Review of Systemic Mock Circulation Loops for Evaluation of Implantable Cardiovascular Devices and Biological Tissues

Implantable cardiovascular devices must undergo evaluation prior to animal testing and clinical trials to ensure their performance and efficiency. Mock circulation loops (MCLs) are on-demand tools capable of reproducing physiological conditions in vivo and are also devices for preventative testing. Recognition of their success as useful tools comes from the fact that over 100 MCLs have been submitted for device assessment in recent years. Mock circulation loops could detect malfunctions that patients might otherwise experience. Thus, MCLs can complement preclinical and prototype evaluation rather than being mutually exclusive. In this review, we emphasize the experimental value of MCLs while providing a brief overview of the history of the field. In addition, the necessary hemodynamic parameters are analyzed to reproduce physiological scenarios in vitro. We also discuss the relevant setups when evaluating devices to assist heart failure and aortic pathologies, namely artificial hearts, left ventricular assist devices, stent-grafts, and artificial heart valves. Finally, we report novel setups developed to evaluate soft biological tissues for translational research. Clinical Impact: On needs-based ex vivo monitoring of implantable devices or tissues/organs in cardiovascular simulators provides new insights and paves new paths for device prototypes. The insights gained could not only support the needs of patients, but also inform engineers, scientists and clinicians about undiscovered aspects of diseases (during routine monitoring). We analyze seminal and current work and highlight a variety of opportunities for developing preclinical tools that would improve strategies for future implantable devices. Holistically, mock circulation loop studies can bridge the gap between in vivo and in vitro approaches, as well as clinical and laboratory settings, in a mutually beneficial manner.