Heart failure is characterized by intricate myocardial remodeling that impairs the heart’s pumping and/or relaxation capacity, ultimately reducing cardiac output. It represents a major public health burden, given its high prevalence and associated morbidity and mortality rates, which continue to challenge healthcare systems worldwide. Despite advancements in medical science, there are no treatments that address the disease at its core. The development of three-dimensional engineered in vitro models that closely mimic the (patho)physiology and drug responses of the myocardium has the potential to revolutionize our insights and uncover new therapeutic avenues. Key aspects of these models include the precise replication of the extracellular matrix structure, cell composition, micro-architecture, mechanical and electrical properties, and relevant physiological and pathological stimuli, such as fluid flow, mechanical load, electrical signal propagation, and biochemical cues. Additionally, to fully capture heart failure and its diversity in vivo, it is crucial to consider factors such as age, gender, interactions with other organ systems and external influences—thereby recapitulating unique patient and disease phenotypes. This review details these model features and their significance in heart failure research, with the aim of enhancing future platforms that will deepen our understanding of the disease and facilitate the development of novel, effective therapies.

Living myocardial slices (LMSs) have shown great promise in cardiac research, allowing multicellular and complex interplay analyses with disease and patient specificity, yet their wider clinical use is limited by the large tissue sizes usually required. We therefore produced mini-LMSs (30 mm²) slices. Size effects on biomechanical properties were examined with mathematical modeling, and viability, contraction profiles, and histological integrity were followed for 14 days. In total, 34 mini-, 25 medium, and 30 large LMS were maintained viable, the smallest measuring only 2 mm². Peak twitch force proved to be size-independent, whereas time-to-peak shortened as slice area decreased. Downsized LMSs displayed excellent contractile behavior for five to six days, after which a gradual functional decline and micro-architectural changes emerged. These findings confirm, for the first time, that mini-LMSs are feasible and viable, enabling short-term, patient-specific functional studies and pharmacological testing when tissue is scarce.