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 (O
2
ER) 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). O
2
ER 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.
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 (O
2
ER) 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. O
2
ER in AR− decreased with increasing pump rotation speed, but O
2
ER in AR+ was hard to decrease. The O
2
ER 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.
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.
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 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.
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.
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 (O
2
ER) 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%. O
2
ER was also increased with AI progression and had a significant positive correlation with the recirculation rate (
p
= 0.000043). O
2
ER 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.
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.
Background Secure distal anastomosis and reliable brain protection are indispensable for successful total arch replacement (TAR). In 2002, we introduced a modified elephant trunk technique, a novel ...approach to distal anastomosis, and employed antegrade selective cerebral perfusion. We retrospectively analyzed 107 consecutive patients to evaluate the efficacy of this technique for TAR with antegrade selective cerebral perfusion. Methods Since 2002 we have employed moderate hypothermic circulatory arrest, selective antegrade cerebral perfusion, and open distal anastomosis with a modified elephant trunk technique in TAR. Between February 2002 and September 2011, 107 TARs were performed in 88 males and 19 females (age, 33 to 88 years; mean, 70.9 ± 9.5 years). Etiologies of cases were as follows: 89 true aneurysm due to atherosclerosis; 5 infectious aneurysm; 1 aortic dilation with bicuspid aortic valve; 12 aortic dissection, including 1 of acute aortic dissection case; and 2 Marfan syndrome. Concomitant procedures included 19 coronary artery bypass grafting (CABG) cases, 2 aortic valve replacement cases, 1 mitral valve plasty case, 1 Bentall procedure case, and 1 case of Bentall with CABG. Results The operative mortality within 30 days was 0.9% (1 of 107), and overall hospital mortality was 1.9% (2 of 107). Temporary and permanent neurologic dysfunction occurred in 5 patients each (4.7%). The Kaplan-Meier survival analysis revealed a 5-year survival rate of 91.8%. Conclusions The modified elephant trunk technique using selective antegrade cerebral perfusion provided secure distal anastomosis and demonstrated excellent results, with low operative mortality and few neurologic complications.
A 65-year-old male was diagnosed with severe aortic stenosis with an indication for surgery and referred to our department. The patient opted for aortic valve replacement using a bioprosthesis. Due ...to the patient's relatively small native aortic valve area, a concurrent root dilatation maneuver (Bo Yang method) was performed to prevent patient-prosthetic mismatch and to allow for the implantation of a sufficiently larger bioprosthesis, facilitating the valve-in-valve procedure. The successful implantation of an Inspiris 25-mm bioprosthesis was achieved. Post-operative 3D-computed tomography revealed no tilting or misalignment of the bioprosthesis, and a properly sized, undistorted Valsalva sinus was observed. Aortic valve replacement using the Bo Yang root enlargement technique is considered a promising alternative for relatively younger patients requiring aortic valve intervention.
