Biomedical subjects

Y Taenaka

Publications and source records attributed to Y Taenaka.

At least 145 records · Page 8Linked to original sources

PubMedDate not supplied

Chronic evaluation of a compact nonseal magnet pump as a nonpulsatile pump for long-term use.

Use of a nonpulsatile pump is one of the most interesting approaches in the development of artificial hearts. A centrifugal pump without a seal around the rotating part was evaluated in five goats. The size of the pump is 8.4 cm x phi 7.0 cm, including an electric motor. A polypropylene impeller with four fins on the top of a column in which a magnetic ring is embedded spins by coupling with a rotating magnet outside the housing. In the goats, the pump was placed paracorporeally to provide total left heart bypass at a flow rate of 4.6-7.6 L/min, and activated clotting time was controlled at 200-300 sec by continuous heparin infusion. Although the first three goats died within 3 days due to bleeding, embolism, and a jammed impeller, respectively, a pump could be driven for 14 days in the fourth goat, and another pump with a rotational control feedback system ran for 32 days in the fifth goat. Plasma free hemoglobin levels were 13.8 +/- 4.3 mg/dl and 9.5 +/- 2.5 mg/dl, and platelet counts were 53.8 +/- 24.7 x 10(4)/mm3 and 62.0 +/- 22.0 x 10(4)/mm3 after 12 hours and 7 days pumping, respectively. No thrombus was observed in the blood chamber in the last two cases. In conclusion, this pump has possibilities as a nonpulsatile pump for long-term use.

Animals↗

PubMedDate not supplied

Easy access for a left ventricular assist system without thoracotomy.

In a previous article, a left ventricular assist system (LVAS) with a percutaneous transseptal cannulation technique for easy application was described. This system was safe and efficient (maximum output greater than 3 L/min) and fitted between the intraaortic balloon pumping and LVAS with thoracotomy. But technical skill for placement was slightly complicated. The cannulation system has been improved. In the new system, the inlet cannula is initially used as a sheath introducer and is quickly inserted into the left atrium after transseptal puncture. The new inlet cannula is made of polyvinyl chloride (TM100, Toyobo, Co., Ltd., Osaka, Japan), which has excellent antithrombogenicity and low friction using a polyester plasticizer. The distal part is designed to be flexible with a spiral wire for easy manipulation. A sealing hub was installed to prevent bleeding at the proximal The simplicity and safety of the new system were examined in chronic animal experiments. The inlet cannula was placed into the left atrium within a few seconds after transseptal puncture. During 20 days of activation, there were no episodes of systemic or pulmonary embolism, although no anticoagulant was used. Under fluoroscopy, there was no thrombus formation around the cannula at removal. On the 14th day after removal, the puncture site of the septum had healed. This system is ready for clinical use and shows promise of satisfactory safety and manageability.

Animals↗

PubMedDate not supplied

The consequence of ventricular assist on acute profound biventricular failure with induced severe myocardial injury.

The effect of ventricular assist on acute profound biventricular failure (BVF) was examined in chronic animal experiments using 10 adult goats. Induction of BVF was achieved by normothermic anoxic arrest for 30-60 min during the use of a left ventricular assist system (LVAS, eight goats), or biventricular assist system (BVAS, two goats). The LVAS could maintain near normal circulation with volume loading in six goats, and three of eight goats were weaned from LVAS after 13-18 days. In the early stages, left atrial pressure was significantly higher, and right atrial pressure was significantly lower, compared with measurements in nonweaned goats. During BVAS, circulation was well maintained without volume loading, but neither of the two goats could be weaned from VAS. Myocardial fibrosis in goats without myocardial recovery was significantly more severe. Left ventricular wall thickness was thinner in nonweaned goats and there was a significant inverse correlation between the thickness of the left ventricular free wall and the assist duration in nonweaned goats. Based on these data, it was concluded that myocardial damage was severe in nonweaned cases, and the potential for healing is affected by the severity of myocardial damage before VAS application. Prolonged unloading with VAS of these severely damaged hearts caused loss of left ventricular wall thickness.

Animals↗

PubMedDate not supplied

An integrated artificial heart-lung device.

