Prolonged Nonpulsatile Left Heart Bypass with Reduced Systemic Pulse Pressure Causes Morphological Changes in the Aortic Wall

Nishimura, Takashi; Tatsumi, Eisuke; Takaichi, Shigeko; Taenaka, Yoshiyuki; Wakisaka, Yoshinari; Nakatani, Takeshi; Masuzawa, Toru; Takewa, Yoshiaki; Nakamura, Makoto; Endo, Sohei; Nakata, M; Takano, Hisateru

doi:10.1046/j.1525-1594.1998.06137.x

Cited by 56 publications

(36 citation statements)

References 19 publications

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“…Although NOSE (1993) reported that a long-term non-pulsatile biventricular bypass did not produce harmful physiological effects in animals, recent studies have suggested that a prolonged non-pulsatile left heart bypass can produce certain effects on the arterial structure and function, such as the wall thickness, smooth muscles and vasoconstrictive function of the vessels (NISHIMURA et al, 1998;NISHINAKA et al, 2001).…”

Section: Comparisons O F Synchronous and Non-synchronous Operations Omentioning

confidence: 99%

Simulation study of the Hemopump as a cardiac assist device

Bai

2002

Med. Biol. Eng. Comput.

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A dynamic model was developed for a Hemopump that withdraws blood from the left ventricle and discharges it to the aorta through a miniature axial-flow pump. Incorporation of the Hemopump model in a previously established model for the canine circulatory system enabled the effects of the Hemopump on various haemodynamic variables of the circulatory system to be studied, and the benefit of the Hemopump to the failing heart was investigated. In addition, the influence of the physiological status of the right ventricle on the Hemopump performances was examined, and the synchronous and non-synchronous operations of the Hemopump were compared. Results verified that the Hemopump assists the failing heart by increasing the oxygen supply, while reducing the oxygen consumption of the heart through a reduction in the workload of the left ventricle. These beneficial effects were enhanced when the pump's rotation speed was increased. When pump speed was increased from 17,000 to 23,000 revolutions min-1, the oxygen supply increased 101%, and the oxygen consumption decreased 60%. However, when the pump rotation speed was too high, the inflow to the pump could be impaired and the pump performance could be negatively affected. Predications from the model were in good agreement with the results previously obtained in animal experiments and in vitro measurements.

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Section: Comparisons O F Synchronous and Non-synchronous Operations Omentioning

confidence: 99%

Simulation study of the Hemopump as a cardiac assist device

Bai

2002

Med. Biol. Eng. Comput.

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“…In this study the pulse pressure was reduced to about 10mmHg, which we considered a clinically available level. Furthermore, although the purpose of this study was to investigate changes in vascular control status that were possibly affected by atrophic changes in the arterial systems accompanying reduced pulse pressure, Nishimura et al [4][5][6] reported that atrophic changes in the arterial system were observed with a pulse pressure of about 10mmHg.…”

Section: Discussionmentioning

confidence: 97%

“…The influences of reduced systemic pulse pressure have been investigated in nonpulsatile left heart bypass (NLHB). Nishimura et al [4][5][6] reported morphological changes in the arterial system caused by prolonged NLHB in a chronic animal study. There was an increase in the ratio of elastin, a decrease in arterial wall thickness, and atrophy of smooth muscle cells.…”

Section: Introductionmentioning

confidence: 99%

Effect of prolonged nonpulsatile left heart bypass on vascular control status

et al. 2000

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We investigated the vascular control status, including vasoactive hormones, systemic vascular resistance (SVR), and baroreceptor sensitivity, in prolonged nonpulsatile left heart bypass (NLHB). Nine goats underwent pulsatile left heart bypass (PLHB) with a ventricular assist device (VAD). Two weeks postoperatively, the VAD was replaced with a centrifugal pump and NLHB was subsequently conducted for 4 weeks. Thirteen healthy goats were also evaluated to obtain normal control data. The aortic pulse pressure on average was 37 mmHg for controls; 36mmHg at the end of PLHB; and 11, 9, 12, and 12mmHg at the end of the first, second, third, and fourth NLHB weeks, respectively. Plasma norepinephrine (NE), vasopressin (VP), renin activity (RA), and endothelin-i (ET) levels were measured for controls and at each point during PLHB and NLHB. The baseline SVR and the minimum SVR values after nitroglycerin injection were determined at each point during PLHB and NLHB. Baroreceptor sensitivity was calculated as the regression slope between R-R intervals and mean aortic pressure for controls and at each point during PLHB and NLHB. The plasma levels of NE, VP, RA, and EN did not change significantly during the entire course of the experiments. The baseline and minimum SVR values after nitroglycerin injection remained unchanged during PLHB and NLHB. Furthermore, the baroreceptor sensitivity did not change significantly during the entire course of the experiments. These results indicate that prolonged NLHB does not affect vascular control

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“…As a natural left ventricle is a pulsatile pump, the long-term effects of a non-pulsatile pump have been an issue of considerable debate (NISHIMURA et al, 1998;LOEBE et al, 2001). …”

Section: Discussionmentioning

confidence: 99%

Optimum control of the Hemopump as a left-ventricular assist device

Bai

Xia

2005

Med. Biol. Eng. Comput.

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A general framework for designing an optimum control strategy for the Hemopump is described. An objective function was defined that includes four membership functions, each constructed based on the desired values of one of the four members: stroke volume, mean left atrial pressure, aortic diastolic pressure and mean pump rotation speed. The Hemopump was allowed to operate either at a constant speed or at two different speeds during a cardiac cycle. The goal was to maximise the objective function by varying the magnitude and timing of the pump speed. Using a canine circulatory model, it was demonstrated that, in general, different cardiac conditions or different clinical objectives require different operation parameters. For example, when a left ventricle with minor ischaemia was simulated, and the main objective was to increase stoke volume, the objective function was maximised, from a value of 0.877 when the pump was off, to 0.946 when the pump was operated at speed 2 (18 500 revolutions min(-1)). On the other hand, for a severely ischaemic heart, the optimum pump speed became speed 3 (20 000 revolutions min(-1)), which maximized the objective function to 0.943 (from 0.707 when the pump was off). The results also suggest that it is more beneficial to operate the Hemopump at two different speeds during a cardiac cycle (a higher speed during systole and early diastole, and a lower speed during late diastole) than to maintain a constant speed throughout the cardiac cycle.

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Prolonged Nonpulsatile Left Heart Bypass with Reduced Systemic Pulse Pressure Causes Morphological Changes in the Aortic Wall

Cited by 56 publications

References 19 publications

Simulation study of the Hemopump as a cardiac assist device

Simulation study of the Hemopump as a cardiac assist device

Effect of prolonged nonpulsatile left heart bypass on vascular control status

Optimum control of the Hemopump as a left-ventricular assist device

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