Cannula Position Research Articles

Quantitative Assessment of Inflow Malposition in Two Continuous-Flow Left Ventricular Assist Devices

We previously investigated preoperative variables associated with qualitative inflow cannula malposition in the HeartMate II (Thoratec-Abbott, Abbott Park, IL) continuous-flow left ventricular assist device. In this report, we assess inflow cannula malposition quantitatively in recipients of both the HeartMate II and the HeartWare (Medtronic-HeartWare, Minneapolis, MN) and examine its association with device thrombosis. Malposition was quantified based on angular deviation from a hypothetic ideal inflow cannula position in two orthogonal computed tomography imaging planes. Ideal position lies on a line from the apex to the center of the mitral valve. Positive anterior plane angulation indicates deviation toward the superior free wall; negative, toward the inferior wall. Positive lateral plane angulation indicates deviation toward the septum; negative, toward the lateral wall. Device thrombosis was assessed based on clinical criteria. Fifty-four HeartMate II patients and 68 HeartWare patients were analyzed. Inflow cannula deviation was significantly higher for HeartMate II than for HeartWare (anterior plane angle 36.7 ± 16.8 versus-18.7 ± 11.6 degrees, p < 0.001; lateral plane angle 23.7 ± 20.1 versus 0.2 ± 15.0 degrees, p < 0.001. Pump thrombosis occurred in 31% of HeartMate II patients and 2.9% of HeartWare patients (p < 0.001). In a multivariate model, HeartMate II and increasing inflow cannula deviation toward the septum were associated with higher thrombosis risk (odds ratio 1.35 per 10-degree increase). We found distinct device-dependent differences in inflow cannula positioning and thrombosis, with HeartWare showing both less malposition and less thrombosis. Malposition toward the ventricular septum may contribute to pump thrombosis through a vicious cycle of suction events, low flow, and speed reduction.

Left Ventricular Assist Device Inflow Cannula Position May Contribute to the Development of HeartMate II Left Ventricular Assist Device Pump Thrombosis.

Pump thrombosis (PT) is a dreaded complication after left ventricular assist device (LVAD) implantation. Problems with inflow cannula (IC) position may precipitate thrombus development. We sought to determine if IC position contributes to the development of PT. We conducted a retrospective review of 76 HeartMate II LVAD implants. The angle of the IC (AIC) to the horizontal plane was measured on chest x-rays. Patients who developed PT (PT group) were compared to the remaining patients (control group). The mean age at implantation was 56 ± 14 years, and 82% of the patients were male. Ten patients (13%) developed PT. Six (60%) required device exchange, and 4 (40%) were managed with anticoagulation and/or thrombolysis. The median AIC for all patients at implantation was 59° (range, 38°-98°; 25th-75th interquartile range, 50°-75°). In the PT group, the median AIC was larger at the time of PT diagnosis compared to implantation (70° vs 60°, P = 0.005). In the control group, the median AIC was also larger at follow-up compared to implantation (61° vs 58°, P < 0.001) although to a lesser degree than in the PT group. No difference was seen in the median AIC between the PT group and the control group at implantation (60° vs 58°, respectively; P = 0.668) or at follow-up (70° vs 61°, respectively; P = 0.309). However, the median AIC at follow-up in the PT group was significantly larger than the median AIC at implantation in the control group (70° vs 58°, respectively; P = 0.014). The HeartMate II LVAD IC position contributes to the development of PT. Regular monitoring of cannula position may help identify patients at risk for this problem.