An integrated artificial heart-lung device (IAHLD) is being developed as a novel system for simultaneous long-term support of heart and lung. The IAHLD consists of an artificial lung component (LC) and two blood pumps. The LC is made with a special composite hollow fiber membrane that prevents serum leakage. The fibers are arranged as piled-up lattices and potted in a cylindrical housing made of polyurethane. The blood pump with a single port is of a pneumatic pusher-plate type, and a Björk-Shiley valve is mounted in the port. The LC is sandwiched between the inlet and outlet pumps, and all components are integrated. This special structure provides high gas exchange efficiency, prevention of flow channeling and stagnation, and reduction of blood contacting surfaces. The prototype IAHLD had exchange rates of up to 170 ml/min of O2 and CO2 and up to 5.5 L/min of pump output. A flow visualization analysis with cineroentgenography revealed that the flow distribution within the IAHLD was uniform, without any stasis. It was concluded that the IAHLD is a promising system for long-term heart and lung support, and can be used without systemic heparinization given thromboresistant surface treatment as the next step of development.

Animals↗

PubMedDate not supplied

Serum silicon levels in recipients of an electrohydraulic ventricular assist system.

This study was designed to determine the permeation rate of silicon oil from the authors' electrohydraulic ventricular assist system (EHVAS), and to evaluate influences on organ function. The permeation rate through the diaphragm of the EHVAS was determined by in vitro experiments. Influences on organ function were evaluated in three goats with EHVAS by monitoring blood chemical parameters and serum silicon levels (S-Si). The permeation rate from the EHVAS was about 0.2 ml/month, calculated from the data obtained in the in vitro experiments. S-Si levels did not increase during chronic animal implantation, and renal and hepatic function were not affected. The permeation rate through the diaphragm must, however, be taken into consideration.

Animals↗

PubMedDate not supplied

Peripheral circulation during nonpulsatile systemic perfusion in chronic awake animals.

Peripheral circulation (PC) during nonpulsatile (NP) perfusion is not satisfactorily understood, although it is known that animals can survive with chronic NP flow. In awake goats, PC was analyzed by hemodynamic and hormonal parameters, tissue blood flow of the ear measured by a noninvasive laser Doppler flowmeter, and distribution of the body surface temperature monitored by thermography. An NP systemic circulation was established in five 40-64 kg goats with a centrifugal pump (MD-10, Iwaki Pump, Japan) that replaced a pulsatile ventricular assist device 2 weeks postoperatively; this was done without anesthesia. Nonpulsatile total left heart bypass was obtained, with flow rates of 78-165 ml/kg/min. Systemic vascular resistance and blood adrenalin and noradrenalin levels were not affected by the depulsation. Tissue blood flow during NP perfusion was well maintained and showed comparable values to those during pulsatile systemic circulation. Vasomotion of 10-20 cycles/min was obvious in the tissue blood flow pattern, indicating adequate PC at each sampling point. Thermography before and after depulsation indicated no change of temperature distribution, and displayed warm peripheral areas. In conclusion, PC of animals on chronic NP systemic perfusion is adequately maintained.

Animals↗

PubMedDate not supplied

Hybrid respiratory support system with extracorporeal placental oxygenation.

The authors developed a novel hybrid system for long-term respiratory support with extracorporeal placental oxygenation. In this system, the patient's blood is oxygenated with O2 saturated artificial blood across the villous membrane during passage through the fetal circuit of the placenta, which is placed in a specially constructed artificial uterus. Human term placentas were obtained immediately after vaginal delivery and used for the experiments. The gas transfer performance of the current apparatus was 60 ml/min for O2 and 40 ml/min for CO2 at a blood flow rate of 1.0 L/min. From these results (and the assured blood compatibility of the placenta), the authors conclude that this system will become one of the most promising modalities for prolonged extracorporeal oxygenation.

Biocompatible Materials↗

PubMedDate not supplied

Practical assessment of natural heart function using echocardiography in mechanically assisted patients.

