Cannula Position Research Articles

Percutaneous Ventricular Assist Device in Hypertrophic Obstructive Cardiomyopathy With Cardiogenic Shock: Bridge to Myectomy

We present the case of a 69-year-old woman with end-stage hypertrophic obstructive cardiomyopathy who developed cardiogenic shock. She underwent emergent placement of a percutaneous left ventricular assist device (TandemHeart) in the catheterization lab as a bridge support device until a septal myectomy could be performed as definitive treatment. This case suggests a novel and promising use of the TandemHeart as a bridge to myectomy.

Spontaneous Ear Hemorrhage During Cardiac Surgery

A 79-year-old patient who underwent mitral valve replacement experienced prolonged elevated central venous pressure associated with poor venous return during a cardiopulmonary bypass. After the procedure, the patient was noted to have spontaneous bleeding from the left ear. Otolaryngologic examination in the operating room showed no trauma in the exterior auditory canal and suggested that the hemorrhage was related to a superior vena cava syndrome and anticoagulation during the cardiopulmonary bypass. Determinants and management considerations of poor venous return, including maintenance of cerebral perfusion pressure, are discussed.

3D MRI flow analysis in an in-vitro system modelling continuous left ventricular support: effect of cannula position in the thoracic aorta

Background Continuous blood flow from left ventricular assist devices (LVAD) has become an important treatment option for heart failure patients. However, recent reports indicate that the complex geometric alterations of the vascular system associated with LVAD implantation as well as the introduction of constant flow into the aorta may alter blood flow patterns. These can potentially affect perfusion patterns to the supra-aortic vessels or cause structural changes to the aortic root leading to regurgitation and valve dysfunction. The purpose of this study was to evaluate the feasibility of flow-sensitive 4D MRI for the investigation of such blood flow alterations in an in-vitro model simulating 3D blood in a physiological model of the left ventricle, aortic valve and aorta.

Frameless multimodal image guidance of localized convection-enhanced delivery of therapeutics in the brain

IntroductionConvection-enhanced delivery (CED) has been shown to be an effective method of administering macromolecular compounds into the brain that are unable to cross the blood-brain barrier. Because the administration is...

Radio-guided occult lesion localisation for breast lesions under computer-aided MRI guidance: the first experience and initial results

The purpose of this study was to present an alternative technique for the pre-operative localisation of solely MRI-detected suspicious breast lesions using a computer-assisted MRI-guided radio-guided occult lesion localisation (ROLL) technique. Between January 2009 and June 2010, 25 females with a total of 25 suspicious breast lesions that could be detected only by MRI, and for whom breast surgery was planned, underwent the computer-assisted MRI-guided ROLL technique. A seven-channel biopsy breast array coil and computerised diagnostic workstation were used for the localisation procedure. Three-phase dynamic contrast-enhanced axial images were taken. After investigating the localisation co-ordinates with the help of intervention software on a workstation, an 18 G coaxial cannula was placed in the exact position determined. Following verification of the cannula position by additional axial scans, (99m)Tc-labelled macroalbumin aggregate and MRI contrast material were injected. Post-procedure MRI scans were used to confirm the correct localisation. All the procedures were technically successful. The mean lesion size was 10.8 mm (range: 4-25 mm). The mean total magnet and the mean localisation times were 28.6 min (range: 18-46 min) and 13.1 min (range: 8-20 min), respectively. Grid and pillar methods were used for localisation in 24 procedures and 1 procedure, respectively. On histopathological examination, 6 malignant, 10 high-risk and 9 benign lesions were identified. All patients tolerated the procedure well. There were no major complications. This is the first report documenting the application of MRI-guided ROLL. Based on our preliminary results, this technique is very efficient and seems to be a good alternative to wire localisation.

