CLINICAL AND INSTRUMENTAL CRITERIA FOR EARLY DIAGNOSIS OF CARDITIS IN PEDIATRICS: AN INTEGRATED, STEPWISE FRAMEWORK

SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 42 CLINICAL AND INSTRUMENTAL CRITERIA FOR EARLY DIAGNOSIS OF CARDITIS IN PEDIATRICS: AN INTEGRATED, STEPWISE FRAMEWORK G.K. Yusupova1, D.T. Ashurova2 PhD1 Tashkent State Medical University1,2 https://doi.org/10.5281/zenodo.17434044 Abstract. To develop an integrated, stepwise framework for early recognition of pediatric carditis—including myocarditis, rheumatic carditis, and cardiac involvement in MIS-C/Kawasaki phenotypes—by combining clinical “red flags,” laboratory markers, electrocardiography (ECG), echocardiography (echo), and cardiac magnetic resonance (CMR) into practical decision pathways for different care settings. Early diagnosis of pediatric carditis remains challenging due to heterogeneous etiologies, age-dependent presentations, and variability in test availability across primary, secondary, and tertiary care. Delayed verification risks progression to heart failure, adverse remodeling, and chronic valvular pathology. Narrative synthesis of contemporary pediatric and cardiology guidance (SERVQUAL omitted; focus on medicine), emphasizing the 2018 updated Lake Louise CMR criteria for myocarditis, echocardiographic standards from the World Heart Federation (WHF) for rheumatic heart disease (2012; 2023 update), the revised Jones criteria (2015), and MIS-C frameworks (post-COVID era). The article translates these into implementable checklists, tables, and a stepwise diagnostic route with escalation triggers. We propose a triad-based workflow—Clinical profile → Core triage tests (troponin/NT-proBNP, ECG, echocardiography) → Etiologic confirmation (CMR for myocarditis; echo-based WHF/Jones pathways for rheumatic disease; MIS-C criteria with cardiac focus)—supported by standardized thresholds, minimum datasets, and quality checkpoints. Tables summarize agespecific red flags, biomarker thresholds and interpretation, ECG and echo findings by etiology, CMR markers per Lake Louise, and differential diagnoses. A structured, context-aware diagnostic route reduces missed early presentations and accelerates therapy initiation while aligning with ethical/operational constraints (radiation minimization, sedation avoidance, and informed consent). The framework is adaptable to resource-variable settings and supports consistent documentation for longitudinal follow-up. Keywords: pediatric carditis; myocarditis; rheumatic carditis; MIS-C; Kawasaki disease; echocardiography; cardiac MRI; Lake Louise criteria; Jones criteria; troponin; NT-proBNP; early diagnosis. Abbreviations ARF — Acute Rheumatic Fever; BNP/NT-proBNP — B-type natriuretic peptide/Nterminal pro-BNP; CMR — Cardiac Magnetic Resonance; CRP — C-reactive protein; ECG — Electrocardiogram; EF — Ejection Fraction; EMB — Endomyocardial Biopsy; ESR — Erythrocyte Sedimentation Rate; LGE — Late Gadolinium Enhancement; LV — Left Ventricle; MIS-C — Multisystem Inflammatory Syndrome in Children; RHD — Rheumatic Heart Disease; WHF — World Heart Federation. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 43 1. Introduction Carditis in the pediatric population encompasses inflammatory involvement of myocardium, pericardium, and/or valves from diverse etiologies: viral (myocarditis), autoimmune (acute rheumatic fever—ARF), and hyperinflammatory post-infectious entities (MIS-C, Kawasaki-like disease). The clinical imperative is early recognition: pediatric myocarditis can present as a subtle viral syndrome with disproportionate tachycardia, while rheumatic carditis may debut with subclinical valve regurgitation only detectable by echocardiography. MIS-C adds hemodynamic instability and coronary involvement risks. Despite advances in imaging, diagnostic inertia persists due to non-specific complaints, variable expertise, and access disparities. This paper synthesizes current standards into an operational, escalation-ready diagnostic route intended for clinicians working across the pediatric care continuum. 