Left ventricular assist systems (LVAS) can maintain the systemic circulation of patients with acute, profound heart failure. The assessment of natural heart (NH) function, however, is difficult in the clinical setting. The authors introduced a new index, heart rate-corrected ejection time/left atrial pressure (ETc/LAP) using echocardiography to evaluate NH function in 15 adult patients on the original LVAS for greater than 2 days. Bypass flow (BF) was gradually decreased according to the recovery of NH. Five patients were weaned from LVAS within 15 days, and LV function was well maintained (Group 1). Another six patients were weaned from LVAS within 21 days but died within 2 weeks (Group 2). The other four patients died on LVAS without recovery of NH (Group 3). In Group 1 patients, ejection time/pre-ejection period (ET/PEP) with LVAS assist increased continuously. In Groups 2 and 3, ET/PEP increased slowly and reached a plateau at approximately 10 days or remained low. Group 1 patients reached an ETc/LAP of 35 +/- 10 on LVAS within 7 days. Group 2 and Group 3 patient values were 18 +/- 2 (p less than 0.05) and 9 +/- 6 (p less than 0.01), respectively, on the seventh day. Based on these data, this new index provides an estimate of global NH function and a prediction of the probability of NH recovery.

Adult↗

PubMedDate not supplied

Continuous monitoring of artificial heart pump performance.

Continuous monitoring of pump performance is essential and effective for optimal driving of a pulsatile blood pump. The authors contrived a practical method for continuous estimation of blood volume in a pump by measurement of electrical impedance (Z). This method was evaluated with the air-driven, diaphragm type pump. The pump was made from polyurethane and had two metal connectors at the inlet and the outlet ports. Z was measured by charging the alternating current (50 kHz, 0.4 mA) between two connectors as electrodes. In in vitro tests, Z reached maximum value during full-empty and minimum value at full-fill. The blood volume calculated by an empirical equation of Z was linearly related to the real blood volume (r = 0.99). In in vivo tests with goats, pump output estimated by this method was linearly related to pump output measured with an electromagnetic flowmeter and effectively evaluated pump performance. For calibration, this method needed only to measure Z at full-fill. This method was useful as a controller of a full-fill to full-empty drive. It was concluded that this method is a practical estimate of pump performance, even if implantable diaphragm type pumps are used, and easily applicable to any kind of pulsatile pump.

Animals↗

PubMedDate not supplied

A VAD and novel high performance compact oxygenator for long-term ECMO with local anticoagulation.

A novel method of long-term ECMO was designed and evaluated experimentally. Special features of this ECMO method include: 1. using a pneumatic diaphragm type VAD with excellent blood compatibility as a pump system; 2. using a newly developed, high performance, compact oxygenator, with a novel gas exchange membrane in which micropores are blind at the blood contacting surface; 3. regional anticoagulation within the ECMO circuit with short-acting protease inhibitor FUT-175; and 4. right heart bypass with direct cannulation through a thoracotomy. Four goats implanted with a VAD between the right atrium and the pulmonary artery underwent ECMO by interposing a compact oxygenator in the return cannula for as long as 14 days. Blood clotting was regulated with continuous infusion of FUT-175 from the inflow cannula of the ECMO circuit. In this system, 2 to 4 L/min of bypass flow, 80 to 120 ml/min of O2, and 40 to 80 ml/min of CO2 gas exchange were obtained. Serum leakage in the oxygenator did not occur, and various blood chemical and hematologic parameters were maintained within the normal range. Regional anticoagulant therapy was successfully achieved with a significant difference of activated clotting time between the blood samples from the systemic circulation and those from the ECMO circuit. These results indicate that this method overcomes several problems with ECMO, and has the capacity for long-term respiratory assistance.

Animals↗

PubMedDate not supplied

An electrohydraulic total artificial heart with a separately placed actuator.

An electrohydraulic total artificial heart (EHTAH) system, consisting of a separately placed actuator and blood pumps with good anatomic fit, was designed. In the actuator is a brushless DC motor sandwiched between two metal bellows or two pusher-plate pumps connected with the blood pumps by polyvinylchloride tubes. A roller-screw system coupled with the bellows is used for alternative pumping, and silicone oil transmits the action. The pumps are elliptical, and the right pump has a flatter and longer shape than the left to fit the extremely short distance between the right atrium and the sternum. To evaluate in vivo performance, the pumps were implanted as a pneumatic system in a calf weighing 53 kg and three goats weighing 54-55 kg. The pump fit well in the animals, and the calf survived for 111 days, and one goat was alive for 8 days. The EHTAH system could provide an output of 6 L/min with pusher-plate pumps as oil chambers on in vitro evaluation. This system could become one of the most suitable approaches for a totally implantable system.

