Inlet Cannula Research Articles

P10: CFD Simulation Of Thrombosis In A Catheter Pump Inside The Left Ventricle

Study: Catheter pumps are small axial flow assist devices indicated for temporary use for a variety of indications. Uniquely positioned within the circulation, the pump impeller and motor are situated in the ascending aorta, and blood is pumped from the left ventricle (LV) via a long angled inlet cannula. The interplay of pulsatile LV blood dynamics with hemocompatibility performance of a catheter pump is not well characterized. The purpose of this study is to conduct computational fluid dynamics (CFD) simulation that includes multifactorial and synergistic models of blood damage to a catheter pump within a virtual in-vivo environment to analyze its hemodynamics. Methods: A generic catheter pump whose shape is inspired by the Impella 5.0 is situated within a static geometry consisting of a semi-realistic LV and aorta. We apply bloodDamageFoam, an OpenFOAM-based CFD code, to predict the hemodynamic flow and blood damage generated by the pump operating at 20 kRPM. The thrombosis model includes seven biochemical and biophysical agonists and accounts for the effects of high shear stress induced activation of von Willebrand factor. Results: CFD predicted 4.43 LPM blood flow rate from the LV delivered into the aorta. Moderate levels of hemolysis were predicted. The thrombosis model showed moderate degrees of platelet deposition on the cage of the inlet cannula and within the catheter pump chamber. Because the LV in this simulation was not beating, unrealistically large regions of flow stagnation and high platelet activation were observed in the LV. To address this, realistic pulsatility of a dilated LV is currently being modeled. Our latest progress will be presented at the meeting.

Abstract 12777: The Lingering Snag in Era of Mechanical Pumps: A Case of Acute Pump Thrombosis Immediately After Heartmate 3 Implantation

Background: Pump thrombosis (PT) remains a dreaded complication of left ventricle assist device (LVAD) implantation. PT immediately after HeartMate 3 (HM3) implantation is rare but should be kelp in mind if early low flow alarms are noted. Case: A 57-year-old male with ischemic cardiomyopathy, Stage D heart failure (LVEF ~20%), INTERMACS category 3 on 5mcg/kg/min Dobutamine drip underwent advanced heart failure therapy evaluation and was deemed suitable candidate for LVAD implant. His ECHO showed LVIDD 6.04 cm and LV Diastolic Volume Index 122 mL. He underwent HM3 implantation via left anterior thoracotomy and upper-hemi sternotomy on 5/24/2022. Surgery was successful and the patient was taken off bypass. Pre-implant some LV trabeculations and debris were removed. However, less than 1 hour from being off bypass, the low flow alarms began which did not resolve after volume and blood pressure optimization. No RV failure was noted on TEE. Decision was made to re-open the sternum. Upon exploration, no compression of the outflow graft was noted, and inlet cannula was not mispositioned. Inspection of LVAD inlet and outlet cannula showed significant amount of white thrombus (Figure 1) and device was ultimately exchanged. Thrombus was confirmed on histopathological analysis. Post-operatively no low flow alarms were noted after pump exchange. Factor V Leiden screen and protein C activity were normal and Antithrombin 3 was falsely low (due to recent thrombus) on post-op day 1. Discussion: This is the second case of HM 3 device thrombosis within 1 hour of implant in the literature. Most of the earlier reported cases were on post-Op Day 3. The etiology of PT is unknown and further investigation is required to elucidate the same. This case will create awareness among physicians to keep PT in differentials when low flow alarms are encountered immediately post-op despite volume and BP optimization.

Multi-constituent simulation of thrombus formation at LVAD inlet cannula connection: Importance of Virchow's triad.

