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Aalpen A Patel

Publications and source records attributed to Aalpen A Patel.

13 recordsLinked to original sources
PubMed2006

Salvage of nonmaturing native fistulas by using angioplasty.

PURPOSE: To retrospectively review outcomes following angioplasty of nonmaturing autogenous hemodialysis fistulas. MATERIALS AND METHODS: Institutional review board exemption was received for this HIPAA-compliant retrospective study; informed consent was waived. During 48 months, 101 patients underwent fistulography for percutaneous salvage of nonmaturing native fistulas. Clinical and technical success, need for secondary interventions, and complications were recorded according to consensus definitions. Patency following angioplasty was estimated with the Kaplan-Meier technique. Patient age, sex, ethnicity, fistula age, fistula type, number of stenoses, maximal angioplastic balloon diameter used, and presence of palpable thrill following angioplasty were examined as predictors of primary patency of the fistula following intervention by using Cox proportional hazards model. RESULTS: Mean patient age was 58 years; 35% were women. Median time from fistula creation to fistulography was 2.5 months. Hemodynamically significant (>50%) stenoses were identified in 88% (89 of 101) of patients; angioplasty was attempted in 96% (85 of 89). Technical success was achieved in 92% (78 of 85) of fistulas following angioplasty; clinical success of normal hemodialysis with total access blood flow of more than 500 mL/min occurred following 88% (75 of 85) of angioplastic interventions. No major and two minor complications occurred. Mean primary unassisted patency at 3, 6, and 12 months was 60%+/-6% (95% confidence interval), 45%+/-6%, and 34%+/-6%, respectively. Additional angioplasty (n=12), stent placement (n=1), or thrombectomy (n=1) during subsequent interventions resulted in mean secondary patency at 3, 6, and 12 months of 82%+/-4%, 79%+/-5%, and 75%+/-6%, respectively. Patients without thrill following angioplasty were more than twice as likely to lose patency as patients with thrill (P=.035). No relationship was seen between primary patency and other predictors examined. CONCLUSION: Early fistulography enables identification of underlying areas of stenosis in nonmaturing fistulas, which can be safely and effectively treated with angioplasty. With continued surveillance and repeat interventions, functional patency can be sustained in the majority of fistulas.

Angioplasty↗
PubMed2006

Asymptomatic central venous stenosis in hemodialysis patients.

PURPOSE: To retrospectively evaluate the natural history of high-grade (>50%) asymptomatic central venous stenosis (CVS) in hemodialysis patients and the outcome of serial treatment of CVS with percutaneous transluminal angioplasty (PTA). MATERIALS AND METHODS: The institutional review board granted exemption for this retrospective study, the need for informed consent was waived, and all data collection was in compliance with HIPAA. Patients with hemodialysis access requiring maintenance procedures between 1998 and 2004 and incidentally found to have ipsilateral (> or =50%) CVS were identified from a departmental database. Thirty-five patients (19 men, 16 women; mean age, 58.7 years) with 38 grafts met inclusion criteria, and 86 venograms were reviewed. CVS was measured by using venograms obtained before and after PTA, if performed. Patients with arm swelling, multiple CVS, indwelling catheters, and stents at the first encounter were excluded. CVS progression was calculated by dividing the change in the degree of stenosis by the time between venographic examinations. Wilcoxon rank sum test was used to evaluate differences in rate of CVS progression between treated and nontreated patients. RESULTS: Mean degree of CVS before intervention was 71% (range, 50%-100%). Sixty-two percent (53 of 86) of lesions had associated collateral vessels; 28% (24 of 86) of CVSs were not treated. Mean degree of stenosis in this group was 72% (range, 30%-100%); mean progression was -0.08 percentage point per day. No untreated CVS progressed to symptoms, stent placement, or additional CVS. Seventy-two percent (62 of 86) of CVSs were treated with PTA. Mean degree of stenosis in this group was 74% (range, 50%-100%) before and 40% (range, 0%-75%) after treatment; mean progression was 0.21 percentage point per day after treatment (P = .03). Six (8%) of 62 treatments were followed by CVS escalation; one patient developed arm swelling, four required stents, and four developed additional CVS. CONCLUSION: PTA of asymptomatic CVS greater than 50% in the setting of hemodialysis access maintenance procedures was associated with more rapid stenosis progression and escalation of lesions, compared with a nontreatment approach.