Animals↗

PubMedDate not supplied

Chronic in vivo evaluation of a portable electrohydraulic ventricular assist system with a linear actuator.

Chronic experiments of the electrohydraulic ventricular assist system with a linear motor actuator were performed in two goats weighing 54 kg and 56 kg, and the system was used for more than 30 days. The actuator was designed to be fixed on the goat's back with a saddle. The pump was connected between the left atrium and descending aorta and placed paracorporeally on the chest wall. Linear action of an actuator bellows was delivered by silicone oil in a U-shaped polyvinylchloride tube to activate the pump. The maximum output in the 56 kg goat was 5.0 L/min. Goats could stand and sit freely. The first goat with a pusher-plate type pump died on the fifth day because of thromboembolism, but the second goat with a diaphragm type pump survived for 42 days. Blood chemistries remained within normal limits. Pump control was easy in both the duty-control mode and the stroke-control mode. With the automatic negative pressure control (ANPC) to prevent atrial wall sucking, the left atrial pressure was kept within +/- 10 mmHg, although left atrial pressure sometimes went below -80 mmHg without ANPC. Considering reliability, automaticity, and portability, the electrohydraulic ventricular assist system has become another choice for a practical, electrically driven ventricular assist system.

Animals↗

PubMedDate not supplied

Bioenergetic recovery processes of injured myocardium.

We employed cervically transplanted nonworking myocardium to simulate the condition of a heart supported by a ventricular assist device, and to investigate the bioenergetic recovery processes of injured myocardium with 31P nuclear magnetic resonance (NMR) techniques. A heterotopic graft was placed in the cervical portion of a recipient rat. One week later, a control 31P NMR spectrum was obtained from the graft. On the same day, the aorta of the graft was clamped for 30 minutes at room temperature. After this procedure, 31P NMR measurements of the graft were performed for 1 week. The phosphocreatine (PCr)/Inorganic phosphate (Pi) ratio, and beta-phosphate from adenosine triphosphate (beta-ATP)/Pi ratio on the first and second day after injury were significantly lower than control (p less than 0.05). However, these ratios recovered to a significant extent on the third and fourth day. These results suggest that 3 or 4 days are required for bioenergetic recovery of reversibly injured myocardium, even under nonworking conditions.

Adenosine Triphosphate↗

PubMedDate not supplied

A composite driving system for LVAS and IABP: practical and effective driving and weaning.

We have devised a new method, termed alternate synchronous driving (ASD), to wean patients from a left ventricular assist system (LVAS) to a pressure assist intraaortic balloon pump (IABP). We have built a new drive unit, VCT200, to apply ASD easily and automatically. After IABP insertion in the final weaning stage, this method drives the LVAS and IABP alternately, with electrocardiogram (ECG) synchronization. The pumping ratio of IABP increases while that of LVAS decreases according to recovery of natural heart function. In in vitro studies, ASD was effective when bypass flow (BF) was less than 50% of total flow (TF) (TF:BF + cardiac output [CO]), and its advantages increased under lower BF conditions. Mean aortic pressure (mAP) and CO increased 10 mmHg and 15%, respectively, with this method (IABP:LVAS = 1:1) when BF was 30% of TF. During in vivo studies, mAP increased 75.7 +/- 6.7 mmHg to 80.1 +/- 3.6 mmHg (p less than 0.001), and the CO increased from 3.1 +/- 0.5 L/min to 3.3 +/- 0.5 L/min (p less than 0.001), while the endocardial viability ratio (DPTI/TTI) increased 20-30%. This method was used in a 62-year-old man in which LVAS was applied after ventricular aneurysmectomy, BF was reduced from 2.2 L/min to 1.1 L/min by using ASD without any change in systemic perfusion. This reduction of BF could not be achieved with LVAS alone. From these data, this system could wean patients from LVAS and then switch to IABP smoothly, easily, and automatically, without hemodynamic instability.

Combined Modality Therapy↗

PubMedDate not supplied

Physiologic reactions of awake animals to an immediate switch from a pulsatile to nonpulsatile systemic circulation.