As pump thrombosis is reduced in current-generation ventricular assist devices (VAD), adverse events such as bleeding or stroke remain at unacceptable rates. Thrombosis around the VAD inlet cannula (IC) has been highlighted as a possible source of stroke events. Recent computational fluid dynamics (CFD) studies have attempted to characterize the thrombosis risk of different IC-ventricle configurations. However, purely CFD simulations relate thrombosis risk to ad hoc criteria based on flow characteristics, with little consideration of biochemical factors. This study investigates the genesis of IC thrombosis including two elements of the Virchow's triad: endothelial injury and hypercoagulability. To this end a multi-scale thrombosis simulation that includes platelet activity and coagulation reactions was performed. Our results show significant thrombin formation in stagnation regions (|u| < 0.005m/s) close to the IC wall. In addition, high shear-mediated platelet activation was observed over the leading-edge tip of the cannula. The current study reveals the importance of biochemical factors to the genesis of thrombosis at the ventricular-cannula junction in a perioperative state. This study is a first step toward the long-term objective of including clinically relevant pharmacological kinetics such as heparin or aspirin in simulations of inflow cannula thrombosis.

Ablation of Ventricular Tachycardia Storm in a Patient with Biventricular Mechanical Support Devices - A Case Report

Background Ventricular tachycardia (VT) has been described in patients who have undergone implantation of ventricular assist devices (VAD). Mechanisms for VT in these patients include scar-mediated reentry, bundle branch reentry, and mechanically-induced arrhythmia related to scar caused by VAD inlet cannula placement or suction events. While the hemodynamic support offered by VAD's can mitigate the harmful effects of ventricular tachyarrhythmias, morbidity can arise from outcomes including RV failure. VT ablation has been utilized with some success in these patients though data in this area is scarce, especially in those with biventricular support devices. Case Report We present a case of a 47 year-old man with a history of hypertension, tobacco and cocaine abuse presenting with STEMI. Despite emergent catheterization with PCI to proximal LAD lesion, he developed cardiogenic shock requiring intra-aortic balloon pump placement. He subsequently suffered V Fib arrest necessitating upgrade to VA-ECMO. Due to persistent biventricular failure with inability to wean support, he was transitioned to durable left ventricular support (Heartmate 3, Abbott) and temporary right ventricular support (Protek Duo, TandemLife). Despite durable support, he remained in VT refractory to antiarrhythmic agents (Amiodarone, Lidocaine, Procainamide), multiple cardioversions, and stellate ganglion block. Given incessant VT leading to RV failure and compromising RVAD removal, the decision was ultimately made to proceed with VT ablation. The patient underwent extensive substrate-based ablation and ablation of the right bundle and left posterior fascicle for bundle branch reentry and interfascicular VT complicated by transient AV block requiring TVP insertion. Other complicating factors involved in this procedure included gaining access and manipulating ablation catheters given presence of prior devices including the LVAD cannula. At the end of the procedure the patient had no further inducible VT. He was successfully weaned off of RVAD support after the ablation. His hospital course was complicated by recurrent slower VT which was successfully managed with medical therapy. Conclusions Our case highlights several complicating factors in managing ventricular tachyarrhythmias in patients with mechanical circulatory support devices. These include limitations to medical management due to side effect profiles or refractoriness, coordination of multiple disciplines (advanced heart failure, EP, VAD team, anesthesia), as well as barriers to successful ablation including technical difficulty given the presence of other devices, the desire to avoid invasive procedures in patients susceptible to or suffering from systemic infection, and high recurrence rates. In this specific case VT ablation was successful in facilitating the goal of weaning the patient off of RVAD support.

Cannula Tip With Integrated Volume Sensor for Rotary Blood Pump Control: Early-Stage Development.

The lack of direct measurement of left ventricular unloading is a significant impediment to the development of an automatic speed control system for continuous-flow left ventricular assist devices (cf-LVADs). We have developed an inlet cannula tip for cf-LVADs with integrated electrodes for volume sensing based on conductance. Four platinum-iridium ring electrodes were installed into grooves on a cannula body constructed from polyetheretherketone (PEEK). A sinusoidal current excitation waveform (250 μA pk-pk, 50 kHz) was applied across one pair of electrodes, and the conductance-dependent voltage was sensed across the second pair of electrodes. The conductance catheter was tested in an acute ovine model (n = 3) in conjunction with the HeartMate II rotary blood pump to provide circulatory support and unload the ventricle. Echocardiography was used to measure ventricular size during pump support for verification for the conductance measurements. The conductance measurements correlated linearly with the echocardiography dimension measurements more than the full range of pump support from minimum support to suction. This cannula tip will enable the development of automatic control systems to optimize pump support based on a real-time measurement of ventricular size.

