The arteriovenous fistula and the history of a forgotten pioneer.

Objective: The radiocephalic arteriovenous fistula (AVF), first introduced by Dr Kenneth Charles Appell, allowed for the provision of hemodialysis for patients with chronic kidney disease (CKD) and remains a reliable method for vascular access today. The purpose of this study is to review the contributions that led to the development of the AVF. We describe the work of Dr Appell, whose procedure bypassed the need for repeated cannulation in achieving vascular access, transforming the management of patients with dialysis-dependent CKD. Methods: A literature search was conducted by searching "arteriovenous fistula," "history of surgery," "hemodialysis," "vascular access," "chronic kidney disease," "repeated cannulation," and "Kenneth Charles Appell" on PubMed, Embase, and Web of Science. Only articles written in English were considered. Results: Before the arteriovenous fistula, glass cannulae were used for vascular access, beginning with Abel's "vividiffusion" apparatus in animals and Haas's experimental dialysis on humans. The use of glass cannulae was continued by Kolff, who transitioned from venipuncture needles to glass cannulae. However, these attempts were complicated by thrombosis, excessive bleeding related to heparin use, and damage to vascular access sites from repeated cannulation. Arteriovenous shunts, using polytetrafluoroethylene tubing, were an improvement from previous attempts at vascular access, but were prone to local bleeding, shunt occlusion, phlebitis, cellulitis, and rarely lasted more than a few months. To address these challenges, Dr Appell created an upper extremity AVF, allowing for the provision of maintenance dialysis without externalized devices, repeated cannulation, and extensive anticoagulant administration. Despite Dr Appell's vision and pioneering contributions to vascular surgery, he has received little credit for his work. Conclusions: The enormous contribution by Dr Appell in the development of the AVF that transformed the modern management of patients with CKD is recognized in this review of the history of vascular access surgery for hemodialysis.

Evaluation of aortic tortuosity as a negative predictor of abdominal aortic aneurysm rupture.

OBJECTIVE: The maximal aortic diameter has been used as a key indication for whether to repair abdominal aortic aneurysms (AAAs). Aortic tortuosity has been proposed as another factor to consider. In the present study, we compared the degree of aortic tortuosity in ruptured AAAs with that of unruptured AAAs using computed tomography. METHODS: We performed a retrospective review of a prospectively maintained database of patients who had undergone AAA repair from December 2014 to December 2019. Patients with a ruptured aneurysm (rAAA) were matched with patients with a nonruptured AAA (nrAAA) with the same maximal aneurysm diameter and age. The degree of aortic tortuosity, defined as the maximum lateral deviation from the aortic centerline, was measured on preoperative coronal computed tomography scans. RESULTS: During a 5-year period, 572 AAA cases were identified. The aortic tortuosity of the 25 rAAA cases was compared with that of a matched control group of 31 nrAAAs, selected by the same mean maximum diameter of 8.4 cm and similar patient age. In the rAAA group, the mean age was 74.8 years (84% men). In the nrAAA group, the mean age was 76.3 years (88% men). The mean aortic tortuosity for the rAAA and nrAAA groups was 9.3 ± 7.9 mm and 18.0 ± 11.2 mm, respectively (P < .01). CONCLUSIONS: Greater aortic tortuosity was seen in the nrAAA cases compared with the rAAA cases at the same matched aneurysm size. Thus, aortic tortuosity might confer a reduced rupture risk. Further studies with larger cohorts are needed to verify this observation.

A comparison of outcomes between open and endovascular arteriovenous access creation for hemodialysis.

