Cannula Position Research Articles

The effect of drainage cannula tip position on risk of thrombosis during venoarterial extracorporeal membrane oxygenation

Background and objectivesVenoarterial extracorporeal membrane oxygenation (VA ECMO) is able to support critically ill patients undergoing refractory cardiopulmonary failure. It relies on drainage cannulae to extract venous blood from the patient, but cannula features and tip position may impact flow dynamics and thrombosis risk. Therefore, this study aimed to investigate the effect of tip position of single-stage (SS) and multi-stage (MS) VA ECMO drainage cannulae on the risk of thrombosis. MethodsComputational fluid dynamics was used to model flow dynamics within patient-specific geometry of the venous vasculature. The tip of the SS and MS cannula was placed in the superior vena cava (SVC), SVC-Right atrium (RA) junction, mid-RA, inferior vena cava (IVC)-RA junction, and IVC. The risk of thrombosis was assessed by measuring several factors. Blood residence time was measured via an Eulerian approach through the use of a scalar source term. Regions of stagnant volume were recognised by identifying regions of low fluid velocity and shear rate. Rate of blood washout was calculated by patching the domain with a scalar value and measuring the rate of fluid displacement. Lastly, wall shear stress values were determined to provide a qualitative understanding of potential blood trauma. ResultsThrombosis risk varied substantially with position changes of the SS cannula, which was less evident with the MS cannula. The SS cannula showed reduced thrombosis risk arising from stagnant regions when placed in the SVC or SVC-RA junction, whereas an MS cannula was predicted to create stagnant regions during all tip positions. When positioned in the IVC-RA junction or IVC, the risk of thrombosis was higher in the SS cannula than in the MS cannula due to both high and low shear flow. ConclusionTip position of the drainage cannula impacts cannula flow dynamics and, subsequently, the risk of thrombosis. The use of MS cannulae can reduce high shear-related thrombosis, but SS cannulae can eliminate stagnant regions when advanced into the SVC. Therefore, the choice of cannula design and tip position should be carefully considered during cannulation.

Comparing left ventricular assist device inflow cannula angle between median sternotomy and thoracotomy using 3D reconstructions.

Left ventricular assist device (LVAD) implantation via thoracotomy has many potential advantages compared to conventional sternotomy, including improved inflow cannula (IFC) positioning. We compared the difference in IFC angles, postoperative, and long-term outcomes for patients with LVADs implanted via thoracotomy and sternotomy. A single-center, retrospective analysis of 14 patients who underwent thoracotomy implantation was performed and matched with 28 patients who underwent sternotomy LVAD implantations for a total of 42 patients. Inclusion required a minimum LVAD support duration of 30 days and excluded concomitant procedures. A postoperative CT-chest was used to measure the angle the between the IFC and mitral valve in two-dimensions and results were compared with three-dimensional reconstruction using the same CT chest. Outcome data were extracted from medical records. There was no significant difference in gender, INTERMACS score, BMI, or age between the two groups. Median cardiopulmonary bypass time was longer in the thoracotomy group compared to the sternotomy group, 107min (86-122) versus 76min (56-93), p < 0.01. 3D reconstructions revealed less deviation of the IFC away from the mitral valve in devices implanted via thoracotomy compared to sternotomy, median (IQR) angle 16.3° (13.9°-21.0°) versus 23.2° (17.9°-26.4°), p < 0.01. Rates of pump thrombosis, stroke, and gastrointestinal bleeding were not significantly different. Devices implanted via thoracotomy demonstrated less deviation away from mitral valve. However, there was no difference in morbidity between the two approaches. 3D reconstruction of the heart is an innovative technique to measure angulation and is clinically advantageous when compared to 2D imaging.

Ex Vivo Evaluation of a Pressure-Sensitive Device to Aid Big Bubble Intrastromal Dissection in Deep Anterior Lamellar Keratoplasty.

