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Antithrombogenicity of extracorporeal membrane oxygenation (ECMO) devices, particularly oxygenators, is a current problem, with numerous studies and developments underway. However, there has been limited progress in developing methods to accurately compare the antithrombogenicity of oxygenators. Animal experiments are commonly conducted to evaluate the antithrombogenicity of devices; however, it is challenging to maintain a steady experimental environment. We propose an innovative experimental animal model to evaluate different devices in a constant experimental environment in real-time.This model uses two venous-arterial ECMO circuits attached to one animal (one by jugular vein and carotid artery, one by femoral vein and artery) and real-time assessment of thrombus formation in the oxygenator by indocyanine green (ICG) fluorescence imaging. Comparison studies were conducted using three pigs: one to compare different oxygenators (MERA vs. CAPIOX) (Case 1), and two to compare antithrombotic properties of the oxygenator (QUADROX) when used under different hydrodynamic conditions (continuous flow vs. pulsatile flow) (Cases 2 and 3).Thrombi, visualized using ICG imaging, appeared as black dots on a white background in each oxygenator. In Case 1, differences in the site of thrombus formation and rate of thrombus growth were observed in real-time in two oxygenators. In Case 2 and 3, the thrombus region was smaller in pulsatile than in continuous conditions.We devised an innovative experimental animal model for comparison of antithrombogenicity in ECMO circuits. This model enabled simultaneous evaluation of two different ECMO circuits under the same biological conditions and reduced the number of sacrificed experimental animals.

The purpose of this study was to observe and clarify the interventricular dysscynchrony caused by continuous-flow left ventricular assist device (CF-LVAD) support using the conductance method. During CF-LVAD support, the systolic phase of the left ventricle (LV) becomes shorter than that of the right ventricle (RV). Accordingly, timing of the systole and diastole during the cardiac cycle is not synchronous between the LV and RV. In this study, we evaluated this phenomenon in a normal heart model using the adult goat (n = 5, body weight 44.5 ± 2.9 kg). A centrifugal LVAD was implanted under general anesthesia. We inserted the conductance catheter into the RV and LV to obtain the pressure–volume relationship of the two ventricles simultaneously. We defined the dyssynchronous status as the sign (plus or minus) of the LV volume-change opposite to that of RV volume-change. Dyssynchronous phase of the cardiac cycle was observed in 5.6 ± 0.65% of hearts under LVAD pump-off and 25.3 ± 3.3% under LVAD full bypass, respectively (p

Under continuous-flow left ventricular assist device (CF-LVAD) support, the ventricular volume change and cardiac cycle between the left ventricle (LV) and right ventricle (RV) become dyssynchronous due to the shortening of the LV systole. The purpose of this study was to quantify interventricular dyssynchrony based on different CF-LVAD support conditions and assess its relationship with LV unloading. In this study, we evaluated seven goats (body weight 44.5 ± 6.5 kg) with normal hearts. A centrifugal LVAD was implanted under general anesthesia. We inserted the conductance catheters into the left ventricle (LV) and right ventricle (RV) to assess the volume signal simultaneously. We defined the interventricular dyssynchrony as a signal (increase or decrease) of LV volume (LVV) change opposite to that of RV volume (RVV) (i.e., (dLVV/dt) × (dRVV/dt)

Although the influence of continuous-flow left ventricular assist device (CF-LVAD) support on peripheral circulation has been widely discussed, its monitoring modalities are limited. The aim of this study was to assess the peripheral circulation using the laser speckle flowgraph (LSFG) which can quantitatively measure the ocular blood flow. We implanted a centrifugal CF-LVAD (EVAHEART®; Sun Medical Technology Research Corporation, Nagano, Japan) in five adult goats (body weight 44.5 ± 2.9 kg) under general anesthesia. The waveform of the central retinal artery using the mean blur rate (MBR) for ocular blood velocity and fluctuations as a parameter of pulsatility were obtained before LVAD implantation and after LVAD full-bypass support. The MBR waveform and LSFG fluctuation data were compared with the waveform and pulsatility index of the external carotid artery using an ultrasonic flow meter to evaluate circulatory patterns at different levels. The MBR waveform pattern of the central retinal artery was pulsatile before LVAD implantation and less pulsatile under LVAD full bypass. The fluctuation was 14.7 ± 1.86 before LVAD implantation and 3.85 ± 0.61 under LVAD full bypass (p

Background Bridge-to-decision (BTD) devices providing temporary mechanical circulatory support should be introduced to patients with advanced heart failure. This study evaluated the effectiveness and safety of a BTD device comprising an innovative extracorporeal continuous-flow temporary ventricular assist device (VAD) driven by a novel hydrodynamically levitated centrifugal flow blood pump.Methods and Results:Nine patients, comprising 3 with dilated cardiomyopathy, 3 with fulminant myocarditis, and 3 with ischemic heart disease, and 6 males, whose mean age was 47.7±8.1 years, were enrolled into the study. Six patients had Interagency Registry for Mechanically Assisted Circulatory Support profile 1, and 3 were profile 2. The primary endpoint was a composite of survival free from device-related serious adverse events and complications during circulatory support. Eight patients received left ventricular support, of whom 3 received concomitant right ventricular support using extracorporeal membrane oxygenation circuits, as a consequence of severe respiratory failure. One patient with fulminant myocarditis received biventricular support using the novel VAD system. After 19.0±13.5 days, 3 patients were weaned from circulatory support, because their native cardiac function recovered, and 6 patients required conversion to a durable device as a bridge-to-transplantation. One patient had non-disabling ischemic stroke episodes, and no patients died. Conclusions This novel extracorporeal VAD system with a hydrodynamically levitated centrifugal pump can safely and successfully bridge patients with advanced heart failure to subsequent therapeutic stages.

We have studied the cardiac beat synchronization (CBS) control for a rotary blood pump (RBP) and revealed that it can promote pulsatility and reduce cardiac load. Besides, patients with LVAD support sometimes suffer from aortic and mitral regurgitation (AR and MR). A control method for the RBP should be validated in wider range of conditions to clarify its benefits and pitfalls prior to clinical application. In this study, we evaluated pulsatility and cardiac load reduction obtained with the CBS control on valvular failure conditions with a mathematical model. Diastolic assist could reduce cardiac load on the left ventricle by decreasing external work of the ventricle even in MR cases while it was not so effective in AR cases. Systolic assist can still promote pulsatility in AR and MR cases; however, aortic valve function should be carefully confirmed since pulse pressure can be wider not due to systolic assist but to AR.