Angioplasty, Balloon↗
PubMed2006

Role of ultrasound surveillance of transjugular intrahepatic portosystemic shunts in the covered stent era.

PURPOSE: To assess ultrasound (US) surveillance of expanded polytetrafluoroethylene (ePTFE)-covered stents in transjugular intrahepatic portosystemic shunts (TIPS). MATERIALS AND METHODS: Procedural data, including stent size and portosystemic gradients (PSG) before and after creation of TIPS, were obtained retrospectively in 55 patients (33 men, 22 women). Chart review provided clinical information, including etiology of liver disease, indication for TIPS creation, and Child-Pugh class. Radiology reports provided US venography data and pathology reports confirmed shunt status in transplant recipients. Patients had baseline US examinations 3-7 days after TIPS creation with scheduled follow-up at 1, 3, 6, and 12 months after the procedure. Clinical and radiology reports were compared to evaluate US surveillance of Viatorr stents. RESULTS: One hundred fifty-nine US examinations were performed on 52 patients, for an average 3.1 studies per patient (range, 1-7) over a mean follow-up duration of 173 days (range, 0-1,013 d). Sixty-four US studies (40%) were baseline studies, 88 studies (55%) were routine follow-up studies, and seven (4%) were interval studies. US predicted TIPS abnormalities in 30 of 159 studies (19%); venography followed 15 of 30 abnormal US findings (50%) and clinical examinations complemented 10 of 15 venograms (67%). Venography and US were concordant in eight of 15 paired studies (53%); clinical examinations, when conducted, accurately predicted shunt status in all but one case. US findings changed management in six of 159 studies (4%): five of six (83%) were baseline evaluations and the other one (17%) was a routine follow-up examination. A total of five baseline US examinations (8%) and one surveillance examination (1%) altered patient management. CONCLUSIONS: A single US examination after a TIPS procedure to confirm immediate function may be valuable, but routine US is not effective for long-term surveillance of ePTFE-covered stents.

Adult↗
PubMed2006

Numerical analysis of the hemodynamics and embolus capture of a greenfield vena cava filter.

BACKGROUND: Vena Cava filters are used to prevent pulmonary embolism in patients with deep vein thrombosis who are unresponsive to anticoagulation therapy. Various filter designs exist in the market with different characteristics distinguishing them. An understanding of the characteristics of these filters is desirable in order to develop better designs. METHODS: A computational fluid dynamical study of the flow over an unoccluded stainless steel Greenfield Vena Cava filter (Boston Scientific, Watertown, MA) to determine its properties has been performed. Simulation of flow over a filter placed axisymmetrically in a rounded inferior vena cava has been performed at a Reynolds numbers of 1000 and the consequences of the flow (by studying parameters like shear stress and stagnation zones) have been discussed. Furthermore, a new finite element based numerical method has been developed that allows the study of capturing properties of Inferior Vena Cava filters. The key idea is the introduction of a thin-wire-model (TWM) that enables a drastic reduction in the computational cost while still maintaining control on the physics of the problem. This numerical technique has been applied to evaluate the embolus capture characteristic of a Greenfield filter. RESULTS: The flow around the unoccluded filter is found to be steady and laminar at the conditions studied. A recirculation/stagnation zone develops immediately downstream of the filter head. This zone is significantly larger when the central hole is occluded. The shear stress and stagnation zone properties for such a flow over a Greenfield filter are compared with existing literature (in vitro studies). A graph showing the regions wherein clots escape or get captured has been determined by a means of numerical simulations. The data has further been analyzed to determine the probability of clot capture as function of the clot size. CONCLUSIONS: The stagnation zone formed behind the head of the Greenfield filter is found to be smaller in size when compared to that of the same filter with the central hole occluded. A map of the shear stress distribution shows a small region having the potential for thrombogenesis. The non-Newtonian properties of blood are not seen to cause much variation in the flow field when compared to the Newtonian model. However variation in the cava size leads to a significant change in the shear stresses. This study also establishes a novel method wherein computational means are used to determine the efficacy of clot capturing of filters. These techniques can further be used to compare the different characteristics among filters.

