Abstract Background Congenital heart disease (CHD) remains one of the most prevalent birth defects worldwide, yet mechanistic studies in pediatric myocardium are limited by the scarcity of viable human tissue. Living myocardial slices (LMS) offer a three-dimensional, near-physiological in-vitro platform, but their application in children has been restricted by the need for large myocardial samples. We recently introduced miniaturized LMS (mini-LMS) as a potential solution for pediatric tissue research. Objective To establish the feasibility of generating mini-LMS from small congenital heart disease specimens, characterize their biomechanical profile, and determine whether patient age or disease phenotype influences myocardial mechanics. Methods Myocardial samples (2–3 mm³) were obtained from 20 CHD patients undergoing surgery, yielding 107 mini-LMS. Contractile activity was monitored in culture, and key biomechanical parameters—including maximum contraction force (Fmax), contraction duration (CD), time-to-peak (TTP), time-to-relaxation (TTR), ±dF/dt, and area under the curve (AUC)—were quantified. Linear mixed-effects modeling assessed the influence of age, while non-parametric group comparisons evaluated differences among three hemodynamic phenotypes: genetic pressure overload (GPO), functional pressure overload (FPO), and volume overload (VO). Results All mini-LMS demonstrated contractile activity on day 0; 56% remained beating on day 2 and 40% on day 3, with some viable up to 14 days, confirming feasibility using very small pediatric tissue samples. Across all slices, the biomechanical profile showed modest force generation and prolonged kinetics. Age did not independently predict Fmax, although patient-level clustering was evident. Significant biomechanical differences were observed between CHD phenotypes (p 0.05). VO slices exhibited higher Fmax, shorter CD, faster relaxation, and larger AUC, consistent with adaptive responses to chronic volume load. GPO slices, predominantly Tetralogy of Fallot tissue, displayed reduced Fmax and prolonged kinetics, reflecting maladaptive pressure-overload remodeling. FPO tissues showed intermediate characteristics. Conclusions This study provides the first evidence that viable and functional mini-LMS can be reliably generated from extremely small pediatric CHD surgical specimens. Distinct biomechanical profiles across CHD phenotypes highlight the strong influence of disease-specific loading conditions on myocardial mechanics. Mini-LMS represent a promising platform for translational CHD research, enabling functional studies on rare pediatric myocardial tissue and supporting future mechanistic and therapeutic investigations.For image description, please refer to the figure legend and surrounding text.
Zhou et al. (Fri,) studied this question.