OBJECTIVE: Preliminary outcomes for percutaneous endovascular autogenous access (endoAVF) have shown promising results; however, comparisons with surgical cohorts in dialysis populations are lacking. This study compares autogenous arteriovenous access created with the EverlinQ endoAVF system with accesses created by conventional surgical technique with respect to functional and patency related outcomes. METHODS: This is a multicenter, retrospective review of autogenous arteriovenous accesses entered into a prospective database. Patients receiving radiocephalic, brachiocephalic, or endoAVF arteriovenous accesses between 2014 and 2019 were included. Autogenous access maturation, primary patency, secondary patency, steal syndrome, and reinterventions were collected and analyzed using standard statistical and survival analyses. RESULTS: A total of 369 accesses were created during the study period, including 61 endovascular accesses, 171 radiocephalic accesses, and 137 brachiocephalic accesses (median follow-up, 17 months; range, 1-71 months). Maturation failure at the end of follow-up was 27% ± 6%, 27% ± 5%, and 18% ± 4% for endovascular, radiocephalic, and brachiocephalic accesses, respectively (P = .049 for brachiocephalic vs endovascular accesses). Primary patencies at 12 and 24 months were 42% ± 5% and 32% ± 7% for endovascular accesses, 43% ± 4% and 24% ± 4% for radiocephalic accesses, and 42% ± 4% and 29% ± 4% for brachiocephalic accesses (P = .906). Secondary patencies at 12 and 24 months were 68% ± 6% and 60% ± 7% for endovascular accesses, 75% ± 3% and 67% ± 4% for radiocephalic accesses, and 91% ± 3% and 81% ± 4% for brachiocephalic accesses (P = .006 for brachiocephalic vs endovascular accesses). There were no statistically significant differences in ischemic steal syndrome (3.3%, 4.1%, and 8.0%; P = .229) or total reinterventions/year (1.0 ± 3.1, 0.9 ± 1.8, and 1.2 ± 1.8; P = .289) for endovascular, radiocephalic, or brachiocephalic arteriovenous accesses, respectively. CONCLUSIONS: EndoAVF compare favorably with respect to maturation and patency compared with surgically created accesses in a real-world cohort. Outcomes and reintervention rates are similar to conventional radiocephalic arteriovenous accesses, but are inferior with respect to patency and maturation to brachiocephalic accesses.

Survey of Canadian vascular surgeons and trainees finds work-related musculoskeletal pain and discomfort is common.

BACKGROUND: Occupational injuries and disability are a source of surgeon morbidity. The purpose of this study was to assess the physical toll of working in operating rooms by Canadian vascular surgeons. OBJECTIVE: To assess workplace musculoskeletal (MSK) complaints and challenges faced by Canadian vascular surgeons and trainees and their implications on surgical practice and occupational longevity. METHODS: An online survey was distributed to resident and surgeon members of the Canadian Society of Vascular Surgery. The survey collected data on demographics, operative volume, and work-related MSK symptoms. RESULTS: The survey was distributed to 188 surgeons and trainees. After three e-mailings, 109 surveys were returned (58% response rate). Of the responders, 87% were male, 51% were 45 years or older, and 56% had been in practice for 10 or more years. Workplace MSK symptoms were reported by 83% of the responders. The most common locations were the low back (78%), neck (74%), and shoulder (30%). Most responders (83%) believed that these symptoms were related to their operative environment. Almost half (48%) sought medical care. As a result of these MSK symptoms, 25% experience chronic pain with 8% reporting time off work as a consequence. Another 11% reported an impact on their operative performance with 14% considering early retirement. A lack of operating room system changes to prevent workplace injury and disability was noted by 85% of the responders although only 3% reported their disability to their department. CONCLUSIONS: Occupational MSK symptoms and disability are common among Canadian vascular surgeons. Further research is needed to create programs to improve surgeon morbidity.

Exploring the Utility of Brain Natriuretic Peptide Measurement in Vascular Surgery.