2. Epidemiology and Clinical Spectrum Incidence estimates for pediatric myocarditis vary globally due to case definition and ascertainment differences, and many cases remain unrecognized until significant LV dysfunction develops. ARF remains prevalent in regions with constrained primary prevention and delayed streptococcal treatment; subclinical RHD is not rare when screened systematically by echo. MISC peaked during and after major SARS-CoV-2 waves but continues to present sporadically, with cardiac involvement a key determinant of severity and resource use. Age effects. Infants may present with poor feeding, lethargy, and non-specific respiratory signs rather than chest pain. School-age children more often report chest discomfort and exercise intolerance; adolescents resemble adults with chest pain, palpitations, or syncope. 3. Pathophysiology (Brief Overview) Myocarditis involves immune-mediated myocyte injury triggered by viral or other agents; edema and necrosis lead to conduction abnormalities and systolic/diastolic dysfunction. In ARF, molecular mimicry post-Group A Streptococcus infection targets valve tissue, especially the mitral and aortic valves. MIS-C features dysregulated post-infectious inflammation affecting myocardium and coronaries, with variable shock physiology. 4. Clinical “Red Flags” and Early Triage A careful history (recent infection, sore throat, epidemiological ARF risk, COVID-19 exposure), examination (vital signs, gallop rhythm, new murmurs, perfusion), and age-aware symptom weighting are the backbone of early suspicion. Table 1. Age-linked clinical red flags prompting cardiac work-up Age group Typical red flags Practical notes Infants Feeding refusal, lethargy, diaphoresis with feeds, tachypnea Low symptom specificity; keep low threshold for ECG + biomarkers + bedside echo School-age Chest pain, fatigue, palpitations, exercise intolerance, fever Pain reproducibility does not exclude myocarditis; assess disproportionate tachycardia Adolescents Chest pain, presyncope/syncope, palpitations Consider myocarditis vs. arrhythmic disorders; review drugs/stimulants SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 44 Age group Typical red flags Practical notes Any age (ARF risk) Migratory polyarthritis, chorea, erythema marginatum, subcutaneous nodules Seek evidence of recent Group A strep; auscultation may be insensitive—echo is key MIS-C context Persistent fever, GI symptoms, rash, hypotension/shock Early echo and lab inflammation panel; consider ICU admission thresholds 5. Laboratory Markers in Early Diagnosis Inflammation. CRP and ESR are supportive but non-specific; markedly elevated profiles, particularly in MIS-C, heighten suspicion. Myocardial injury/strain. Troponin I/T elevation supports myocardial involvement; NT-proBNP/BNP reflects stress and is useful in risk stratification. Strep evidence (ARF). Antistreptolysin-O and anti-DNase B titers (paired if possible) support recent infection when aligned with Jones criteria. MIS-C panels. Include ferritin, D-dimer, fibrinogen, and IL-6 where available—cardiac markers (troponin/BNP) are central. Biomarker panel and interpretation in pediatric carditis Marker Early signal Interpretation caveats CRP/ESR ↑ supports inflammation Non-specific; integrate with clinical picture Troponin I/T ↑ suggests myocyte injury Mild rises may occur in non-carditis states; trend with ECG/echo NT-proBNP/BNP ↑ indicates myocardial stress/dysfunction Age-dependent reference ranges; correlate with echo EF/strain ASO/anti-DNase B Evidence of recent strep A Need clinical context per Jones criteria Ferritin/D-dimer (MIS-C) Hyperinflammation/coagulopathy Helpful for severity; not diagnostic of carditis alone 6. Electrocardiography Sinus tachycardia, ST-T abnormalities, and AV conduction delays (first-degree to higherdegree block) are frequent in myocarditis and can be seen in ARF carditis. Ventricular ectopy or non-sustained VT warrants close monitoring. A normal ECG does not exclude myocarditis; repeat testing can improve sensitivity. Common ECG findings and suggested actions Finding Possible implication Action Sinus tachycardia out of proportion to fever Early