Pulsatile Circulation Research Articles

Near-wall hemodynamic changes in subclavian artery perfusion induced by retrograde inner branched thoracic endograft implantation

ObjectiveLeft subclavian artery (LSA)-branched endografts with retrograde inner branch configuration (thoracic branch endoprosthesis [TBE]) offer a complete endovascular solution when LSA preservation is required during zone 2 thoracic endovascular aortic repair. However, the hemodynamic consequences of the TBE have not been well-investigated. We compared near-wall hemodynamic parameters before and after the TBE implantation using computational fluid dynamic simulations. MethodsEleven patients who had undergone TBE implantation were included. Three-dimensional aortic arch geometries were constructed from the pre- and post-TBE implantation computed tomography images. The resulting 22 three-dimensional aortic arch geometries were then discretized into finite element meshes for computational fluid dynamic simulations. Inflow boundary conditions were prescribed using normal physiological pulsatile circulation. Outlet boundary conditions consisted of Windkessel models with previously published values. Blood flow, modeled as Newtonian fluid, simulations were performed with rigid wall assumptions using SimVascular's incompressible Navier-Stokes solver. We compared well-established hemodynamic descriptors: pressure, flow rate, time-averaged wall shear stress (TAWSS), the oscillatory shear index (OSI), and percent area with an OSI of >0.2. Data were presented on the stented portion of the LSA. ResultsTBE implantation was associated with a small decrease in peak LSA pressure (153 mm Hg; interquartile range [IQR], 151-154 mm Hg vs 159 mm Hg; IQR, 158-160 mm Hg; P = .005). No difference was observed in peak LSA flow rates before and after implantation: 40.4 cm3/ (IQR, 39.5-41.6 cm3/s) vs 41.3 cm3/s (IQR, 37.2-44.8 cm3/s; P = .59). There was a significant postimplantation increase in TAWSS (15.2 dynes/cm2 [IQR, 12.2-17.7 dynes/cm2] vs 6.2 dynes/cm2 [IQR, 5.7-10.3 dynes/cm2]; P = .003), leading to decreases in both the OSI (0.088 [IQR, 0.063 to –0.099] vs 0.1 [IQR, 0.096-0.16]; P = .03) and percentage of area with an OSI of >0.2 (10.4 [IQR, 5.8-15.8] vs 15.7 [IQR, 10.7-31.9]; P = .13). Neither LSA side branch angulation (median, 81°, IQR, 77°-109°) nor moderate compression (16%-58%) seemed to have an impact on the pressure, flow rate, TAWSS, or percentage of area with an OSI of >0.2 in the stented LSA. ConclusionsThe implantation of TBE produces modest hemodynamic disturbances that are unlikely to result in clinically relevant changes.

A cadaveric perfused model with antegrade arteriovenous pulsatile circulation: a new tool for teaching endovascular skills.

Background:The benefits of using cadaveric humans in surgical training are well documented, and knowledge of the latest endovascular techniques is essential in the daily practice of vascular surgeons. Our study explores the feasibility of an affordable human cadaveric model with pulsatile and heated antegrade perfusion for reliable and reproducible endovascular or surgical simulation.Methods:We undertook cannulation of 7 human cadavers embalmed in a saturated salt solution to create a left-to-right central perfusion with a heated solution, from the ascending thoracic aorta to the right atrium. To that end, we used surgically created carotidojugular and femorofemoral arteriovenous fistulas. Biomedical engineers designed a prototype pump for pulsatile circulation. We monitored invasive blood pressure and temperature. We used this model for training for endovascular thoracic aortic procedures and open vascular surgeries.Results:The prototype pump achieved a pulsatile flow rate of 4.7 L/min. Effective cadaveric perfusion was achieved for several hours, not only with an arterioarterial pathway but also with arteriovenous circulation. The arterial pressures and in situ temperatures accurately restored vascular functions for life-like conditions. This new model made it possible to successfully perform thoracic endovascular aortic repair, subclavian artery stenting and simulation of abdominal open vascular trauma management. The saturated salt solution method and a specifically designed pump improved cost competitiveness.Conclusion:Endovascular simulation on human cadavers, optimized with the pulsatile and heated perfusion system, can be a dynamic adjunct for surgical training and familiarization with new devices. This reproducible teaching tool could be relevant in all surgery programs.