Analysis of a simulation algorithm for direct brain drug delivery

Convection enhanced delivery (CED) achieves targeted delivery of drugs with a pressure-driven infusion through a cannula placed stereotactically in the brain. This technique bypasses the blood brain barrier and gives precise distributions of drugs, minimizing off-target effects of compounds such as viral vectors for gene therapy or toxic chemotherapy agents. The exact distribution is affected by the cannula positioning, flow rate and underlying tissue structure. This study presents an analysis of a simulation algorithm for predicting the distribution using baseline MRI images acquired prior to inserting the cannula. The MRI images included diffusion tensor imaging (DTI) to estimate the tissue properties. The algorithm was adapted for the devices and protocols identified for upcoming trials and validated with direct MRI visualization of gadoinium in 20 infusions in non-human primates. We found strong agreement between the size and location of the simulated and gadolinium volumes, demonstrating the clinical utility of this surgical planning algorithm.

Flow and Volume Dependence of Rat Airway Resistance During Constant Flow Inflation and Deflation

The aim of this study was to measure the flow and volume dependence of both the ohmic and the viscoelastic pressure dissipations of the normal rat respiratory system separately during inflation and deflation. The study was conducted in the Respiratory Physiology Laboratory in our institution. Measurements were obtained for Seven albino Wistar rats of both sexes by using the flow interruption method during constant flow inflations and deflations. Measurements included anesthesia induction, tracheostomy and positioning of a tracheal cannula, positive pressure ventilation, constant flow respiratory system inflations and deflations at two different volumes and flows. The ohmic resistance exhibited volume and flow dependence, decreasing with lung volume and increasing with flow rate, during both inflation and deflation. The stress relaxation-related viscoelastic resistance also exhibited volume and flow dependence. It decreased with the flow rate at a constant lung volume during both inflation and deflation, but exhibited a different behavior with the lung volume at a constant flow rate (i.e., increased during inflations and decreased during deflations). Thus, stress relaxation in the rat lungs exhibited a hysteretic behavior. The observed flow and volume dependence of respiratory system resistance may be predicted by an equation derived from a model of the respiratory system that consists of two distinct compartments. The equation agrees well with the experimental data and indicates that the loading time is the critical parameter on which stress relaxation depends, during both lung inflation and deflation.

681 Cannula Neointima Growth and Thrombi: Impact on LVAD Long Term Function and Outcome

Purpose: Use of Left ventricular assist devices (LVAD) as bridge and destination therapy is currently common, as survival has significantly improved allowing longer implant times. Little information exists regarding the normal or abnormal healing reaction at LVAD anastomotic sites. We sought to characterize the neointima present at the aortic anastomosis and fibrous overgrowth at the ventricular anastomosis along with any thrombi present at either site. Methods and Materials: During the period June, 2005 through July, 2010 a total of 34 left ventricular assist devices (LVAD) including 6 Heartmate XVE and 28 Heartmate II were implanted in 29 males and 5 females, mean age of 54.4 yr (range 29-68). Only 13 were available for examination at the time of transplant (n 11), or autopsy (n 2). Mean implant duration was 138 days (range 4-512). Gross and histologic examination was performed on the aortic and ventricular tubing and anastomoses evaluating neointima and thrombus formation, as well as adjacent ventricular endocardium, myocardium and epicardium. Results: Thrombi were present in device housing (n 1), mural endocardium (n 1), and ventricular tubing (n 2). Little or neointima was seen in LVAD implanted less than 30 days. Pseudointima of less than 1.0 cm length and less than 50% of tube circumference was present in one explant at 41 days and 3 explants from 151 to 211days. Pseudointima of greater than 1.0 cm in length and greater than 50% of tube circumference was seen in 3 explants from 111 to 196 days. In one patient despite adequate LVAD function the ventricular tubing was partially wedged into the left ventricular free wall endocardium with fibrous overgrowth and thrombus partially obstructing the lumen. In this same patient there was 1.5 cm length and 80% circumference pseudointima involving the aortic anastomosis. Conclusions: Compromise of anastomotic luminal flow through thrombosis or abnormal healing reaction may become a significant factor in LVAD function as survival in such patients increases. Cannula positioning may play important role in this process.