To develop and perform ex vivo testing for a device designed for semiquantitative determination of intracorneal dissection depth during big bubble (BB) deep anterior lamellar keratoplasty. A prototype device connected to a syringe and cannula was designed to determine depth of intrastromal placement based on air rebound pressure emitted by a software controlled generator. Ex vivo testing of the device was conducted on human corneas mounted on an artificial anterior chamber in three experiments: (1) cannula purposely introduced at different depths measured with anterior segment optical coherence tomography, (2) cannula introduced as per the BB technique, and (3) simulation of the BB technique guided by the device. A positive pressure differential and successful BB were observed only when the cannula was positioned within 150 microns from the endothelial plane. In all successful BB cases (21/40), a repeatable increase in tissue rebound pressure was detected, which was not recorded in unsuccessful cases. The device was able to signal to the surgeon correct placement of the cannula (successful BB) in 16 of 17 cases and incorrect placement of the cannula (unsuccessful BB) in 8 of 8 cases (94.1% sensitivity, 100% specificity). In our ex vivo model, this novel medical device could reliably signal cannula positioning in the deep stroma for effective pneumatic dissection and possibly aid technical execution of BB deep anterior lamellar keratoplasty. A medical device that standardizes big bubble deep anterior lamellar keratoplasty could increase the overall success rate of the surgical procedure and aid popularization of deep anterior lamellar keratoplasty.

The Role of Echocardiography in Extracorporeal Membrane Oxygenation.

Extracorporeal membrane oxygenation (ECMO) is increasingly used to temporarily support patients in severe circulatory and/or respiratory failure. Echocardiography is a core component of successful ECMO deployment. Herein, we review the role of echocardiography at different phases on extracorporeal support including candidate identification, cannulation, maintenance, complication vigilance, and decannulation. During cannulation, ultrasound is used to confirm intended vascular access and appropriate inflow cannula positioning.While on ECMO, echocardiographic evaluation of ventricular loading conditions and hemodynamics, cannula positioning, and surveillance for intracardiac or aortic thrombi is needed for complication mitigation. Echocardiography is crucial during all phases of ECMO use. Specific echocardiographic queries depend on the ECMO type, V-V, or V-A, and the specific cannula configuration strategy employed.

Variability in low-flow oxygen delivery by nasal cannula evaluated in neonatal and infant airway replicas

BackgroundThe nasal cannula is considered a trusted and effective means of administering low-flow oxygen and is widely used for neonates and infants requiring oxygen therapy, despite an understanding that oxygen concentrations delivered to patients are variable.MethodsIn the present study, realistic nasal airway replicas derived from medical scans of children less than 3 months old were used to measure the fraction of oxygen inhaled (FiO2) through nasal cannulas during low-flow oxygen delivery. Parameters influencing variability in FiO2 were evaluated, as was the hypothesis that measured FiO2 values could be predicted using a simple, flow-weighted calculation that assumes ideal mixing of oxygen with entrained room air. Tidal breathing through neonatal and infant nasal airway replicas was controlled using a lung simulator. Parameters for nasal cannula oxygen flow rate, nasal airway geometry, tidal volume, respiratory rate, inhalation/exhalation, or I:E ratio (ti/te), breath waveform, and cannula prong insertion position were varied to determine their effect on measured FiO2. In total, FiO2 was measured for 384 different parameter combinations, with each combination repeated in triplicate. Analysis of variance (ANOVA) was used to assess the influence of parameters on measured FiO2.ResultsMeasured FiO2 was not appreciably affected by the breath waveform shape, the replica geometry, or the cannula position but was significantly influenced by the tidal volume, the inhalation time, and the nasal cannula flow rate.ConclusionsThe flow-weighted calculation overpredicted FiO2 for measured values above 60%, but an empirical correction to the calculation provided good agreement with measured FiO2 across the full range of experimental data.