Pulsatility hemodynamics during speed modulation of continuous-flow total artificial heart in a chronic in vivo model.

BackgroundThe evaluation of pulsatile flow created by the new Cleveland Clinic continuous‐flow total artificial heart (CFTAH100), which has a re‐designed right impeller and motor, had not been tested in vivo. The purpose of this study was to evaluate the feasibility of pulsatility with the CFTAH100 during the application of pump speed modulation protocols in a chronic animal model.MethodsA 30‐day chronic animal experiment was conducted with a calf. Five pulsatile studies were performed on the alert animal. The mean pump speed was set at 2800 rpm, and modulated sinusoidally within a range of 0 to ± 35% of mean speed, in increments of 5% at 80 beats per minute (bpm). The pressures and pump flow were collected and a pulsatility index (PI) was calculated.ResultsThe calf was supported with the CFTAH100 without any major complications. The maximum and minimum pump flows changed significantly from baseline in all conditions, while the mean pump flow did not change. All flow pulsatility (FP) readings in all conditions significantly increased from baseline, and the percent modulation (%S) and FP had a strong positive correlation (r = 0.99, p < 0.01). The PI also increased significantly in all conditions (maximum at %S of 35%, 2.2 ± 0.05, p < 0.01), and a positive correlation between %S and PI (r = 0.99, p < 0.01) was observed.ConclusionThe CFTAH100 showed the feasibility of creating pulsatile circulation with sinusoidal pump speed modulation.

In vitro flow study in a compliant abdominal aorta phantom with a non-Newtonian blood-mimicking fluid

In vitro aortic flow simulators allow studying hemodynamics with a wider range of flow visualization techniques compared to in vivo medical imaging and without the limitations of invasive examinations. This work aims to develop an experimental bench to emulate the pulsatile circulation in a realistic aortic phantom. To mimic the blood shear thinning behavior, a non-Newtonian aqueous solution is prepared with glycerin and xanthan gum polymer. The flow is compared to a reference flow of Newtonian fluid. Particle image velocimetry is carried out to visualize 2D velocity fields in a phantom section. The experimental loop accurately recreates flowrates and pressure conditions and preserves the shear-thinning properties of the non-Newtonian fluid. Velocity profiles, shear rate, and shear stress distribution maps show that the Newtonian fluid tends to dampen the observed velocities. Preferential asymmetrical flow paths are observed in a diameter narrowing region and amplified in the non-Newtonian case. Wall shear stresses are about twice higher in the non-Newtonian case. This study shows new insights on flow patterns, velocity and shear stress distributions compared to rigid and simplified geometry aorta phantom with Newtonian fluid flows studies. The use of a non-Newtonian blood analog shows clear differences in flows compared to the Newtonian one in this compliant patient-specific geometry. The development of this aortic simulator is a promising tool to better analyze and understand aortic hemodynamics and to aid in clinical decision-making.

Use of a disposable vascular pressure device to guide balloon inflation of resuscitative endovascular balloon occlusion of the aorta: a bench study