Introduction: Recently, the use of veno-venous extracorporeal membrane oxygenation for adult patients with severe acute respiratory failure has increased. We previously investigated the optimal return cannula position; however, the optimal drainage cannula position has not yet been fully clarified. The aim of this study was to investigate the optimal drainage cannula position. Methods: Veno-venous extracorporeal membrane oxygenation was performed in four adult goats (mean body weight 59.6 ± 0.6 kg). The position of the drainage cannula was varied among the right atrium, the upper inferior vena cava, and the lower inferior vena cava, whereas the position of the return cannula was fixed in the superior vena cava. The recirculation fraction and arterial oxygen saturation and pressure (SaO2, PaO2) were measured in all drainage cannula positions. Results: In the lower inferior vena cava drainage cannula position, the recirculation fraction was the lowest. In the lower inferior vena cava, upper inferior vena cava, and right atrium drainage cannula positions at 3 L/min, SaO2 and PaO2 after 20 min were 92.9% ± 4.9% and 75.1 ± 26.0 mm Hg, 99.5% ± 0.5% and 113.8 ± 20.9 mm Hg, and 93.8% ± 6.2% and 91.9 ± 17.7 mm Hg, respectively. Conclusion: With respect to blood oxygenation, the optimal position for the drainage cannula was the upper inferior vena cava. These findings suggested that blood from the superior vena cava, inferior vena cava, and hepatic vein was most efficiently drained in the upper inferior vena cava cannula position.

Aortic insufficiency (AI) is a crucial complication during continuous-flow left ventricular assist device (LVAD) support. Our previous clinical study suggested that a larger angle between the outflow graft and the aorta (O–A angle) could cause AI progression. This study examined the effect of the O–A angle on the hemodynamics of AI under LVAD support in an acute animal experimental model. An LVAD was installed in seven calves, with the inflow cannula inserted from the LV apex and with the outflow graft sutured at the ascending aorta. The AI model was made using a temporary inferior vena cava filter inserted from the LV apex and placed at the aortic valve. Cardiac dysfunction was induced by continuous beta-blocker infusion. Hemodynamic values and the myocardial oxygen extraction rate (O2ER) were evaluated at three O–A angles (45°, 90°, and 135°) over three levels of AI (none, Sellers I–II AI, and Sellers III–IV AI). The recirculation rate, defined as the percentage of regurgitation flow to LVAD output, was calculated. Systemic flow tended to decrease with a larger O–A angle. The recirculation rate was significantly increased with a larger O–A angle (22, 23, and 31% at 45°, 90°, and 135° in Sellers III–IV AI, respectively). Coronary artery flow was decreased at a larger O–A angle (86, 76 and 75 mL/min at 45°, 90°, and 135° in Sellers I–II AI, respectively, and 77, 67, and 56 mL/min at 45°, 90°, and 135° in Sellers III–IV AI, respectively). O2ER tended to increase with a larger O–A angle (40, 43, and 49% at 45°, 90°, and 135° in Sellers III–IV AI, respectively). A larger O–A angle can increase the recirculation due to AI and can be disadvantageous to LVAD-AI hemodynamics and myocardial oxygen metabolism.

In the development of a new device for extracorporeal circulation, long-term durability and biocompatibility are required. The CAPIOX SL Pump (SL pump, Terumo Corporation, Tokyo, Japan), which is a centrifugal pump using a two-pivot bearing, was developed with the hope of suppressing pump thrombus formation around the bearings. This study aimed to evaluate the in vivo performance of the SL pump in the condition assumed severe clinical situation for long-term extracorporeal membrane oxygenation (ECMO) support. Extracorporeal circulation using the SL pump was installed in three goats, with drainage from the inferior vena cava and infusion into the right jugular artery. The animals were maintained with target pump flow of 2.0-3.0 L/min for 3 or 7 days. Anticoagulation was performed by continuous infusion of heparin with a target activated coagulation time (ACT) of 200 ± 50 s. Blood tests were performed regularly. After 3 or 7 days, autopsies were performed on all animals. The pumps were disassembled and observed for thrombus formation. The results were compared with those of our previous study of the current model of the centrifugal pump (SP pump). All animals were successfully managed within target pump flows and ACT values during the scheduled period, with no adverse events. No thrombus formation was found around the bearing of the SL pump. The blood tests showed normal major organ functions, and platelet consumption and hemolysis were significantly lower in this study compared to the previous study of the SP pump. The CAPIOX SL Pump showed excellent durability and biocompatibility in a large animal experiment.

Several species of domestic animals are used in preclinical studies evaluating the safety and feasibility of medical devices; however, the relevance of animal models to human health is often not clear. The purpose of this study was to compare the clotting parameters of animal models to determine which animals most adequately mimic human clotting parameters. The clotting parameters of the different species were assessed in whole blood by in vitro thromboelastography using the clotting activators, such as tissue factor (extrinsic clotting screening test, EXTEM®) and partial thromboplastin phospholipid (intrinsic clotting screening test, IINTEM®). The measurements were performed using normal blood samples from humans (n = 13), calves (n = 18), goats (n = 56) and pigs (n = 8). Extrinsic clotting time (CT) and the intrinsic CT were significantly prolonged in calves compared to humans (249.9 ± 91.3 and 376.4 ± 124.4 s vs. 63.5 ± 11.8 and 192.5 ± 29.0 s, respectively, p

Objectives Continuous-flow left ventricular assist devices (CF-LVADs) are widely used to treat patients with end-stage heart failure. Although continuous flow is different from physiological flow, patients show improved outcomes after CF-LVAD implantation. A novel rotational speed (RS) modulation system used with CF-LVAD (EVAHEART) has been developed, which can change RS in synchronization with the native cardiac cycle. We conducted the present study to investigate the influence of the system on pulsatility in peripheral perfusion. Methods We implanted EVAHEART devices at the left ventricular apex drainage and the descending aortic perfusion via a left thoracotomy in 7 adult goats (56.8 ± 8.1 kg). Cardiogenic shock was induced by a beta-adrenergic antagonist. We evaluated the pulsatility index and maximal time derivative of flow rate (max dQ/dt) of the carotid, mesenteric and renal arteries. These data were collected with a bypass rate of 100% under 4 conditions: circuit clamp, continuous mode, co-pulse mode (increased RS during systole) and counter-pulse mode (increased RS during diastole). Results The pulsatility indexes of the carotid and renal artery in the co-pulse mode were significantly higher than in the other modes. Max dQ/dt of the carotid and mesenteric arteries were significantly higher in the co-pulse mode than in the counter-pulse mode. Conclusions The co-pulse mode of this novel RS modulation system may provide better pulsatility not only in the large vessels but also in the peripheral vasculature.

