Validation of Feature-Tracking Cardiac CT for Left Ventricular Strain Assessment in Pediatric Acute Myocarditis: Comparison With Cardiac MRI.
OBJECTIVE This study aimed to validate feature-tracking cardiac CT (FT-CCT) for left ventricular (LV) strain assessment against cardiac MRI (CMR) in pediatric acute myocarditis, evaluating its potential as a pragmatic solution when CMR is delayed after a clinically indicated coronary CT angiography (CCTA). MATERIALS AND METHODS Forty-five children with acute myocarditis underwent CCTA and CMR. Global longitudinal (GLS), circumferential (GCS), and radial strain were measured. Intermodality agreement (Bland-Altman, ICC), diagnostic performance for detecting late gadolinium enhancement (LGE) (ROC analysis, DeLong test), and heart rate influence were assessed. RESULTS FT-CCT showed excellent agreement with CMR for LV ejection fraction (bias: -0.1%) and strain (ICCs: 0.750-0.854), independent of heart rate. For detecting LGE, CCTA-derived GCS and GLS demonstrated diagnostic performance equivalent to CMR (AUCs: 0.716 vs. 0.718, P=0.974; 0.705 vs. 0.703, P=0.972). CCTA-derived GLS provided high specificity (93.1%) and PPV (77.8%), serving as a robust "rule-in" tool. Measurements were highly reproducible (ICCs: 0.746-0.809). CONCLUSION FT-CCT applied to clinically indicated CCTA provides a heart rate-robust, reproducible alternative to CMR for LV strain assessment in pediatric myocarditis. Its high specificity and diagnostic equivalence support its role as a complementary tool for initial myocardial injury detection and risk stratification when CMR is not immediately available.