Resuscitative endovascular balloon occlusion of the aorta (REBOA) for rapid hemorrhage control is increasingly being used in trauma management. Its beneficial hemodynamic effects on unstable patients beyond temporal hemostasis has led to growing interest in its use in other patient populations, such as during cardiac arrest from nontraumatic causes. The ability to insert the catheters without fluoroscopic guidance makes the technique available in the prehospital setting. However, in addition to correct positioning, challenges include reliably achieving aortic occlusion while minimizing the risk of balloon rupture. Without fluoroscopic control, inflation of the balloon relies on estimated aortic diameters and on the disappearing pulse in the contralateral femoral artery. In the case of cardiac arrest or absent palpable pulses, balloon inflation is associated with excess risk of overinflation and adverse events (vessel damage, balloon rupture). In this bench study, we examined how the pressure in the balloon is related to the surrounding blood pressure and the balloon's contact with the vessel wall in two sets of experiments, including a pulsatile circulation model. With this data, we developed a rule of thumb to guide balloon inflation of the ER-REBOA catheter with a simple disposable pressure-reading device (COMPASS). We recommend slowly filling the balloon with saline until the measured balloon pressure is 160 mmHg, or 16 mL of saline have been used. If after 16 mL the balloon pressure is still below 160 mmHg, saline should be added in 1-mL increments, which increases the pressure target about 10 mmHg at each step, until the maximum balloon pressure is reached at 240 mmHg (= 24 mL inflation volume). A balloon pressure greater than 250 mmHg indicates overinflation. With this rule and a disposable pressure-reading device (COMPASS), ER-REBOA balloons can be safely filled in austere environments where fluoroscopy is unavailable. Pressure monitoring of the balloon allows for recognition of unintended deflation or rupture of the balloon.

Abstract 12817: Experimental Analysis of Bicuspid Aortic Valve Hemodynamics: Effect of Mild Aortic Dilatation on Systolic Flow Characteristics

Introduction: Aortic diameter is a determinant index in deciding surgical intervention for aortic aneurysm with bicuspid aortic valve (BAV). However, the treatment of a mildly dilated ascending aorta remains controversial. We experimentally investigated influence of mild dilatation of the ascending aorta on BAV-related hemodynamics in 3 BAV morphologies. Methods: An MRI-compatible pulsatile flow circulation system incorporating an aortic valve model and aortic arch model was developed. Tricuspid aortic valve (TAV) and 3 asymmetric BAV models including RL-, RN-, and LN-BAV were constructed by suturing bovine pericardium as cusps to aorta. The aortic arch models with the ascending diameters of 30 mm (non-dilatation) and 40 mm (mildly dilatation) were compared. Streamlines and the circulations (m 2 /s) of peak systolic flow in non- and mildly dilated ascending aorta were assessed using 4D-flow MRI in each BAV morphology (Fig). Results: Streamlines showed eccentric aortic valvular outflow jets impinging on the outer curvature of the ascending aorta, proximal arch, and left-anterior supra-valvular aortic wall in RL-, RN-, and LN-BAV, respectively. Regardless of the non-dilated or mildly dilated aorta, the circulations of peak systolic flow were larger in the BAVs than the TAV model (non-dilated aorta, TAV 0.005; RL- 0.016; RN- 0.026; LN-BAV 0.011 m 2 /s, mildly dilated aorta, TAV 0.009; RL- 0.017; RN- 0.028; LN-BAV 0.025 m 2 /s). Right-handed rotation was observed in RL- and RN-BAV, whereas LN-BAV presented left-handed rotation. In LN-BAV, the circulation markedly increased in the mildly dilated ascending aorta. Conclusions: Asymmetric BAV morphology was associated with highly eccentric aortic valvular outflow jet that directly impinged on the aortic wall, and the large circulation of peak systolic flow. The dilatation of the ascending aorta, even mild dilatation, might induce further increase in the circulation of systolic flow, especially in LN-BAV morphology.