BACKGROUND: The Canadian Cardiovascular Society 2016 guidelines recommend pre-operative measurement of brain natriuretic peptide (BNP) to risk-stratify patients for a 30-day composite outcome of death, myocardial infarction, or asymptomatic myocardial injury after noncardiac surgery (MINS). Whether this practice affects outcomes is unclear. The aim of this study was to examine the clinical utility of brain natriuretic peptide and myocardial injury after noncardiac surgery. METHODS: Analysis of a prospectively maintained database identified all elective open vascular surgery cases at an academic teaching hospital from January 2015 to December 2018. Pre-operative BNP values were available from June 2018 onward after becoming institutionally mandated. Co-morbidities were also collected to stratify patients using the Revised Cardiac Risk Index. The composite outcome of 30-day mortality, myocardial infarction, or MINS was determined. RESULTS: Prior to BNP becoming an institutionally required test, data was available from 1176 open cases. The 30-day mortality was 1.3% (15/1176) and post-operative myocardial infarction rate was 2.3% (27/1176). BNP measurements were collected in 91 consecutive patients. Ten patients (11%) experienced the composite outcome of mortality, myocardial infarction, or MINS. Elevated BNP was associated with increased odds of the composite outcome (P = 0.04), but not with mortality or myocardial infarction. Revised Cardiac Risk Index score was not predictive of outcomes. The majority of patients who qualified for the composite outcome experienced only an asymptomatic troponin rise (80%). Two patients met the universal definition of myocardial infarction, one of whom died. No other deaths occurred within 30 days. Detection of MINS did not result in any significant changes to patient management. CONCLUSIONS: Elevated BNP correlates with increased MINS. An asymptomatic troponin rise is the most commonly observed event, with unclear clinical implications. BNP may over-estimate surgical risk. Further studies on the long-term outcomes of patients with elevated BNP and MINS are required before widely adopting this strategy in vascular surgery patients.

Deformation mechanics of self-expanding venous stents: Modelling and experiments.

Deformation properties of venous stents based on braided design, chevron design, Z design, and diamond design are compared using in vitro experiments coupled with analytical and finite element modelling. Their suitability for deployment in different clinical contexts is assessed based on their deformation characteristics. Self-expanding stainless steel stents possess superior collapse resistance compared to Nitinol stents. Consequently, they may be more reliable to treat diseases like May-Thurner syndrome in which resistance against a concentrated (pinching) force applied on the stent is needed to prevent collapse. Braided design applies a larger radial pressure particularly for vessels of diameter smaller than 75% of its nominal diameter, making it suitable for a long lesion with high recoil. Z design has the least foreshortening, which aids in accurate deployment. Nitinol stents are more compliant than their stainless steel counterparts, which indicates their suitability in veins. The semi-analytical method presented can aid in rapid assessment of topology governed deformation characteristics of stents and their design optimization.

Managing central venous access during a health care crisis.

OBJECTIVE: During the COVID-19 pandemic, central venous access line teams were implemented at many hospitals throughout the world to provide access for critically ill patients. The objective of this study was to describe the structure, practice patterns, and outcomes of these vascular access teams during the COVID-19 pandemic. METHODS: We conducted a cross-sectional, self-reported study of central venous access line teams in hospitals afflicted with the COVID-19 pandemic. To participate in the study, hospitals were required to meet one of the following criteria: development of a formal plan for a central venous access line team during the pandemic; implementation of a central venous access line team during the pandemic; placement of central venous access by a designated practice group during the pandemic as part of routine clinical practice; or management of an iatrogenic complication related to central venous access in a patient with COVID-19. RESULTS: Participants from 60 hospitals in 13 countries contributed data to the study. Central venous line teams were most commonly composed of vascular surgery and general surgery attending physicians and trainees. Twenty sites had 2657 lines placed by their central venous access line team or designated practice group. During that time, there were 11 (0.4%) iatrogenic complications associated with central venous access procedures performed by the line team or group at those 20 sites. Triple lumen catheters, Cordis (Santa Clara, Calif) catheters, and nontunneled hemodialysis catheters were the most common types of central venous lines placed by the teams. Eight (14%) sites reported experience in placing central venous lines in prone, ventilated patients with COVID-19. A dedicated line cart was used by 35 (59%) of the hospitals. Less than 50% (24 [41%]) of the participating sites reported managing thrombosed central lines in COVID-19 patients. Twenty-three of the sites managed 48 iatrogenic complications in patients with COVID-19 (including complications caused by providers outside of the line team or designated practice group). CONCLUSIONS: Implementation of a dedicated central venous access line team during a pandemic or other health care crisis is a way by which physicians trained in central venous access can contribute their expertise to a stressed health care system. A line team composed of physicians with vascular skill sets provides relief to resource-constrained intensive care unit, ward, and emergency medicine teams with a low rate of iatrogenic complications relative to historical reports. We recommend that a plan for central venous access line team implementation be in place for future health care crises.