Invited Commentary

The ideal position for the orifice of the inflow cannula of a ventricular assist device (VAD) is in the center of the ventricular cavity, because this position allows unrestricted flow into the VAD. In contrast, if the cannula tip rests on the ventricular septum or papillary muscle, flow restriction to the VAD, ventricular arrhythmias, or both, may result. Therefore, properly positioning the inflow cannula during VAD implantation is important. We have found that placing the inflow cannula through the diaphragmatic region of the left ventricle, rather than more apically, usually results in better positioning of the cannula, keeping it away from the ventricular septum. Transesophageal echocardiography can help confirm that the cannula is in proper alignment. Occasionally, the position of the cannula shifts during the postoperative period as a result of mechanical factors or hypovolemia. If flow to the VAD is severely restricted, reoperation to reposition the cannula may be necessary. Shiose and colleagues [1Shiose A. Kim H.I. Takaseya T. et al.Performance of extracorporeally adjustable ventricular assist inflow cannula.Ann Thorac Surg. 2010; 90: 1682-1687Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar] have designed an inflow cannula that can be adjusted extracorporeally by using cables attached to the cannula. The authors achieved a maximum of ±15-degree mobility in a short-term calf model, and the cannula performed well. Flows could be increased or decreased by changing the position of the cannula. If similar results can be achieved in long-term animal studies, this technology may significantly improve VAD design, assuming that it can be adapted to currently used VADs. One drawback of the current design is the need to have the steering cables exit the skin separately. The more hardware that exits through the skin, the higher the risk of infection. The authors have indicated they are designing detachable cables that could be removed once the optimal cannula position has been achieved. Performance of Extracorporeally Adjustable Ventricular Assist Device Inflow CannulaThe Annals of Thoracic SurgeryVol. 90Issue 5PreviewThis study evaluated the feasibility and efficacy of a newly developed adjustable left ventricular assist device inflow cannula in a short-term calf model. Full-Text PDF

Flow Analysis of Ventricular Assist Device Inflow and Outflow Cannula Positioning Using a Naturally Shaped Ventricle and Aortic Branch

Tip geometry and placement of rotary blood pump inflow and outflow cannulae influence the dynamics of flow within the ventricle and aortic branch. Cannulation, therefore, directly influences the potential for thrombus formation and end-organ perfusion during ventricular assist device (VAD) support or cardiopulmonary bypass (CPB). The purpose of this study was to investigate the effect of various inflow/outflow cannula tip geometries and positions on ventricular and greater vessel flow patterns to evaluate ventricular washout and impact on cerebral perfusion. Transparent models of a dilated cardiomyopathic ventricle and an aortic branch were reconstructed from magnetic resonance imaging data to allow flow measurements using particle image velocimetry (PIV). The contractile function of the failing ventricle was reproduced pneumatically, and supported with a rotary pump. Flow patterns were visualized around VAD inflow cannulae, with various tip geometries placed in three positions in the ventricle. The outflow cannula was placed in the subclavian artery and at several positions in the aorta. Flow patterns were measured using PIV and used to validate an aortic flow computational fluid dynamic study. The PIV technique indicated that locating the inflow tip in the left ventricular outflow tract improved complete ventricular washout while the tip geometry had a smaller influence. However, side holes in the inflow cannula improved washout in all cases. The PIV results confirmed that the positioning and orientation of the outflow cannula in the aortic branch had a high impact on the flow pattern in the vessels, with a negative blood flow in the right carotid artery observed in some cases. Cannula placement within the ventricle had a high influence on chamber washout. The positioning of the outflow cannula directly influences the flow through the greater vessels, and may be responsible for the occasional reduction in cerebral perfusion seen in clinical CPB.

Kyphoplasty: Traditional imaging compared with computer-guided intervention – time to rethink technique?