POTENTIAL OF ULTRASOUND-GUIDED LUMBAR FACET RADIOFREQUENCY DENERVATION

The aim of the study was to evaluate the possibility of US navigation for Radiofrequency denervation (RFD) of the lumbar facets.Material and methods. The authors performed a prospective controlled cohort study which included 50 patients with chronic pain syndrome who underwent RFD LIII-SI facets on both sides. The main group (US) included 25 patients, who underwent US guided navigation with FScontrol of the correct placement of the cannula prior to ablation. In the control group (FS) the RFD was performed only under FS control. Patients were selected after preliminary test block of medial branch with 50% pain reduction from the baseline. Patients with overweight, spinal deformity, pronounced degenerative changes, spinal stenosis and developmental anomalies were not included in the study. For the evaluation of outcomes, the numeric pain scale NRS-11 and the Oswestry index (ODI) were used, the accuracy of the cannula position was assessed and factors determining the accuracy were searched.Results. As a result of the intervention, there was a significant decrease of NRS-11 and ODI criteria in both groups (p0.001), a positive outcome was achieved in 18 (72%) of US patients and 16 (64%) of FS patients, p = 0.564. Of the 200 attempts to position the cannula under the ultrasound control, 169 (84.5%) were successful, in most cases (187 out of 200, 93.5%) at least 3 attempts were required to reposition the cannula. The average time for performing the procedure under the ultrasound control was 47.3±1.13 minutes. The facet angle and procedure level were defined as predictors of the cannula positioning accuracy, odds ratio 0.93 (95% CI 0.894–0.963) and 0.51 (95% CI 0.32–0.805), respectively.Conclusion. RFD of lumbar facet under ultrasound navigation allows to achieve a relatively high accuracy of the cannula position into the zone of passage of the articular branch. The navigation capabilities are reduced at the level of LV and SI vertebrae due to structural features of the joints, namely coronary orientation of the facets with the formation of a narrow space between the transverse and upper articular process, which create difficulties for scanning. The disadvantage of ultrasound control is the lengthy procedure and the need for repeated reinsertion of the cannulae worsening the patient’s tolerance of procedure.

Virtual 3D planning of tracheostomy placement and clinical applicability of 3D cannula design: a three-step study

AimWe aimed to investigate the potential of 3D virtual planning of tracheostomy tube placement and 3D cannula design to prevent tracheostomy complications due to inadequate cannula position.Materials and methods3D models of commercially available cannula were positioned in 3D models of the airway. In study (1), a cohort that underwent tracheostomy between 2013 and 2015 was selected (n = 26). The cannula was virtually placed in the airway in the pre-operative CT scan and its position was compared to the cannula position on post-operative CT scans. In study (2), a cohort with neuromuscular disease (n = 14) was analyzed. Virtual cannula placing was performed in CT scans and tested if problems could be anticipated. Finally (3), for a patient with Duchenne muscular dystrophy and complications of conventional tracheostomy cannula, a patient-specific cannula was 3D designed, fabricated, and placed.Results(1) The 3D planned and post-operative tracheostomy position differed significantly. (2) Three groups of patients were identified: (A) normal anatomy; (B) abnormal anatomy, commercially available cannula fits; and (C) abnormal anatomy, custom-made cannula, may be necessary. (3) The position of the custom-designed cannula was optimal and the trachea healed.ConclusionsVirtual planning of the tracheostomy did not correlate with actual cannula position. Identifying patients with abnormal airway anatomy in whom commercially available cannula cannot be optimally positioned is advantageous. Patient-specific cannula design based on 3D virtualization of the airway was beneficial in a patient with abnormal airway anatomy.

Avalon catheters in pediatric patients requiring ECMO: Placement and migration problems

PurposeThe Avalon dual-lumen venovenous catheter has several advantages, but placement techniques and management have not been adequately addressed in the pediatric population. We assessed our institutional outcomes and complications using the Avalon catheter in children. MethodsWe reviewed all pediatric patients who had Avalon catheters placed for respiratory failure at our institution, excluding congenital heart disease patients, from April 2009 to March 2016. All patients were managed using our standard ECMO protocol, and cannula position was followed by daily chest x-ray and intermittent echocardiography (ECHO). Data included demographics, diagnosis, PRISM3 predicted mortality, ECMO duration, complications, and survival. The primary outcome was the need for catheter repositioning. ResultsTwenty-five patients were included, with mean age 8.3±6.9years and 15±22days of ECMO support. Overall survival was 68% (17/25). Fourteen patients (56%) underwent placement with fluoroscopy in addition to ultrasound and ECHO, primarily after 2013. Overall, thirteen patients (52%) had problems with cannula malposition. 9 of these (69%) required cannula repositioning. Three of 14 (21%) cannulas placed with fluoroscopy required repositioning, compared to 7/11 (64%) placed without fluoroscopy (p=0.05). ConclusionsComplications are common with the Avalon catheter in children. Safe percutaneous access requires ultrasound guidance, and use of intraoperative fluoroscopy in addition to echocardiography decreases malposition rates. Level of evidenceIV (Prognosis study).