Blood flow but not cannula positioning influences the efficacy of Veno-Venous ECMO therapy

Despite being vital in treating intensive-care patients with lung failure, especially COVID-19 patients, Veno-Venous Extra-Corporeal Membrane Oxygenation does not exploit its full potential, leaving ample room for improvement. The objective of this study is to determine the effect of cannula positioning and blood flow on the efficacy of Veno-Venous Extra-Corporeal Membrane Oxygenation, in particular in relationship with blood recirculation. We performed 98 computer simulations of blood flow and oxygen diffusion in a computerized-tomography-segmented right atrium and venae cavae for different positions of the returning and draining cannulae and ECMO flows of 3 L/min and 5,hbox {L}/hbox {min}. For each configuration we measured how effective Veno-Venous Extra-Corporeal Membrane Oxygenation is at delivering oxygen to the right ventricle and thus to the systemic circulation. The main finding is that VV-ECMO efficacy is largely affected by the ECMO flow (global peak blood saturation: {92.8},%; average inter-group saturation gain: 9 percentage points) but only scarcely by the positioning of the cannulae (mean saturation ± standard deviation for the 3 L/min case: 83.12 pm 0.49; for the 5,hbox {L}/hbox {min} case: 92.21 pm 0.37). An important secondary outcome is that recirculation, more intense with a higher ECMO flow, is less detrimental to the procedure than previously thought. The efficacy of current ECMO procedures is intrinsically limited and fine-tuning the positions of the cannulae, risking infections, offers very little gain. Setting a higher ECMO flow offers the biggest benefit despite mildly increasing blood recirculation.

Identification of the Optimal Position of a Nasal Oxygen Cannula for Apneic Oxygenation: A Technical Simulation.

In a cannot-ventilate-cannot-intubate situation, careful preoxygenation with high FiO2 allowing subsequent apneic oxygenation can be life-saving. The best position for an oxygen supply line within the human airway at which oxygen insufflation is more effective than standard preoxygenation with a face mask is unknown. In this experimental study, we compared the effectiveness of preoxygenation by placing an oxygen cannula at the nose entrance, through the nose at the soft palatine, or at the base of the tongue; as a control we used ambient air. We connected a fully preoxygenated test lung on one side to an oximeter with a flow rate of 200 mL/min simulating the oxygen consumption of a normal adult on the other side of the trachea of an anatomically correctly shaped airway manikin over a 20 min observation period five times for each cannula placement in a random order. The oxygen percentage in the test lung dropped from 100% in all groups to 53 ± 1% in the ambient air control group, to 87 ± 2% in the nasal cannula group, and to 96 ± 2% in the soft palatine group; it remained at 99 ± 1% in the base of the tongue group (p = 0.003 for the soft palatine vs. base of the tongue and p &lt; 0.001 for all other groups). When simulating apneic oxygenation in a preoxygenated manikin, oxygen insufflation at the base of the tongue kept the oxygen percentage at baseline values of 99%, demonstrating a complete block of ambient air flowing into the airway of the manikin. Oxygen insufflation at the soft palatine or insufflation via a nasal cannula were less effective regarding this effect.

Confirmation of Dual Lumen Cannula Position Before Extracorporeal Membrane Oxygenation Initiation Using a Microbubbles Contrast Technique.

Dual lumen cannulas (DLCs) for venovenous extracorporeal membrane oxygenation (ECMO) therapy are introduced in the right internal jugular vein, passing through the superior vena cava and the right atrium (RA) down to the inferior vena cava. The correct placement is challenging and needs careful positioning to limit mechanical complications. The outflow port needs to be located in the RA and directed toward the tricuspid valve (TV) to optimize therapy and reduce recirculation rate. Transesophageal echocardiography (TEE) is considered the standard to monitor insertion and optimal placement of this type of cannula. In addition to TEE 2D imaging, confirmation of optimal positioning is possible after ECMO initiation using color Doppler in a bicaval view to visualize the reinfusion jet located in the RA and pointing toward the TV. We present an example of DLC implantation where correct positioning was confirmed before ECMO initiation using a microbubbles contrast technique. Using TEE 2D imaging, in a bicaval (Figure 1, A and B) and modified bicaval view (Figure 1, C and D), we depict the contrast obtained while flushing the reinjection port of the DLC with saline, simulating the reinfusion jet adequately directed toward the TV (arrows in Figure 1, B and D). We use a 50 cc catheter tip syringe (conical tip) with 0.9% saline to rapidly flush the DLC. The turbulences and bubbles created provide sufficient contrast.Figure 1.: A: Bicaval view and (C) modified bicaval view without contrast; (B) bicaval and (C) modified bicaval view with contrast. DLC, dual lumen cannula; IVC, inferior vena cava; RA, right atrium; SVC, superior vena cava; TV, tricuspid valve.The authors believe that this technique helps to ensure immediate optimal efficiency of venovenous ECMO and avoid further correction of cannula position after ECMO initiation (See Video, Supplemental Digital Content 1, https://links.lww.com/ASAIO/A878).

