To develop an millimeter-waves (mm-waves) channel model for in-room access scenarios, a double-directional channel measurement campaign conducted in a conference room environment is presented. In the ...measurements, a custom-developed channel sounder with a 12° angle and 2.5-ns delay resolutions at 58.5 GHz was used. From the measured data, the multi-path components were extracted using a high-resolution path parameter estimation algorithm; then, they were clustered based on the actual physical propagation paths to identify the scattering processes explicitly. The cluster analysis revealed that the signal paths by line-of-sight, single-bounce, and double-bounce reflections were power-dominant and well predicted by ray-tracing, but the contribution of random clusters was not significant. In this study, to express diffuse scattering on the rough surface of an ambient reflector, an intra-cluster model of plasterboard wall reflection was parameterized. Furthermore, the proposed intra-cluster model was experimentally validated by analyzing the small-scale fading captured along the wall in the time domain which is caused by the constructive and destructive interference of the specular reflection and diffuse scattering components.
ABSTRACT Background This study aimed to evaluate the effect of aggressive embolization of side branches arising from the aneurysmal sac before endovascular aneurysm repair. Methods This retrospective ...study included 95 patients who underwent endovascular infrarenal abdominal aortic aneurysm repair at Tottori University Hospital between October 2016 and January 2021. Of these, 54 underwent standard endovascular aneurysm repair (conventional group), and 41 underwent coiling of the inferior mesenteric and lumbar arteries before undergoing endovascular aneurysm repair (embolization group). The occurrence of type II endoleak, change in aneurysmal sac diameter, and reintervention rate due to type II endoleak during follow-up were evaluated. Results Compared to the conventional group, the embolization group had a significantly lower incidence of type II endoleak, more frequent aneurysmal sac shrinkage, and lower aneurysmal sac growth related to type II endoleak. Conclusion Our results demonstrated the effectiveness of aggressive aneurysmal sac embolization before endovascular aneurysm repair to prevent type II endoleak and the consequent long-term aneurysmal sac enlargement.
Aneurysms of the tibioperoneal trunk (TPT) with peripheral arterial lesions are extremely rare. We present a case of a 68-year-old man who underwent surgical treatment for a mycotic aneurysm of the ...TPT. This report highlights the importance of en bloc surgical resection of the mycotic aneurysm and an appropriate approach with an air tourniquet for the prevention of injuries to the adherent tissues.
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.
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 <60 bpm using propranolol and controlled the heart rates at 80 and 120 bpm using ventricular pacing. We shifted the timing of increasing RS from −60 to +60 ms in the systolic phase. We found significant increases in all the following parameters when assessments of delayed timing (+60 ms) were compared with assessments of advanced timing (−60 ms): pulse pressure, mean d
P
/d
t
max of aortic pressure, and energy-equivalent pulse pressure. During continuous-flow LVAD support, pulsatility can be controlled using a rotary pump. In particular, pulsatility can be shifted by delaying increased RS.
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.
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.
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.
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 clinical use of veno-venous extracorporeal membrane oxygenation (VVECMO) in adult patients with respiratory failure is rapidly increasing. However, recirculation of blood oxygenated by ECMO back ...into the circuit may occur in VVECMO, resulting in insufficient oxygenation. The cannula position and bypass flow rate are two major factors influencing recirculation, but the relationship and ideal configuration of these factors are not fully understood. In the present study, we attempted to clarify these parameters for effective gas exchange. VVECMO was performed in eight adult goats under general anesthesia. The position of the drainage cannula was fixed in the inferior vena cava (IVC), but the return cannula position was varied between the IVC, right atrium (RA), and superior vena cava (SVC). At each position, the recirculation rates calculated, and the adequacy of oxygen delivery by ECMO in supplying systemic oxygen demand was assessed by measuring the arterial oxygen saturation (SaO
2
) and pressure (PaO
2
). Although the recirculation rates increased as the bypass flow rates increased, SaO
2
and PaO
2
also increased in any position of return cannula. The recirculation rates and PaO
2
were 27 ± 2 % and 162 ± 16 mmHg, 36 ± 6 % and 139 ± 11 mmHg, and 63 ± 6 % and 77 ± 9 mmHg in the SVC, RA and IVC position at 4 L/min respectively. In conclusion, the best return cannula position was the SVC, and a high bypass flow rate was advantageous for effective oxygenation. Both the bypass flow rates and cannula position must be considered to achieve effective oxygenation.
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