Abstract 14618: Bicuspid Aortic Valve Morphology and Risk Factors of Abnormal Hemodynamics: An Experimental Investigation of Velocity, Vorticity and Eccentricity of Systolic Jet Stream, Using a Magnetic Resonance Imaging Compatible Pulsatile Flow Circulation System

Introduction: Abnormal hemodynamics with bicuspid aortic valve (BAV) is influenced by the BAV morphology. However, due to the morphological variety, the relationship between BAV morphology and hemodynamics has not been well clarified. We experimentally investigated influences of BAV morphology on hemodynamics. Methods: An MRI compatible pulsatile flow circulation system incorporating an aortic valve model and morphologically relevant aortic arch model was developed. Two types of BAV models with cusp angles of 240-120 (asymmetric BAV) and 180-180 (symmetric BAV) were prepared using bovine aorta and pericardium. The vorticity and eccentricity of jet in the aortic arch model in systolic phase were assessed using 4D-flow MRI. Streamlines at peak systole were compared among 5 BAV morphologies defined based on the symmetry and the position of leaflets (Fig). Results: Eccentric supra-valvular jets directed to the aortic wall faced to the smaller leaflet were present in the 3 asymmetric BAVs. In the ABAV-1, a markedly eccentric jet impinging on the aortic outer curvature was present. In the ABAV-2, a left-posterior directed jet shifting to the outer curvature of proximal arch was present. The asymmetric BAVs induced larger flow vorticity in the ascending aorta than the symmetric BAVs (ABAV-1 vs -2 vs -3 vs SBAV-1 vs -2, 0.018 vs 0.019 vs 0.014 vs 0.010 vs 0.011 m 2 /s). The ABAV-2 had a larger vortex in the middle arch than the ABAV-1 (ABAV-2 vs -1, 0.010 vs 0.005 m 2 /s). Conclusion: Our study indicated that the angles and orientations of the BAV impacted on the locations of jets impinging on the aortic wall and magnitudes of vorticities in systole. In the asymmetric BAVs, the direction of jet was influenced by the position of smaller leaflet. Our data suggests that the ABAV-1 morphology may be a risk factor inducing asymmetric aneurysm bulged toward the aortic outer curvature, while the ABAV-2 morphology may be a risk factor of an aortic aneurysm involving the transvers arch.

In Vitro Investigation of an Electrically Actuated Antireflux Valve for a Multiuse Contrast Agent Injection System.

OBJECTIVE. The purpose of this study was to determine the capability of a newly developed antireflux valve for a multiuse contrast agent injection system. MATERIALS AND METHODS. Multiuse contrast agent injection systems require an antireflux valve to eliminate the risk of cross-patient blood contamination. An electrically actuated antireflux valve developed for this purpose can control risk of contamination because it is under forced control and surveillance. In this study, the injection system was connected to a pulsatile circulation system that reproduced an aortic flow environment in vitro. The transvalvular pressure difference was measured, and flow dynamics during valve opening and closing were visualized by high-speed flow visualization. A total of 30 injection conditions were tested, which included two catheters (6- and 2-French diameter), five contrast agent concentrations (100%, 90%, 50%, 10%, and 0%), and a wide range of flow rates (0.1-25.0 mL/s). RESULTS. The transvalvular pressure difference and flow dynamics during valve opening and closing were characterized. Just before valve opening, a minimum transvalvular pressure difference of 0.20 MPa (1500 mm Hg) was confirmed. The positive pressure difference prevented regurgitation during valve opening. During valve closing, the front of the backflow was monitored continuously, and we confirmed that the front failed to reach the valve before complete closure. CONCLUSION. This study provided proof of concept for an electrically actuated antireflux valve to be used in a multiuse contrast agent injection system.

Pre-clinical assessment of a prototype non-invasive diagnostic device to detect aortic aneurysms.

