Existing functional simulators are generally passively driven by flow, the heart walls do not actively contract, and they don’t simulate 3-D twisting motion (with the exception of the Chamberlain surgical trainer) or allow simulation of pathological motion. This limits the clinical relevance of device testing on these test-beds.
Inspired by biological muscle, where contractile elements are arranged in a soft matrix, soft custom-molded McKibben actuators were fabricated then embedded in a soft elastomeric matrix with material properties close to physiological tissue.
Initial models used simple configurations of actuators in elastomer matrix. Basic geometric properties such as actuator spacing and matrix width/length were varied, and the force and strain behaviors of these models when the actuators are pressurized were observed via image tracking of markers and a tensile test machine.
Once these simple units were characterized, the same principles were applied to the helical arrangement of muscle fibers in an actual heart.
EM trackers were placed on molded alignment features on the simulated ventricle to evaluate its motion. When all actuators were pressurized, apical and basal rotation of the ventricle matching the range of clinical values was observed. In addition, the effect of deactivating select actuators on the overall motion of the ventricle was observed. This mimics the effect of a section of heart wall losing its function via myocardial infarct or other cardiac diseases and simulates the subsequent pathological motion.