The purpose of this study is to clarify physiologic reactions to an immediate switch of flow pattern from pulsatile to nonpulsatile. A pulsatile ventricular assist device (VAD) was implanted in four 40-64 kg goats. Blood was drawn from the left atrium and ventricle and expelled into the aorta. After 2 weeks the VAD was quickly replaced by a centrifugal pump, MD-10 (Iwaki Pump, Tokyo, Japan), 760 g in weight and phi 70 mm x 84 mm in size, set on the back, without anesthesia. A 100% nonpulsatile bypass flow was immediately obtained, and the pump was set to maintain the same mean aortic pressure as before the switch; central venous pressure, cardiac output, systemic vascular resistance, oxygen consumption, blood lactate, plasma adrenalin, noradrenalin, renin activity, angiotensin II, and aldosterone were measured. Behavior of the goats did not change, and fluid infusion and higher cardiac outputs were not required. Most of the parameters did not deviate from control levels after the switch. In conclusion, a mammal immediately accommodates well to nonpulsatile flow.

Aldosterone↗

PubMedDate not supplied

A blood-liquid interface for prolonged extracorporeal oxygenation with excellent antithrombogenicity.

The authors verified the excellent antithrombogenicity of a blood-liquid interface (BLI) and introduced an oxygenator based on the principle of gas exchange across direct BLI. In a newly developed oxygenator, three layers of liquid flowed horizontally, contacting one another: O2 saturated silicone oil on the top, O2 saturated fluorcarbon at the bottom, and blood in the middle. Gas exchange was carried out across both direct BLIs. This system provided excellent antithrombogenicity as well as good gas exchange. The results indicate that this method will become a promising modality for prolonged extracorporeal oxygenation.

Blood Coagulation↗

PubMedDate not supplied

Thrombus in a natural left ventricle during left ventricular assist: another thromboembolic risk factor.

Systemic thromboembolism is one of the serious complications during use of a left ventricular assist system (LVAS). The authors' original LVAS has excellent antithrombogenicity to reduce this risk, but thrombus formation in a natural left ventricle (LV) is another risk factor for systemic embolization. We used our LVAS in 22 patients. Of these, LV wall motion was studied in 15, and a smoke-like echo disclosed thrombus in the LV in eight. When LVAS sufficiently supported the systemic circulation, LV wall motion was irregular upon closure of the aortic valve. Upon recovery of LV function and decrease of LVAS flow, the smoke-like echo diminished and LV thrombus decreased in one, but LV thrombus remained unchanged or increased in seven. Systemic administration of antithrombotic agents had an unclear effect. Seven of eight patients with LV thrombus on echo died during or after LVAS. In these seven, a high incidence of LV thrombus (71%), and systemic embolism to the brain (29%) or kidney (86%), were revealed at necropsy. We subsequently used local heparinization to prevent LV thrombus formation. One patient with a smoke-like echo had no evidence of LV thrombus or systemic embolism. During LV assist, careful management of the LVAS, and intra-LV heparinization should be considered to reduce the risk of thrombus formation in the natural LV.

Adult↗

PubMedDate not supplied

Altered humoral control of circulating volume during artificial circulation.

UNLABELLED: Plasma atrial natriuretic polypeptide (ANP) levels and plasma renin activity (PRA) were measured in six left ventricular assist device (LVAD) goats, four single artificial heart (SAH) goats, i.e., LVAD animals with fibrillated hearts, and 3 total artificial heart (TAH) calves. During the 4 week experiment, the ANP levels in the SAH goats increased to 516 pg/ml from the control value of 61.8 pg/ml because of an elevated CVP of 13-21 mmHg, while those of the LVAD goats were near the lower limit of the control values. The TAH calves had slightly decreased ANP levels at 23-46 pg/ml after the third postoperative week, which did not increase after the steep increase in CVP induced by the changes in the driving conditions. The PRA levels were 10-50 times higher than control in the SAH goats and a TAH calf whose CVP rose to 19 mmHg, although the cardiac output was within normal limits. IN CONCLUSION: 1) The secretion of ANP secondary to alteration in CVP was preserved in the LVAD recipients and enhanced diuresis, while it was compromised in the TAH cases. 2) The PRA levels in cases with elevated CVPs were high enough to suppress diuresis.

Animals↗