Study design: Equivalence trial (IRB not required for cadaveric studies).Objective: To compare computer-guided and fluoroscopic kyphoplasty. Factors of interest were radiation exposure, position of cannula within pedicles and procedure time.Methods: Kyphoplasty was performed on two cadavers. Computer-navigated, cross-sectional images from a cone-beam CT were used for one and fluoroscopic imaging for the other. In each, T6–9 and T11–L2 vertebrae were selected. For both imaging methods, anteroposterior and lateral x-rays were taken. Radiation exposure for both procedures was measured by four dosimeters. Procedure time, radiation to surgeon and cadaver, and position of cannula placement within pedicles were recorded. The surgeon wore one under the lead gown, another on the lead gown at shoulder level, and a third as a ring on the dominant hand. A dosimeter was also placed on the cadaver.Results: The radiation from the cone-beam, computer-guided imaging system was 0.0 mrem to the surgeon and 0.52 rads to the cadaver. Using fluoroscopic imaging, surgeon's and cadaver's exposure was 5 mrem and 0.047 rads, respectively. Procedure times were similar and neither device resulted in cannula malposition.Conclusions: Cone-beam CT appears as accurate as the fluoroscopy; radiation exposure to the surgeon is eliminated, and radiation levels to the patient are acceptable.

Case Scenario: Perioperative Airway Management of a Patient with Tracheal Stenosis

TRACHEAL stenosis is a rare but a life-threatening condition and is caused by congenital problems, postintubation injury, trauma, tracheal tumor, and compression of the trachea by tumor. Although accurate prevalence of this condition is unknown, an incidence of 4.9 cases per million per year is estimated for postintubation tracheal stenosis. A stenosis commonly occurs at the cuff of the tube (intrathoracic trachea) or at the level of the tracheostomy stoma (extrathoracic trachea). Anesthesia of a patient with tracheal stenosis is challenging for anesthesiologists. Depending on the severity and location of the stenosis and the type of surgical procedure, there may be a variety of choices for perioperative airway management such as a facemask, laryngeal mask airway, an tracheal intubation tube, cardiopulmonary bypass, and extracorporeal membrane oxygenation. The American Society of Anesthesiologists practice guidelines for management of the difficult airway primarily focus airway problems caused at the extrathoracic airway and may not be helpful, particularly for managing patients with intrathoracic tracheal stenosis. In this case scenario, we present a patient with severe intrathoracic tracheal stenosis, who required surgery for a lumbar fracture in the prone position. Various airway management strategies and the actual management used are discussed.

Angioscopy — a valuable tool in guiding hybrid stent grafting and decision making during type A aortic dissection surgery☆

During hypothermic circulatory arrest (HCA), a briefly visible descending aorta is exposed, enabling direct vision to the surgeon. This study evaluated the impact of angioscopy on arch and descending aortic surgery for type A aortic dissection (AD). From December 2007 to March 2009, a flexible bronchovideoscope was used in 21 patients to assure true lumen (TL) positioning of the arterial cannula during open vision aortic cannulation (OVAC; nine of 21 cases) and to inspect the arch and descending aorta for re-entries, guide wire position and target zone for hybrid stent graft (SG) landing (20 of 21 cases). In OVAC, angioscopy secured positioning of the arterial cannula within the TL requiring additional 10-15s of cerebral ischaemia. In 10 of 21 cases, no additional re-entries were found, thus obviating arch replacement in 2 of 21 and stent grafting in 8 of 21. In 11 of 21 cases, SG deployment was guided to the target zone, in three cases incomplete unfolding initiated balloon dilatation. Angioscopy has become an indispensable tool for decision making in AD to apply OVAC, downstream stent grafting and landing zone control with the ability to indicate ballooning at neglectable time requirements during HCA.

Optimal Placement of a Superior Vena Cava Cannula in Minimally Invasive Robot-Assisted Cardiac Surgery

Minimally invasive robot-assisted cardiac surgery is generally performed nowadays. To avoid the interference of a superior vena cava (SVC) cannula during surgery, it should be inserted before the operation. The position of this cannula is very important because it can cause poor venous drainage during operation. The proper position of the SVC cannula was investigated in the present study. The position of the SVC cannula using the transesophageal echocardiography (TEE) and chest X-ray in 45 patients was ascertained. The distances from the SVC cannula tip to the carina, sternal end of the right clavicle and the lower margin of the T4 vertebral body on chest X-rays were measured. The mean depth of the SVC cannula was 142.0+/-11.6 mm. The correlation coefficients of cannula depth with sex, weight and height were 0.519, 0.399 and 0.382, respectively. The appropriate depth of an SVC cannula has weakly positive relationships with sex, weight and height. The results of the present study suggest that chest X-rays might be necessary to confirm the appropriate location of the cannula and that TEE might be the method of choice for correct positioning of the SVC cannula in minimally invasive robot-assisted cardiac surgery.

