Volumetric 3D Printing and Melt‐Electrowriting to Fabricate Implantable Reinforced Cardiac Tissue Patches

Cardiac patches to repair myocardial defects require mechanically stable materials that prevent bleeding and can be implanted via suturing. The current clinical standard, bovine pericardial patches (BPPs), serve this purpose but do not degrade or integrate with the myocardium, limiting their long‐term effectiveness. Here, we present the reinforced cardiac tissue patch (RCPatch). This multimaterial patch comprises a stiffness‐tuned, cardiomyocyte‐infiltrated 3D metamaterial and a suturable, hydrogel‐infiltrated mesh to reduce permeability and bleeding. Anisotropic metamaterials are designed and computationally optimized using a generative modeling approach and fabricated from poly(ε‐caprolactone) (PCL) via volumetric 3D printing (VP). The metamaterial supports the infiltration of cardiomyocytes, which are viable and contract in vitro. The implantability and low blood permeability of the patch is enabled by adding a melt‐electrowritten (MEW) mesh infiltrated with a fibrin hydrogel. In an acute large animal trial, the RCPatch was applied on an induced myocardial defect, where it withstood intraventricular blood pressure, prevented bleeding, and enabled hemodynamic restabilization (intraventricular pressure of 81 mmHg before, vs 66 mmHg after implantation). These findings establish a scalable framework for fabricating cardiac tissue patches that integrate mechanical reinforcement with biological function, offering a surgically implantable and future regenerative solution for intraventricular myocardial repair.