Cannula and Pump Positions Are Associated With Left Ventricular Unloading and Clinical Outcome in Patients With HeartWare Left Ventricular Assist Device

BackgroundCannula and pump positions are associated with clinical outcomes such as device thrombosis in patients with HeartMate II; however, clinical implications of HVAD (HeartWare International, Framingham, Massachusetts) cannula position are unknown. This study aims to assess the relationship among cannula position, left ventricular (LV) unloading, and patient prognosis. Methods and resultsTwenty-seven HVAD patients (60.0 ± 12.6 years of age and 19 males [70%]) underwent ramp test. Device position was quantified from chest X-ray parameters obtained at the time of the hemodyamic ramp test: (1) cannula coronal angle, (2) pump depth, (3) cannula sagittal angle, and (4) pump area. Lower cannula coronal angle was associated with LV unloading (as measured by smaller LV diastolic dimension and lower pulmonary capillary wedge pressure). Smaller pump area was associated with LV dynamic unloading, as assessed by steeper negative slopes of LV diastolic dimension and pulmonary capillary wedge pressure during incremental rotational speed change. Cannula coronal angle ≤65° was associated with reduced heart failure readmission rate (hazard ratio, 10.33; P = .007 by log-rank test). ConclusionHVAD cannula and pump positions are associated with LV unloading and improved clinical outcomes. Prospective studies evaluating surgical techniques to ensure optimal device positioning and its effects on clinical outcomes are warranted.

Ecografía en el niño con oxigenación por membrana extracorpórea

The use of ultrasound in children with extracorporeal membrane oxygenation (ECMO) is a non-invasive method for pulmonary monitoring, as well as to check the position of cannulas, and the precise measurement of haemodynamic variables. It is a vital tool in multimodal monitoring, and can be performed during admission, evolution and weaning of the child with ECMO, admitted to a paediatric intensive care unit.In this article, we describe findings of lung ultrasound, the position of the ECMO cannula in the inferior vena cava, and the most important haemodynamic parameters that can be obtained with transthoracic echocardiography in critically ill children with ECMO.

The Effect of Inflow Cannula Length on the Intraventricular Flow Field: An In Vitro Flow Visualization Study Using the Evaheart Left Ventricular Assist Device.

Left ventricular assist device (LVAD) inflow cannula malposition is a significant risk for pump thrombosis. Thrombus development is influenced by altered flow dynamics, such as stasis or high shear that promote coagulation. The goal of this study was to measure the intraventricular flow field surrounding the apical inflow cannula of the Evaheart centrifugal LVAD, and assess flow stasis, vortex structures, and pulsatility for a range of cannula insertion depths and support conditions. Experimental studies were performed using a mock loop with a customized silicone left ventricle (LV) and the Evaheart LVAD. A transparent inflow cannula was positioned at 1, 2, or 3 cm insertion depth into the LV and the velocity field in the LV midplane was measured for 2 levels of LVAD support: 1800 and 2300 rpm. The LV velocity field exhibits a diastolic vortex ring whose size, path, and strength are affected by the flow conditions and cannula position. During diastole, the large clockwise midplane vortex grows, but its circulation and kinetic energy are reduced with cannula insertion depth. The counterclockwise vortex is smaller and exhibits more complex behavior, reflecting a flow split at 3 cm. Overall, the 1 cm cannula insertion depth produces the flow pattern that exhibits the least apical flow stasis and greatest pulsatility and should correlate to a lower risk of thrombus formation.