Flow Distribution During Cardiopulmonary Bypass in Dependency on the Outflow Cannula Positioning

Oxygen deficiency in the right brain is a common problem during cardiopulmonary bypass (CPB). This is linked to an insufficient perfusion of the carotid and vertebral artery. The flow to these vessels is strongly influenced by the outflow cannula position, which is traditionally located in the ascending aorta. Another approach however is to return blood via the right subclavian artery. A computational fluid dynamics (CFD) study was performed for both methods and validated by particle image velocimetry (PIV). A 3-dimensional computer aided design model of the cardiovascular (CV) system was generated from realtime computed tomography and magnetic resonance imaging data. Mesh generation (CFD) and rapid prototyping (PIV) were used for the further model creation. The simulations were performed assuming usual CPB conditions, and the same boundary conditions were applied for the PIV validation. The flow distribution was analyzed for 55 cannula positions inside the aorta and in relation to the distance between the cannula tip and the vertebral artery branch for subclavian cannulation. The study reveals that the Venturi effect due to the cannula jet appears to be the main reason for the loss in cerebral perfusion seen clinically. It provides a PIV-validated CFD method of analyzing the flow distribution in the CV system and can be transferred to other applications.

Noninvasive assessment of left ventricular assist devices with cardiovascular computed tomography and impact on management

Left ventricular assist devices (LVADs) provide a bridge to recovery or heart transplantation but require serial assessment. Echocardiographic approaches may be limited by device artifact and acoustic window. Cardiovascular computed tomography (CCT) may provide improved non-invasive imaging of LVADs. We evaluated the diagnostic findings and clinical impact of CCT for non-invasive assessment of patients with LVADs. CCT examinations performed between 2005 and 2008 in patients with LVADs were identified. Acquisitions were completed on the identical 64-detector-row scanner with intravenous contrast administration. Electrocardiographic gating was used in patients with pulsatile devices, and peripheral pulse gating was used in patients with continuous-flow devices. Comparison was made between CCT results and 30-day outcomes, including echocardiographic and intraoperative findings. We reviewed 32 CCT examinations from 28 patients. Indications included evaluation of low cardiac output symptoms, assessment of cannula position, low flow reading on the LVAD, and surgical planning. CCT identified critical findings in 6 patients, including thrombosis and inlet cannula malposition, all confirmed intraoperatively. CCT missed 1 case of intra-LVAD thrombus. Using intraoperative findings as the gold standard, CCT's sensitivity was 85% and specificity was 100%. Echocardiographic LVAD evaluation did not correlate with findings on CCT (kappa = -0.29, 95% confidence interval, -0.73 to 0.13). This preliminary observational cohort study indicates that non-invasive imaging using CCT of LVADs is feasible and accurate. CCT warrants consideration in the initial evaluation of symptomatic patients with LVADs.

The Impact of Aortic/Subclavian Outflow Cannulation for Cardiopulmonary Bypass and Cardiac Support: A Computational Fluid Dynamics Study

Approximately 100 000 cases of oxygen deficiency in the brain occur during cardiopulmonary bypass (CPB) procedures each year. In particular, perfusion of the carotid and vertebral arteries is affected. The position of the outflow cannula influences the blood flow to the cardiovascular system and thus end organ perfusion. Traditionally, the cannula returns blood into the ascending aorta. But some surgeons prefer cannulation to the right subclavian artery. A computational fluid dynamics study was initially undertaken for both approaches. The vessel model was created from real computed tomography/magnetic resonance imaging data of young healthy patients. The simulations were run with usual CPB conditions. The flow distribution for different cannula positions in the aorta was studied, as well as the impact of the cannula tip distance to vertebral artery for the subclavian position. The study presents a fast method of analyzing the flow distribution in the cardiovascular system, and can be adapted for other applications such as ventricular assist device support. It revealed that two effects cause the loss of perfusion seen clinically: a vortex under the brachiocephalic trunk and low pressure regions near the cannula jet. The results suggest that cannulation to the subclavian artery is preferred if the cannula tip is sufficiently far away from the branch of the vertebral artery. For the aortic positions, however, the cannula should be injected from the left body side.

