Clinical outcomes of handmade polytetrafluoroethylene trileaflet-valved conduit used for pulmonary valve replacement.

OBJECTIVES: To mitigate the shortage of homograft sources, the use of handmade trileaflet expanded polytetrafluoroethylene valves in pulmonary valve replacement has shown excellent results from multicentre studies conducted in Japan. However, world-wide data outside Japan are relatively insufficient. This study presents the long-term results of a single surgeon's use of flipped-back trileaflet method in a 10-year case series. METHODS: We have developed an efficient way to make a trileaflet-valved conduit utilizing flipped-back method for pulmonary valve replacement and have employed the technique since 2011. Retrospective data were studied between October 2010 and January 2020. Echocardiography, electrocardiogram, Pro-Brain Natriuretic Peptide and Magnetic Resonance Imaging data were analysed. RESULTS: Fifty-five patients were reviewed and median follow-up duration was 2.9 years. The majority of diagnoses was Tetralogy of Fallot (n = 41), and these patients subsequently underwent secondary pulmonary valve replacement at a median age of 15.6 years. Survival was 92.7% with the longest follow-up period being 10 years. There was no need for reoperation, and freedom from reintervention was 98.0% at 10 years. There were 4 deaths (3 in-hospital and 1 outpatient). One patient eventually received transcatheter pulmonary valve implantation. Postoperative echocardiography showed mild or less pulmonary stenosis and pulmonary regurgitation degree in 92.2% and 92.0% of patients, respectively. Comparable magnetic resonance imaging data (n = 25) showed significant reduction in right ventricular volumes but not in ejection fractions. CONCLUSIONS: Our series showed satisfactory long-term function of handmade flipped-back trileaflet-valved conduit used in our patients. The simple design is efficiently reproducible without complex fabrication process.

Luminal pressure gradient and risk of arteriovenous fistula nonmaturation.

While arteriovenous fistula (AVF) nonmaturation is a major issue of hemodialysis care, an effective treatment to improve AVF maturation remains lacking. AVF introduces pulsatile arterial blood flow into its venous limb and produces high luminal pressure gradient, which may have adverse effect on vascular remodeling. As such, the aim of the present study is to investigate effect of luminal pressure gradient on AVF nonmaturation. This single-center, prospective observational study includes patients receiving autologous AVF creation. Participants received early postoperative ultrasound 5-7 days after surgery to collect parameters including diameters, flow rates, and volume at inflow and outflow sites. Luminal pressure gradient was estimated by using modified Bernoulli equation. The outcome was spontaneous AVF maturation within 8 weeks after surgery without intervention. Thirty patients were included, of which the mean age was 66.9 years and 70% were male. At the end of study, 13 (43.3%) patients had spontaneous AVF maturation. All demographic and laboratory characteristics were similar between patients with mature and nonmature AVF. Regarding ultrasonographic parameters, nonmature AVF showed significantly higher inflow/outflow diameter ratio, inflow velocity, and luminal pressure gradient. While these 3 parameters were significantly correlated, multivariate logistic regression showed their significant association with AVF nonmaturation. Receiver operating characteristic curve exhibited their high predictive value for AVF nonmaturation. Our findings showed that higher inflow/outflow ratio, inflow velocity, and AVF luminal pressure gradient in early postoperative ultrasound predicted risk of AVF nonmaturation. Reducing inflow/outflow diameter ratio or inflow rate may be an approach to improve AVF maturation. The predictive value of this early assessment might have impact on the clinical practice of AVF care.

Evolution of pulmonary valve reconstruction with focused review of expanded polytetrafluoroethylene handmade valves.

OBJECTIVES: Many surgeons develop unique techniques for unmet needs for right ventricular outflow reconstruction to resolve pulmonary regurgitation after corrective surgery for congenital heart diseases. Expanded polytetrafluoroethylene (ePTFE) stands out as a reliable synthetic material, and clinical results with handmade ePTFE valves have been promising. This review focuses on the historical evolution of the use of ePTFE in pulmonary valve replacement and in the techniques for pioneering the translation of the handmade ePTFE trileaflet design for the transcatheter approach. METHODS: We searched for and reviewed publications from 1990 to 2020 in the Pubmed database. Nineteen clinical studies from 2005 to 2019 that focused on ePTFE-based valves were summarized. The evolution of the ePTFE-based valve over 3 decades and recent relevant in vitro studies were investigated. RESULTS: The average freedom from reintervention or surgery in the recorded ePTFE-based valve population was 90.2% at 5 years, and the survival rate was 96.7% at 3 years. CONCLUSIONS: Non-inferior clinical results of this ePTFE handmade valve were revealed compared to allograft or xenograft options for pulmonary valve replacement. Future investigations on transferring ePTFE trileaflet design to transcatheter devices should be considered.

Effects of cardiovascular medications on primary patency of hemodialysis arteriovenous fistula.