Catheter-directed guidance for ECMO cannulation with unfavorable caval anatomy

Extracorporeal membrane oxygenation (ECMO) has become the standard of care for potentially reversible cardiopulmonary conditions intractable to conventional medical management. Single site, dual-lumen veno-venous ECMO has proven to be safe and advantageous with respect to mobilization of the patient. Nevertheless, adequate respiratory support demands optimal cannula positioning and catastrophic cannulation complications have been reported. We describe herein the utilization of an angulated guiding catheter to obtain trans-caval access for the successful placement of a single site dual-lumen cannula for veno-venous ECMO in a patient with unfavorable trans-caval anatomy.

Effect of Negative Angle Cannulation during Cardiopulmonary Bypass - A Computational Fluid Dynamics Study

Creation of emboli in the aortic root and changes in flow distribution between supra-aortic arteries and descending aorta can lead to stroke and perfusion related tissue damage during cardiopulmonary bypass. A thorough understanding of how the angle of cannulation affects the overall success of cardiopulmonary bypass during cannulation of the ascending aorta is needed. Previous simulation research has observed the effect of outflow cannula position by changing the location of the cannulation site to the subclavian artery and other vessels, as well as positions for innovative cannula designs. The purpose of this study is to evaluate the success of the procedure while using a straight cannula, modulating the angle of cannulation below horizontal in the frontal plane. A simplified geometry of the aorta was used. The success of the procedure was quantified by observing wall shear stress, normal stress, intra-fluid shear stress, and flow distribution. A numerical study was performed to solve the Reynolds Averaged Naiver Stokes governing equations, which were used in conjunction with a constant density fluid to simulate blood, and a realizable two-layer k-e turbulence model.

Device-specific evaluation of intraventricular left ventricular assist device position by quantitative coaxiality analysis

BackgroundPatient-specific anatomy may influence the final intraventricular positioning of inflow cannula in left ventricular assist device (LVAD) recipients. An association exists between such positioning and clinical outcomes (specifically, orientation toward the interventricular septum has negative prognostic implications). Alternative commercially available LVADs are characterized by markedly different design, with potential consequences on intrathoracic fitting among individual patients. Material and methodsA cohort of 13 LVAD recipients (either HeartMate II–group A or Jarvik 2000 Flowmaker–group B) was evaluated. On postoperative computed tomography scans, we reconstructed the implanted LVAD (semiautomatic segmentation), defined the target mitral orifice (3D Slicer software), and built a coordinate system to quantify the coaxiality of the cannula with the mitral valve axis (angles φ and θ, expressed as percentage variation from the ideal value φ = θ = 0°). ResultsGroup A presented significantly greater average percentage variation of the φ angle (significantly greater orientation of the intraventricular cannula toward the interventricular septum; 33.2% ± 32.1% versus 1.9% ± 0.9%, P = 0.001). Group A presented significantly greater average percentage variation of the θ angle (52.7% ± 23.6% versus 14.5% ± 6.3%, P = 0.013). ConclusionsThe device assessed in group B showed in the present series better average coaxiality with the mitral orifice. Such finding is related with its design (total intraventricular placement) and interaction with thoracic structures. The present method is being integrated in the development of LVAD virtual implantation tools and may help physicians in patient-specific selection among alternative devices.