Wireless Hyperthermia Stent System for Restenosis Treatment and Testing With Swine Model.

This paper reports the first in vivo testing of a resonant-heating stent toward wireless hyperthermia treatment of in-stent restenosis. The stent, made of gold-coated medical-grade stainless steel, is designed to function as an electrical inductor and forms a radiofrequency (RF) resonant circuit with an integrated capacitor microchip. Upon implantation and deployment with the balloon catheter, the stent device serves as a wireless heater as part of the resonant wireless power transfer system, which allows for the device to produce mild heat only when the stent is resonated with a tuned RF electromagnetic field supplied from the external antenna. The wireless power transmitter includes an independent omnidirectional booster antenna that enhances the power delivery to the implanted stent device. The entire stent device is packaged with 40-µm-thick Parylene C film that is shown to be essential for minimizing electrothermal damping in a conductive liquid like blood. The in vitro tests of the prototype system show a temperature increase of 3.3 °C in the stent device couple in a flow loop of saline pumped at a flow rate relevant to the condition of coronary stenosis. In swine models, the system demonstrates RF heating of the stent devices expanded to different diameters, in live blood stream, achieving temperature rises of up to 2.6 °C in a consistent and repeatable manner. These results bring the technology one step closer toward clinical realization of wireless thermal therapy of in-stent restenosis.

Influence of artery and vein diameters on autogenous arteriovenous access patency.

OBJECTIVE: Previous investigations have suggested that a minimum venous outflow diameter (MVOD) and perianastomotic arterial diameter are associated with successful autogenous arteriovenous maturation and patency. The goal of this study was to determine anatomic and clinical variables that may influence access patency to guide optimal autogenous access configuration selection. METHODS: Accesses created from 2010 to 2016 were analyzed from data entered into a prospective database. Preprocedure duplex ultrasound mapping data of artery and tourniquet-derived vein diameters and demographic and clinical variables were collected. Survival-based cut point analysis was used to determine anatomic parameters most predictive of access failure. Kaplan-Meier and Cox proportional hazards analyses were used to assess patencies and maturation and to identify independent predictors of access failure. RESULTS: A total of 356 first-time autogenous accesses were created (median follow-up, 20 months; range, 0-73 months). Of these, 202 (56.7%) were radiocephalic and 154 (43.3%) were brachiocephalic. Maturation failure at end of follow-up for arteriovenous accesses was 26% ± 3% for radiocephalic accesses and 15% ± 3% for brachiocephalic accesses (P < .001). For radiocephalic accesses, MVOD <3.0 mm and radial artery diameter <2.1 mm independently predicted access maturation failure (MVOD <3.0 mm: hazard ratio [HR], 2.62 [95% confidence interval (CI), 1.27-5.39; P = .009]; radial artery diameter <2.1 mm: HR, 2.20 [95% CI, 1.20-4.05; P = .011]) and secondary patency loss (MVOD <3.0 mm: HR, 2.21 [95% CI, 1.24-3.96; P = .007]; radial artery diameter <2.1 mm: HR, 2.11 [95% CI, 1.26-3.63; P = .004]). A combination of radial artery diameter <2.1 mm and MVOD <3.0 mm most strongly predicted maturation failure (HR, 4.24; 95% CI, 1.71-10.49; P = .002) and loss of secondary patency (HR, 4.03; 95% CI, 1.88-8.64; P < .001). Only diabetes mellitus (HR, 2.24; P = .012) predicted secondary patency loss. For brachiocephalic accesses, MVOD <3.4 mm (HR, 2.12; 95% CI, 1.02-4.46; P = .043) was found to independently predict secondary patency loss in addition to previous ipsilateral (HR, 2.37; P = .038) and bilateral (HR, 4.00; P = .015) tunneled hemodialysis catheters. Brachial artery diameter was not associated with either access maturation or patency. CONCLUSIONS: Artery and tourniquet-derived vein diameters independently predict radiocephalic access patency and functional outcomes. A combination of a radial artery diameter <2.1 mm and MVOD <3.0 mm best predicts maturation failure and patency loss for radiocephalic access. MVOD <3.4 mm was associated with increased loss of brachiocephalic access secondary patency, but MVOD was not associated with maturation.