Implantation of Left Ventricular Assist Device in the setting of heavily calcified left ventricular apex using an apex preserving technique

A heavily calcified ventricular apex represents a challenging, rare and unique situation in LVAD implantation. A 44-year-old male was admitted with myocardial infarction. Left heart catheterization was complicated by episodes of ventricular fibrillation. After an acute stabilization with veno-arterial extracorporeal membrane oxygenation (VA-ECMO), an LVAD implantation was approved. Pre-operative work-up had shown a heavily calcified ventricular apex and an intraventricular thrombus, which was confirmed intraoperatively. To retain a viable ventricular geometry, the decision was made to preserve the calcified apex rather than to excise the entire calcified left ventricular aneurysm. Sutures for the inlet cannula were placed around the calcific apex (Apex Preserving) away from the core site, parachuting the inflow sewing ring into an intramyocardial position (Telescope) and assuring hemostasis by placing a felt strip on the epicardial tissue in a purse string fashion (Cerclage). The HeartMate II LVAD inflow cannula was secured into the sawing ring, and the rest of the procedure was conducted in the standardized fashion. The patient was discharged into a rehabilitation center eight weeks after LVAD implantation. Thus, if the calcific area is maintained by coring just the inflow site, the spherical shape of the ventricle is maintained to all for better positioning of the inlet cannula. The second suture line enhances hemostasis around the inflow insertion site and stays away from the calcium, which sits in a deeper layer. This procedure, the apex preserving cerclage technique (APCT), does not increase surgical time and reinforces the tissue around the inlet site.

Effects of Cone-Shaped Bend Inlet Cannulas of an Axial Blood Pump on Thrombus Formation: An Experiment and Simulation Study.

BackgroundCannula shape and connection style influence the risk of thrombus formation in the blood pump by varying the blood flow characteristics inside the pump. Inlet cannulas should be designed based on the need for anatomical fit and reducing the risk of thrombus generation in the blood pump. The effects on thrombus formation of the cone-shaped bend inlet cannulas of axial blood pumps should be studied.Material/MethodsThe cannulas were designed as cone-shaped, with 1 bent section connecting 2 straight sections. Both the silicone tube and novel cone-shaped cannula were simulated for comparison. The flow fields of a blood pump with inlet cannula were simulated by computational fluid dynamics (CFD) at flows of 2.0, 2.5, and 3.0 liters per minute (lpm), with pump rotational speeds of 7500, 8000, and 8500 rpm, respectively. Then, 6 two-dimensional (2D) particle image velocimetry (PIV) tests were conducted and the velocity distributions were analyzed.ResultsA low-velocity region was located inside the pump entrance when a soft silicone tube was used. At 8500 rpm and 3.0 lpm working condition, the minimum velocity inside the pump with cone-shaped cannulas was 2.5×10−1 m/s. The cone-shaped cannulas eliminated the low-velocity region inside the pump. Both CFD and PIV results showed that the low-velocity region did not spread to the entrance of the blood pump within the flow range from 2.0 lpm to 7.0 lpm.ConclusionsThe designed cone-shaped bent cannulas can eliminate the low-velocity region inside the blood pump and reduce the risk of thrombus formation in the blood pump.

A Physiological Controller for Turbodynamic Ventricular Assist Devices Based on Left Ventricular Systolic Pressure.

The current article presents a novel physiological feedback controller for turbodynamic ventricular assist devices (tVADs). This controller is based on the recording of the left ventricular (LV) pressure measured at the inlet cannula of a tVAD thus requiring only one pressure sensor. The LV systolic pressure (SP) is proposed as an indicator to determine the varying perfusion requirements. The algorithm to extract the SP from the pump inlet pressure signal used for the controller to adjust the speed of the tVAD shows robust behavior. Its performance was evaluated on a hybrid mock circulation. The experiments with changing perfusion requirements were compared with a physiological circulation and a pathological one assisted with a tVAD operated at constant speed. A sensitivity analysis of the controller parameters was conducted to identify their limits and their influence on a circulation. The performance of the proposed SP controller was evaluated for various values of LV contractility, as well as for a simulated pressure sensor drift. The response of a pathological circulation assisted by a tVAD controlled by the introduced SP controller matched the physiological circulation well, while over- and underpumping events were eliminated. The controller presented a robust performance during experiments with simulated pressure sensor drift.

