Global Longitudinal Strain as a Sensitive Marker of Left Ventricular Dysfunction in Pediatric Dilated Cardiomyopathy: A Case-Control Study

Pediatric dilated cardiomyopathy (DCM) is a rare but important cause of heart failure (HF) and a major indication for cardiac transplantation. Early detection of subclinical myocardial dysfunction is essential for risk stratification and management. This study aimed to evaluate left ventricular (LV) systolic function in children with DCM using conventional echocardiographic parameters and speckle-tracking echocardiography (STE) and to explore the relationship between deformation indices, clinical severity and biomarkers. Methods: We conducted a case-control study including 29 children diagnosed with DCM and 27 healthy controls matched by age and sex. All participants underwent clinical evaluation, NT-proBNP measurement, and transthoracic echocardiography. LV systolic function was assessed using conventional echocardiographic parameters, while STE was used to measure LV global longitudinal strain (GLS) and strain rate (SR) from all apical views. Results: GLS and SR were significantly reduced in the DCM group across all apical views (Global GLS: -11.13 ± 6.79% vs. -19.98 ± 3.25%, Global SR: -0.74 ± 0.39 s^-1 vs. -1.12 ± 0.16 s^-1; p < 0.01). GLS strongly correlated with functional indices (LV ejection fraction, shortening fraction, S' lateral wave), LV end-diastolic diameter Z-score and NT-proBNP (p < 0.05), but not with MAPSE. In the primary model, GLS was associated with NYHA/Ross III-IV (OR 1.54 per 1% increase; 95% CI 1.14-2.07; p = 0.005); adding systolic blood pressure (p = 0.798) or heart rate (p = 0.973) did not materially change the GLS estimate (Δ ≤ 2%). In separate collinearity-avoiding models, LVEF (OR 1.12 per 1% decrease; 95% CI 1.03-1.22; p = 0.009), LVSF (OR 1.19 per 1% decrease; 95% CI 1.04-1.36; p = 0.011), and NT-proBNP (≈OR 1.11 per 100 units; p = 0.013) were also associated with advanced class. ROC analysis showed excellent discrimination for NT-proBNP (AUC 0.948) and GLS (AUC 0.906), and good-excellent performance for LVEF (AUC 0.869) and LVSF (AUC 0.875). Conclusions: Speckle-tracking derived parameters such as GLS and SR are sensitive and clinically relevant markers of LV dysfunction in pediatric DCM. Global longitudinal strain demonstrated a strong association with both clinical and biochemical markers of disease severity, after accounting for heart rate and blood pressure, supporting its integration into routine evaluation and risk stratification in pediatric DCM.