The authors developed a system to use skeletal muscle as an artificial heart actuator. This system consists of a flexible rod, sheath, crank, and cam to transmit the muscle power to a pusher plate pump and actuate it. The latissimus dorsi muscle was dissected at the lower ribs, and its end was connected with the flexible rod. The contraction of skeletal muscle was linearly transmitted, with the rod introduced inside the sheath, to the pump. The whole system was implanted in dogs (14-18 kg) and pump performance was evaluated with a mock circulatory system (preload = 10 mmHg, afterload = 75 mmHg). In these experiments, the pump output was maintained at 0.8 to 2.0 L/min (60 bpm) for 200 min, with a non-preconditioned muscle that was stimulated continuously. The output obtained was 2.5 mW/gram. Efficiency of this system was about 50% of the muscle power available. When the muscle was stimulated intermittently every 30 min, pump flow was maintained at > 0.8 L/min for 20 hr. Advantages of this system are: 1) the muscle power was linearly transmitted effectively, 2) this system could be installed with minimal surgery and without interruption in blood flow to the muscle, 3) the muscle is free from high intraventricular pressure that caused ischemia and, 4) the muscle can be set to the proper length in diastole to potentiate strong contractions.

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PubMedDate not supplied

Evaluation of hypothermic heart preservation with University of Wisconsin solution in heterotopically and orthotopically transplanted canine hearts.

In simple cold storage of the heart, 4 hours has been proved to be a clinically safe ischemic time. The University of Wisconsin solution has been reported to extend cold ischemic time in preservation of the liver, kidney, and pancreas. The purpose of this study is to clarify the safe cold ischemic time in heart preservation with University of Wisconsin solution experimentally in heterotopically and orthotopically transplanted canine hearts. In heterotopic heart transplantation, 120 minutes after reperfusion, maximum slope of the left ventricular end-systolic pressure-volume relationship was recovered to 94% +/- 13% in the 4-hour simple cold preservation group with GIK solution and 104% +/- 11% in the 8-hour simple cold preservation group with University of Wisconsin solution but was not recovered in the 8-hour simple cold preservation with GIK solution and 16-hour simple cold preservation with University of Wisconsin solution groups. One hundred twenty minutes after reperfusion, myocardial tissue blood flow measured by laser Doppler flowmeter was recovered to 90% +/- 19% after 4 hours with simple cold preservation with GIK solution and 98% +/- 9% after 8 hours with simple cold preservation with University of Wisconsin solution but was not recovered after 8 hours with simple cold preservation with GIK solution and 16 hours with simple cold preservation with University of Wisconsin solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗

PubMedDate not supplied

Monitoring and regulating latissimus dorsi muscle performance for circulatory assist.

The purposes of this study were monitoring and regulating latissimus dorsi muscle (LDM) performance with muscle internal pressure and thickness, and with burst stimulation parameters, respectively. The unconditioned LDM flap of a pig was connected to a measurement system to examine force and contraction length. Internal pressure was measured using a catheter pressure transducer with a fluid-filled balloon inserted into the muscle, and correlated linearly with force during both contraction and relaxation. During contraction, thickness change correlated linearly with contraction length and the area enclosed within an internal pressure-thickness curve, and the X-axis was correlated linearly with muscle work. Stroke work increased incrementally according to the pulse width up to 6.72 msec or burst rate up to 120 Hz, and then plateaued at 240 Hz. The authors conclude that muscle work during contraction could be monitored with internal pressure and thickness, and that stroke work could be regulated with pulse width or burst rate.

Animals↗