While the patency of vascular access is essential for hemodialysis patients, optimal pharmaceutical treatment to maintain arteriovenous fistula (AVF) patency remains lacking. As cardiovascular diseases are highly prevalent in patients with end-stage renal disease, various cardiovascular medications have also been used to maintain AVF patency. However, previous studies revealed inconsistent therapeutic effects and a comprehensive evaluation of this issue is needed. The present retrospective, longitudinal cohort study included patients receiving successful AVF creation. The evaluated cardiovascular medications included antiplatelet agents, antihypertensive agents, nitrates and nitrites, statins, dipyridamole, and pentoxifylline. The outcome was AVF primary patency. All laboratory data and medication profiles were recorded at baseline and followed at 3-month interval, until the end of the 2-year study period. Cox proportional regression model with time-dependent covariates was used to evaluate the risk for AVF patency loss. A total of 349 patients were included in the present study, in which 57% were men and the mean age was 65 ± 14 years. Among the included patients, 40% used antiplatelet agents, 27% used dipyridamole and 36% used statins at baseline. Of all the evaluated cardiovascular medications, only dipyridamole showed significant association with a higher risk for loss of AVF patency. To evaluate the effect of combination of antiplatelet agents and dipyridamole, the patients were classified into four groups, I: combine use of antiplatelet agents and dipyridamole, II: antiplatelet only, III: dipyridamole only; IV: none of both were used. Of the four groups, group IV exhibited highest AVF patency (52.4%), which was followed by group III (42.7%), group II (40%), and group I (28.6%), respectively. Compared with group IV, only group I showed a significantly higher risk for AVF patency loss. None of the cardiovascular medications evaluated in the present study showed a beneficial effect on AVF patency. Furthermore, dipyridamole showed an association with a higher risk of AVF patency loss. We do not suggest a beneficial effect of dipyridamole on maintaining AVF patency, particularly in combination with antiplatelet agents.

In vitro study of trileaflet polytetrafluoroethylene conduit and its valve-in-valve transformation.

OBJECTIVES: Handmade trileaflet expanded polytetrafluoroethylene valved conduit developed using the flip-over method has been tailored for pulmonary valve reconstruction with satisfactory outcomes. We investigated the in vitro performance of the valve design in a mock circulatory system with various conduit sizes. In our study, the design was transformed into a transcatheter stent graft system which could fit in original valved conduits in a valve-in-valve fashion. METHODS: Five different sizes of valved polytetrafluoroethylene vascular grafts (16, 18, 20, 22 and 24 mm) were mounted onto a mock circulatory system with a prism window for direct leaflets motion observation. Transvalvular pressure gradients were recorded using pressure transducers. Mean and instant flows were determined via a rotameter and a flowmeter. Similar flip-over trileaflet valve design was then carried out in 3 available stent graft sizes (23, 26 and 28.5 mm, Gore aortic extender), which were deployed inside the valved conduits. RESULTS: Peak pressure gradient across 5 different sized graft valves, in their appropriate flow setting (2.0, 2.5 and 5.0 l/min), ranged from 4.7 to 13.2 mmHg. No significant valve regurgitation was noted (regurgitant fraction: 1.6-4.9%) in all valve sizes and combinations. Three sizes of the trileaflet-valved stent grafts were implanted in the 4 sizes of valved conduits except for the 16-mm conduit. Peak pressure gradient increase after valved-stent graft-in-valved-conduit setting was <10 mmHg in all 4 conduits. CONCLUSIONS: The study showed excellent in vitro performance of trileaflet polytetrafluoroethylene valved conduits. Its valved stent graft transformation provided data which may serve as a reference for transcatheter valve-in-valve research in the future.

Study protocol for a prospective observational study to investigate the role of luminal pressure on arteriovenous fistula maturation.

INTRODUCTION: Arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis due to its higher patency and lower infection rate. However, its suboptimal maturation rate is a major weakness. Although substantial risk factors for AVF maturation failure have been disclosed, modifiable risk factors remain unknown. During the AVF maturation process, an elevated luminal pressure is required for outward remodeling; however, excessively high luminal pressure may also be detrimental to AVF maturation, which remains to be defined. We hypothesized that higher AVF luminal pressure is harmful to its maturation, and investigate its potential as a modifiable factor to improve AVF maturation. METHODS AND ANALYSIS: This prospective study includes patients undergoing surgical creation for a native AVF. The exclusion criteria were as follows: age <20 years, inability to sign an informed consent, and failure to create a native AVF due to technical difficulties. Demographic and laboratory profiles will be collected before AVF surgery. Vascular sonography will be performed within 1 week of AVF creation to measure the diameters, flow rates, and flow volumes of AVF and its branched veins. The pressure gradient within AVF will be estimated from the blood flow rates using the modified Bernoulli equation. The primary outcome is spontaneous AVF maturation defined as provision of sufficient blood flow for hemodialysis within 2 months of its creation without any interventional procedures. The secondary outcome is assisted AVF maturation, which is defined as AVF maturation within 2 months from its creation aided by any interventional procedure before the successful use of AVF. DISCUSSION: While contemporary theory for AVF maturation failure focuses on disturbed wall shear stress, complicate assumptions and measurement preclude its clinical applicability. AVF luminal pressure, which may be manipulated pharmaceutically and surgically, may be a target to improve the outcome of AVF maturation. TRIAL REGISTRATION: This study has been registered at the protocol registration and results system. The Protocol ID: NCT04017806.

