An Ovine Model of Awake Veno-Arterial Extracorporeal Membrane Oxygenation

Background: Large animal models are developed to help understand physiology and explore clinical translational significance in the continuous development of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) technology. The purpose of this study was to investigate the establishment methods and management strategies in an ovine model of VA-ECMO.Methods: Seven sheep underwent VA-ECMO support for 7 days by cannulation via the right jugular vein and artery. The animals were transferred into the monitoring cages after surgery and were kept awake after anesthesia recovery. The hydraulic parameters of ECMO, basic hemodynamics, mental state, and fed state of sheep were observed in real time. Blood gas analysis and activated clotting time (ACT) were tested every 6 h, while the complete blood count, blood chemistry, and coagulation tests were monitored every day. Sheep were euthanized after 7 days. Necropsy was performed and the main organs were removed for histopathological evaluation.Results: Five sheep survived and successfully weaned from ECMO. Two sheep died within 24–48 h of ECMO support. One animal died of fungal pneumonia caused by reflux aspiration, and the other died of hemorrhagic shock caused by bleeding at the left jugular artery cannulation site used for hemodynamic monitoring. During the experiment, the hemodynamics of the five sheep were stable. The animals stayed awake and freely ate hay and feed pellets and drank water. With no need for additional nutrition support or transfusion, the hemoglobin concentration and platelet count were in the normal reference range. The ECMO flow remained stable and the oxygenation performance of the oxygenator was satisfactory. No major adverse pathological injury occurred.Conclusions: The perioperative management strategies and animal care are the key points of the VA-ECMO model in conscious sheep. This model could be a platform for further research of disease animal models, pathophysiology exploration, and new equipment verification.

Perfusion Strategy for Minimally Invasive Cardiac Surgery

Minimally invasive cardiac surgery (MICS) has a number of proven advantages compared to median sternotomy. Safe cannulation and perfusion are some of the main components of the success of MICS. The aim. To present our perfusion strategy and describe the methods of cannulation, technical features, contraindications and potential complications. Materials and methods. We examined the results of 1088 adult patients who underwent primary cardiac surgery in our hospital (coronary artery bypass grafting, valve surgery, aortic surgery, left ventricle repair, congenital cardiac surgery and combined procedures) from July 2017 to May 2021. Of these, 851 patients were qualified for MICS. To select a safe cannulation strategy, we performed contrast enhanced computed tomography (CT) of the aorta and main branches for all the patients, also we calculated the body surface area according to the DuBois and DuBois formula. Results. We performed 838 minimally invasive on-pump procedures, which is 98.5% of all patients qualified for MICS. According to the results of the preoperative CT scan, 13 (1.5%) patients were not operated with the minimally invasive approach due to the hazards related to the provision of cardiopulmonary bypass. Peripheral cannulation was performed in 754 (90%) patients and an alternative cannulation site was selected in 62 (8.2%) patients based on preoperative CT data. There were 10 (1.32%) patients who developed major complications (stroke, acute aortic dissection, acute renal failure requiring hemodialysis) after peripheral cannulation. Conclusions. Preoperative CT scan is mandatory for planning a perfusion strategy in minimally invasive cardiac surgery. The required surgical techniques should include cannulation of the right and left femoral and right axillary arteries.

Fibrin Sealant Patch for the Management of Intractable Bleeding From an LVAD Apex Cannula

Background: Intractable bleeding from the apical cannulation site of a left ventricular assist device (LVAD) is a dreaded complication. Case report: A 52-year-old male suffering from dilative cardiomyopathy (DCM) with fixed pulmonary hypertension underwent reoperative LVAD implantation after previous mitral valve surgery. The patient underwent three rethoracotomies for bleeding from the apex cannulation site without achieving hemostasis. Conventional techniques and application of fibrin sealants and polymeric sealing devices did not fix the problem. The bleeding stopped after application of the EVARREST® Fibrin Sealant Patch (FSP), and he needed no further transfusions. Conclusion: This patch might become a useful tool for intractable bleeding problems in LVAD surgery.

Direct true lumen cannulation for type A aortic dissection (Samurai technique) in emergency scenarios

Choosing the optimal arterial cannulation site in type A aortic dissection may be challenging. Aortic dissection is a dynamic condition that can change at any time. Thus all the alternatives available should be known by surgeons in order to adapt to the possible problems that may arise. In this video tutorial, we present a patient with acute type A aortic dissection who, after cardiopulmonary bypass with axillary arterial cannulation, developed a major complication: intraoperative malperfusion due to pressurization of the false lumen. The patient developed occlusion of the right coronary artery with electrocardiogram changes, inferior akinesia, and ventricular arrhythmias. Cerebral saturation was also significantly decreased. This scenario of acute malperfusion calls for immediate action. We proceeded to switch the cardiopulmonary bypass configuration from axillary to direct true lumen cannulation. This technique, also known as the Samurai technique, is feasible in most cases and advantageous in this emergency situation, allowing prompt reestablishment of adequate perfusion of the true lumen . Some authors even advocate more widespread use of this technique because it may ensure antegrade perfusion while avoiding progression of the dissection flap and reduce the rate of the most common complications of other cannulation sites such as plexus injury during axillary cannulation or cerebral embolization through mobilization of thrombi or calcification from femoral retrograde perfusion. This technique is useful in cases of circumferential dissection and in patients with relative contraindications for peripheral cannulation such as morbid obesity or peripheral arterial occlusion by atherosclerosis or by the dissection itself.