Abstract 285: Traditional Cardiopulmonary Resuscitation In Cardiac Arrest For Patients On Venovenous Extracorporeal Membrane Oxygenation

Introduction: Mortality for patients on VV-ECMO remains high despite increased use during the COVID-19 pandemic. Unlike VA-ECMO which provides life support for cardiac failure and can be used as a bridge to definitive therapy during cardiac arrest (e-CPR), patients who arrest while on VV-ECMO currently may undergo traditional cardiopulmonary resuscitation (CPR). This poses many challenges such as potential cannula position disruption of the VV-ECMO system during compressions and it is unclear if patients on VV-ECMO will benefit from being offered traditional CPR. Hypothesis: Traditional CPR is effective in patients who arrest while on VV-ECMO. Methods: A retrospective chart review of inpatient cardiac arrest data from a high-volume ECMO center was performed. Patients who arrested while on VV-ECMO were included. Data including demographics, etiology of arrest, return of spontaneous circulation (ROSC) and survival to discharge were reviewed. Survival data was compared with the ECLS International Summary of Statistics. Results: We identified 19 patients on VV-ECMO who underwent CPR for cardiac arrest between September 2012 and November 2021. The average age of the patients was 42.7 years and 89.5% (n=17) were men. Seven of the nineteen total patients (36.8%) were being treated for ARDS from COVID-19 pneumonia. The arrest occurred on average 35.6 days into hospitalization (range: 1-132 days). The initial rhythm was pulseless electrical activity in 13 patients (68.4%), and the etiologies of arrest included hypoxemia (n=10, 52.6%), ECMO machine failure or during oxygenator exchange (n=3, 15.8%), pneumothorax (n=2, 10.5%), and cardiac tamponade (n=1, 5.3%). ROSC occurred in all 19 patients (100%), however only 4 patients (21.1%) survived to discharge with good neurologic recovery. Survival to discharge for all-comers on VV-ECMO is 66%. Conclusions: While there is limited evidence for the effectiveness of traditional CPR for patients on VV-ECMO, in this sample, ROSC was universal and one-fifth of patients survived to discharge. Future studies should continue to study the utility of CPR on VV-ECMO and how to optimize technique to improve outcomes for these critically-ill patients.

Airway Ultrasound for Anesthesia and in Intensive Care Patients-A Narrative Review of the Literature.

Ultrasound is an everyday diagnostic tool. In anesthesia and intensive care, it has a role as an adjuvant for many procedures, including the evaluation of the airway. Ultrasound airway evaluation can help predict a difficult airway, visualize the proper positioning of an intubation cannula, or evaluate the airway post-intubation. Protocols need to be established for the better integration of ultrasound in the airway evaluation, however until a consensus is reached in this respect, the ultrasound is a reliable aid in anesthesia and intensive care.