We have developed a non-invasive diagnostic device for treating thoracic aortic aneurysm that can be applied at a peripheral artery. This study aimed to examine how configuration and size of an aneurysm as well as endoluminal pressure affect our diagnostic device's ability to detect an aneurysm, using a pulsatile mock circulation. We created three different-sized (12, 16, and 20mm) saccular and fusiform aneurysm models using silicone and incorporated them in a pulsatile perfusion circuit to evaluate vertical vessel wall velocity wave form at a location apart from the aneurysm. We also varied the pressure condition to evaluate the changes in the detected wave forms. In both fusiform and saccular aneurysm models, biphasic wave forms indicating the presence of aneurysm within the circuit were observed. Regarding aneurysm diameter, biphasic wave forms were observed in all aneurysm models. However, in the 12-mm model, which is relevant to the minimum diameter of clinical diagnostic criteria for an aneurysm relative to normal size, no biphasic waveform was detected when the endoluminal pressure was relatively low. In the 16- and 20-mm models, biphasic waveform was detected without being affected by the configuration and endoluminal pressure. The detectability of aneurysms within a pulsatile mock circulation using our non-invasive diagnostic device was not affected by the clinically relevant configuration and size of the aneurysm under slightly hypertensive endoluminal pressure condition. Low endoluminal pressure may lower the diagnostic sensitivity for relatively small saccular aneurysm.

Are Hygromas and Hydrocephalus After Decompressive Craniectomy Caused by Impaired Brain Pulsatility, Cerebrospinal Fluid Hydrodynamics, and Glymphatic Drainage? Literature Overview and Illustrative Cases

Poorly understood cranial fluid accumulations are frequently observed after decompressive craniectomy and often termed "external hydrocephalus." These findings are difficult to explain using traditional models of hydrocephalus. Representative cases, clinical management, and literature overview are presented. We present a hypothesis that abnormal cranial fluid accumulations develop after decompressive craniectomy in a vulnerable subset of patients as a result of 1) the large compliant cranial defect with durotomy causing reduced internal brain expansion, ventricular squeezing, and pulsatile cerebrospinal fluid (CSF) circulation; 2) impaired pulsatile CSF flow along major cerebral arteries and the adjoining perivascular spaces (Virchow-Robin spaces); 3) reduced clearance of interstitial fluid by the glymphatic system; and 4) redistribution of CSF from the subarachnoid space into the subdural and subgaleal compartments and the ventricles. Closure of the cranial defect with cranioplasty improves cerebral blood flow and CSF pulsatile circulation and is frequently sufficient to resolve the external hydrocephalus.

A Comparison of Middle Cerebral Artery and Central Retinal Artery Hemodynamics in HM II Patients

Purpose In the normal, pulsatile circulation, the hemodynamic pattern of the middle cerebral artery (MCA) differs from the central retinal artery (CRA). Whether continuous flow from a left ventricular assist device (LVAD) alters this relationship is not known. Since serious adverse events in different end-organs, such as stroke and GI bleeding, are frequent in LVAD patients, comparing hemodynamics in different arterial beds may enhance our understanding of the specific pathophysiology of these complications. Hypothesis Because of continuous flow, hemodynamic patterns between the MCA and CRA are more similar in HeartMate II (HM II) patients compared with healthy individuals. Methods MCA and CRA time-averaged maximal flow velocity (TAMAX), pulsatility index (PI) and resistance index (RI) were determined using Doppler ultrasound with angle correction, in 20 HM II pts and 21 healthy individuals. To test the study hypothesis, data were statistically analysed for both group differences and group variances. Results Although PI and RI were markedly lower in HM II patients in both the MCA and CRA (P Conclusion The typical differences that are observed in small- and microcirculatory hemodynamics of healthy individuals are altered in HM II patients. Notably, the wide ranges of haemodynamics observed in the HM II group may carry important implications with respect to the pathophysiology of specific end-organ complications, and, eventually, the identification of high-risk patients.