Abstract 12486: An Early Survey of the Incidence and Distribution of LVAD Thrombus Using a High-avidity Tc-99m Fibrin Probe

Background: 99mTc-F4A is a tetrameric, fibrin-specific probe characterized in vitro, in mice and in left ventricular assist devices (LVAD) explanted from patients. Objective: To survey the incidence and spatial distribution of thrombus by 99mTc-F4A signal intensity in LVADs removed for pump exchange (n=9) or heart transplant (n=11) in an early cohort of patients. Methods: LVADs excised from patients were rewired and operated (~9,400 RPM) in a mock circulatory loop (1/2 tygon, 200ml, 50:50, PBS: plasma; heparin). 99mTc-F4A (500μCi) was injected into the loop, circulated for 30 min. Activity was localized within LVADs by NanoSPECT/CT. Results: The median time of LVAD support prior to explant was 7.6 ± 7.2 months. Thrombus was detected in 19/20 LVADs by high 99mTc-F4A signal and corroborated by gross pathology in 4 LVADs by the manufacturer. 99mTc-F4A signal was scored as strong, weak, or none, and was assessed for the inlet cannula (metallic and Gor-Tex tubing segments), the inlet stator/bearing, turbine, outlet bearing, and outlet cannula regions. Inlet cannulas were available for 8/20 LVADs with 7/8 having thrombus. Strong signal was noted in 4/7 of the metallic segment and in 5/7 of the Gor-Tex segments. 99mTc-F4A signal occurred around the inlet bearing in 8/20 LVADs and the outlet bearing region in 5/20 LVADs, but the incidence of thrombus within the axial turbine was negligible. Thrombus was observed in the outlet cannula in 10/20 pumps. (Fig) Strong 99mTc-F4A signal was noted most often at the inlet bearing 75% (6/8) and in outlet cannulas 50% (5/10). Strong signal was noted in 13/20 LVADs in at least one location. Of 5/20 LVADs with multiple deposits, 4/5 of these pumps had a strong 99mTc-F4A signal. Conclusion: These initial ex vivo survey data reveal a high incidence of LVAD thrombus in exchanged and routinely transplanted LVADs. 99mTc-F4A imaging may offer a sensitive and specific diagnostic tool to noninvasively assess and better manage LVAD thrombus.

Anatomy and Physiology of Left Ventricular Suction Induced by Rotary Blood Pumps.

This study in five large greyhound dogs implanted with a VentrAssist left ventricular assist device focused on identification of the precise site and physiological changes induced by or underlying the complication of left ventricular suction. Pressure sensors were placed in left and right atria, proximal and distal left ventricle, and proximal aorta while dual perivascular and tubing ultrasonic flow meters measured blood flow in the aortic root and pump outlet cannula. When suction occurred, end-systolic pressure gradients between proximal and distal regions of the left ventricle on the order of 40-160 mm Hg indicated an occlusive process of variable intensity in the distal ventricle. A variable negative flow difference between end systole and end diastole (0.5-3.4 L/min) was observed. This was presumably mediated by variable apposition of the free and septal walls of the ventricle at the pump inlet cannula orifice which lasted approximately 100 ms. This apposition, by inducing an end-systolic flow deficit, terminated the suction process by relieving the imbalance between pump requirement and delivery from the right ventricle. Immediately preceding this event, however, unnaturally low end-systolic pressures occurred in the left atrium and proximal left ventricle which in four dogs lasted for 80-120 ms. In one dog, however, this collapse progressed to a new level and remained at approximately -5 mm Hg across four heart beats at which point suction was relieved by manual reduction in pump speed. Because these pressures were associated with a pulmonary capillary wedge pressure of -5 mm Hg as well, they indicate total collapse of the entire pulmonary venous system, left atrium, and left ventricle which persisted until pump flow requirement was relieved by reducing pump speed. We suggest that this collapse caused the whole vascular region from pulmonary capillaries to distal left ventricle to behave as a Starling resistance which further reduced right ventricular output thus contributing to a major reduction in pump flow. We contend that similar complications of manual speed control also occur in the human subject and remain a major unsolved problem in the clinical management of patients implanted with rotary blood pumps.