Aortic valve regurgitation (AR) is a serious complication under left ventricular assist device (LVAD) support. AR causes LVAD-left ventricular (LV) recirculation, which makes it difficult to continue LVAD support. However, the hemodynamics and myocardial oxygen metabolism of LVAD support with AR have not been clarified, especially, how pump rotation speed influences them. An animal model of LVAD with AR was newly developed, and how pump rotation speed influences hemodynamics and myocardial oxygen metabolism was examined in acute animal experiments. Five goats (55 ± 9.3 kg) underwent centrifugal type LVAD, EVAHEART implantation. The AR model was established by placing a vena cava filter in the aortic valve. Hemodynamic values and the myocardial oxygen consumption, delivery, and oxygen extraction ratio (O2ER) were evaluated with changing pump rotation speeds with or without AR (AR+, AR-). AR+ was defined as Sellers classification 3 or greater. AR was successfully induced in five goats. Diastolic aortic pressure was significantly lower in AR+ than AR- (p = 0.026). Central venous pressure, mean left atrial pressure, and diastolic left ventricular pressure were significantly higher in AR+ than AR- (p = 0.010, 0.047, and 0.0083, respectively). Although systemic flow did not improve with increasing pump rotation speed, LVAD pump flow increased over systemic flow in AR+, which meant increasing pump rotation speed increased LVAD-LV recirculation and did not contribute to effective systemic circulation. O2ER in AR- decreased with increasing pump rotation speed, but O2ER in AR+ was hard to decrease. The O2ER in AR+ correlated positively with the flow rate of LVAD-LV recirculation (p = 0.012). AR caused LVAD-LV recirculation that interfered with the cardiac assistance of LVAD support and made it ineffective to manage with high pump rotation speed.

Although the innovation has come in ECMO field, many problems remain unresolved. One of the main problems is about long-term durability and biocompatibility. Another is the system’s size, weight, and its complicated equipment. For the former problem, we have previously developed ECMO system which consists of a tiny, hydrodynamically levitated centrifugal pump (BIOFLOAT-NCVC), a membrane oxygenator with hollow polyolefin fibers (BIOCUBE-NCVC), and the circuit treated with a heparin-bonding material (T-NCVC coating), and reported three cases of animal experiments for 30-day heparin-free drive. For the latter problem, we have integrated these elements to the compact system with sensors of temperature, pressure, and SvO2, and blood flow. Its installation area is 595 cm2, weighs 8.9 kg with attachable oxygen cassette, and battery which could last an hour at least. To evaluate the biocompatibility of this system, this ECMO was installed in four goats. Scheduled duration was 14 days. Heparin was continuously infused to control their ACT between 150 and 200 s except one 2-week experiment without systemic heparinization. All of the four goats survived till the scheduled termination. Function of the pump and the oxygenator during ECMO was stable. No obvious adverse events were observed. All lab data were of normal range after 1 week. Small infarctions were found at kidneys, but they were not clinically significant. No thrombus was found in the pump system. The oxygenators were extremely clean except a little thrombus formation; while, the heparin-free examination revealed acceptable cleanliness. The present study revealed good anti-thrombogenicity of this ultra-compact durable ECMO system with heparinization. Our system encourages awake and extubated management, rehabilitation, inter-hospital transfer, and prehospital initiation of ECMO.

Background We are developing a novel autologous tissue-engineered heart valve with a unique in-body tissue engineering. This is expected to be a viable bioprosthesis keeping better biocompatibility. Purpose We developed a conduit-type valve without any foreign materials and tested the feasibility and long-term availability in large animal experiments. Methods We created plastic molds for Biovalves with 3D printer easily and quickly considering the recipient character. We embedded them in the subcutaneous spaces of adult goats about 2 months. After extracting the molds with the tissue en-block and removing the plastic molds only, Biovalve with tri-leaflets similar to those of the native valves were constituted from completely autologous connective tissues and fibroblasts. Total 21 conduit-type Biovalves were implanted in the apico-aortic bypass or the pulmonary artery of goats, (8 and 13, respectively). No anticoagurants were used after implantation. Results The valves were successfully implanted and showed smooth movement of the leaflets with a little regurgitation in angiogram, and the maximum duration reached to 3 years 7 months. Histological examination of the Biovalves showed the autologous cells covering the laminar surface of the valve leaflets as the endothelium and also getting inside to construct characteristic tissues like native leaflets. Conclusion The valves have a potential to be used for viable bioprosthetic valves and to keep better function and biocompatibility longer than current ones.

Continuous-flow left ventricular assist devices (LVADs) have improved the prognosis of end-stage heart failure. However, continuous-flow LVADs diminish pulsatility, which possibly result in bleeding, aortic insufficiency, and other adverse effects. We previously developed a novel control system for a continuous-flow LVAD (EVAHEART®; Sun Medical), and demonstrated that we could create sufficient pulsatility by increasing its rotational speed (RS) in the systolic phase (Pulsatile Mode) in the normal heart model. Here, we aimed to evaluate differences between systolic assist with advanced and delayed loads by shifting the timing of increased RS. We implanted EVAHEART in six goats (55.3 ± 4.3 kg) with normal hearts. We reduced their heart rates to

This study evaluates a newly designed autologous heart valve-shaped tissue with a stent [stent-biovalve (SBV)] for transcatheter pulmonary valve implantation using the "in-body tissue architecture" technology. In the previously developed SBV with flat-shaped leaflets (FS-SBV), the valve could not close rapidly, because the leaflets were fixed in the open position, which induced regurgitant volume in the closing phase. Therefore, a novel mold to fabricate an SBV with round-shaped leaflets (RS-SBV) was developed, and its hydrodynamic performance with different valve diameters was evaluated in this study. A specially designed, self-expandable, stent-mounted, acrylic mold, which has 3 hemispheres, was placed in dorsal subcutaneous pouches of goats for 2 months. After extraction, the acrylic mold was removed from the implant, and a tubular tissue impregnated with the stent strut was obtained. Half of the tubular tissue with 3 hemispheres was completely folded in half inwards. The acrylic mold was designed, such that the folded half of the tubular tissue became the round-shaped leaflets. The 3 commissure parts were connected to form 3 leaflets, resulting in the preparation of the RS-SBV (internal diameter 25 mm). The RS-SBV closed more rapidly than the FS-SBV in a pulsatile mock circulation circuit under the pulmonary circulation conditions. The regurgitant fraction of the RS-SBV was approximately 6 %, which was lower than that of the FS-SBV. The appropriate pulmonary annulus diameter of the RS-SBV was from 24 to 25 mm based on the pressure difference and effective orifice area.