Successful Transcatheter Handmade-Valved Graft Stent for Branch Pulmonary Regurgitation: Novel Approach in a Special Event.

Right heart failure is not uncommon in the patients with repaired tetralogy of Fallot (rTOF). Although commercialized transcatheter stent-mounted pulmonary valves are effective treatment options for improving functional class and for normalizing right ventricular volumes in such patients, they are not available in Taiwan. To provide a handmade alternative, we report our successful transcatheter attempt of a handmade assembled left pulmonary artery valved stent graft implantation in a 61-year-old man who had a history of rTOF and severe branch pulmonary regurgitation.

The outcome of patients requiring multiple extracorporeal membrane oxygenation: how many runs of ECMO is reasonable?

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) has been proven effective in life support for patients with refractory cardiopulmonary failure. Deteriorating patients who have removed their first ECMO support and required second or more courses of ECMO support have rarely been discussed. METHODS AND RESULTS: All the records of the patients who experienced at least 2 courses of ECMO during single admission were retrieved. Survival was defined as survival to discharge. Demographic data and clinical information were compared between survival and nonsurvival groups. There were 86 patients who received at least 2 courses of ECMO in the 20-year database, and 27 (31.3%) were <18 years old. Of them, 87.3% received 2 runs of ECMO, 10.4% 3 runs, and 2.3% 4 runs. Overall survival rate was 30.2%. The survival rate for patients with 2 runs of ECMO was 33.3% (25 out of 75), 11.1% (1 out of 9) for 3 runs, and 0% (0 out of 2) for 4 runs. Multivariate analysis revealed that only ARF with hemodialysis was the independent risk factor. CONCLUSIONS: The decision to perform repeated ECMO implantation is a complex and difficult process. Despite the arguments debating the consumption of resources and increased complications, there are still nearly 1 out of 3 patients who will survive to discharge. More than 2 courses of ECMO may be carefully considered for further rescue.

A Novel Bubble-Mixture Method to Improve Dynamic Images in Carbon Dioxide Angiography.

PURPOSE: To present a novel method of preparing carbon dioxide (CO2) for contrast enhancement. TECHNIQUE: CO2 angiography can often produce poor image enhancement, especially in dependent vessels due to buoyancy of the gas. A new technique for premixing the CO2 gas with the patient's blood and dispersing it into the bubble mixture before injection was developed. Comparative dynamic images showed bubble-mixed CO2 angiography had less fragmentation, more even distribution, and more sustainability than the same volume of pure CO2. CONCLUSION: The alteration of CO2 gas toward a semiliquid form demonstrates an easy and reproducible concept to improve the dynamic image quality of traditional CO2 angiography.

An efficient way to make a trileaflet conduit for pulmonary valve replacement.

Pulmonary regurgitation after repair of tetralogy of Fallot has always been an important issue for pediatric cardiac surgeons. Some of the patients may need pulmonary valve replacement in the future. Conventional prosthesis valves were seldom custom made for the pulmonary valve and were often inadequate to use because of variable age and size of these patients. Through evolution of techniques, we have developed a simple, efficient, and theoretically anatomic way of constructing trileaflet polytetrafluoroethylene valved conduit used for right ventricle outflow tract reconstruction. It was surprisingly straightforward, time efficient, and capable of being produced in various sizes.

Biliary complications after liver transplantation: an 18-year single-center experience.

BACKGROUND/PURPOSE: Biliary complications remain a major weakness of liver transplantation. The purpose of this retrospective study was to determine risk factors associated with biliary complications after liver transplantation, and how they were managed. METHODS: From October 1989 to December 2007, we collected all variables of interest in 253 consecutive liver transplant recipients at the National Taiwan University Hospital. Risk factors and the outcome of different treatments of the biliary complications were analyzed. RESULTS: Forty-three (17.0%) of the 253 liver transplant patients developed biliary complications. Bile leakage and biliary stricture rate was 7.9% and 6.7%, respectively. By univariate analysis, risk factors associated with bile leakage were older age, cadaveric liver donation, and use of a T-tube. The only protecting factor against bile leakage was the use of a straight intrahepatic stent. Risk factors associated with biliary stricture were rejection and male sex. Multivariate analysis demonstrated that T-tube [odds ratio (OR) =3.45] and older age group (OR =7.98) were the only independent risk factors for bile leakage, whereas graft rejection (OR =4.89) and male sex (OR =5.56) were the only independent risk factors for biliary stricture. Percutaneous transhepatic cholangiography drainage (37.2%) or computed-tomography-guided drainage (27.9%) was the most frequent initial treatment. Biliary event-free rate after initial treatment was 67.6% and 66.7% in the non-surgical and surgical group, respectively. CONCLUSION: The risk factors for bile leakage and biliary stricture were different due to different pathogenesis. Straight biliary stent in our series showed a protective effect against bile leakage. Non-surgical management can be a highly successful initial treatment, and surgery should be reserved for patients who have failed conservative treatment.