myocarditis or hemodynamic stress Add troponin/BNP; proceed to echo ST-T changes (diffuse) Myopericardial inflammation Exclude ischemia; trend markers; echo PR prolongation/AV block Conduction system involvement (myocarditis/ARF) Telemetry; consider ICU if high-grade block Ventricular ectopy/NSVT Myocardial irritability Telemetry, echo, consider CMR escalation 7. Echocardiography: First-Line Imaging SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 45 Myocarditis. Look for LV global/segmental hypokinesia, reduced EF, chamber dilation, pericardial effusion; speckle-tracking strain may precede EF decline. Rheumatic carditis. Apply WHF pathological regurgitation criteria (color Doppler jets, jet length/velocity, pansystolic/holodiastolic persistence, morphological leaflet abnormalities). Subclinical carditis is diagnosable by echo even without audible murmurs. MIS-C. Assess LV function, pericardial fluid, and coronary artery Z-scores; repeat serially in acute and subacute phases. Echocardiographic pointers by etiology Etiology Key echo features Notes Myocarditis ↓ EF, regional WMA, pericardial effusion, strain impairment Strain may be earliest abnormality Rheumatic carditis Pathologic MR/AR per WHF, leaflet thickening, chordal elongation Subclinical disease detectable; follow standardized WHF criteria MIS-C LV dysfunction, pericardial effusion, coronary dilation (Z-scores) Repeat studies to track recovery 8. Cardiac MRI (CMR): Updated Lake Louise Criteria (2018) Multiparametric CMR is the non-invasive reference standard when myocarditis is suspected and echo/ECG/biomarkers are inconclusive or severity must be clarified. The 2018 Lake Louise update requires ≥1 T1-based marker of non-ischemic injury (elevated native T1, increased ECV, non-ischemic LGE) and ≥1 T2-based marker of edema (elevated T2 or regional T2-weighted abnormalities). In pediatric practice, protocols should minimize sedation and scan time; gadolinium safety and renal function must be considered. CMR markers and practical read-outs (Lake Louise 2018) Domain Marker Practical interpretation T2 (edema) Elevated global/regional T2; T2-weighted hyperintensity Active inflammation/edema T1 (injury/fibrosis) Elevated native T1; increased ECV; nonischemic LGE Myocyte injury; scar if LGE persists Combined rule ≥1 T2 + ≥1 T1 marker Supports myocarditis diagnosis 9. Endomyocardial Biopsy (EMB) EMB is reserved for fulminant or refractory cases or when diagnosis will change management and non-invasive tests are non-diagnostic. Pediatric risk-benefit must be carefully weighed; many centers prioritize CMR-guided management. 10. Differential Diagnosis Chest pain and troponin elevations are not myocarditis-specific. Consider pericarditis, anomalous coronaries (rare but critical), congenital/acquired channelopathies, hypertrophic or dilated cardiomyopathy, pulmonary embolism (adolescents), sepsis-related myocardial dysfunction, and non-cardiac etiologies (costochondritis, GERD). Differential diagnosis highlights Condition Distinguishing features First tests Pericarditis Pleuritic pain, pericardial rub, diffuse ST elevation with PR depression ECG, echo (effusion), inflammatory markers SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 46 Condition Distinguishing features First tests Coronary anomalies/ischemia Exertional pain/syncope, ischemic ECG Echo (origins), CMR/CT if needed Cardiomyopathies Family history, chronic symptoms, abnormal wall thickness Echo, ECG, genetics if indicated Sepsis-related dysfunction Systemic infection, elevated lactate Labs, echo (global dysfunction) Non-cardiac chest pain Reproducible tenderness, GI symptoms Focused exam, reassurance, selective testing 11. Etiology-Specific Frameworks 11.1. Rheumatic Carditis and Jones Criteria The 2015 Jones criteria integrate clinical major/minor criteria with evidence of recent Group A strep infection; in moderate/high-risk populations, echocardiography is emphasized to detect subclinical carditis. Early identification enables secondary prophylaxis to prevent RHD progression. 