Excessive left ventricular (LV) volume unloading can affect right ventricular (RV) function by causing a leftward shift of the interventricular septum in patients with mitral regurgitation (MR) receiving left ventricular assist device (LVAD) support. Optimal settings for the LVAD should be chosen to appropriately control the MR without causing RV dysfunction. In this study, we assessed the utility of our electrocardiogram-synchronized rotational speed (RS) modulation system along with a continuous-flow LVAD in a goat model of MR. We implanted EVAHEART devices after left thoracotomy in six adult goats weighing 66.4 ± 10.7 kg. Severe MR was induced through inflation of a temporary inferior vena cava filter placed within the mitral valve. We evaluated total flow (TF; the sum of aortic flow and pump flow [PF]), RV fractional area change (RVFAC) calculated by echocardiography, left atrial pressure (LAP), LV end-diastolic pressure (LVEDP), LV end-diastolic volume (LVEDV), and LV stroke work (LVSW) with a bypass rate (PF divided by TF) of 100% under four conditions: circuit-clamp, continuous mode, co-pulse mode (increased RS during systole), and counter-pulse mode (increased RS during diastole). TF tended to be higher in the counter-pulse mode. Moreover, RVFAC was significantly higher in the counter-pulse mode than in the co-pulse mode, whereas LAP was significantly lower in all driving modes than in the circuit-clamp condition. Furthermore, LVEDP, LVEDV, and LVSW were significantly lower in the counter-pulse mode than in the circuit-clamp condition. The counter-pulse mode of our RS modulation system used with a continuous-flow LVAD may offer favorable control of MR while minimizing RV dysfunction.

We have previously developed a native heart load control system for a continuous-flow left ventricular assist device (LVAD) ((EVAHEART®; Sun Medical) and demonstrated that the rotational speed (RS) in synchronization with the cardiac cycle can alter pulsatility and left ventricular (LV) load under general anesthesia. In this study, we assessed the effects of different levels of increase in RS on pulsatility and LV load in the chronic awake phase. We implanted the EVAHEART via left thoracotomy in 7 normal goats (59.3 ± 4.6 kg). Two weeks after implantation, we examined the effects of co-pulse mode (increased RS in the systolic phase) and counter-pulse mode (increased RS in the diastolic phase), as well as shifting the change in RS from 250 to 500 rpm, and 750 rpm in both modes on pulsatility and LV load. Pulsatility was assessed using pulse pressure and mean dP/dt max of aortic pressure. LV load was assessed using stroke work and left ventricle end-diastolic volume determined from LV pressure–volume loops. In the co-pulse mode, pulsatility values increased as the change in RS increased. By contrast, in the counter-pulse mode, these values decreased as the change in RS increased. LV load increased significantly in the co-pulse mode compared with the counter-pulse mode, but there were no significant differences among the three levels of RS increase in either mode. Increasing RS to varying degrees with our newly developed system could contribute to pulsatility. However, it appeared to have little effect on LV load in normal hearts.

A cardiopulmonary bypass (CPB) can preserve life. However, interactions between blood and large artificial surfaces might help to provoke a series of chain reactions during CPB that result in the formation and release of numerous powerful inflammatory mediators including hormones and autacoids. We postulated that small CPB circuits with reduced priming volumes and less surface areas that come into contact with blood would attenuate systemic inflammatory responses by reducing the levels of cytokines and organ tissue damage during CPB. Rats were assigned to groups that underwent CPB with a high priming volume (PV) of 15 ml and a surface area of 0.044 m or a low PV of 7 ml and a surface area of 0.034 m. We measured serum levels of cytokines and biochemical markers during CPB. Levels of proinflammatory cytokines and biochemical markers were significantly elevated in the group with a high PV, than low PV at 60 min, whereas none of these factors significantly differed between the groups at 120 min. These data suggested that in addition to blood being in contact with surfaces, the duration of CPB exposure is also an important factor for nonlinear time variances in damage caused by the systemic inflammatory response.

We studied a control method of rotary blood pumps (RBPs), which is called as the cardiac beat synchronization (CBS) system. Usually, RBPs operate at constant target rotational speed, meanwhile, the CBS system modulates target speed synchronizing with cardiac beat. We built a computer simulation method to evaluate the CBS system. This simulator acquires a mathematical model of a circulatory system including a RBP and can provide us the theoretical hemodynamics when our control method is applied. We compared theoretical results with experimental ones with the model focusing on both pulsatility and aortic valve (AV) opening interval enhanced by the CBS system. Our simulator could reproduce behavior of the circulatory system whether the RBP is connected or not. Comparison among no RBP, constant assist, systolic assist, and diastolic assist modes indicated that pulsatility is enhanced with systolic assist theoretically. While systolic assist decreased AV opening interval, diastolic assist made it longer than the ones in other control strategies.

We developed a novel miniaturized extracorporeal centrifugal pump "BIOFLOAT NCVC (Nipro Corporation Osaka, Japan) as a ventricular assist device (VAD) and performed a preclinical study that is part of the process for its approval as a bridge to decision by the pharmaceutical and medical device agencies. The aim of this study was to assess the postoperative performance, hemocompatibility, and anticoagulative status during an extended period of its use. A VAD system, consisting of a hydrodynamically levitated pump, measuring 64 mm by 131 mm in size and weighing 635 g, was used. We installed this assist system in 9 adult calves (body weight, 90 ± 13 kg): as left ventricular assist device (LVAD) in 6 calves and right ventricular assist device (RVAD) in 3 calves, for over 30 days. Perioperative hemodynamic, hematologic, and blood chemistry measurements were obtained and end-organ effects on necropsy were investigated. All calves survived for over 30 days, with a good general condition. The blood pump was operated at a mean rotational speed and a mean pump flow of 3482 ± 192 rpm and 4.08 ± 0.15 L/min, respectively, for the LVAD and 3902 ± 210 rpm and 4.24 ± 0.3 L/min, respectively, for the RVAD. Major adverse events, including neurological or respiratory complications, bleeding events, and infection were not observed. This novel VAD enabled a long-term support with consistent and satisfactory hemodynamic performance and hemocompatibility in the calf model. The hemodynamic performance, hemocompatibility, and anticoagulative status of this VAD system were reviewed.

