Extracorporeal membrane oxygenation (ECMO): Radiographic appearances, complications and imaging artefacts for radiologists.

Extracorporeal membrane oxygenation (ECMO) is a form of cardiopulmonary support primarily used in cardiothoracic and intensive care unit (ICU) settings. The purpose of this review is to familiarise radiologists with the imaging features of ECMO devices, their associated complications and appropriate imaging protocols for contrast-enhanced CT imaging of ECMO patients. This paper will provide a brief introduction to ECMO and the imaging modalities utilised in ECMO patients, followed by a description of the types of ECMO available and cannula positioning. Indications and contraindications for ECMO will be outlined followed by a description of the complications associated with ECMO, which radiologists should recognise. Finally, the imaging protocol and interpretation of contrast-enhanced CT imaging in ECMO patients will be discussed. In the current clinical climate with millions of COVID-19 cases around the world and tens of thousands of critically ill patients, many requiring cardiopulmonary support in intensive care units, the use of ECMO in adults has increased, and thus so has the volume of imaging. Radiologists need to be familiar with the types of ECMO available, the correct positioning of the catheters depending on the type of ECMO being utilised, and the associated complications and imaging artefacts.

Features of carcinoid heart disease identified by cardiac computed tomography.

BACKGROUND: Carcinoid heart disease (HD) is a rare form of valvular heart disease, the features of which have not been fully described by cardiac computed tomography (CT). METHODS: All patients with carcinoid HD that underwent cardiac CT, either preoperatively or for assessment of coronary arteries, between Apr-2006 and Dec-2019 at the Royal Free Hospital, UK, were reviewed. RESULTS: Of 32 patients with carcinoid HD, 29 (91%) had heart valve involvement. Abnormalities of the tricuspid and pulmonary valves were present in all patients, affecting all three leaflets in 23/26 (89%) unoperated patients for both valves. The aortic valve was affected in 4/29 (14%) patients and the mitral valve in 5/29 (17%). Left heart valves were affected in 6/29 (21%) patients. One patient (1/29; 3%) had all four valves affected. Severe changes with significant valvular regurgitation were seen in ≥75% of patients with tricuspid, pulmonary, and aortic valve abnormalities. Three patients had carcinoid myocardial metastases (3/32; 9%) and one patient had constrictive pericarditis (1/32; 3%). Ten patients had surgery of whom four (40%) had invasive coronary angiography preoperatively. Ten patients had a patent foramen ovale. Cardiac CT allowed an accurate assessment of damage to different leaflets/cusps, particularly of the pulmonary valve, where visualization with echocardiography was often (3/8; 38%) incomplete. CONCLUSION: Cardiac CT is a powerful tool for assessment of cardiac valve abnormalities, coronary arteries and the spatial relationship of coronary arteries with myocardial metastasis in patients with carcinoid HD, and should form part of multimodal imaging of this complex pathology.

High-pitch versus conventional cardiovascular CT in patients being assessed for transcatheter aortic valve implantation: a real-world appraisal.

OBJECTIVE: High-pitch protocols are increasingly used in cardiovascular CT assessment for transcatheter aortic valve implantation (TAVI), but the impact on diagnostic image quality is not known. METHODS: We reviewed 95 consecutive TAVI studies: 44 (46%) high-pitch and 51 (54%) standard-pitch. Single high-pitch scans were performed regardless of heart rate. For standard-pitch acquisitions, a separate CT-aortogram and CT-coronary angiogram were performed with prospective gating, unless heart rate was ≥70 beats/min, when retrospective gating was used. The aortic root and coronary arteries were assessed for artefact (significant artefact=1; artefact not limiting diagnosis=2; no artefact=3). Aortic scans were considered diagnostic if the score was >1; the coronaries, if all three epicardial arteries scored >1. RESULTS: There was no significant difference in diagnostic image quality for either the aorta (artefact-free high-pitch: 31 (73%) scans vs standard-pitch: 40 (79%), p=0.340) or the coronary tree as a whole (10 (23%) vs 15 (29%), p=0.493). However, proximal coronary arteries were less well visualised using high-pitch acquisitions (16 (36%) vs 30 (59%), p=0.04). The median (IQR) radiation dose was significantly lower in the high-pitch cohort (dose-length product: 347 (318-476) vs 1227 (1150-1474) mGy cm, respectively, p<0.001), and the protocol required almost half the amount of contrast. CONCLUSIONS: The high-pitch protocol significantly reduces radiation and contrast doses and is non-inferior to standard-pitch acquisitions for aortic assessment. For aortic root assessment, the high-pitch protocol is recommended. However, if coronary assessment is critical, this should be followed by a conventional standard-pitch, low-dose, prospectively gated CT-coronary angiogram if the high-pitch scan is non-diagnostic.