Blood Flow Velocity↗
PubMed2005

Single-center experience with the Arrow-Trerotola Percutaneous Thrombectomy Device in the management of thrombosed native dialysis fistulas.

PURPOSE: The present study sought to evaluate the performance of the Arrow-Trerotola Percutaneous Thrombolytic Device (PTD) in the treatment of native fistula thrombosis in a U. S. hemodialysis population. Specifically, the technical success, clinical success, complication rate and type, primary and secondary patency rates, effect of adjunctive thrombolytic therapy, and any variables that affected outcomes of procedures in which this device was used were analyzed. MATERIALS AND METHODS: Forty-two patients with 44 thrombosed native fistulas (17 radiocephalic, 10 brachiocephalic, 10 transposed or superficialized, five graft/fistula hybrids, and two leg fistulas) were treated with 62 mechanical thrombolysis procedures with use of the PTD. All patients had large clot burden. The device type was recorded in 43 procedures: standard (n = 21), over-the-wire (OTW; n = 19), or both (n = 3). No device was used in two cases because of inability to cross the anastomosis. Adjunctive therapies (n = 18) included the use of tissue plasminogen activator (tPA; n = 16) and deployment of the AngioJet device with (n = 1) or without tPA (n = 1). Stents were inserted in four procedures. Outcome variables included technical and clinical success, complications, and primary and secondary patency. Cox proportional-hazards regression and Kaplan-Meier analyses were performed. RESULTS: The technical success rate was 87% (54 of 62) and the clinical success rate was 79% (49 of 62). Percutaneous transluminal angioplasty was performed in all but two procedures. Complications occurred in 13% of procedures (n = 8); three resulted in technical failure. The primary patency rates were 38% at 6 months and 18% at 12 months; secondary patency rates were 74% and 69%, respectively. Outcomes were not affected by adjunctive techniques, fistula type, age of fistula, device type (ie, OTW vs standard), or patient sex. Secondary patency was superior when no residual clot or stenosis was present (P = .003). CONCLUSIONS: The PTD is effective for percutaneous treatment of thrombosed hemodialysis fistulas, with good short- and long-term outcomes in a U.S. population. Within the limitations of a retrospective study with a small sample size, use of an adjunctive thrombolytic agent did not appear to improve results compared with the use of the device alone.

Adult↗
PubMed2005

Prospective study of balloon inflation pressures and other technical aspects of hemodialysis access angioplasty.