Tissue-engineered heart valves (TEHVs) are expected to be viable grafts. However, it is unknown whether they transit their histological structure after implantation. We developed a novel autologous TEHV (named stent biovalve) for transcatheter implantation, using in-body tissue engineering based on a tissue encapsulation phenomenon. In this study, a time-course histological transition of implanted biovalves was investigated in goats. Three types of stent biovalves were prepared by 2 month embedding of plastic molds mounted with metallic stents, in the subcutaneous spaces. After extracting the molds with tissue and removing the molds only, stent biovalves were constituted entirely from the connective tissues. Stent biovalves were implanted in the aortic or pulmonary valve position of other goats with transcatheter technique. In each animal, the stent biovalve was explanted at 1 month step (from 1 to 6 months) or as long as possible. Total 12 goats (five for aortic and seven for pulmonary) were successfully implanted. The maximum duration became 19 months as a result. Even then the leaflets of the biovalves kept their shape and elasticity, and neither calcification nor thrombi were observed in any cases and duration. Histology showed the recipients' cells covering the laminar surface of the leaflets like the endothelium even after 1 month. The cells have also migrated in the leaflets gradually and finally constructed characteristic 3 layered tissues like native leaflets. Implanted stent biovalves can adapt their histological structure to the environment. They have a potential as viable grafts keeping better function and biocompatibility.

Purpose Mechanical circulatory support devices are needed to enable recovery or provide a bridge to decision for patients with heart failure. The effectiveness of extending treatment duration in this therapy was previously reported to increase adverse events, such as acquired von Willebrand disease and gastrointestinal bleeding. Blood-related damage caused by medical devices is one of the most critical parameters needed to determine the performance of medical devices. For the treatment of these complications, we considered that it is very important to analyze the relationship between the cleavage of von Willebrand factor (VWF) due to shear stress and re-supply of VWF from activated platelets during blood pump circulation. We aimed to examine the alterations in the dynamics of VWF multimers in the circulating blood during VAD therapy. Methods In this study, two types (axial and centrifugal) of implantable blood pumps and a disposable blood pump (centrifugal type) for temporary use were used. A simple mock circulation test (5L/min, 100 mmHg) was performed to investigate with both whole-blood samples and platelet-poor plasma (PPP) using fresh bovine blood. Results In an analysis based on SDS-agarose gel electrophoresis and serum VWF values (antigen and activity), high-molecular-weight multimers (HMWMs) in VWF are reduced immediately after the initiation of blood circulation using the axial flow pump, and it had plateaued 60 minutes later. On the other hand, in the study using a centrifugal pump, cleavage of the HMWMs compared to that in the case of using a centrifugal pump was very slight. Moreover, in the whole-blood sample study, HMWMs reduced once, and it had been observed to recover after 60 minutes. However, HMWMs in the PPP sample was observed to reduce continuously during a circulation test. Conclusion In this result, the dynamics of VWF within the blood pump was shown to depend on the type of the blood pump, and this study demonstrated that re-supply of VWF due to platelet activation and cleavage of VWF due to shear stress in the pump occurred at the same time by circulating within the blood pump.

We have developed a rotational speed (RS) modulation system for a continuous-flow left ventricular assist device (EVAHEART) that can change RS in synchronization with a patient's electrocardiogram. Although EVAHEART is considered not to cause significant acquired von Willebrand syndrome, there remains a concern that the repeated acceleration and deceleration of the impeller may degrade von Willebrand factor (vWF) multimers. Accordingly, we evaluated the influence of our RS modulation system on vWF dynamics. A simple mock circulation was used. The circulation was filled with whole bovine blood (650 mL), and the temperature was maintained at 37 ± 1°C. EVAHEART was operated using the electrocardiogram-synchronized RS modulation system with an RS variance of 500 rpm and a pulse frequency of 60 bpm (EVA-RSM; n = 4). The pumps were operated at a mean flow rate of 5.0 ± 0.2 L/min against a mean pressure head of 100 ± 3 mm Hg. The continuous-flow mode of EVAHEART (EVA-C; n = 4) and ROTAFLOW (ROTA; n = 4) was used as controls. Whole blood samples were collected at baseline and every 60 min for 6 h. Complete blood counts (CBCs), normalized indexes of hemolysis (NIH), vWF antigen (vWF:Ag), vWF ristocetin cofactor (vWF:Rco), the ratio of vWF:Rco to vWF:Ag (Rco/Ag), and high molecular weight multimers (HMWM) of vWF were evaluated. There were no significant changes in CBCs throughout the 6-h test period in any group. NIH levels of EVA-RSM, EVA-C, and ROTA were 0.0035 ± 0.0018, 0.0031 ± 0.0007, and 0.0022 ± 0.0011 g/100 L, respectively. Levels of vWF:Ag, vWF:Rco, and Rco/Ag did not change significantly during the test. Immunoblotting analysis of vWF multimers showed slight degradation of HMWM in all groups, but there were no significant differences between groups in the ratios of HMWM to low molecular weight multimers, calculated by densitometry. This study suggests that our RS modulation system used with EVAHEART does not have marked adverse influences on vWF dynamics. The low NIH and the absence of significant decreases in CBCs indicate that EVAHEART is hemocompatible, regardless of whether it is operated with the RS modulation system.

