Design and Haemodynamic Analysis of a Novel Anchoring System for Central Venous Pressure Measurement.

BACKGROUND/OBJECTIVE: In recent years, treatment of heart failure patients has proved to benefit from implantation of pressure sensors in the pulmonary artery (PA). While longitudinal measurement of PA pressure profoundly improves a clinician's ability to manage HF, the full potential of central venous pressure as a clinical tool has yet to be unlocked. Central venous pressure serves as a surrogate for the right atrial pressure, and thus could potentially predict a wider range of heart failure conditions. However, it is unclear if current sensor anchoring methods, designed for the PA, are suitable to hold pressure sensors safely in the inferior vena cava. The purpose of this study was to design an anchoring system for accurate apposition in inferior vena cava and evaluate whether it is a potential site for central venous pressure measurement. MATERIALS AND METHODS: A location inferior to the renal veins was selected as an optimal site based on a CT scan analysis. Three anchor designs, a 10-strut anchor, and 5-struts with and without loops, were tested on a custom-made silicone bench model of Vena Cava targeting the infra-renal vena cava. The model was connected to a pulsatile pump system and a heated water bath that constituted an in-vitro simulation unit. Delivery of the inferior vena cava implant was accomplished using a preloaded introducer and a dilator as a push rod to deploy the device at the target area. The anchors were subjected to manual compression tests to evaluate their stability against dislodgement. Computational Fluid Dynamics (CFD) analysis was completed to characterize blood flow in the anchor's environment using pressure-based transient solver. Any potential recirculation zones or disturbances in the blood flow caused by the struts were identified. RESULTS: We demonstrated successful anchorage and deployment of the 10-strut anchor in the Vena Cava bench model. The 10-strut anchor remained stable during several compression attempts as compared with the other two 5-strut anchor designs. The 10-strut design provided the maximum number of contact points with the vessel in a circular layout and was less susceptible to movement or dislodgement during compression tests. Furthermore, the CFD simulation provided haemodynamic analysis of the optimum 10-strut anchor design. CONCLUSIONS: This study successfully demonstrated the design and deployment of an inferior vena cava anchoring system in a bench test model. The 10-strut anchor is an optimal design as compared with the two other 5-strut designs; however, substantial in-vivo experiments are required to validate the safety and accuracy of such implants. The CFD simulation enabled better understanding of the haemodynamic parameters and any disturbances in the blood flow due to the presence of the anchor. The ability to place a sensor technology in the vena cava could provide a simple and minimally invasive approach for heart failure patients.

A novel wireless implant for central venous pressure measurement: First animal experience.

Background/Objective: Central venous pressure (CVP) serves as a surrogate for right atrial pressure, and thus could potentially predict a wider range of heart failure conditions. The purpose of this work is to assess CVP, through an implantable sensor incorporated with a novel anchor design, in the inferior and superior vena cava of an animal model. Methods: Two animals (Dorset sheep) were implanted with sensors at 3 different locations: inferior vena cava (IVC), superior vena cava (SVC), and pulmonary artery (PA). Two sensors with distinct anchor designs considering anatomical requirements were used. A standard PA sensor (trade name Cordella) was deployed in the PA and SVC, whereas a sensor with a modified cylindrical anchor with various struts was designed to reside in the IVC. Each implant was calibrated against a Millar catheter reference sensor. The ability of the central venous sensors to detect changes in pressure was evaluated by modifying the fluid volume of the animal. Results: The sensors implanted in both sheep were successful, which provided an opportunity to understand the relationship between PA and CVP via simultaneous readings. The mapping and implantation in the IVC took less than 15 minutes. Multiple readings were taken at each implant location using a hand-held reader device under various conditions. CVP recorded in the IVC (6.49 mm Hg) and SVC (6.14 mm Hg) were nearly the same. PA pressure (13-14 mm Hg) measured was higher than CVP, as expected. The SVC waveforms showed clear beats and respiration. Respiration could be seen in the IVC waveforms, but not all beats were easily distinguishable. Both SVC and IVC readings showed increases in pressure (3.7 and 2.7 mm Hg for SVC and IVC, respectively) after fluid overload was induced via extra saline administration. Conclusion: In this work, the feasibility of measuring CVP noninvasively was demonstrated. The established ability of wireless PA pressure sensors to enable prevention of decompensation events weeks ahead can now be explored using central venous versions of such sensors.

Changes in left ventricular shape and morphology in the presence of heart failure: a four-dimensional quantitative and qualitative analysis.

PURPOSE: The presence and progression of heart failure (HF) are associated with cardiac remodelling, defined as cellular, molecular and interstitial changes which occur after injury and manifest as changes in left ventricular (LV) size, mass, geometry and function. This research study was designed to investigate the changes to LV morphology and shape which occur in the presence of heart failure using three-dimensional (3D) modelling and analysis of cardiac-gated CT scans from both healthy individuals and patients classified with HF. METHODS: A number of quantitative and qualitative strategies were applied to cardiac CT scans of HF patients and healthy controls (n = 7) in order to analyse changes to LV size, shape and structure and to examine LV remodelling in the different classes of HF. Three-dimensional wireframe representations of endocardial and epicardial borders were created, three-dimensional computer stereolithography models of the inner LV cavity and myocardial wall segments were generated and three-dimensionally printed and a number of clinical LV dimension and shape indices were measured. All data were analysed using one-way ANOVA with post hoc Tukey method for multiple comparisons for significant variables. RESULTS: Results of most significance included abnormalities in LV mass and end-systolic dimensions and significantly increased septal wall thickness among mid-range ejection fraction cases. Also of importance were significant increases in both dimension-based and volumetric sphericity index measures in all HF cases. Three-dimensional printed models provided qualitative information as to changes in inner LV cavity and myocardial wall morphology across the cardiac cycle for healthy and HF cases and validated quantitative findings. CONCLUSION: Findings from this study can successfully be applied to motivate the research and development of new HF treatment strategies and devices as well as for the development of a realistic cardiac simulator system.