A low-dose, dual-phase cardiovascular CT protocol to assess left atrial appendage anatomy and exclude thrombus prior to left atrial intervention.

Assessment of the left atrial appendage (LAA) for thrombus and anatomy is important prior to atrial fibrillation (AF) ablation and LAA exclusion. The use of cardiovascular CT (CCT) to detect LAA thrombus has been limited by the high incidence of pseudothrombus on single-pass studies. We evaluated the diagnostic accuracy of a two-phase protocol incorporating a limited low-dose delayed contrast-enhanced examination of the LAA, compared with a single-pass study for LAA morphological assessment, and transesophageal echocardiography (TEE) for the exclusion of thrombus. Consecutive patients (n = 122) undergoing left atrial interventions for AF were assessed. All had a two-phase CCT protocol (first-past scan plus a limited, 60-s delayed scan of the LAA) and TEE. Sensitivity, specificity, diagnostic accuracy, positive (PPV) and negative predictive values (NPV) were calculated for the detection of true thrombus on first-pass and delayed scans, using TEE as the gold standard. Overall, 20/122 (16.4 %) patients had filling defects on the first-pass study. All affected the full delineation of the LAA morphology; 17/20 (85 %) were confirmed as pseudo-filling defects. Three (15 %) were seen on late-pass and confirmed as true thrombi on TEE; a significant improvement in diagnostic performance relative to a single-pass scan (McNemar Chi-square 17, p < 0.001). The sensitivity, specificity, diagnostic accuracy, PPV and NPV was 100, 85.7, 86.1, 15.0 and 100 % respectively for first-pass scans, and 100 % for all parameters for the delayed scans. The median (range) additional radiation dose for the delayed scan was 0.4 (0.2-0.6) mSv. A low-dose delayed scan significantly improves the identification of true LAA anatomy and thrombus in patients undergoing LA intervention.

Clinical and economic consequences of non-cardiac incidental findings detected on cardiovascular computed tomography performed prior to transcatheter aortic valve implantation (TAVI).

Transcatheter aortic valve implantation (TAVI) is an effective treatment option for patients with severe degenerative aortic valve stenosis who are high risk for conventional surgery. Computed tomography (CT) performed prior to TAVI can detect pathologies that could influence outcomes following the procedure, however the incidence, cost, and clinical impact of incidental findings has not previously been investigated. 279 patients underwent CT; 188 subsequently had TAVI and 91 were declined. Incidental findings were classified as clinically significant (requiring treatment), indeterminate (requiring further assessment), or clinically insignificant. The primary outcome measure was all-cause mortality up to 3 years. Costs incurred by additional investigations resultant to incidental findings were estimated using the UK Department of Health Payment Tariff. Incidental findings were common in both the TAVI and medical therapy cohorts (54.8 vs. 70.3%; P = 0.014). Subsequently, 45 extra investigations were recommended for the TAVI cohort, at an overall average cost of £32.69 per TAVI patient. In a univariate model, survival was significantly associated with the presence of a clinically significant or indeterminate finding (HR 1.61; P = 0.021). However, on multivariate analysis outcomes after TAVI were not influenced by any category of incidental finding. Incidental findings are common on CT scans performed prior to TAVI. However, the total cost involved in investigating these findings is low, and incidental findings do not independently identify patients with poorer outcomes after TAVI. The discovery of an incidental finding on CT should not necessarily influence or delay the decision to perform TAVI.

Habib EndoHPB: a novel endobiliary radiofrequency ablation device. An experimental study.

