Optimization of skeletal muscle for actuator of assisted circulation

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Reduction of the putput power of skeletal muscle after preconditioning is one of the important problems in application of skeletal muscle for assited circulation. To solve this problem we constructed skeletal muscle ventricle (SMV) composed of rabbit latissimus dorsi muscle (LDM) with which new training methods can be established. Left LDMs of rabbit were electrically preconditioned in situ by 2 Hz continuous stimulation for 10 weeks and defined as trained, while right LDMs were defined as control. We constructed SMV uisng both LDMs and evaluated the basic performance of SMV with mock circulation. Stroke work (SW) was smaller in trained LDM and maximum SW at afterload of 80 mmHg was equal to 67% of rabbit left heart (LH) SW and maximum SW at afterload of 30 mmHg was equal to 184% of rabbit right heart (RH) SW.In endurance test, only trained LDM could work over 4 min and maintained 66% of rabbit RH SW at 1 hour. Next study was conducted to develop the pump system with anactuator of the LDM in linear configuration. The power of the LDM was estimated and the deasibility of a linear-skeletal muscle pump system was investigated based on the muscular property. To evaluate the power, in-situ LDMs in adult goats received 12-week preconditioning, followed by power analysis. Good fatigue resistance and the highest maximum external power of 3.16 Watts/kg at 120 minutes was derived from preconditioned LDM.Assuming that the weight of human bilateral LDMs is 0.5kg, estimated power became 1.58 Watts. If the system is applied to LH assistance, the efficiency of the system should be more than 50 %. To realize the linear-skeletl muscle pump system, much effort should be make to decrease the power loss.