Lessons learnt from the initiation of ECMO experience in Lebanon

Introduction: At the start of every new extracorporeal membrane oxygenation (ECMO) center, safe and effective use of ECMO therapy requires unique institutional resources and strategies to optimize patient care and outcome. This is a report of the initial experience at the first ECMO center in Lebanon; the course of five patients is described, focusing on the monitoring considerations.1–4 Lessons learnt help improve patient ECMO care, safety, and outcome. Methods: Two adult cases treated with veno-arterial (VA) ECMO for refractory cardiac failure, and three neonates (two veno-arterial and one veno-venous (VV) ECMO) treated for refractory respiratory failure were retrospectively reviewed with special focus on both medical and mechanical complications. Results: All complications were recognized early and managed successfully. The main complications encountered were: limb ischemia (1 patient), bleeding and clotting requiring circuit change (2 patients), overflow and aortic regurgitation (1 patient), hemolysis (1 patient), acute kidney injury and fluid overload (3 patients), patient–ventilator asynchrony, and technical problems (mainly related to cannula's positioning) (2 patients). In some instances, diagnosis was limited or delayed due to unavailability of monitoring tools, mainly multimodal coagulation studies. All five patients were successfully decannulated. Two patients died following decannulation and three patients were discharged home; one among them needed to go to a rehabilitation center for a few weeks before going back home. Conclusion: Optimal monitoring tools such as cerebral and somatic near infrared spectroscopy, echocardiography, head ultrasound, and multimodal coagulation studies (activated clotting time, aPTT, antiXa, thromboelastogram, and others) would allow for early recognition of complications. This would prevent or at least help anticipate catastrophic events, thus minimizing the impact of life-threatening complications and improving the quality of care and outcome. Furthermore, organizational structure with investment in training and technology is needed to optimize patient care.5

Management strategy during neonatal/paediatric VV ECMO run

Introduction: Strategy during extracorporeal membrane oxygenation (ECMO) support is guided by available outcome data. Boundaries limiting selection of cases are shifting with advances in ECMO technology, conventional support, and destination therapies. Evolution: Neonatal respiratory ECMO numbers continue to decline due to improved conventional therapies, whereas infants historically excluded from ECMO (for example, ex-premature infants with O2-dependent chronic lung disease and severe RSV) are now successfully supported. ECMO for bridging of children to lung transplant is now established.1 Advances are also being made in mobile ECMO,2 long duration of ECMO support, and ECMO while wide awake. Initiation: Flow requirements and patient or vessel size govern cannula choice. Percutaneous cannulation of vessels with ultrasound guidance is described in all sizes of children, including small infants.3 Serial imaging and ECHO control are needed for optimisation of cannula position and orientation. Transoesophageal ECHO is preferable to transthoracic where available. Reconfiguration of the circuit may prove necessary in some cases and is better done early in the run.4Troubleshooting: Protocol and bundle adherence are the keys to preventing complications. Detection requires vigilance and rigorous checks along with comprehensive handover and tight teamwork. Management is about appropriate escalation and pathway utilisation. Simulation is an essential component of staff training and a powerful tool for reinforcing these points.5Lung recovery: ECMO can be considered the ultimate in “lung rest” techniques. Enhancing lung recovery during the rest provided by ECMO is mainly achieved by attention to fluid balance, pulmonary toilet, and adoption of ventilator rest settings. Bronchoscopy is also particularly useful in this context.6 Other therapies such as prone position, steroid use, surfactant, perfluorocarbon,7 and even individual lung ventilation2 have a role in selected cases. De-cannulation: Patience can be needed when timing the end to VV ECMO support. Removing the sweep gas from the oxygenator can be done simply without having to wean ECMO flow. In more difficult situations, 12–24 h trial off can be used. Radiological lung clearance, improving lung compliance, reduction of sweep gas requirements, and oxygen challenges are all informative in the run up to a decision to trial off. Lung biopsy8 or genetic test results are useful when recovery is absent to help establish futility. Earlier de-cannulation can be indicated in the setting of an intractable or severe complication. Summary: Strategy for management of VV ECMO support is evolving with improvements in ECMO techniques and advances in supporting therapies. A proactive, rigorous but flexible approach to individual cases can deliver excellence.