The impact of ECMO lower limb cannulation on the aortic flow features under differential blood perfusion conditions

The purpose of this study is to investigate the impact of veno-arterial (VA) ECMO cannulation on hemodynamic distribution and organ perfusion within aorta under differential blood perfusion conditions. The total blood flow volume supplied by failure heart and ECMO keep constant, flow volume ratio of heart output (FVR-HO) increases from 0% to 100% and correspondingly flow volume ratio of ECMO (FVR-ECMO) decreases from 100% to 0%. The flow patterns within aorta, wall shear stress (WSS), oscillatory shear index (OSI), relative retention time (RRT) were analyzed. The locations of oxygenated and de-oxygenated blood mixing region (BMR) was influenced by FVR-HO. With FVR-HO increasing, BMR moves from proximal to distal side of heart. When FVR-HO was 0%, oxygenated blood supplied by ECMO completely perfuses the aortic vessels. High WSS appears in the iliac artery and abdominal aorta vessel walls closed to cannula position. When FVR-HO was in the range of 10%–30%, the BMR was in aortic arch. The higher OSI and RRT were exhibited in ascending aorta and aorta arch. When FVR-HO was 40% and 50%, the BMR was in ventral trunk for systolic period and in aortic arch for diastolic period. The higher OSI and RRT regions enlarge and metastasize to the descending aorta. When FVR-HO was larger than 50%, the BMR was in the downstream region of the renal artery. Of note, when FVR-HO increases from 0% to 100%, the flow ratios in the two renal arteries change from significant different to be closed at systolic period. Peripheral VA-ECMO with various perfusion levels from cardiac output and ECMO has significant effect on aortic flow surrounding. Partial recovery of heart function can impel BMR moves from proximal to distal side of the heart, which may lead to inadequate supply of oxygenated blood to the upper limb and cephalic vessels.

Continuous manual agitation significantly improves temperature distribution during closed hyperthermic intraperitoneal chemotherapy: Results of a porcine model

BackgroundDebate persists regarding the need for shaking during hyperthermic intraperitoneal chemotherapy. Studies assessing the thermal behaviors of the perfusate throughout the abdomen during hyperthermic intraperitoneal chemotherapy are limited. MethodsA closed hyperthermic intraperitoneal chemotherapy technique was performed in an institutional International Animal Care and Use Committee approved porcine model targeting a 41°C outflow temperature. Continuous temperature monitoring was conducted. Abdominal shaking was performed for 60 second intervals and temperatures were allowed to equilibrate without shaking between intervals. Temperature distributions and changes due to shaking were evaluated. These findings were validated against human subjects’ data. ResultsThe experimental procedure was conducted in 2 different animals and with 6 total shaking intervals assessed. Without shaking, temperatures were highly variable ranging between 38.0 to 42.2°C. Shaking the abdomen reduced the mean range of temperatures across all locations observed from 3.9°C to 0.8°C (P < .01). The locations of the most divergent temperatures varied based on perfusion cannula position. The point of minimum temperature heterogeneity was achieved in 28.3 (19.1–37.5) seconds. After shaking stopped, heterogeneity equal to the baseline measurements was seen on average within 25.7 (13.3–38.0) seconds. The outflow catheter differed from the system mean temperature by 1.4°C and from the coldest-reading probe by 2.8°C and outperformed the inflow catheter for all time points. With shaking these were significantly reduced to 0.4°C (P < .01) and 0.6°C (P < .01). The patient data mirrored that of the pig data. ConclusionShaking significantly reduces temperature variability within the abdomen during hyperthermic intraperitoneal chemotherapy, and significantly improves the ability of the outflow catheter to estimate internal temperatures.

HeartMate 3 implantation for dextro-transposition of the great arteries after Mustard procedure: A technique of papillary muscle repositioning.

Systemic right ventricular failure after physiologic repair for dextro-transposition of the great arteries can be managed with durable mechanical circulatory support; however, the right ventricular morphology, such as intervening papillary muscles, presents challenges to inflow cannula positioning. Papillary muscle repositioning is an innovative technique to circumvent obstructive anatomy.