PURPOSE: Balloon angioplasty is a mainstay in the treatment of failing or thrombosed hemodialysis access grafts and fistulas. A sizable body of outcomes data exists concerning percutaneous transluminal angioplasty (PTA) in hemodialysis access, yet there is a relative paucity of technical information available, especially regarding dilation pressures. The aim of the present study was to compile such information, which can be critical to the choice of devices for PTA and to the design of future clinical trials seeking to improve outcomes in this area. MATERIALS AND METHODS: Technical data were collected prospectively for 102 PTA procedures (66 prophylactic PTA procedures and 36 PTA procedures performed during access thrombectomy). Demographic data concerning the access were collected. Technical data were collected individually for each lesion treated, including lesion location; degree of stenosis (in quartiles); lesion length; PTA balloon brand, size, and length; pressure at which the waist of the balloon was effaced; residual stenosis; and reason for additional balloons or inflations if used. Outcomes data other than residual stenosis were not collected, but the endpoint for all interventions was a thrill in the access. RESULTS: A total of 230 lesions were treated. Two (1%) could not be successfully treated with PTA despite the use of "ultra high" pressure (approximately 40 atm); one was treated successfully with parallel wire technique and the other was revised surgically after the use of a cutting balloon also failed. Overall, 55% of lesions required pressures greater than 15 atm to efface the waist. Excluding initial failures, 20% of lesions in native fistulas and 9% in grafts required very high pressure (>20 atm) to efface the waist (P = .02). High pressure was needed less frequently in PTA procedures performed in the setting of thrombectomy procedures than in prophylactic PTA procedures (P = .0001). Residual stenosis was positively correlated with severity of initial stenosis and negatively correlated with duration of inflation. CONCLUSIONS: Conventional angioplasty balloons are inadequate for the treatment of most hemodialysis access stenoses. High pressures (>15 atm) are commonly needed for PTA in hemodialysis access. Very high pressures (>20 atm) are more frequently needed in native fistulas.

Angioplasty, Balloon↗
PubMed2004

Do simultaneous bilateral tunneled infusion catheters in patients undergoing bone marrow transplantation increase catheter-related complications?

PURPOSE: Secure venous access with multiple lumens is necessary for the care of allogeneic hematopoietic stem cell transplant (HSCT) recipients. The outcomes associated with simultaneous bilateral tunneled internal jugular infusion catheter placement in the HSCT recipient population were investigated in an attempt to determine whether simultaneous introduction of these catheters compounds or magnifies the risks (infection, venous thrombosis) associated with tunneled catheters. MATERIALS AND METHODS: Patients undergoing HSCT and receiving bilateral tunneled infusion catheters in a single procedure were identified using a quality assurance data base. Medical records for the duration of catheterization were reviewed; 43 patients were included in the study (mean age, 42 years; range, 22-56). Diagnoses included acute lymphocytic leukemia (n = 4), acute myelogenous leukemia (n = 8), aplastic anemia (n = 2), chronic myelogenous leukemia (n = 17), chronic lymphocytic leukemia (n = 1), Hodgkin lymphoma (n = 1), myelodysplasia (n = 4), myelofibrosis (n = 2), and non-Hodgkin lymphoma (n = 4). Cox proportional hazards regression analysis was performed to determine differences in infection rates between dual- and triple-lumen catheters. RESULTS: Forty-three pairs of catheters were placed. All met venous access needs for HSCT recipient care. Complete follow-up was achieved for 77 of 87 (89%) catheters. The overall infection rate was 0.25 per 100 catheter-days. The rate was 0.19 and 0.33 for dual- and triple-lumen catheters, respectively (P =.15). Mechanical failure did not differ between catheter types (dual: 0.14 episodes per 100 days, triple: 0.05 per 100 days, P =.2). CONCLUSIONS: Bilateral multilumen tunneled infusion catheter placement in a single procedure using imaging guidance is safe with acceptable outcomes and meets venous access needs for HSCT. There is a trend toward higher infection rates, with more lumens and more mechanical failure with dual-lumen catheters.

Adult↗
PubMed2004

Relationship between chest port catheter tip position and port malfunction after interventional radiologic placement.