Lessons learned from catheter ablation of ventricular arrhythmias in patients with a fully magnetically levitated left ventricular assist device

Introduction Data on catheter ablation of ventricular arrhythmias (VA) are scarce in patients with left ventricular assist devices (LVADs) and current evidence predominantly consists of case reports with outdated LVAD. This prospective observational study reports our experience in terms of catheter ablation of VAs in patients with novel 3rd generation LVADs. Methods and results Between 2018 and 2020, nine consecutive patients undergoing a total number of ten ablation procedures for VAs were analyzed. The mean duration between LVAD implantation and catheter ablation was 23 ± 16 months. Acute procedural success was achieved in all patients. VA substrates were not related to the LVAD scarring (cannula) site in the majority of patients. All procedures were conducted without any relevant procedure-related complications. In terms of follow-up, only one patient presented with a repeat episode of electrical storm requiring ICD-shocks 16 months after the initial ablation procedure. Four patients suffered of singular VA effectively treated with antitachycardia pacing via their ICD. The remainder were free of any VA relapse (n = 4). Two non-procedure-related deaths occurred during follow-up. Conclusions Catheter ablation of VAs in patients with 3rd generation LVAD is feasible and leads to satisfying clinical results in terms of freedom from VA recurrence and quality of life. The majority of arrhythmia substrates in these patients are not directly related to the LVAD cannulation site and may represent a progress of heart failure. Graphic abstract

Novel surgical management of an extensive recurrent Hickman line thrombosis involving the SVC and right atrium

Intravenous central line catheters are often at risk of line-related thrombosis. We report on how the cardiopulmonary bypass strategy was tailored to the particular anatomical challenges with the use of an unconventional venous cannulation site to optimise intraoperative venous drainage, improve surgical exposure and avoid circulatory arrest in a case with a complex intracardiac thrombosis. This report also highlights the importance of assiduously monitoring the efficacy of anticoagulation therapy, especially in the context of small bowel syndrome.

Effect of cannulation site on emboli travel during cardiac surgery

Background During cardiac surgery, micro-air emboli regularly enter the blood stream and can cause cognitive impairment or stroke. It is not clearly understood whether the most threatening air emboli are generated by the heart-lung machine (HLM) or by the blood-air contact when opening the heart. We performed an in vitro study to assess, for the two sources, air emboli distribution in the arterial tree, especially in the brain region, during cardiac surgery with different cannulation sites. Methods A model of the arterial tree was 3D printed and included in a hydraulic circuit, divided such that flow going to the brain was separated from the rest of the circuit. Air micro-emboli were injected either in the HLM (“ECC Bubbles”) or in the mock left ventricle (“Heart Bubbles”) to simulate the two sources. Emboli distribution was measured with an ultrasonic bubble counter. Five repetitions were performed for each combination of injection site and cannulation site, where air bubble counts and volumes were recorded. Air bubbles were separated in three categories based on size. Results For both injection sites, it was possible to identify statistically significant differences between cannulation sites. For ECC Bubbles, axillary cannulation led to a higher amount of air bubbles in the brain with medium-sized bubbles. For Heart Bubbles, aortic cannulation showed a significantly bigger embolic load in the brain with large bubbles. Conclusions These preliminary in vitro findings showed that air embolic load in the brain may be dependent on the cannulation site, which deserves further in vivo exploration.

Arteriovenous Fistula Creation for Hemodialysis: Evaluation of Complications

Background: Vascular access care is a classic example of multidisciplinary team work among nephrologists, vascular surgeons, duplex specialists, dialysis nurses and dialysis staff. The objectives of this study were to determine the complication of arteriovenous fistula (AVF) for hemodialysis (HD) and to find out the role of duplex study for the management of fistula complications. Methods: This was a prospective type of study done on 121 arteriovenous fistulas. All operations were done in different hospitals in Dhaka city. After duplex study of upper limb vessels, the site of fistula creation was determined. All Radio-cephalic, ulnar-basilic and brachiocephalic fistulas were done under local anesthesia. Other fistula of the series was done under brachial block. Immediate postoperative bruit, thrill and distal pulses were monitored. Fistulas were considered mature after at least 6 weeks of fistula creation with good visualization of arterialized vein and good thrill. Patients were advised to report if any complication arises. Results: The most common fistula was Radio-cephalic fistulas (72.73%) and then Brachio-cephalic fistulas (19.84%). The left upper limb was the first choice for fistula creation as a non-dominant limb. Most fistula was created in left upper limb (76.86%). The most common complication was stenosis of arterialized veins (4.13%) and another type of stenosis was found at anastomotic site (2.48%). Second most common complication was cannulation site infections (3.31%). Another common type of infection was found at the site of fistula creation (2.48%). Thrombosis, aneurysm and pseudoaneurysm were identified as the most detrimental complications. Conclusion: Arteriovenous fistula is an important issue for hemodialysis patient as the life line. Dialysis nurses and technician should have knowledge about antisepsis and potential complication of AVFs. Early diagnosis and early treatment prevent loss of vascular access and reduce serious morbidity and mortality. Both the patients and dialysis staffs should give highest care for the AVF to reduce the complications. Bangladesh Heart Journal 2020; 35(2) : 100-105