Transesophageal Echocardiography-Guided Extracorporeal Membrane Oxygenation Cannulation in COVID-19 Patients

ObjectivesA paucity of data supports the use of transesophageal echocardiography (TEE) for bedside extracorporeal membrane oxygenation (ECMO) cannulation. Concerns have been raised about performing TEEs in patients with COVID-19. The authors describe the use and safety of TEE guidance for ECMO cannulation for COVID-19.DesignSingle-center retrospective cohort study.SettingThe study took place in the intensive care unit of an academic tertiary center.ParticipantsThe authors included 107 patients with confirmed SARS-CoV-2 infection who underwent bedside venovenous ECMO (VV ECMO) cannulation under TEE guidance between May 2020 and June 2021.InterventionsTEE-guided bedside VV ECMO cannulation.MeasurementsPatient characteristics, physiologic and ventilatory parameters, and echocardiographic findings were analyzed. The primary outcome was the number of successful TEE-guided bedside cannulations without complications. The secondary outcomes were cannulation complications, frequency of cannula repositioning, and TEE-related complications.Main ResultsTEE-guided cannulation was successful in 99% of the patients. Initial cannula position was adequate in all but 1 patient. Fourteen patients (13%) required cannula repositioning during ECMO support. Forty-five patients (42%) had right ventricular systolic dysfunction, and 9 (8%) had left ventricular systolic dysfunction. Twelve patients (11%) had intracardiac thrombi. One superficial arterial injury and 1 pneumothorax occurred. No pericardial tamponade, hemothorax or intraabdominal bleeding occurred in the authors’ cohort. No TEE-related complications or COVID-19 infection of healthcare providers were reported during this study.ConclusionsBedside TEE guidance for VV ECMO cannulation is safe in patients with severe respiratory failure due to COVID-19. No tamponade or hemothorax, nor TEE-related complications were observed in the authors’ cohort.

Left ventricular assist device and pump thrombosis: the importance of the inflow cannula position

Pump thrombosis is a devastating complication after left ventricular assist device implantation. This study aims to elucidate the relation between left ventricular assist device implantation angle and risk of pump thrombosis. Between November 2010 and March 2020, 53 left ventricular assist device-patients underwent a computed tomography scan. Using a 3-dimensional multiplanar reformation the left ventricular axis was reconstructed to measure the implantation angle of the inflow cannula. All patients were retrospectively analyzed for the occurrence of pump thrombosis. In 10 (91%) patients with a pump thrombosis, the implantation angle was towards the lateral wall of the left ventricle. In only 20 patients (49%) of the patients without a pump thrombosis the inflow cannula pointed towards the lateral wall of the left ventricle. The mean angle in patients with a pump thrombosis was 10.1 ± 11.9 degrees towards the lateral wall of the left ventricle compared to 4.1 ± 19.9 degrees towards the septum in non-pump thrombosis patients (P = 0.005). There was a trend towards a significant difference in time to first pump thrombosis between patients with a lateral or septal deviated left ventricular assist device (hazard ratio of 0.15, P = 0.07). This study demonstrates that left ventricular assist device implantation angle is associated with pump thrombosis. Almost all patients in whom a pump thrombosis occurred during follow-up had a left ventricular assist device implanted with the inflow-cannula pointing towards the lateral wall of the left ventricle.

Computational fluid dynamics analysis of endoluminal aortic perfusion.

In peripheral percutaneous (VA) extracorporeal membrane oxygenation (ECMO) procedures the femoral arteries perfusion route has inherent disadvantages regarding poor upper body perfusion due to watershed. With the advent of new long flexible cannulas an advancement of the tip up to the ascending aorta has become feasible. To investigate the impact of such long endoluminal cannulas on upper body perfusion, a Computational Fluid Dynamics (CFD) study was performed considering different support levels and three cannula positions. An idealized literature-based- and a real patient proximal aortic geometry including an endoluminal cannula were constructed. The blood flow was considered continuous. Oxygen saturation was set to 80% for the blood coming from the heart and to 100% for the blood leaving the cannula. 50% and 90% venoarterial support levels from the total blood flow rate of 6 l/min were investigated for three different positions of the cannula in the aortic arch. For both geometries, the placement of the cannula in the ascending aorta led to a superior oxygenation of all aortic blood vessels except for the left coronary artery. Cannula placements at the aortic arch and descending aorta could support supra-aortic arteries, but not the coronary arteries. All positions were able to support all branches with saturated blood at 90% flow volume. In accordance with clinical observations CFD analysis reveals, that retrograde advancement of a long endoluminal cannula can considerably improve the oxygenation of the upper body and lead to oxygen saturation distributions similar to those of a central cannulation.