Wirelessly Heating Stents via Radiofrequency Resonance toward Enabling Endovascular Hyperthermia.

Thermal therapy known as hyperthermia has served as an effective method for cancer treatment. This therapeutic approach has also been attracting attention for treatment of in-stent restenosis, the most common complication of stenting. Mild heating of stents has been shown to be a possible path to addressing this problem. Despite various studies on stent-based thermotherapy, this area still lacks a clinically viable method and technology. Here, a radiofrequency-powered "hot" stent prototype is reported in vitro and in vivo. An implantable stent device based on medical-grade stainless steel acts as an electrical resonator, or an efficient wireless heater operating only when resonated using tuned external electromagnetic fields. The system architecture uses a custom-developed power transmitter for wireless resonant powering/heating of the stent. An eight-shaped antenna is shown to be highly effective for near-field power transfer to the device and potentially to other smart implants, revealing stent heating efficiencies of up to 120 °C W-1 , 206% of the level provided by a conventional loop antenna. Testing with swine models, the prototyped system achieves stent heating in blood flow by powering through air and skin tissue in vivo in a fully controlled manner. The results advance stent hyperthermia technology toward possible future clinical application.

Enabling Angioplasty-Ready "Smart" Stents to Detect In-Stent Restenosis and Occlusion.

Despite the multitude of stents implanted annually worldwide, the most common complication called in-stent restenosis still poses a significant risk to patients. Here, a "smart" stent equipped with microscale sensors and wireless interface is developed to enable continuous monitoring of restenosis through the implanted stent. This electrically active stent functions as a radiofrequency wireless pressure transducer to track local hemodynamic changes upon a renarrowing condition. The smart stent is devised and constructed to fulfill both engineering and clinical requirements while proving its compatibility with the standard angioplasty procedure. Prototypes pass testing through assembly on balloon catheters withstanding crimping forces of >100 N and balloon expansion pressure up to 16 atm, and show wireless sensing with a resolution of 12.4 mmHg. In a swine model, this device demonstrates wireless detection of blood clot formation, as well as real-time tracking of local blood pressure change over a range of 108 mmHg that well covers the range involved in human. The demonstrated results are expected to greatly advance smart stent technology toward its clinical practice.

An age-based comparison of fistula location, patency, and maturation for elderly renal failure patients.