BACKGROUND: The Habib EndoHPB is a bipolar radiofrequency (RF) catheter developed to be introduced across malignant strictures of the bile ducts, so that RF energy can locally ablate the tumor prior to stent placement. This experiment aims to assess the ability of the catheter to coagulate the wall of the common bile duct (CBD) in a porcine model, to establish power requirement and time parameters and correlate them to the depth of thermal injury, and to assess the ease of operation of the device. METHODS: The CBD was catheterized using the device in 20 pigs. RF energy was applied to the CBD wall with various generator settings. The pigs were sacrificed 24 hr after the application and the CBD was excised for histological analysis. RESULTS: The device was easy to handle. Statistically significant correlations between the power, the time of RF application, and the thermal injury depth were found. CONCLUSION: The Habib EndoHPB catheter can effectively deliver RF energy intraluminally in the porcine CBD. Clinical studies are warranted in order to define proper settings for safe and efficient use in malignant biliary obstruction.

A new endovascular radiofrequency device for dilatation of vascular stenosis in a rabbit model.

PURPOSE: To investigate the use of a new endovascular radiofrequency (RF) device, the Habib™ VesCoag™ Catheter, to induce vascular remodeling and dilatation of arterial stenosis in a rabbit model. MATERIALS AND METHODS: RF was used to induce arterial stenosis in 10 rabbits and this was confirmed by angiography and color Doppler ultrasound. Two groups of five animals were then subjected to (1) balloon dilatation of the stenosis (intervention group), (2) no intervention (control group). Two rabbits from each group were sacrificed following the procedures to investigate vessel histopathology. At six weeks, the remaining six rabbits underwent follow-up angiogram and color Doppler ultrasound to assess vessel patency. They were then sacrificed and the vessels prepared for histopathological analysis. Three-dimensional images with confocal microscopy of the arterial lumen were also acquired. RESULTS: In the intervention group, stenosis was reversed and patency confirmed by angiography and color Doppler ultrasound six weeks later in all surviving rabbits. Histopathology revealed degenerative changes of elastic fibers, focal losses of elastica lamella, disorganization of myocytes and extensive hyalinization of the tunica adventitia. Focal elastin changes of the arterial elastic lamella were also shown by three-dimensional confocal microscopy images. CONCLUSION: We have developed a novel endovascular RF catheter that can be safely and effectively used to induce vascular remodeling and dilatation of arterial stenosis in an experimental rabbit model.

Influence of the learning curve on safety and efficiency of laparoscopic sleeve gastrectomy.

BACKGROUND: Laparoscopic sleeve gastrectomy (LSG) is a relatively new bariatric procedure, and data regarding the learning curve are scarce. The aim of this study is to assess how the procedure can be safely implanted in a newly established bariatric unit and to define the learning curve. METHODS: Proctorship and mentorship in bariatric surgery were attended by two surgeons who were previously experienced in advanced laparoscopic surgery. The first consecutive 102 patients who underwent LSG in our newly established bariatric center were included. Patients were divided into three groups of 34 (groups 1, 2, and 3) according to case sequence. Data on demographics, operative time, conversion rate, hospital stay, morbidity, mortality, and excess weight loss (EWL) over time were compared between the groups. RESULTS: The operative time was significantly lower in groups 2 (p = 0.016) and 3 (p = 0.003) compared to group 1. The learning curve was flat up to the 68th case. A significant decrease in hospital stay was noted for group 3 compared to groups 1 (p < 0.001) and 2 (p = 0.002). The conversion rate, mortality and morbidity rates, and EWL did not differ significantly between the groups. Mortality was 0.98% and procedure-related morbidity was 7.8%. CONCLUSIONS: LSG can be safely and efficiently performed in a newly established bariatric center following a mentorship procedure. Proficiency seems to require 68 cases. The operative time and hospital stay may significantly decrease with experience early in the learning curve, as opposed to mortality and morbidity rates, conversion rate, and EWL.

Experimental animal study of a novel radiofrequency endovascular occlusion device.