We previously developed a novel control system for a continuous-flow left ventricular assist device (LVAD), the EVAHEART, and demonstrated that sufficient pulsatility can be created by increasing its rotational speed in the systolic phase (pulsatile mode) in a normal heart animal model. In the present study, we assessed this system in its reliability and ability to follow heart rate variability. We implanted an EVAHEART via left thoracotomy into five goats for the Study for Fixed Heart Rate with ventricular pacing at 80, 100, 120 and 140 beats/min and six goats for the Study for native heart rhythm. We tested three modes: the circuit clamp, the continuous mode and the pulsatile mode. In the pulsatile mode, rotational speed was increased during the initial 35 % of the RR interval by automatic control based on the electrocardiogram. Pulsatility was evaluated by pulse pressure and dP/dt max of aortic pressure. As a result, comparing the pulsatile mode with the continuous mode, the pulse pressure was 28.5 ± 5.7 vs. 20.3 ± 7.9 mmHg, mean dP/dt max was 775.0 ± 230.5 vs 442.4 ± 184.7 mmHg/s at 80 bpm in the study for fixed heart rate, respectively (P

Completely autologous in vivo tissue-engineered connective tissue tubes (Biotubes) have promise as arterial vascular grafts in animal implantation studies. In this clinical study of patients undergoing peritoneal dialysis (PD) (n = 11; age: 39-83 years), we evaluated human Biotubes' (h-Biotubes) mechanical properties to determine whether Biotubes with feasibility as vascular grafts could be formed in human bodies. We extracted PD catheters, embedded for 4-47 months, and obtained tubular connective tissues as h-Biotubes (internal diameter: 5 mm) from around the catheter' silicone tubular parts. h-Biotubes were composed mainly of collagen with smooth luminal surfaces. The average wall thickness was 278 ± 178 μm. No relationship was founded between the tubes' mechanical properties and patients' ages or PD catheter embedding periods statistically. However, the elastic modulus (2459 ± 970 kPa) and tensile strength (623 ± 314 g) of h-Biotubes were more than twice as great as those from animal Biotubes, formed from the same PD catheters by embedding in the beagle subcutaneous pouches for 1 month, or beagle arteries. The burst strength (6338 ± 1106 mmHg) of h-Biotubes was almost the same as that of the beagle thoracic or abdominal aorta. h-Biotubes could be formed in humans over a 4-month embedding period, and they satisfied the mechanical requirements for application as vascular grafts. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1431-1437, 2016.

We have been developing an autologous heart valve-shaped tissue with a stent (stent-biovalve) for transcatheter pulmonary valve implantation (TPVI) using “in-body tissue architecture” technology. In this study, the hydrodynamic performance of a stent-biovalve with tubular leaflets was evaluated by changing its leaflet height in an in vitro test in order to determine the appropriate stent-biovalve form for the pulmonary valve. A specially designed, self-expandable, stent-mounted, cylindrical acrylic mold was placed in a dorsal subcutaneous pouch of goat, and the implant was extracted 2 months later. Only the cylindrical acrylic mold was removed from the implant, and a tubular hollow structure of membranous connective tissue impregnated with the stent strut was obtained. Half of tubular tissue was completely folded in half inwards, and 3 commissure parts were connected to form 3 leaflets, resulting in the preparation of a stent-biovalve with tubular leaflets (25-mm ID). The stent-biovalve with adjusting leaflet height (13, 14, 15, 17, 20, and 25 mm) was fixed to a specially designed pulsatile mock circulation circuit under pulmonary valve conditions using 37 °C saline. The mean pressure difference and effective orifice area were better than those of the biological valve. The lowest and highest leaflet heights had a high regurgitation rate due to lack of coaptation or prevention of leaflet movement, respectively. The lowest regurgitation (ca. 11 %) was observed at a height of 15 mm. The leaflet height was found to significantly affect the hydrodynamics of stent-biovalves, and the existence of an appropriate leaflet height became clear.

An extracorporeal centrifugal blood pump with a hydrodynamically levitated impeller was developed for use in a durable extracorporeal membrane oxygenation (ECMO) system. The present study examined the biocompatibility of the blood pump during long-term use by conducting a series of 30-day chronic animal experiments. The ECMO system was used to produce a percutaneous venoarterial bypass between the venae cavae and carotid artery in adult goats. No anticoagulation or antiplatelet therapy was administered during the experiments. Three out of four animals survived for the scheduled 30-day period, and the blood pumps and membrane oxygenators both exhibited sufficient hydrodynamic performance and good antithrombogenicity, while one animal died of massive bleeding from the outflow cannulation site. The animals' plasma free hemoglobin had returned to within the normal range by 1 week after the surgical intervention, and their hemodynamic and biochemistry parameters remained within their normal ranges throughout the experiment. The explanted centrifugal blood pumps did not display any trace of thrombus formation. Based on the biocompatibility demonstrated in this study, the examined centrifugal blood pump, which includes a hydrodynamically levitated impeller, is suitable for use in durable ECMO systems.

Aortic insufficiency (AI) is an intractable complication during long term left ventricular assist device (LVAD) support. Conventional evaluation of AI depends on ultrasound evaluation, which is mainly a qualitative, not a quantitative method. The pathophysiology of AI during LVAD is shunt formation. Conversely, the methods to quantify the shunt of congenital heart disease are already established, and among these is the thermodilution technique. To develop an accurate quantification method for AI (namely, a shunt), we have adopted this conventional thermodilution technique. The purpose of this study was to determine whether this technique could calculate the shunt magnitude accurately in a simulated cardiac circuit. The magnitude of AI was represented by the recirculation rate (RR), defined by regurgitant flow (RF) divided by pump flow (PF). A mock circulatory system for an LVAD endurance test (Laboheart NCVC; Iwaki & Co., Ltd, Tokyo, Japan) was used. A centrifugal LVAD was equipped in the Laboheart in parallel from the left ventricle to the aorta. A parallel shunt circuit was created across the aortic valve to mimic AI. To control the magnitude of AI, the resistance of the AI circuit was changed. Heart failure was simulated by controlling the parameters of the Laboheart. The LVAD was driven in full bypass condition, confirming that the heart did not eject forward flow via the aortic valve. PF, RF, and the temperatures of two points of the outflow graft measured with two thermistors were monitored. Analyses were started after confirming that circuit water temperature was the same as room temperature. Hot water was injected from a port between the two thermistors of the outflow conduit. The time-temperature curves of both thermistors were recorded, and RR was calculated. Two values of RR calculated in two different ways (by analyzing thermistors and by calculating from flowmeter values) were compared. Multiple measurements were done by changing the magnitude of AI. The existence of AI could be easily confirmed by analyzing the temperature data. There was a good correlation between RR by thermistor and RR by flowmeter data (r = 0.984). Furthermore, the two RR values were almost the same. This novel technique could provide an accurate method for quantifying AI during LVAD support. This method can be clinically applied by left-sided cardiac catheterization if a dedicated catheter with two thermistors and an injection hole is developed.

