Measurement of global longitudinal strain using the apical four-chamber view as a simple indicator for assessing myocardial longitudinal deformation in patients with functional single ventricle

BACKGROUND: Currently, no unified standardized protocols exist for myocardial longitudinal strain measurement in functional single ventricle (FSV) patients, causing inconsistent methodologies in clinical practice and related studies. Some studies use only the apical four-chamber view, while others employ three apical views. OBJECTIVE: This study aimed to determine whether longitudinal strain (LS-4CH) measured from the apical four-chamber view can serve as an effective substitute for the average global longitudinal strain (GLS-AV) derived from multiple apical views in different subtypes of FSV patients. METHODS: This retrospective study enrolled 34 FSV patients. The consistency between LS-4CH and GLS-AV was assessed via Bland-Altman analysis, intraclass correlation coefficient (ICC), Lin's concordance correlation coefficient (CCC), and Passing-Bablok regression, with Two One-Sided Tests (TOST) for formal equivalence verification. Intra- and inter-observer ICC were used to evaluate the repeatability of the two methods. Spearman's correlation analyzed the associations of LS-4CH and GLS-AV with cardiac magnetic resonance-derived ejection fraction (CMR-EF). Receiver operating characteristic (ROC) curve analysis evaluated the predictive value of each index for predicting CMR-EF < 50%; DeLong test, net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were used for predictive efficacy comparison and incremental value assessment. RESULTS: LS-4CH and GLS-AV exhibited good consistency (all ICC > 0.87, CCC > 0.83) and excellent intra- and inter-observer repeatability, with TOST confirming their statistical equivalence within a predefined margin of ± 3% (all P < 0.05). Both GLS-AV and LS-4CH showed significant negative correlations with CMR-EF in the overall cohort and both SLV/SRV subgroups (all P < 0.05). ROC curve analysis showed that GLS-AV had significant predictive value for CMR-EF < 50% in the SLV group (AUC = 0.86, P = 0.02). CONCLUSION: When multi-view measurement of GLS-AV is impractical due to poor image quality, technical limitations, or urgent assessment needs, LS-4CH may serve as an effective alternative assessment indicator for patients with functional single ventricle. However, GLS-AV remains the preferred method when feasible, since LS-4CH cannot reflect regional dysfunction beyond the apical four-chamber view.