Chaotic dynamics in circulation with Tohoku University vibrating flow pump

For the development of a totally implantable ventricular assist system (VAS ), we have been developing the vibrating flow pump (VFP), which can generat e oscillated blood flow with a relative high frequency (10-50 Hz) for a tot ally implantable system. In this study, the effects of left ventricular ass istance with this unique oscillated blood flow were analyzed by the use of nonlinear mathematics for evaluation as the whole circulatory regulatory sy stem, not as the decomposed parts of the system. Left heart bypasses using the VFP from the left atrium to the descending aorta were performed in chro nic animal experiments using healthy adult goats. The ECG, arterial blood p ressure, VFP pump flow, and the flow of the descending aorta were recorded in the data recorder during awake conditions and analyzed in a personal com puter system through an A-D convertor. By the use of nonlinear mathematics, time series data were embedded into the phase space, the Lyapunov numerica l method, fractal dimension analysis, and power spectrum analysis were perf ormed to evaluate nonlinear dynamics. During left ventricular assistance wi th the VFP, Mayer wave fluctuations were decreased in the power spectrum, t he fractal dimension of the hemodynamics was significantly decreased, and p eripheral vascular resistance was significantly decreased. These results su ggest that nonlinear dynamics, which mediate the cardiovascular dynamics, m ay be affected during left ventricular (LV) bypass with oscillated flow. Th e decreased power of the Mayer wave in the spectrum caused the limit cycle attractor of the hemodynamics and decreased peripheral resistance. Decrease d sympathetic discharges may be the origin of the decreased Mayer wave and fractal dimension. These nonlinear dynamic analyses may be useful to design optimal VAS control.