Experimental study of cavitation phenomenon in a centrifugal blood pump induced by the failure of inlet cannula

Cavitation of centrifugal blood pump is a serious problem accompany with the blocking failure of short inlet cannula. However, hardly any work has been seen in published literature on this complex cavitation phenomenon caused by the coupling effect of inlet cannula blocking and pumps suction. Even for cavitation studies on ordinary centrifugal pumps, similar researches on this issue are rare. In this paper, the roles of throttling, rotation speed and fluid viscosity on bubble inception and intensity in a centrifugal blood pump are studied, on the basis of experimental observations. An adjustable throttle valve installed just upstream blood pump inlet is used to simulate the throttling effect of the narrowed inlet cannula. The rotation speed is adjusted from 2 600 r/min to 3 200 r/min. Glycerin water solutions are used to investigate the influences of kinetic viscosity. Bubbles are recorded with a high-speed video camera. Direct observation shows that different from cavitation in industrial centrifugal pumps, gas nuclei appears at the nearby of vane leading edges while throttling is light, then moves upstream to the joint position of inlet pipe and pump with the closing of the valve. It’s found that the critical inlet pressure, obtained when bubbles are first observed, decreases linearly with viscosity and the slope is independent with rotation speeds; the critical inlet pressure and the inlet extreme pressure which is obtained when the throttle valve is nearly closed, fall linearly with rotation speed respectively and the relative pressure between them is independent with rotation speed and fluid viscosity. This paper studies experimentally on cavitation in centrifugal blood pump that caused by the failure of assembled short inlet cannula, which may beneficial the design of centrifugal blood pump with inlet cannula.

In Vitro Assessment of the Apico Aortic Blood Pump: Anatomical Positioning, Hydrodynamic Performance, Hemolysis Studies, and Analysis in a Hybrid Cardiovascular Simulator

The Apico Aortic Blood Pump (AABP) is a centrifugal continuous flow left ventricular assist device (LVAD) with ceramic bearings. The device is in the initial development phase and is being designed to be attached directly to the left ventricular apex by introducing an inlet cannula. This paper reports results from in vitro experiments. In order to evaluate implantation procedures and device dimensioning, in vitro experiments included an anatomic positioning study for the analysis of surgical implantation procedure and device dimensions and positioning that was performed using the body of a pig. The results revealed no damage caused by the device, and the surgical implantation procedure was considered feasible. Hydrodynamic performance curves were obtained to verify the applicability of the device as an LVAD, showing adequate performance. Mechanical blood trauma was analyzed through 6-h hemolysis tests, with total pressure head of 100 mm Hg and flow of 5 L/min. Mean normalized index of hemolysis was 0.009 g/100 L (±0.002 g/100 L). Studies using a hybrid cardiovascular simulator were conducted for three types of circulatory conditions: normal healthy conditions, concentric hypertrophic heart failure (CHHF), and CHHF with AABP assistance. Analysis of cardiovascular parameters under those three conditions demonstrated that when the AABP was assisting the system, parameters under CHHF conditions went back to normal healthy values, indicating the AABP's effectiveness as CHHF therapy. Our preliminary results indicate that it is feasible to use the AABP as a LVAD. The next steps include long-term in vivo experiments.

