echocardiographic outcomes were collected. RESULTS: The cohort included 144 patients with a median age of 4.3 years (interquartile range, 8.5). Inferior SVASD was present in 24 patients (17%). A single autologous untreated pericardial patch was used for 114 patients (79%), a two-patch technique for 20 patients (14%, last performed in 2000), and a Warden procedure in 10 patients (7%). Median length of stay was 4 days (interquartile range, 2). On echocardiogram follow-up, no patient had pulmonary vein stenosis. One patient who had the Warden procedure required a balloon dilation of the superior caval vein 2 years postoperatively and a stent 3 years later. Two-patch patients were substantially less likely to be in normal sinus rhythm (41%) on postoperative electrocardiograms compared with the other two techniques (81% one-patch and 89% Warden, P = .02). CONCLUSIONS: The great majority of patients with sinus venosus atrial septal defects can be successfully repaired with a single patch of autologous pericardium. We transitioned to using either a single pericardial patch or the Warden procedure, resulting in a higher frequency of normal sinus rhythm on postoperative electrocardiograms.

Cooperative interactions between TLR4 and TLR9 regulate interleukin 23 and 17 production in a murine model of gram negative bacterial pneumonia.

Toll like receptors play an important role in lung host defense against bacterial pathogens. In this study, we investigated independent and cooperative functions of TLR4 and TLR9 in microbial clearance and systemic dissemination during Gram-negative bacterial pneumonia. To access these responses, wildtype Balb/c mice, mice with defective TLR4 signaling (TLR4(lps-d)), mice deficient in TLR9 (TLR9(-/-)) and TLR4/9 double mutant mice (TLR4(lps-d)/TLR9(-/-)) were challenged with K. pneumoniae, then time-dependent lung bacterial clearance and systemic dissemination determined. We found impaired lung bacterial clearance in TLR4 and TLR9 single mutant mice, whereas the greatest impairment in clearance was observed in TLR4(lps-d)/TLR9(-/-) double mutant mice. Early lung expression of TNF-alpha, IL-12, and chemokines was TLR4 dependent, while IFN-gamma production and the later expression of TNF-alpha and IL-12 was dependent on TLR9. Classical activation of lung macrophages and maximal induction of IL-23 and IL-17 required both TLR4 and TLR9. Finally, the i.t. instillation of IL-17 partially restored anti-bacterial immunity in TLR4(lps-d)/TLR9(-/-) double mutant mice. In conclusion, our studies indicate that TLR4 and TLR9 have both non-redundant and cooperative roles in lung innate responses during Gram-negative bacterial pneumonia and are both critical for IL-17 driven antibacterial host response.

Cytokine networks in the infected lung.

The generation of an innate immune response is essential for rapid clearance of microbes from the respiratory tract, whereas acquired immunity is required for the generation of cellular immunity necessary for the killing of certain intracellular pathogens and the development of immunological memory. Cytokines play an integral role in host defense by serving as leukocyte chemoattractants, leukocyte-activating factors or afferent signals in the induction or regulation of other effector molecules. This review assesses the contribution of cytokine networks to the generation of antimicrobial host defenses in the lung, with an emphasis on cytokines/cytokine networks that are instrumental in innate antibacterial responses, including mucosal immunity, and also introduces networks that instruct the development of adaptive immunity.