Extraction of Atrial and Pulmonary Thrombi Using Angiovac Aspiration System with Transesophageal Echocardiography and Fluoroscopic Guidance

Surgical embolectomy is widely used to treat massive or submassive pulmonary thromboembolism and chronic thromboembolic pulmonary hypertension. [1]-[3] However, recently a new minimally invasive transvenous approach to clot evacuation using the AngioVac aspiration system (Vortex Medical, Norwell, Massachusetts) such as AngioVac aspiration system has been successfully used for retrieval of right atrial clot [4]-[6]. This is the first case report describing evacuation of trans-septal thrombus using an AngioVac aspiration system utilizing transesophageal echocardiograph (TEE) and fluoroscopic guidance. This case report also highlights the potential complications involved in AngioVac system which were readily diagnosed using TEE. We present a 66-year-old Caucasian female with a right atrial thrombus extending into left atrium through a patent for ovale (PFO) defect and a pulmonary artery thrombus. She underwent suction evacuation with an AngioVac aspiration system under TEE and fluoroscopic guidance. The right atrial thrombus extending into left atrium through a PFO was successfully evacuated through the PFO. However, the evacuation of the clot in the pulmonary artery was complicated by a rupture of the right ventricle requiring emergent sternotomy, cardiopulmonary bypass (CPB) and transient extracorporeal mechanical oxygenation (ECMO) support. The patient rapidly improved post-operatively and was discharged from hospital. Echocardiographic documentation of right heart thrombus and pulmonary emboli has poor prognostic implications. This report delineates the utility of TEE for visualization of cannula placement and real time aspiration of clots through the cannula. Potential complications associated with this technique are mechanical dislodge of thrombus from its attachment with subsequent embolization and rupture of cardiac chambers. Accessing the thrombus in the PA can be challenging and actual visualization of the cannula in the PA is often difficult and available only through TEE. This report highlights the utility of TEE for demonstrating trans-septal clot and the importance of precise positioning of cannula in avoiding complications. In spite of complications, AngioVac aspiration system under TEE and fluoroscopic guidance may become a safe alternative for surgical removal of intracardiac thrombi.

Cannula Design and Recirculation During Venovenous Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is used as a lifesaving rescue treatment in refractory respiratory or cardiac failure. During venovenous (VV) ECMO, the presence of recirculation is known, but quantification and actions to minimize recirculation after measurement are to date not routinely practiced. In the current study, we investigated the effect of draining cannula design on recirculation fraction (Rf) during VV ECMO; conventional mesh cannula was compared with a multistage cannula. The effect of adjusting cannula position was also studied. Recirculation was measured with ultrasound dilution technique at different ECMO flows and after cannula repositioning. All patients who were admitted to our unit between October 2014 and July 2015 catheterized by the atrio-femoral single lumen method were included. A total of 108 measurements were conducted in 14 patients. The multistage cannula showed significantly less recirculation (19.0 ± 12.2%) compared with the conventional design (38.0 ± 13.7). Pooled data in cases improved from adjustment showing reduced Rf by 7%. In conclusion, the choice of cannula matters, as does adjustment of the draining cannula position during atrio-femoral VV ECMO. By utilizing the ultrasound dilution technique to measure Rf before and after repositioning, effective ECMO flow can be improved for a more effective ECMO treatment.

Fine-tuning management of the Heart Assist 5 left ventricular assist device with two- and three-dimensional echocardiography.