A Computed Tomography Reconstruction Software To Model Ventricular Assist Device Implantation Position

<h3>Introduction</h3> As ventricular assist device (VAD) technology continues to evolve, the target population for left and right sided support continues to grow. Therefore the degree of variability in cardiac anatomy and geometry in potential VAD recipients is likely to increase. Studying the cardiac geometry in relation to HeartMate 3 or HVAD device dimensions can help preoperative evaluation for ideal cannulation placement, and thereby potentially improve long term outcomes. Aims: Our project aims to develop a program that virtually models a VAD into the three-dimensional-rendering of the myocardium and chest using computed tomography images. <h3>Methods and Results</h3> We created a Python code process, a 4D retrospective cardiac CT dataset and then integrated a high definition 3D VAD model. Rather than creating a full-fledged viewer and analytics tool, which would be too costly and time-intensive, we created a tool that can be used to complement the capabilities of professional imaging processing software such as 3mensio or Visage (Figure 1 Demonstrates the program graphical user interface). The user can adjust the viewer to better isolate the heart prior to simulated VAD implant placement. The DICOM directories produced by our program can be opened directly in the software already used in daily clinical imaging to allow for more in-depth analysis of desired implant placement and cannula positioning, which can aid in pre-operative and intra-operative planning. <h3>Conclusions</h3> The next steps of the project will be to enable VAD implant model to be propagated across the 3D scan time series, increase computational efficiency and view clarity, as well as output the resulting DICOM directory so it can be opened in Visage or a similar tool. In a future version of the project, we will include an automatic placement feature and fluid dynamic analysis to validate the proposed implant location.

Association of Outflow Cannula Angulation with Adverse Neurological Events in Patients with CF-LVAD

<h3>Purpose</h3> Adverse neurological outcomes are the Achilles heel of the current day LVAD technology and are associated with worse survival. Our previous data suggests that outflow cannula (OFC) angles measured using cardiac CT may correlate with stroke in continuous-flow HeartMate II patients. Therefore, the aim of our study was to assess the relationship of inflow cannula (IFC) and outflow cannula (OFC) position with neurological outcomes centrifugal flow pumps (HM3 and HVAD). <h3>Methods</h3> 108 patients underwent LVAD implantation between 2015 and 2019 at our institution. Of these, 68 patients underwent cardiac CT, and 6 were excluded due to poor image quality. Of these patients, a total of 32 neurological events (NE) occurred in 20 patients. These cases were compared to patients with CT data who did not have NEs. 2D angle measurements were performed on positions of OFC relative to the ascending aorta and IFC relative to the mitral valve. Further we used a novel point-based 3D measurement system to determine the angles in an x-y-z plane. Baseline demographic data and outcome data were collected for all patients. Optimal cut-point of the OFC angle was determined using ROC curve analysis. <h3>Results</h3> Of the 62 patients recruited for this study, 65% had HM3 and 35% had HVAD. The median OFC angle on 2D in patients with NE was 59.8 degrees relative to the aorta, compared with a median angle of 51.7 degrees in patients without NE (p=0.02). Similarly on 3D angle measurements, a median OFC angle of 86.7 degree was observed in patients with NE, compared to a median angle of 77.4 degrees in patients without NE (p=0.01). IFC angle was not associated with an increased risk of NE. The ROC curve analysis showed optimal OFC angle was < 53 degrees in 2D measurements, with sensitivity of 79% and specificity of 61% at predicting NEs. In 3D measurements the optimal OFC angle was less than < 83 degrees with a sensitivity of 79% and a specificity of 61% at predicting NEs. <h3>Conclusion</h3> Optimal angulation of the outflow cannula in LVAD patients can lead to decreased risk for HRAE. Using cardiac CT chest imaging for 2D and 3D measurements, an optimal outflow cannula angulation of < 53 degrees and < 83 degrees, respectively, should be preferred to minimize the risk for HRAE in patients with centrifugal flow LVAD support.