OBJECTIVE: Current Kidney Disease Outcomes Quality Initiative guidelines do not incorporate age in determining autogenous arteriovenous hemodialysis access placement, and the optimal initial configuration in elderly patients remains controversial. We compared patency, maturation, survival, and complications between several age cohorts (<65 years, 65-79 years, >80 years) to determine whether protocols should be modified to account for advanced age. METHODS: All patients at two teaching hospitals undergoing a first autogenous arteriovenous access creation in either arm between 2007 and 2013 were retrospectively analyzed from a prospectively maintained database. Kaplan-Meier survival and Cox hazards models were used to compare access patency and risk factors for failure. RESULTS: There were 941 autogenous arteriovenous accesses (median follow-up, 23 months; range, 0-89 months) eligible for inclusion; 152 (15.3%) accesses were created in those >80 years, 397 (42.2%) in those 65 to 79 years, and 392 (41.8%) in those <65 years. Primary patencies in patients >80 years, 65 to 79 years, and <65 years were 40% ± 4%, 38% ± 3%, and 51% ± 3% at 12 months and 12% ± 5%, 13% ± 3%, and 27% ± 3% at 36 months (P < .001). Primary assisted patencies were 72% ± 4%, 70% ± 2%, and 78% ± 2% at 12 months and 52% ± 5%, 52% ± 3%, and 67% ± 3% at 36 months (P < .001). Secondary patencies were 72% ± 4%, 71% ± 2%, and 79% ± 2% at 12 months and 54% ± 5%, 55% ± 3%, and 72% ± 3% at 36 months (P < .001). Radiocephalic patencies were lowest among older cohorts; in those >80 years, 65 to 79 years, and <65 years, they were 65% ± 7%, 67% ± 4%, and 77% ± 3% at 12 months and 41% ± 8%, 51% ± 5%, and 68% ± 4% at 36 months (P = .019). Secondary brachiocephalic access patencies in these cohorts were 78% ± 5%, 80% ± 3%, and 82% ± 3% at 12 months and 68% ± 7%, 66% ± 5%, and 77% ± 4% at 36 months (P = .206). Both the age groups 65 to 79 years and >80 years demonstrated superior brachiocephalic vs radiocephalic secondary patencies (P = .048 and P = .015, respectively); however, no differences between configuration and secondary patency were observed within the cohort <65 years. Radiocephalic access maturation failure at 12 and 24 months was 25% ± 3% and 29% ± 4% in those <65 years, 32% ± 3% and 39% ± 4% in those 65 to 79 years, and 40% ± 7% and 48% ± 8% in those >80 years (P = .006). Brachiocephalic access maturation failures were 17% ± 3% and 20% ± 3% at 12 and 24 months in those <65 years, 21% ± 3% and 25% ± 4% in those 65 to 79 years, and 18% ± 5% and 21% ± 5% in those >80 years (P = .740). On multivariate analysis, coronary disease, female sex, previous ipsilateral or bilateral catheters, radiocephalic configuration, and age >65 years were associated with secondary patency loss. CONCLUSIONS: Patients aged 65 to 79 years and >80 years had inferior primary, primary assisted, and secondary patency and maturation compared with those <65 years. When stratified by configuration, radiocephalic accesses demonstrated lower patency and maturation compared with brachiocephalic accesses for patients aged 65 to 79 years and >80 years and were an independent predictor of secondary patency loss.

Reassessing the normal toe-brachial index in young healthy adults.

OBJECTIVE: The purpose of this study was to measure the toe-brachial index (TBI) in healthy young adults and to compare it with the accepted reference range. METHODS: Medical students from the undergraduate classes at the University of British Columbia were prospectively recruited. Participants were surveyed on physical parameters (height, weight), lifestyle factors (physical activity and type, smoking status, alcohol consumption), and medical history (current medications, medical conditions, family history). Bilateral brachial, ankle (using both dorsalis pedis and posterior tibial arteries), and toe blood pressures were measured by stethoscope, Doppler device, and photoplethysmograph, respectively. Ankle-brachial index (ABI) and TBI were calculated and assessed against published reference ranges. TBI was calculated as the mean great toe blood pressure divided by the average of the higher arm systolic blood pressures. RESULTS: Seventy-three medical students with a mean age of 24.3 ± 2.0 years without any comorbidity were studied. Participants maintained relatively healthy lifestyles (hours of activity per week, 4.6 ± 2.7; body mass index, 21.9 ± 2.4). Caffeine and alcohol consumption was modest (8.2 ± 8.0 and 1.7 ± 2.6 servings/week, respectively). There were no current or past smokers. No significant differences in lifestyle factors were observed between men and women. Mean brachial blood pressure was 116 ± 10 mm Hg (left) and 120 ± 11 mm Hg (right). Mean TBI was 0.98 ± 0.12 (left) and 0.97 ± 0.12 (right) for men and 0.95 ± 0.21 (left) and 0.94 ± 0.21 (right) for women. The overall ABI was 1.10 ± 0.07 when averaged by gender and side. Whereas men had significantly higher blood pressures in the arm, toe, and ankle compared with women, these differences disappeared when the indices were determined. There were no significant differences in TBI or ABI between men and women. CONCLUSIONS: In comparison to published reference values, the TBI in young, healthy individuals is significantly higher. Whereas no gender difference existed, greater variability of the TBI was observed in women. Further studies are recommended to determine if the threshold for diagnosis of peripheral arterial disease based on TBI should be raised.