246 * A MONITORING AND PHYSIOLOGICAL CONTROL SYSTEM FOR DETERMINING AORTIC VALVE CLOSING

Objectives: Accurate monitoring and assessment of the residual cardiac function of a patient supported by a ventricular assist device (VAD) is critical for better patient management and potential weaning. Information regarding the VAD speed at which the aortic valve remains closed can assist clinicians to maintain appropriate unloading, reduce the risk of aortic insufficiency and potentially reduce the risk of aortic leaflet fusion. Methods: A pressure sensor implanted in the inlet cannula determines the left ventricular (LV) pressure. The area of the LV pressure and motor power is calculated for each heart beat. A feedback signal is monitored at high speed and low speed to determine the change in the system. Small amplitude (<300 rpm) and low frequency (<0.1 Hz) square wave changes to the VAD speed are made. Results: Ten ovine trials have been completed with the DP3 pump (LV to aortic cannulation). The feedback variable (pressure power area) proved to have a peak at the speed of aortic valve closure The gradient (Δ pressure power area) could be measured by using the square wave speed modulation. In both the baseline and beta blocked heart the zero-crossing of gradient occurred at the aortic closure speed. Conclusions: Feedback gives a definite peak around aortic valve closure point and uses pump speed modulation for more accuracy; there is no sensitivity to sensor drift or haematocrit changes, and it provides noninvasive, continuous measurement.

Transthoracic Echocardiography of the HeartWare Left Ventricular Assist Device

BackgroundThe unique findings on transthoracic echocardiography of the HeartWare left ventricular assist device (LVAD) have not been previously described. Methods and ResultsHeartWare LVADs were implanted in 19 patients from May 2009 through December 2010; 152 comprehensive transthoracic echocardiograms (TTEs) performed postoperatively on these patients were retrospectively analyzed for device component visualization, inlet cannula/outflow conduit flow velocities, and imaging artifacts. The inlet cannula was adequately visualized in 66% of studies, incompletely visualized in 14%, and not visualized in 20%. Spectral Doppler interrogation of inlet cannula flow velocity was always uninterpretable due to artifact. Standard parasternal long-axis and apical views always included the inlet cannula in the imaging sector, resulting in a prominent “waterfall” color Doppler artifact obscuring the mitral valve. Inclusion of the inlet cannula in the imaging sector also precluded spectral Doppler interrogation of the mitral valve owing to artifact. The outflow conduit was partially visualized and interrogated by spectral Doppler in 68% of studies, and the average measured peak flow velocity was 1.4 m/s (range 1.0–1.9 m/s). ConclusionsThe HeartWare LVAD inlet cannula and outflow conduit are both readily visualized by TTE in a majority of patients. However, significant color and spectral Doppler artifacts occur when the inlet cannula is visualized in the imaging sector, necessitating routine off-axis Doppler interrogation of the mitral valve.

말기 심질환 환자를 위한 심실보조장치용 심박조율기의 개발

In this paper, we developed a pacemaker that can increase the efficacy of a left ventricular assist device (LVAD) and increase the survival rate for patients suffering end-stage heart failure. Because LVAD patients can experience arrhythmia, the pacemaker incorporated into the LVAD has the important role of sustaining sufficient blood circulation during arrhythmia. The electrode of the pacemaker is located at the apex of the left ventricle, where the VAD's inlet cannula is connected. This is efficient placement, in that the electrode can transmit electrical stimulation directly to the Purkinje fibers of the myocardium. The pacemaker can change the stimulation rate from 0 bpm to 191.4 bpm when a button is pressed on the external control module, and the pacemaker normally stimulates the heart at 60 bpm with 0.25 J of energy. We performed animal experiments to evaluate the performance and reliability of the combination of the LVAD and pacemaker. At pacemaker stimulation rates of 86.4 bpm, 100.2 bpm, 126.6 bpm, we recorded the ECGs, aortic pressures, and flow rates to analyze the heart loads.

Comparison of Preload‐Sensitive Pressure and Flow Controller Strategies for a Dual Device Biventricular Support System