PURPOSE: The relationship between catheter tip position of implanted subcutaneous chest ports and subsequent port malfunction was investigated. Tip movement from initial supine position to subsequent erect position was also evaluated. MATERIALS AND METHODS: Patients who underwent imaging-guided internal jugular chest port placement between July 2001 and May 2003 were identified with use of a quality-assurance database. Sixty-two patients were included in the study (22 men and 40 women), with a mean age of 58 years (range, 27-81 years). Catheter tip location on the intraprocedural chest radiograph was determined with use of two methods. First, the distance from the right tracheobronchial angle (TBA) was recorded (TBA distance). Second, tip location was classified into six anatomic regions: 1, internal jugular veins; 2, brachiocephalic veins; 3, superior vena cava (SVC; n = 11); 4, SVC/right atrial junction (n = 22); 5, upper half of right atrium (n = 25); and 6, lower half of right atrium (n = 4). For the duration of follow-up, catheter tip location was documented, as were all episodes of catheter malfunction. RESULTS: Patients with catheter tips initially placed in position 3 had a higher risk of port malfunction (four of 11; 36%) than patients with catheter tips located in position 5 (two of 25; 8%). This difference narrowly fell short of statistical significance (P =.057). When comparing intraprocedural chest radiographs to the first erect chest radiographs, significant upward tip movement was noted. The tips migrated cephalad an average of 20 mm (P =.003) and 1.0 position units (P =.001). DISCUSSION: Catheter tips placed in the SVC tended to have a greater risk of port malfunction compared with those positioned in the right atrium. Chest ports migrated cephalad between the supine and erect positions.

Adult↗
PubMed2003

Physical examination versus normalized pressure ratio for predicting outcomes of hemodialysis access interventions.

PURPOSE: The ratio of intragraft venous limb pressure (VLP) to systemic pressure (S) has been proposed to help determine the endpoint of hemodialysis access interventions. It was hypothesized that physical examination of the access could be used in the same way and these techniques were compared as predictors of outcome. PATIENTS AND METHODS: With use of a quality-assurance database, records from 117 hemodialysis access interventions were retrospectively reviewed. Only interventions in grafts were included. The database included physical examination (to establish thrill, thrill with slight pulsatility [TSP], pulse with slight thrill [PST], and pulse) at three locations along the graft (proximal, midportion, and distal), normalized pressure ratio calculated with S from a blood pressure cuff (S(cuff)) and S within the graft with outflow occluded (S(direct)), graft configuration and location, indication, operator, and time to next intervention (outcome of primary patency). Only procedures with complete follow-up data were included in the analysis (n = 97; declotting, n = 51; prophylactic percutaneous transluminal angioplasty [PTA], n = 46). Statistical analysis was performed with use of Cox proportional-hazards regression. RESULTS: Graft configuration, location, side, VLP, S(direct), and S(cuff) did not affect outcomes. An operator effect was noted for two physicians and was adjusted for in all analyses. Pressure ratios were weak predictors of outcome (VLP/S(direct), P =.07; VLP/S(cuff), P =.08) and suggested that patency increased with increasing pressure ratio, contrary to earlier studies. Procedure type predicted outcome (declotting, median patency of 50 days; PTA, median patency of 105 days; P =.01). Thrill at distal physical examination was predictive of outcome (P =.04) and even more so when thrill and TSP combined were compared with PST and pulse combined (P =.03). Similar but less-pronounced effects were seen at midportion and proximal physical examinations. CONCLUSIONS: The presence of a thrill or slightly pulsatile thrill at the distal (venous) end of a dialysis graft is the best predictor of outcome after percutaneous intervention. Based on the present study, the authors believe that physical examination of dialysis access should supplant pressure measurements as an endpoint of intervention and should serve as an essential component of quality assurance of access interventions.

Arteriovenous Shunt, Surgical↗
PubMedDate not supplied

Mechanical thrombectomy of hemodialysis fistulae and grafts.

In this article, the authors present approaches they use in performing dialysis access intervention-in particular clotted access. It is not meant to be a comprehensive review of dialysis access management. At our institution, mechanical thrombectomy is the primary mode of treatment for clotted hemodialysis access. We will present physical examination findings in clotted dialysis access and contraindications for mechanical thrombectomy in dialysis access. We will also discuss the devices for mechanical thrombectomy and the techniques we use. Finally, we will discuss the difficulties encountered in these procedures and their solutions.

Arteriovenous Shunt, Surgical↗