In this study, self-expanding valved stents were prepared by in-body tissue architecture technology. As molds, plastic rods (outer diameter; 14 or 25 mm), mounted with specially designed self-expanding stents, whose strut was a combination of two wavy rings and three pillars, were embedded into the subcutaneous pouches of goats or beagles for 1 month. Upon harvesting, the molds were fully encapsulated with membranous connective tissues, in which the stent strut was completely embedded. The tubular tissues with the stents were obtained by removing the internal rods. About a half of the tubular tissues as a leaflet part was folded inside the remaining tubular tissues having ring strut as a conduit part. When the overlapped tubular tissues were fixed at the three pillars, two different-sized self-expanding valved stents (internal diameter; 14 or 25 mm) with autologous tubular leaflet tissues were obtained as Stent-Biovales. After shape formation of the leaflets at the closed form, regurgitation rate was approximately 5 and 22 % at pulmonary and aortic condition, respectively. The Stent-Biovalves developed here may be useful as a heart valve for patients undergoing transcatheter heart valve implantation.

We developed an autologous, trileaflet tissue valve ("biovalve") using in-body tissue architecture technology to overcome the disadvantages of current bioprosthetic valves. We designed a novel biovalve with a balloon-expandable stent: the stent biovalve (SBV). This study evaluated the technical feasibility of sutureless aortic valve replacement using the SBV in an orthotopic position, as well as the functionality of the SBV under systemic circulation, in an acute experimental goat model. Three adult goats (54.5-56.1 kg) underwent sutureless AVR under cardiopulmonary bypass (CPB). The technical feasibility and functionality of the SBVs were assessed using angiography, pressure catheterization, and two-dimensional echocardiography. The sutureless AVR was successful in all goats, and all animals could be weaned off CPB. The mean aortic cross-clamp time was 45 min. Angiogram, after weaning the animals off CPB, showed less than mild paravalvular leakage and central leakage was not detected in any of the goats. The mean peak-to-peak pressure gradient was 6.3 ± 5.0 mmHg. Epicardial two-dimensional echocardiograms showed smooth leaflet movement, including adequate closed positions with good coaptation; the open position demonstrated a large orifice area (average aortic valve area 2.4 ± 0.1 cm2). Sutureless AVR, using SBVs, was feasible in a goat model. The early valvular functionalities of the SBV were sufficient; future long-term experiments are needed to evaluate its durability and histological regeneration potential.

Aortic insufficiency (AI) is a worrisome complication under left ventricular assist device (LVAD) support. AI progression causes LVAD-left ventricular (LV) recirculation and can require surgical intervention to the aortic valve. However, the limitations of LVAD support are not well known. Using an animal model of LVAD with AI, the effect of AI progression on hemodynamics and myocardial oxygen metabolism were investigated. Five goats (Saanen 48 ± 2 kg) underwent centrifugal type LVAD, EVAHEART, implantation. The AI model was established by placing a vena cava filter in the aortic valve. Cardiac dysfunction was induced by continuous beta-blockade (esmolol) infusion. Hemodynamic values and myocardial oxygen extraction ratio (O2ER) were evaluated while changing the degree of AI which was expressed as the flow rate of LVAD-LV recirculation (recirculation rate). Diastolic aortic pressure was decreased with AI progression and correlated negatively with the recirculation rate (p = 0.00055). Systolic left ventricular pressure (LVP) and mean left atrial pressure (LAP) were increased with AI progression and correlated positively with the recirculation rate (p = 0.010, 0.023, respectively). LVP and LAP showed marked exponential increases when the recirculation rate surpassed 40%. O2ER was also increased with AI progression and had a significant positive correlation with the recirculation rate (p = 0.000043). O2ER was increased linearly, with no exponential increase. AI progression made it difficult to reduce the cardiac pressure load, worsening myocardial oxygen metabolism. The exponential increase of left heart pressures could be the key to know the limitation of LVAD support against AI progression.

In the development of a new device for extracorporeal circulation, long-term durability and biocompatibility are required. The CAPIOX SL Pump (SL pump, Terumo Corporation, Tokyo, Japan), which is a centrifugal pump using a two-pivot bearing, was developed with the hope of suppressing pump thrombus formation around the bearings. This study aimed to evaluate the in vivo performance of the SL pump in the condition assumed severe clinical situation for long-term extracorporeal membrane oxygenation (ECMO) support. Extracorporeal circulation using the SL pump was installed in three goats, with drainage from the inferior vena cava and infusion into the right jugular artery. The animals were maintained with target pump flow of 2.0-3.0 L/min for 3 or 7 days. Anticoagulation was performed by continuous infusion of heparin with a target activated coagulation time (ACT) of 200 ± 50 s. Blood tests were performed regularly. After 3 or 7 days, autopsies were performed on all animals. The pumps were disassembled and observed for thrombus formation. The results were compared with those of our previous study of the current model of the centrifugal pump (SP pump). All animals were successfully managed within target pump flows and ACT values during the scheduled period, with no adverse events. No thrombus formation was found around the bearing of the SL pump. The blood tests showed normal major organ functions, and platelet consumption and hemolysis were significantly lower in this study compared to the previous study of the SP pump. The CAPIOX SL Pump showed excellent durability and biocompatibility in a large animal experiment.

Although the outcomes of patients with end-stage heart failure treated with implantable left ventricular assist devices have improved, extracorporeal left ventricular assist devices continue to play an important role, especially in pediatric patients. The present study aimed to examine the long-term biocompatibility of a small-sized extracorporeal pneumatic left ventricular assist device (NIPRO-LVAD) used in a 30- to 90-day animal experiment. The NIPRO-LVAD was designed for pediatric patients or small-sized adults. The left ventricular assist device system was installed in four adult Shiba goats weighing 25.7 ± 4.78 kg via a left thoracotomy. The outflow graft was sewn to the descending aorta and the inflow cannula was placed in the left ventricle through the left ventricular apex. Oral antiplatelet (aspirin) and oral anticoagulation therapies (warfarin) were also administered. Three out of four animals survived for a 30-day period and two goats survived for 90 days. One animal was killed early because of low pump flow due to obstruction of the inflow cannula by a left ventricular endocardial vegetation. The blood pump exhibited sufficient hydrodynamic performance with blood flows of 1.5–2.0 L/min. The animals’ laboratory values were within normal limits by postoperative day 7. There was no significant thrombus formation on the housing, diaphragm, or valves of the explanted pumps. Based on the biocompatibility demonstrated in this animal study, the explanted small-sized pump may be suitable for use in left ventricular assist device systems for pediatric patients.