SummaryIntroduction:Left ventricular assist device (LVAD) implantation is a viable therapy for patients with severe end-stage heart failure, providing effective haemodynamic support and improved quality of life. The Heart Assist 5 (Micromed Cardiovascular Inc, Houston, TX) continuous-flow LVAD has been on the market in Europe since May 2009.Methods:We evaluated nine Heart Assist 5 LVAD patients with two- and three-dimensional transthoracic echocardiographic (TTE) and transoesophageal echocardiographic (TEE) parameters between December 2011 and December 2013. The pre-operative TTE LVAD evaluations included left ventricular (LV) function and structure, quantification of right ventricular (RV) function and tricuspid regurgitation (TR), assessment of aortic and mitral regurgitation, and presence of patent foramen ovale and intra-cardiac clots. Peri-operative TEE determined the inflow cannula and septum position, and assessed the de-airing process while weaning from cardiopulmonary bypass. Post-operative serial follow-up TTE showed the surgical results of LVAD implantation, determined the overall structure and function of the LV, RV and TR, and observed the inflow and outflow cannula position.Results:Nine patients who had undergone Heart Assist 5 LVAD implantation and had been followed up for more than 30 days were included in this study. Eight patients had ischaemic cardiomyopathy and one had adriamycin-induced cardiomyopathy. Pre-implantation data: the mean age of the patients was 52 ± 13 (34–64) years, mean body surface area (BSA) was 1.8 ± 0.2 (1.6–2.0) m2, mean cardiac index (CI) was 2.04 ± 0.4 (1.5–2.6) l/min/m2, mean cardiac output (CO) was 3.7 ± 0.7 (2.6–4.2) l/min, mean ejection fraction (EF) was 23 ± 5 (18–28)%, and right ventricular fractional area contraction (RVFAC) was 43 ± 9 (35–55)%. One patient had aortic valve replacement (AVR) during the LVAD implantation, and excess current alarms and increased power were suspected to be caused by a possible thrombus. Close follow up with TTE studies were carried out to clear the LV of thrombus formation, and the inflow cannula position was checked to maintain the septum in the midline, so preventing the suction cascade. Four patients were followed up for more than two years, and two were followed up for more than a year. Three patients died due to multi-organ failure. Follow-up speed-change TTE studies of six patients showed that the mean speed was 9 800 ± 600 (9 500–10 400) rpm, and mean CO was 4.7 ± 0.3 (4.3– 5.0) l/min during the three-month post-implant period.Conclusion:We believe that TTE can play a major role in managing LVAD patients to achieve optimal settings for each patient. A large series is mandatory for assessment of echocardiographic studies on Heart Assist 5 LVAD.

Left ventricular assist device implantation in patients after left ventricular reconstruction.

Left ventricular assist device (LVAD) implantation can be challenging in patients with a prior surgical ventricular restoration (SVR). In this case series of heart failure patients with a history of SVR, we describe the surgical technique and outcome of a customized approach for inflow cannula orientation. Seven patients with a history of SVR with end-stage chronic heart failure were accepted for long-term LVAD support. In all patients, the Dacron patch was removed through left ventriculotomy and a Hegar 22 dilator was inserted at the estimated optimal position of the LVAD inflow cannula. The left ventricle was reconstructed around the dilator from the left ventricular (LV) apex to the base. Finally, the LVAD sewing ring was sutured onto the remaining apical defect and a HeartWare® LVAD was implanted. LVAD implantation was successful in all 7 patients. Transoesophageal echocardiography ensured an adequate LVAD position and inflow and outflow cannula Doppler flow recordings. The mean intensive care unit stay was 5.8 ± 2.6 days, and the hospital stay after surgery was 32 ± 16 days. All patients follow regular visits (follow-up 20 ± 16 months) at the outpatient clinic without any remarkable event. Using the technique described, LVAD implantation in patients after SVR is feasible and safe.

Evaluation of different types of inferior vena cava cannulae placement by transesophageal echocardiography and its impact on hepatic dysfunction.

Postoperative hepatic dysfunction may occur in an otherwise uncomplicated open heart surgery. One of the reasons is malpositioning of the inferior vena cava (IVC) cannula in the hepatic vein (HV) or beyond. A straight cannula is considered more likely to be malpositioned compared to the angled cannula and a malpositioned cannula can lead to hepatic dysfunction. In this prospective study, forty adult patients undergoing atrial septal defect repair were randomized into two groups as: straight cannula group (n=20) and angled cannula group (n=20). The cannula position was assessed by transesophageal echocardiography (TEE) (hepatic vein view). Alanine aminotransferase levels (ALT) and bilirubin levels were measured immediately, at 6 hours and on day 1, day 2 and day 7 after surgery as a marker of hepatic injury. TEE localization of the IVC cannula was achieved in all patients except one. Visualization was good in 85% of patients. A cannula in the HV or beyond the HV in the IVC was considered malpositioned. The number of cases of cannula malposition was 10 (50%) and 4 (20%) in the straight and angled cannula groups, respectively. The pattern of change in serum bilirubin and liver enzymes levels in the postoperative period was similar in both the groups (p>0.05). The mean distance between the right atrium (RA) - inferior vena cava (IVC) junction to the hepatic vein was 1.94±0.56 cm and the mean diameters of the IVC and HV were 1.95±0.5 and 1.31±0.33 cm, respectively. TEE can be used to monitor IVC cannula position. A higher frequency of cannula malposition was observed with the straight cannula compared to the angled cannula, but was not found to be associated with hepatic dysfunction.