Exploring the Benefit of Thoracotomy LVAD Implant on Subsequent Sternal Entry for Heart Transplantation

<h3>Purpose</h3> Minimally invasive left ventricular assist device (LVAD) implantation via left thoracotomy has previously been shown to be a safe operation with potential advantages compared to sternotomy. These advantages include improved inflow cannula positioning as well as minimising adhesions for subsequent sternal entry for heart transplantation. We wanted to assess the impact of LVAD implant technique on subsequent heart transplantation. <h3>Methods</h3> All patients who received an LVAD via thoracotomy and subsequently transplanted were included. This group was matched 2:1 with patients who received an LVAD via sternotomy and were subsequently transplanted. Patients in the sternotomy group were excluded if they had a prior sternotomy to LVAD insertion. Parameters such as cardiopulmonary bypass time, blood usage, post-operative length of stay, morbidity and mortality measures were extracted. <h3>Results</h3> 12 Thoracotomy patients and 24 sternotomy patients were included in the study. There was no significant difference in gender, BMI or age between the two groups. When assessing operation variables, there was no significant difference in operation duration, cardiopulmonary bypass time or cross clamp time between the sternotomy and thoracotomy groups. Similarly, there was no significant difference in blood product administration (red blood cells, cryoprecipitate, fresh frozen plasma, platelets) intraoperatively. There was no difference in total length of stay, ICU length of stay, ventilation time and 30-day mortality. <h3>Conclusion</h3> In our sample size of 36 patients, we could not demonstrate a significant difference in peri-operative variables between VAD patients who presented for their heart transplant subsequent to receiving an LVAD implanted via either sternotomy or thoracotomy. These findings suggest that while thoracotomy for LVAD insertion may present advantages such as improved inflow cannula positioning, we could not demonstrate a clear benefit in sternal entry for subsequent transplant.

Accuracy of Robotic and Frame-Based Stereotactic Neurosurgery in a Phantom Model

BackgroundThe development of robotic systems has provided an alternative to frame-based stereotactic procedures. The aim of this experimental phantom study was to compare the mechanical accuracy of the Robotic Surgery Assistant (ROSA) and the Leksell stereotactic frame by reducing clinical and procedural factors to a minimum.MethodsTo precisely compare mechanical accuracy, a stereotactic system was chosen as reference for both methods. A thin layer CT scan with an acrylic phantom fixed to the frame and a localizer enabling the software to recognize the coordinate system was performed. For each of the five phantom targets, two different trajectories were planned, resulting in 10 trajectories. A series of five repetitions was performed, each time based on a new CT scan. Hence, 50 trajectories were analyzed for each method. X-rays of the final cannula position were fused with the planning data. The coordinates of the target point and the endpoint of the robot- or frame-guided probe were visually determined using the robotic software. The target point error (TPE) was calculated applying the Euclidian distance. The depth deviation along the trajectory and the lateral deviation were separately calculated.ResultsRobotics was significantly more accurate, with an arithmetic TPE mean of 0.53 mm (95% CI 0.41–0.55 mm) compared to 0.72 mm (95% CI 0.63–0.8 mm) in stereotaxy (p < 0.05). In robotics, the mean depth deviation along the trajectory was −0.22 mm (95% CI −0.25 to −0.14 mm). The mean lateral deviation was 0.43 mm (95% CI 0.32–0.49 mm). In frame-based stereotaxy, the mean depth deviation amounted to −0.20 mm (95% CI −0.26 to −0.14 mm), the mean lateral deviation to 0.65 mm (95% CI 0.55–0.74 mm).ConclusionBoth the robotic and frame-based approach proved accurate. The robotic procedure showed significantly higher accuracy. For both methods, procedural factors occurring during surgery might have a more relevant impact on overall accuracy.