The management of heart failure patients presenting in a moribund state remains challenging, despite significant advances in the field of ventricular assist systems. Bridge to decision involves using temporary devices to stabilize the hemodynamic state of such patients while further assessment is performed and a decision can be made regarding patient management. We developed a new temporary left ventricular assist system employing a disposable centrifugal pump with a hydrodynamically levitated bearing. We used three adult goats (body weight, 58–68 kg) to investigate the 30-day performance and hemocompatibility of the newly developed left ventricular assist system, which included the pump, inflow and outflow cannulas, the extracorporeal circuit, and connectors. Hemodynamic, hematologic, and blood chemistry measurements were investigated as well as end-organ effect on necropsy. All goats survived for 30 days in good general condition. The blood pump was operated at a rotational speed of 3000–4500 rpm and a mean pump flow of 3.2 ± 0.6 L min. Excess hemolysis, observed in one goat, was due to the inadequate increase in pump rotational speed in response to drainage insufficiency caused by continuous contact of the inflow cannula tip with the left ventricular septal wall in the early days after surgery. At necropsy, no thrombus was noted in the pump, and no damage caused by mechanical contact was found on the bearing. The newly developed temporary left ventricular assist system using a disposable centrifugal pump with hydrodynamic bearing demonstrated consistent and satisfactory hemodynamic performance and hemocompatibility in the goat model.

Our research institute has been working on the development of a compact wearable drive unit for an extracorporeal ventricular assist device (VAD) with a pneumatically driven pump. A method for checking the pump blood flow on the side of the drive unit without modifying the existing blood pump and impairing the portability of it will be useful. In this study, to calculate the pump flow rate indirectly from measuring the flow rate of the driving air of the VAD air chamber, we conducted experiments using a mock circuit to investigate the correlation between the air flow rate and the pump flow rate as well as its accuracy and error factors. The pump flow rate was measured using an ultrasonic flow meter at the inflow and outflow tube, and the air flow was measured using a thermal mass flow meter at the driveline. Similarity in the instantaneous waveform was confirmed between the air flow rate in the driveline and the pump flow rate. Some limitations of this technique were indicated by consideration of the error factors. A significant correlation was found between the average pump flow rate in the ejecting direction and the average air flow rate in the ejecting direction (R2 = 0.704-0.856), and the air flow rate in the filling direction (R2 = 0.947-0.971). It was demonstrated that the average pump flow rate was estimated exactly in a wide range of drive conditions using the air flow of the filling phase.

In-body tissue architecture--a novel and practical regeneration medicine technology--can be used to prepare a completely autologous heart valve, based on the shape of a mold. In this study, a three-dimensional (3D) printer was used to produce the molds. A 3D printer can easily reproduce the 3D-shape and size of native heart valves within several processing hours. For a tri-leaflet, valved conduit with a sinus of Valsalva (Biovalve type VII), the mold was assembled using two conduit parts and three sinus parts produced by the 3D printer. Biovalves were generated from completely autologous connective tissue, containing collagen and fibroblasts, within 2 months following the subcutaneous embedding of the molds (success rate, 27/30). In vitro evaluation, using a pulsatile circulation circuit, showed excellent valvular function with a durability of at least 10 days. Interposed between two expanded polytetrafluoroethylene grafts, the Biovalves (N = 3) were implanted in goats through an apico-aortic bypass procedure. Postoperative echocardiography showed smooth movement of the leaflets with minimal regurgitation under systemic circulation. After 1 month of implantation, smooth white leaflets were observed with minimal thrombus formation. Functional, autologous, 3D-shaped heart valves with clinical application potential were formed following in-body embedding of specially designed molds that were created within several hours by 3D printer.

Purpose Ventricular Assist devices are essential but challenging therapeutic options for advanced heart failure patients with critical conditions including cardiogenic shock. In such cases, bridge to decision (BTD) strategies using temporary mechanical circulatory (MCS) support should be introduced to stabilize the systemic conditions and to connect to the next therapeutic stages. We conducted a clinical study (NCVC-BTD_01, National Cerebral and Cardiovascular Center-Bridge to Decision_01) to assess the safety and effectiveness of the novel developed extracorporeal continuous-flow ventricular assist system employing a disposable and hydrodynamically leviated centrifugal pump (BR16010) for BTD strategies. Methods NCVC-BTD_01 is a single-center, single-arm, open-label, exploratory, medical device, investigator-initiated clinical study. The study was planned using Simon's minimax two-stage phase design. The primary endpoint is a composite of survival free of device-related serious adverse events and complications during device support. Results A total of nine patients (6 males, average 47.7±8.1 years) were enrolled for the study. Study subjects included 3 dilated cardiomyopathy, 3 fulminant myocarditis, 2 acute myocardial infarction and 1 chronic ischemic cardiomyopathy. Six patients were interagency registry for mechanically circulatory support (INTERMACS) profile 1 with temporary MCS and all remaining were INTERMACS profile 2. Eight patients received left ventricular support of which 3 initially received concomitant right ventricular support using extracorporeal membrane oxygenation circuit due to severe respiratory failure. One patient with fulminant myocarditis received biventricular support both using BR16010. After average of 19.0±13.5 days of support (Range, 9 to 48 days), 3 patients weaned from BR16010 because of native cardiac recovery, whereas 6 patients without cardiac recovery required conversion to durable implantable LVAD for bridge to transplantation. Although 1 patient developed non-disabling ischemic stroke, no patient died during the study period. Conclusion From the result of NCVC-BTD_01, BTD strategies using BR16010 safely and successfully bridged patients with advanced heart failure to the next therapeutic stages.

We designed a novel method for constructing an autologous heart valve with a stent, called a stent-biovalve. In constructing completely autologous heart valves, named biovalves, which used in-body tissue architecture technology, tissues for leaflets were formed via ingrowths into narrow apertures in the preparation molds, frequently leading to delayed or incomplete biovalve preparation. In this technique, self-expandable nitinol stents after everting were mounted on an acrylic column-shaped part and partially covered with an acrylic cylinder-shaped part with three slits. This assembled mold was placed into subcutaneous abdominal pouches in beagles or goats for 4 weeks. Upon removing the acrylic parts after harvesting and trimming of capsulated tissues, a tubular hollow structure with three pocket-flaps of membranous tissue rigidly fixed to the stent's outer surface was obtained. Then, the stent was turned inside out to the original form, thus moving the pocket-flaps from outside to the inside. Stent-biovalves with a sufficient coaptation area were thus obtained with little tissue damage in all cases. The valve opened smoothly, and high aperture ratio was noted. This novel technique was thus highly effective in constructing a robust, completely autologous stent-biovalve with adequate valve function.