11.2. MIS-C and Coronary-Focused Echo MIS-C requires prompt evaluation of LV function, arrhythmic risk, and coronaries (proximal segments by Z-scores). Cardiac markers guide severity; shock physiology mandates ICU care and consideration of inotropes alongside immunomodulatory therapy. 12. Stepwise Diagnostic Pathways (Setting-Specific) 12.1. Primary/ED Setting (First 2–6 Hours) 1. Clinical screen: red flags (Table 1). 2. Core labs: troponin, NT-proBNP, CRP/ESR; plus CBC, electrolytes. 3. ECG with telemetry if arrhythmias suspected. 4. Bedside echo (focused if comprehensive is unavailable). Escalate to tertiary care if high-grade AV block, sustained VT, hypotension/shock, or severe LV dysfunction. 12.2. Secondary/Tertiary Setting (24–72 Hours) 1. Comprehensive echo (strain if available). 2. CMR if myocarditis remains suspected or to characterize severity. 3. ARF pathway: apply Jones criteria + WHF echo standards. 4. MIS-C pathway: inflammatory panel, cardiac markers, echo serially; ICU if shock. Table 7. Minimal datasets by level of care Level Must-have Nice-to-have Primary/ED ECG, troponin, NT-proBNP, CRP/ESR, focused echo Strain echo; rapid strep tests if ARF suspected Secondary Comprehensive echo (with Doppler), telemetry Strain, serial markers Tertiary CMR (Lake Louise), advanced labs, ICU protocols EMB (selected), cardiac CT, genetics (when indicated) 13. Quality and Safety Considerations  Radiation minimization: Prefer echo and CMR over CT where feasible. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 47  Sedation strategies: Pediatric CMR protocols to reduce need for sedation; consider feed-and-sleep in infants.  Consent and communication: Age-appropriate explanations; parental counseling on trajectory and follow-up.  Documentation: Structured templates for clinical, ECG, echo, and CMR findings improve continuity and auditability. 14. Implementation: Checklists and Triggers Adopt a diagnostic passport for key metrics (owner, frequency, thresholds) and set green/amber/red zones with predefined actions: e.g., troponin > reference + abnormal ECG → echo within 2 hours; EF <40% or high-grade AV block → ICU; echo-defined pathological MR/AR (WHF) → ARF pathway and secondary prophylaxis. Table 8. Example trigger map for early actions Trigger Action Troponin ↑ + ECG abnormal Comprehensive echo within hours; telemetry EF <40% or high-grade AV block ICU transfer; inotrope/readiness; rhythm management Pathologic MR/AR (WHF) ARF/RHD pathway; secondary prophylaxis plan MIS-C suspected with hypotension ICU; immunomodulatory protocol; serial echo 15. Discussion A unified, stepwise framework reconciles heterogeneity in pediatric presentations with the reality of multi-level care. Its strengths are (i) simplicity at the front door (clinical triage + core markers + ECG + echo), (ii) clarity in escalation (CMR when needed; EMB selectively), and (iii) specificity for etiologies (Jones/WHF for ARF; MIS-C cardiac focus). The approach supports earlier therapy, better documentation, and standardized follow-up. Limitations include variability in access to CMR and pediatric echo expertise; the framework should be adapted to local resources (e.g., hub-and-spoke referral models). Future multicenter work should quantify how pathway adherence affects time-to-diagnosis, ICU transfers, and medium-term LV recovery. 16. Conclusions Early pediatric carditis diagnosis is best achieved through a structured route: clinical suspicion → core triage (troponin/BNP, ECG, echo) → targeted confirmation (CMR for myocarditis; WHF/Jones echo standards for ARF; MIS-C cardiac pathway). The framework is implementable across care levels, reduces missed cases, and expedites definitive therapy while balancing safety, consent, and resource constraints. REFERENCES 1. Law YM, et al. Diagnosis and Management of Myocarditis in Children. Circulation. 2021. 2. Ferreira VM, et al. Cardiovascular Magnetic Resonance in Non-Ischemic Myocardial Inflammation. J Am Coll Cardiol. 2018. 3. Luetkens JA, et al. Comparison of Original and 2018 Lake Louise Criteria for CMR in Myocarditis. Radiol Cardiothorac Imaging. 2019. 4. Gewitz MH, et al. 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