Safety of transesophageal echocardiography during extracorporeal life support.

Use of extracorporeal life support (ECLS) has significantly increased in critically ill patients refractory to medical management. ECLS requires systemic anticoagulation to avoid thromboembolic complications and superimposed coagulopathies are common. Transesophageal echocardiography (TEE) is frequently employed to assess cannula position and cardiac function during extracorporeal therapy. The goal of this study was to assess whether TEE probe insertion and removal in systemically anticoagulated ECLS patients was safe compared to patients without ECLS and normal coagulation studies. Eighty-seven separate TEE examinations in 53 adult ECLS patients were analyzed. Detailed complication profiles were logged for each patient from initiation through discontinuation of ECLS. Routine coagulation testing was recorded within two hours prior to the TEE exams. Controls consisted of age- and gender-matched patients undergoing perioperative TEE without ECLS and normal coagulation (N=87). Overall TEE-associated morbidity in ECLS patients was 2.3% and consisted of minor oropharyngeal bleeding (2/87 TEE exams) exclusively. The patients presenting with oropharyngeal bleeding received heparin for anticoagulation and had two or more abnormal coagulation studies at the time of TEE. Seventy-nine percent of ECLS patients received intravenous heparin infusions, 6.8% argatroban and 3.4% epoprostenol. Ten-point-eight percent of patients were not anticoagulated at the time of TEE because of pre-existing bleeding complications and/or deranged plasmatic coagulation profiles. No major complications (e.g., esophageal perforation, gastrointestinal bleeding, accidental extubation) were recorded in either group. TEE remained safe in critically ill patients under ECLS, despite systemic anticoagulation, during probe insertion, manipulation and removal. TEE-related complications pertained solely to oropharyngeal bleeding amenable to conservative management.

In Vivo Porcine Model of Venous Air Embolism During Pars Plana Vitrectomy

Venous air embolism (VAE) during pars plana vitrectomy (PPV) can occur owing to improper positioning of the infusion cannula in the suprachoroidal space and may lead to sudden compromise of cardiac circulation and death. This was an invivo demonstration of fatal VAE during PPV to show that air can travel from the suprachoroidal space into the central circulation. Experimental invivo surgical study on porcine eyes. Experimental PPV under general anesthesia was performed on porcine eyes (Yorkshire species) at a University Surgical Training & Education Center. Infusion cannulas were placed into the suprachoroidal space and fluid-air exchange (FAE) was started with sequential increases in infusion air pressure. Vital signs of porcine animals were continuously monitored and recorded in real time during the PPV, including end-tidal carbon dioxide (ETCO2), oxygen saturation (SaO2), intra-arterial blood pressure, electrocardiography (EKG), and transesophageal echocardiography (TEE). Intracardiac air was detected on TEE less than 30 seconds after increasing air infusion pressure to 60mm Hg. ETCO2 declined precipitously, followed by hypotension and EKG changes. Oxygen desaturation was a late phenomenon. The animal died within 7minutes of VAE. During autopsy, the heart was open under water and air escaped from the right ventricle. This invivo porcine model confirms that during the FAE in PPV, pressurized air from an infusion cannula malpositioned in the suprachoroidal space can transit through the eye to the central circulation, resulting in fatal VAE.