A Systematic Review of Outcomes After Transanal Mesorectal Resection for Rectal Cancer.

BACKGROUND: Transanal mesorectal resection has been developed to facilitate minimally invasive proctectomy for rectal cancer. OBJECTIVE: The purpose of this study was to evaluate the evidence regarding technical parameters, oncological outcomes, morbidity, and mortality after transanal mesorectal resection. DATA SOURCES: The Cochrane Library, PubMed, and MEDLINE databases were reviewed. STUDY SELECTION: Systematic review of the literature from January 2005 to September 2015 was used for study selection. INTERVENTION: Intervention included transanal mesorectal resection for rectal cancer. MAIN OUTCOME MEASURES: Technical parameters, histological outcomes, morbidity, and mortality were the outcomes measured. RESULTS: Fifteen predominately retrospective studies involving 449 patients were included (mean age, 64.3 years; 64.1% men). Different platforms were used. The operative mortality rate was 0.4% and the cumulative morbidity rate 35.5%. Circumferential resection margins were clear in 98%, and the resected mesorectum was grade III in 87% of patients. Median follow-up was 14.7 months. There were 4 local recurrences (1.5%) and 12 patients (5.6%) with metastatic disease. No study followed patients long enough to report on 5-year overall and disease-free survival rates. Functional outcome was only reported in 3 studies. LIMITATIONS: A low number of procedures were performed by expert early adopters. There are no comparative or randomized data included in this study and inconsistent reporting of outcome variables. CONCLUSIONS: Transanal mesorectal resection for rectal cancer may enhance negative circumferential margin rates with a reasonable safety profile. Contemporary randomized, controlled studies are required before there can be universal recommendation.

Late presentation of a large Morgagni hernia in an adult.

A 57-year-old man with no medical history and comorbidities presented to the outpatient clinic with a 2-week history of increasing cough and shortness of breath following a recent viral upper respiratory tract infection. Chest X-ray showed increased mediastinal opacity. A CT scan of the thorax was performed which revealed a large right-sided diaphragmatic hernia extending across the mediastinum to the left side of the chest. Repair was performed via combined transthoracic and transabdominal approaches.

Combined enzyme replacement and haematopoietic stem cell transplantation in Hurler syndrome.

We report the long-term follow-up of successful treatment of mucopolysaccharidosis type I H (MPS IH, Hurler syndrome) with combined enzyme replacement therapy and haematopoietic progenitor stem cell transplant.

The management of mycotic femoral pseudoaneurysms in intravenous drug abusers.

Mycotic femoral pseudoaneurysms, particularly in the drug-abusing population, pose a difficult problem to the vascular surgeon. Management ranges from ligation with debridement to extra-anatomical bypass. This study reviewed the management of mycotic femoral pseudoaneurysms presenting in intravenous drug abusers to an inner city tertiary referral center. Between 2001 and 2006, 11 cases presenting in nine patients were treated. The mean age was 30.7 years with a male-to-female ratio of 1:2. Eight patients had a positive viral status for the human immunodeficiency virus and/or hepatitis C. Two patients re-presented with a contralateral pseudoaneurysm. A combination of groin pain and swelling was the most common presentation. Two patients presented with significant hemorrhage. The diagnosis was confirmed by ultrasound in the majority of cases. Nine cases were managed with arterial ligation and debridement of the necrotic tissue. The two remaining cases were managed with ultrasound-guided thrombin injection and arterial puncture closure. On follow-up, one patient required a below-knee amputation following reinjection into the postoperative wound site. One further patient underwent a fifth metatarsal amputation due to ischemia. Ligation and debridement are well tolerated in the majority of drug-abusing patients diagnosed with mycotic femoral pseudoaneurysms.

Radiographic work-up and treatment of lower gastrointestinal bleeding.

Lower gastrointestinal hemorrhage is a common reason for hospital admission. Spontaneous cessation occurs in the majority of these patients; however, continued major bleeding is a difficult clinical problem. Emergency surgery, without prior knowledge of the bleeding site is associated with high morbidity and mortality rates. Accurate localization is therefore desirable. The authors present a review of current radiological imaging modalities and therapeutic options available to the clinician. They also provide a management algorithm to aid in the strategic management of this group of patients.

Tetrahydrobiopterin-responsive phenylketonuria: the New South Wales experience.

Recent studies have shown that a subgroup of phenylketonuric patients respond to high doses of BH4 (20 mg/kg) by a decrease of plasma phenylalanine. A clinically significant response has been defined as a decrease in phenylalanine by more than 30% within 24 h, after a BH4 challenge. We report our experience with 37 patients diagnosed with hyperphenylalaninemia, mild, moderate, or classical Phenylketonuria (PKU) using a seven day combined BH4 and phenylalanine load. Nine of the 37 patients responded with a 30% decrease in their phenylalanine levels in the first 8 h of treatment. A total of 17 patients (46%) had a decrease of at least 30% during the study period. This study confirms that a significant number of patients with mild to moderate PKU will respond to a BH4 load. Furthermore, it confirms that the seven-day phenylalanine test is more sensitive in detecting BH4 responsive patients.