BACKGROUND: The purpose of this study was to present a radiofrequency (RF) endovascular occlusion device (ie, Habib VesCoag Catheter; EMcision Ltd, London, UK) and to evaluate safety and efficacy of the device for complete occlusion of normal porcine vessels. METHODS: The study included 20 pigs. In each pig, a segmental branch of the right hepatic artery, a branch of the splenic artery, and a branch of one of the renal arteries were catheterized. A single or multiple applications of RF energy were performed until vessel occlusion was achieved. Fifteen days later, angiography was repeated to assess vessel patency. The vessels were then excised for pathological analysis. RESULTS: Vessels 2.5 to 6 mm in diameter were treated. Complete occlusion with a single attempt was achieved using a mean amount of energy of 110.67 J in vessels 2.5 to 3 mm, 111.67 J in vessels 3.5 to 4 mm, and 116.63 J in vessels 5 to 6 mm in diameter and was confirmed by angiography at the 15-day follow-up. CONCLUSIONS: Vascular occlusion can be effectively and safely achieved by endovascular application of RF energy to normal porcine arteries using the Habib VesCoag catheter.

A novel experimental animal model of arterial stenosis based on endovascular radiofrequency energy application.

PURPOSE: To develop a new rabbit model of arterial stenosis using endovascular radiofrequency (RF) energy. MATERIALS AND METHODS: Ten rabbits were used for multiple endovascular RF applications to the aorta and left common carotid artery through the Habib™ VesCoag™ catheter. Angiography and color Doppler ultrasound were used to assess vessel patency immediately following the procedure and six weeks later. One rabbit was sacrificed following the procedure for histopathologic analysis of the vessel wall. Two rabbits died of aortic and carotid rupture, respectively, immediately after the procedure. The remaining seven rabbits were sacrificed after six-week follow-up for histopathological analysis. RESULTS: Optimal RF generator settings to induce significant arterial stenosis (>50%) without complications were standardized at 24-26 watts (W) for 1.5 min for the aorta and 6 W for 1 min for the common carotid artery. The six-week follow-up showed permanent results in all surviving rabbits. Histopathology revealed intima and medial smooth muscle layer necrosis. CONCLUSION: We have developed a novel rabbit model of arterial stenosis using endovascular RF energy. Our model is fast, safe, inexpensive, and reproducible. It would be useful for experimental investigations and new therapeutic devices.

Symptoms of gastroesophageal reflux following laparoscopic sleeve gastrectomy are related to the final shape of the sleeve as depicted by radiology.

BACKGROUND: Laparoscopic sleeve gastrectomy (LSG) is gaining popularity as a primary procedure in selected morbidly obese patients. Like most other bariatric procedures LSG results in alterations of the upper GI anatomy that might affect gastroesophageal reflux postoperatively. The study was conducted to assess the presence of reflux symptoms in patients before and after laparoscopic sleeve gastrectomy and any possible relation of these symptoms to the postoperative gastric anatomy as depicted by gastrografin swallow studies. METHODS: The study included 85 consecutive morbidly obese patients who underwent LSG as a primary bariatric procedure. Patients were evaluated for symptoms of gastroesophageal reflux (heartburn, regurgitation, and vomiting) preoperatively and at 1 and 6 months and 1 year postoperatively. To assess the postoperative gastric anatomy, the gastrografin studies that were routinely performed in all patients on the third postoperative day were retrospectively evaluated. Changes of each one of the reflux symptoms were assessed in relation to the radiological pattern of the gastric sleeve. RESULTS: Three radiological patterns of the gastric sleeve were identified: (a) the tubular (65.9%), (b) the superior pouch (25.9%), and (c) the inferior pouch pattern (8.2%). Patients showed an overall tendency towards relief of heartburn and increase of regurgitation and vomiting postoperatively. However, only changes in regurgitation and vomiting were found to be statistically significant (p < 0.01); interestingly, those were observed in patients with the tubular gastric pattern. CONCLUSIONS: The final shape of the gastric sleeve as depicted by radiological studies seems to have an impact on reflux symptoms after laparoscopic sleeve gastrectomy.

Anatomy and complications following laparoscopic sleeve gastrectomy: radiological evaluation and imaging pitfalls.