The use of rotary left ventricular assist devices (LVADs) has extended to destination and recovery therapy for end-stage heart failure. Incidence of right ventricular failure while on LVAD support requires a second device be implanted to support the failing right ventricle. Without a commercially available implantable rotary right ventricular assist device, rotary LVADs are cannulated into the right heart and operation modified to provide suitable support for the pulmonary system. While this approach can alleviate the demand for transplant through long-term biventricular support, it uncovers a new challenge with respect to controller strategies for these dual device support systems. This study compares the preload sensitivity of rotary, dual device biventricular assistance controllers in light of their ability to adjust the flow rate according to physiological demand. A Frank-Starling-like flow controller which requires both inlet pressure and flow sensors is compared to pressure controllers which maintain atrial or inlet cannula pressures through the use of a single pressure sensor. It was found that cannula selection and the location of a pressure controller's single pressure sensor can be tailored to adjust the preload sensitivity. When located within the atria, this sensitivity is effectively infinite. Moving the sensor to the base of a 450-mm cannula, however, decreased the sensitivity to 0.22 (L/min)/mm Hg. This indicates the potential for simple and reliable VAD controllers with increased preload sensitivity without the need for complex controllers requiring an array of hemodynamic sensors.

Transthoracic Echocardiography of the HeartWare Left Ventricular Assist Device

Transthoracic Echocardiography of the HeartWare Left Ventricular Assist Device

Diaphragmatic implantation of the HeartWare ventricular assist device

The HeartWare (HeartWare Inc., Framingham, MA) ventricular assist device (HVAD) is designed to be implanted with the pump in the pericardial space and its integrally attached inflow cannula in the left ventricle. The uniquely incorporated inflow cannula was originally designed to be inserted into the diaphragmatic surface of the heart, allowing the pump to sit on the flattened diaphragmatic surface. Commonly, however, the inflow cannula is placed through the usual left ventricular assist device insertion site, anterolateral to the left ventricular apex. We describe the original, intended technique for inflow cannula insertion and HVAD placement on the diaphragmatic surface of the left ventricle. Our experience has confirmed that this placement results in the optimal left ventricular position, with orientation of the inlet cannula parallel to the short axis of the left ventricle and anterior to the papillary muscle insertion. This approach should protect against inflow obstruction and endocardial contact, with resulting arrhythmias. In addition, this position results in lateral placement of the outflow graft, avoiding the anterior and retrosternal surface of the right ventricle.

402 複合低エネルギによる金属と生体組織の接合技術(OS5-(1)オーガナイズドセッション《ライフサポートにおける工学技術》)

We have proposed an adhesion method by using integrated low-level energy sources of heat, vibration and pressure. This adhesion method is expected to be applied to adhere biological tissue to the metal specimen such as stent-graft and blood inlet cannula of ventricular assist devices. Shear tensile tests on porcine aorta adhered to stainless steel were performed to determine the relationship between adhesive strength and adhesion conditions, such as pre heated temperature at heater tip, method for applying heat to biological tissue and stainless steel. The average adhesive strength was 0.148 MPa under the condition with pre heated temperature of 200 ℃, on adhesion time 120 seconds, on adhesion pressure of 2.5 MPa, in the heating from stainless steel. The adhesive performance was found to be improved by applying heat from metal in adhesion biological tissue to metal.

In Vivo Biocompatibility Evaluation of a New Resilient, Hard-Carbon, Thin-Film Coating for Ventricular Assist Devices

The purpose of this study was to evaluate in vivo the biocompatibility of BioMedFlex (BMF), a new resilient, hard-carbon, thin-film coating, as a blood journal bearing material in Cleveland Heart's (Charlotte, NC, USA) continuous-flow right and left ventricular assist devices (RVADs and LVADs). BMF was applied to RVAD rotating assemblies or both rotating and stator assemblies in three chronic bovine studies. In one case, an LVAD with a BMF-coated stator was also implanted. Cases 1 and 3 were electively terminated at 18 and 29 days, respectively, with average measured pump flows of 4.9 L/min (RVAD) in Case 1 and 5.7 L/min (RVAD) plus 5.7 L/min (LVAD) in Case 3. Case 2 was terminated prematurely after 9 days because of sepsis. The sepsis, combined with running the pump at minimum speed (2000 rpm), presented a worst-case biocompatibility challenge. Postexplant evaluation of the blood-contacting journal bearing surfaces showed no biologic deposition in any of the four pumps. Thrombus inside the RVAD inlet cannula in Case 3 is believed to be the origin of a nonadherent thrombus wrapped around one of the primary impeller blades. In conclusion, we demonstrated that BMF coatings can provide good biocompatibility in the journal bearing for ventricular assist devices.