Video-assisted right atrial surgery with a single two-stage femoral venous cannula

In the present paper, we report our experience with a single two-stage femoral venous cannula, ideated to drain simultaneously both the superior and the inferior vena cava during minimally invasive cardiac surgery. This cannula has been used in 79 patients (mean age 66.2+/-11.3 years; mean body surface area 1.9+/-0.2 m2) who underwent limited access mitral and tricuspid valve surgery at our institution. In our experience, this cannula permits to obtain a safe venous drainage (mean arterial flow 4.7+/-0.6 l/min, 104+/-13.3% of the theoretical flow) and it allows for a correct functioning of the pump even when the right atrium is opened. In redo cases (17 patients) the procedure was conducted without snaring the caval veins. In all cases, insertion and positioning of the venous cannula was easily obtained and no patients required a conversion to an alternative perfusion strategy. In conclusion, during minimally invasive procedures requiring opening the right atrium, venous return can be safely accomplished with this two-stage femoral venous cannula. The use of this cannula permits the avoidance of the risk associated with the insertion of a second venous cannula and, in so doing, significantly simplifies the procedure.

Tentacles: A Novel Device for Exposing the Heart for the Insertion of Left Apical Assist Device Cannulae

The implantation of ventricular assist devices is a well-established procedure for the treatment of imminent heart failure. The exact positioning of the left ventricular apical inflow cannula is crucial, because inflow restrictions might occur when the cannula is placed too close to the interventricular septum or a papillary muscle. We report a novel technique using the Tentacles 3-point fixation device for the exposure of the left ventricular apex during ventricular fibrillation under cardiopulmonary bypass. We used the Tentacles, a device originally designed for positioning the heart during off-pump coronary artery bypass grafting, for implantation of a biventricular Berlin Heart Excor in a 64-year-old man. The procedure was successful and echocardiographic examinations documented the exact placement of the left ventricular cannula. Our new technique ensures a very precise insertion of apical cannulae, because the left ventricular shape and filling are not impaired.

Intraoperative transesophageal echocardiography is beneficial for hemodynamic stabilization during left ventricular assist device implantation in children

Mechanical circulatory support, with a left ventricular assist device (LVAD) is used in an increasing number of children for treatment of advanced heart failure as bridge-to-transplant. To date no data are available and no studies have defined the role of intraoperative transesophageal echocardiography (TEE) for hemodynamic stabilization during Centrimag Levitronix centrifugal pump implantation in children. Children with therapy resistant heart failure, undergoing LVAD implantation using Berlin Heart Excor pediatric cannula connected to a Levitronix Centrifumag pump, are intraoperatively monitored using an Oldelft micromultiplane TEE. Intraoperative TEE is specially used to monitor right ventricular (RV) and left ventricular (LV) function, correct position of the cannulas and response to pharmacological treatment. In five consecutive patients RV function was assessed by TEE after starting LVAD Levitronix centrifugal pump. Initial RV failure presents with RV dilation and LV collapse. After titration of vasopressor and inotropic agents, RV contractility improved and thereby the filling of the LV. In one child, despite those measures the RV showed no improvement by TEE and a Levitronix right ventricular assist device to support the RV function was implanted as well. All patients could hemodynamically be stabilized before transport to the intensive care unit. The complex interaction of the RV and LV function and correct positioning of the cannula, during LVAD implantation in children with end-stage cardiac failure is improved by simultaneous visualization of cardiac performance of both ventricles and cannula positioning by means of intraoperative multiplane TEE.