BACKGROUND: To evaluate the post-operative gastric anatomy depicted by upper gastrointestinal gastrografin swallow studies (UGI) and report radiological work-up and management of complications following laparoscopic sleeve gastrectomy (LSG). METHODS: The study included 85 consecutive patients who underwent LSG for the treatment of morbid obesity. In all patients, a UGI was routinely performed on POD 3 to exclude early complications. In patients with suspected complications, further radiological evaluation with computed tomography (CT) was performed. The anatomy of the gastric remnant depicted by UGI was retrospectively evaluated in all patients. RESULTS: The patterns of the gastric remnant identified were the tubular (65.9%), the superior pouch (25.9%), and the inferior pouch pattern (8.2%). Three patients had small superior pouches that resembled leaks, and the diagnosis was based on clinical symptoms. Post-operative complications were observed in 12.9% and included leaks (3.5%), hemorrhages (3.5%), strictures (2.3%), pulmonary embolism (1.2%), trocar site hernia (1.2%), and hematoma of the rectus abdominal muscle (1.2%). No mortality was noted. CONCLUSIONS: Post-operative radiological evaluation by UGI and CT is important for diagnosis and management of complications following LSG. Familiarity with the anatomy of the gastric remnant at UGI is essential for correct image interpretation.

Radiofrequency-assisted hemostasis in a trauma model: a new indication for a bipolar device.

BACKGROUND: Hemorrhage control in severe splenic and hepatic injuries remains a challenge, despite recent improvements in equipment technology. Radiofrequency (RF) energy-assisted surgery for the spleen and liver has been recently reported; however, the technique has not gained wide acceptance, mainly due to surgeons' unfamiliarity with the technique and the risk of complications caused by uncontrolled disseminated energy. In this study, the safety and efficacy of the Habib 4X (AngioDynamics, Latham, NY), a hand-held bipolar RF energy device, was evaluated in a porcine trauma model. MATERIALS AND METHODS: Five white male Landrace pigs were included in the study. Multiple stab wounds were inflicted to the splenic and hepatic parenchyma, both centrally and peripherally. Hemostasis was achieved by using the Habib 4X RF bipolar device. The pigs were humanely sacrificed 6 weeks postoperatively, and histology of the ablated spleen and liver was evaluated. RESULTS: Hemorrhage was successfully controlled at all bleeding sites, using appropriate RF generator settings. The splenic artery and vein, as well as the hepatic veins, were successfully ligated using the device. No complications were noted immediately postoperatively or 6 weeks following the procedure. CONCLUSIONS: The bipolar Habib 4X device delivers RF energy that can achieve hemostasis of the injured splenic and hepatic parenchyma. The method is feasible and safe. Clinical studies are warranted to assess short- and long-term results of this promising technique and compare it to the gold standards.

Incidental non-cardiac findings of a coronary angiography with a 128-slice multi-detector CT scanner: should we only concentrate on the heart?

OBJECTIVE: To evaluate the spectrum, prevalence, and significance of incidental non-cardiac findings (INCF) in patients referred for a non-invasive coronary angiography using a 128-slice multi-detector CT (MDCT). MATERIALS AND METHODS: The study subjects included 1,044 patients; 774 males (mean age, 59.9 years) and 270 females (mean age, 63 years), referred for a coronary CT angiography on a 128-slice MDCT scanner. The scans were acquired from the level of the carina to just below the diaphragm. To evaluate INCFs, images were reconstructed with a large field of view (> 300 mm) covering the entire thorax. Images were reviewed in the axial, coronal, and sagittal planes, using the mediastinal, lung, and bone windows. The INCFs were classified as severe, indeterminate, and mild, based on their clinical importance, and as thoracic or abdominal based on their locations. RESULTS: Incidental non-cardiac findings were detected in 56% of patients (588 of 1,044), including 435 males (mean age, 65.6 years) and 153 females (mean age, 67.9 years). A total of 729 INCFs were observed: 459 (63%) mild (58% thoracic, 43% abdominal), 96 (13%) indeterminate (95% thoracic, 5% abdominal), and 174 (24%) severe (87% thoracic, 13% abdominal). The prevalence of severe INCFs was 15%. Two severe INCFs were histologically verified as lung cancers. CONCLUSION: The 128-slice MDCT coronary angiography, in addition to cardiac imaging, can provide important information on the pathology of the chest and upper abdomen. The presence of severe INCFs is not rare, especially in the thorax. Therefore, all organs in the scan should be thoroughly evaluated in daily clinical practice.