A comparison of revision using distal inflow and distal revascularization-interval ligation for the management of severe access-related hand ischemia.

OBJECTIVE: Access-related hand ischemia (ARHI) is a potentially limb-threatening complication of arteriovenous access for dialysis. The distal revascularization-interval ligation (DRIL) and revision using distal inflow (RUDI) procedures both allow treatment of ischemic symptoms while maintaining fistula patency. Although outcomes with the DRIL are well established, experience with the RUDI for ARHI remains preliminary. We compared outcomes in these procedures with respect to cumulative patency, resolution of symptoms, and patient survival. METHODS: A large, prospectively maintained database was used to identify all patients after autogenous arteriovenous fistula construction at two hospitals between 2005 and 2015. Patients with severe Society for Vascular Surgery grade 3 ARHI were included for analysis. RESULTS: A total of 2035 autogenous accesses were created during the study period, and 58 (3%) developed grade 3 ARHI. Of this cohort, RUDI was performed in 20 and DRIL in 21. The indication for intervention was tissue loss (61%) or ischemic rest pain (39%). Mean age was 57.5 years, and 54% of patients were female. Most patients had diabetes (86%) and symptomatic peripheral arterial disease (63%). The mean preoperative digital-brachial index was 0.25 ± 0.12. There were no preoperative differences in patient comorbidities between the RUDI and DRIL cohorts. Primary patency between the RUDI and DRIL cohorts at 12 months (58% ± 11% vs 55% ± 12%) and 36 months (51% ± 12% vs 41% ± 12%) were similar (P = .841). Cumulative secondary patency at 12 months (84% ± 8% vs 94% ± 6%) and 36 months (78% ± 9% vs 86% ± 9%) showed no significant difference (P = .398). Resolution of ischemic symptoms, including resolution or improvement in pain or healing of ischemic ulcers or amputations, occurred in 90% with RUDI and in 81% with DRIL (P = .131). Survival for patients who underwent RUDI or DRIL procedures at 1 and 3 years was 85% vs 86% (P = .948) and 55% vs 49% (P = .278). CONCLUSIONS: In this preliminary study, the RUDI demonstrated similar patency, symptom resolution, and survival compared with the DRIL for patients with severe ARHI. All-cause mortality after any procedure for severe steal syndrome is high, and the particular intervention for management of steal must account for anatomic-, patient-, and disease-related considerations.

Intelligent telemetric stent for wireless monitoring of intravascular pressure and its in vivo testing.

This paper reports a sensor-integrated telemetric stent targeted at wireless detection and monitoring of restenosis, a common vascular complication induced by stent implantation. The developed "smart" stent incorporates the design and fabrication approaches that raise the practicality of the device, being tested in an in vivo study that validates its operating principle. The stent is produced to have a gold-coated helical-like structure that serves as a high-performance inductor/antenna and integrated with a novel capacitive pressure sensor chip, all based on medical-grade stainless steel. The stent device forms an inductor-capacitor resonant tank that enables radio-frequency (RF) wireless pressure sensing in an operating frequency range of 30-80 MHz. With an overall length of 20 mm, the device is designed to be compatible with standard balloon catheters and necessary crimping process. The balloon-expanded devices are characterized in saline and blood to determine selective coating of passivation layer, Parylene C, with tailored thicknesses in order to maximize both RF and sensing abilities. In vitro testing of the devices reveals a frequency sensitivity up to 146 ppm/mmHg over a pressure range of 250 mmHg. Tests in pig models show wireless detection of device's resonance and frequency response to variations in local blood pressure, the targeted function of the device.