Experimental study of the effects of sinotubular junction taper on artificial bioprosthesis valve in pulsatile flow condition

The aim of the present experimental study is to determine the effects of sinotubular junction diameter on artificial bioprosthesis valves. An experimental study was performed for aortic root models with different sinotubular junction taper under pulsatile flow condition. The sinotubular junction diameters were modified to create four models with different sinotubular junction tapers with 0, 1, 3 and 5 degrees, respectively, using three dimensional printing techniques. After installing the testing bioprosthesis valve on the aortic root models, we conducted experiments of the pulsatile flow testing with different stroke volume in the pulsatile circulation simulation system. The testing condition was set at the pulse frequency of 70 beats/min and the stroke volume of 2-7 L/min. The status of the valves in 10 continuous pulse cycles was tested and the average results were obtained for each stroke volume. The results of testing showed that the mean transvalvular pressure gradients agreed well with the national standard, and all smaller than 10 mm Hg. The sinotubular junction taper had an influence on regurgitation fraction of the artificial bioprosthesis valve. The smaller sinotubular junction taper showed beneficial effect to decrease the regurgitation fraction. In the case of smaller stroke volume, the smaller sinotubular junction taper was beneficial to increase the effective valve orifice area. In the case of larger stroke volume, the larger sinotubular junction taper was beneficial to increase the effective valve orifice area. This study indicates that a doctor should consider the smaller sinotubular junction taper in the case of smaller stroke volume more. In the case of larger stroke volume, the doctor should consider the larger sinotubular junction taper more.

Minimally Circulatory‐Assisted On‐Pump Beating Coronary Artery Bypass Grafting for Patients With Complex Conditions for Off‐Pump Surgery

Off-pump coronary artery bypass grafting (OPCAB) in patients with acute myocardial infarction (AMI) is difficult because of circulatory deterioration during displacement of the heart. At our institution, we performed minimally circulatory-assisted on-pump beating coronary artery bypass grafting (MICAB) in these patients. During MICAB, support flow was controlled at a minimal level to maintain a systemic blood pressure of approximately 100 mmHg and a pulmonary arterial systolic pressure of <30 mmHg, providing optimal pulsatile circulation for end-organ perfusion and prevention of heart congestion. From September 2006 to March 2012, MICAB was performed in 37 patients. Either emergent or urgent MICAB was performed in 27 patients following AMI because of hemodynamic instability during reconstruction. Elective MICAB was performed in the remaining 10 patients because of dilated left ventricle (LV) or small target coronary arteries. The details of bypass grafts, perioperative renal function, and early and mid-term morbidity and mortality were compared between the patients who received MICAB and the 37 consecutive patients who underwent OPCAB during the study period at our hospital. The assist flow indices (actual support flow/body surface area) during anastomosis to the left anterior descending artery, left circumflex artery, and right coronary artery were 0.95 ± 0.48 L/min/m2 , 1.32 ± 0.53 L/min/m2 , and 1.15 ± 0.47 L/min/m2 , respectively, in the emergent and urgent patients following AMI, and 0.44 ± 0.39 L/min/m2 , 1.25 ± 0.39 L/min/m2 , and 1.14 ± 0.43 L/min/m2 , respectively, in the elective patients with either dilated LVs or small target vessels. The lowest mixed venous oxygen saturation during pump support in the MICAB group was significantly higher than that in the OPCAB group (83.8 ± 10.8%, 71.6 ± 7.5%, P < 0.001). Comparing MICAB and OPCAB, the median number of distal bypass grafts for both groups was 4 (25th, 75th percentile: 3, 4) (P = 0.558); the complete revascularization rates were 94.6 and 97.3%, respectively (not significant [NS]); the acute patency rates were 98.9 and 99.2%, respectively (NS); and the 30-day mortality rates were 2.7 and 0%, respectively (NS). No instances of either cerebrovascular complications or newly occurring postoperative renal failure were noted in either group. There were no statistically significant differences between the groups with respect to early and mid-term results (freedom from all-cause death: 82.9 vs. 86.5%, respectively, and freedom from cardiac events at 3 years: 96.4 vs. 96.4%, respectively). MICAB is a safe alternative to OPCAB, particularly in patients with AMI and dilated LV. MICAB is associated with high rates of complete revascularization and acute graft patency, adequate preservation of end-organ function, and early and mid-term results comparable with those observed following OPCAB.

Transcranial Doppler Changes in Patients Treated with Extracorporeal Membrane Oxygenation

Transcranial Doppler (TCD) has significant implications for neurovascular assessment in patients being treated with venoarterial-extracorporeal membrane oxygenation (VA-ECMO). However, there have been no studies demonstrating the changes in pulsatility indices (PIs) seen in these patients. Nonpulsatile waveforms are seen during on-pump coronary artery bypass graft, but low or low-normal PIs have never been reported. It is important to be aware of these changes, as they can be misinterpreted as cerebral vasodilation, vasoconstriction, increased intracranial pressures (ICPs), or cerebral circulatory arrest. Data from 11 TCDs from 8 patients on VA-ECMO in the Cedars Sinai Medical Center Cardiac Surgical Intensive Care Unit were reviewed. Mean pulsatility indices were calculated for each patient using Gosling's PI formula. The values obtained were correlated with ejection fraction (EF) values obtained from a transthoracic or transesophageal echocardiogram. PIs were globally low or absent in all 11 TCDs. In 3 patients, TCDs were performed at the initiation and conclusion of the VA-ECMO cannulation. The PI values for these TCDs correlated directly with changes in EFs. Also, an abrupt rise in PI to normal value was seen with the placement of a total artificial heart and the return of pulsatile circulation. We demonstrate that PIs on TCDs in patients treated with VA-ECMO are either low or cannot be calculated depending on the severity of myocardial suppression, and should not be mistaken for cerebral vasodilation or cerebral circulatory arrest. Moreover, rising PIs in these patients can represent improving cardiac function and should not be confused with elevated ICPs.

SimLife a new model of simulation using a pulsated revascularized and reventilated cadaver for surgical education

Alike becoming a pilot requires competences, acquisition of technical skills is essential to become a surgeon. Halsted's theory on surgical education "See one, do one, and teach one" is not currently compatible with the reality of socio-economic constraints of the operating room, the patient's safety demand and the reduction of residents' work hours. In all countries, this brings mandatory to simulation education for surgery resident's training. Many models are available: video trainers or pelvi-trainers, computed simulator, animal models or human cadaver… Human cadaveric dissection has long been used to teach surgical anatomy. Surgery on human cadaveric model brings greatest accuracy to the haptic characteristics of surgical procedures. Learning in an appropriate and realistic simulation context increases the level of acquisition of the residents' skills and reduces stress and anxiety when performing real procedures. We present a technique of perfusion and ventilation of a fresh human cadaver that restores pulsatile circulation and respiratory movements of the model.

Development of a stent-biovalve with round-shaped leaflets: in vitro hydrodynamic evaluation for transcatheter pulmonary valve implantation (TPVI).

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 2months. 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 25mm). 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 25mm based on the pressure difference and effective orifice area.

Abstract 11955: Development of in vivo , Tissue-Engineered, Autologous, 3D Heart Valvular Tissue, Type SC Biovalve With Excellent Mechanical Properties, Valular Functions, and in vivo Performances

Background: Autologous pericardium is widely used for the reconstruction of intracardiac structures and pulmonary artery, and for aortic valve leaflets after fixation with glutaraldehyde for mechanical strengthening. We developed autologous prosthetic tissues by using in-body tissue architecture (IBTA) technology, which is a novel and practical approach of regenerative medicine based on the tissue encapsulation phenomenon of foreign materials in living bodies. In this study, IBTA-based heart valves with robust tissue wall [Biovalve (BV) Type SC] were prepared by using a novel caged mold. The mechanical properties of the valves were compared with human pericardium, and in vivo durability was evaluated in animal implantation study after in vitro evaluation using a pulsatile circulation circuit. Methods and Results: The BV preparation molds could be produced rapidly by using a 3D printing machine, based on the designed 3D-shape and size of native heart valves regardless of their type. Upon 1- or 2-month goat subcutaneous embedding of the molds aortic or pulmonary valve-shaped BVs (diameter 5-30 mm) were formed as type SC from completely autologous connective tissue with collagen and fibroblasts. All surfaces of the BVs that were in contact with blood were highly smooth and flat. The three leaflet tissues were seamlessly connected with the surrounding conduit tissue, and showed homogeneous wall thickness and excellent mechanical strength that was equivalent to or more than that of the human pericardium, with individual or regional differences. As an aortic valve, in vitro evaluation of the BV showed excellent valvular functions (regurgitation ratio 5.7% at 70 beats per minute). In a goat model, postoperative echocardiography after surgical replacement of the biovalves with stents showed smooth movement of the leaflets with little regurgitation under systemic circulation. In all implantation studies, the luminal surface after implantation was very smooth and fully covered with thin neointima, including endothelial cells without thrombus formation. Conclusion: Functional, completely autologous, robust, 3D aortic or pulmonary BVs showing the potential for clinical application were developed by in-body embedding of specially designed molds.

New continuous-flow total artificial heart and vascular permeability

BackgroundWe tested the short-term effects of completely nonpulsatile versus pulsatile circulation after ventricular excision and replacement with total implantable pumps in an animal model on peripheral vascular permeability. MethodsTen calves underwent cardiac replacement with two HeartMate III continuous-flow rotary pumps. In five calves, the pump speed was rapidly modulated to impart a low-frequency pulse pressure in the physiologic range (10–25 mm Hg) at a rate of 40 pulses per minute (PP). The remaining five calves were supported with a pulseless systemic circulation and no modulation of pump speed (NP). Skeletal muscle biopsies were obtained before cardiac replacement (baseline) and on postoperative days (PODs) 1, 7, and 14. Skeletal muscle-tissue water content was measured, and morphologic alterations of skeletal muscle were assessed. VE-cadherin, phospho–VE-cadherin, and CD31 were analyzed by immunohistochemistry. ResultsThere were no significant changes in tissue water content and skeletal muscle morphology within group or between groups at baseline, PODs 1, 7, and 14, respectively. There were no significant alterations in the expression and/or distribution of VE-cadherin, phospho–VE-cadherin, and CD31 in skeletal muscle vasculature at baseline, PODs 1, 7, and 14 within each group or between the two groups, respectively. Although continuous-flow total artificial heart (CFTAH) with or without a pulse pressure caused slight increase in tissue water content and histologic damage scores at PODs 7 and 14, it failed to reach statistical significance. ConclusionsThere was no significant adherens-junction protein degradation and phosphorylation in calf skeletal muscle microvasculature after CFTAH implantation, suggesting that short term of CFTAH with or without pulse pressure did not cause peripheral endothelial injury and did not increase the peripheral microvascular permeability.

Total artificial hearts: past, present, and future.

A practical artificial heart has been sought for >50 years. An increasing number of people succumb to heart disease each year, but the number of hearts available for transplantation remains small. Early total artificial hearts mimicked the pumping action of the native heart. These positive-displacement pumps could provide adequate haemodynamic support and maintain the human circulation for short periods, but large size and limited durability adversely affected recipients' quality of life. Subsequent research into left ventricular assist devices led to the use of continuous-flow blood pumps with rotating impellers. Researchers have attempted to integrate this technology into modern total artificial hearts with moderate clinical success. The importance of pulsatile circulation remains unclear. Future research is, therefore, needed into positive-displacement and rotary total artificial hearts.

1B43 拍動循環装置を用いたステントレス僧帽弁(Normo弁)の機能性評価(OS8-4:循環器系のバイオメカニクスと医療機器(4))

1B43 拍動循環装置を用いたステントレス僧帽弁(Normo弁)の機能性評価(OS8-4:循環器系のバイオメカニクスと医療機器(4))