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Timothy W I Clark

Publications and source records attributed to Timothy W I Clark.

50 records · Page 3Linked to original sources
PubMed2002

Outcome and prognostic factors of restenosis after percutaneous treatment of native hemodialysis fistulas.

PURPOSE: To assess patency after percutaneous treatment of dysfunctional and thrombosed native arteriovenous fistulas and to examine predictors of patency after intervention. MATERIALS AND METHODS: A cohort of 65 consecutive patients with dysfunctional (n = 53) or occluded (n = 12) native fistulas who underwent 96 percutaneous interventions over an 18-month period was retrospectively analyzed. Fistula locations were radiocephalic (n = 37), brachiocephalic (n = 10), or brachiobasilic (n = 18). Primary interventions consisted of angioplasty (n = 50), stent placement (n = 3), or percutaneous thrombolysis/thrombectomy (n = 12). Additional interventions during follow-up consisted of angioplasty (n = 22), stent placement (n = 6), or percutaneous thrombolysis/thrombectomy (n = 3). Duration of fistula function was assessed clinically and examined as a function of anatomic and clinical variables with use of Cox hazards models and the Kaplan-Meier method. RESULTS: Clinical success with resumption of at least one session of normal dialysis occurred in 94% (90 of 96) of interventions. The 30-day morbidity rate was 2.1%; no procedure-related deaths occurred. Primary, assisted primary, and secondary patency rates (+/- SE) of dysfunctional fistulas after intervention at 12 months were 26% +/- 11%, 80% +/- 6%, and 82% +/- 6%. Occluded fistulas after intervention had 3-month primary, assisted primary, and secondary patency rates of 60% +/- 15%, 60% +/- 15%, and 80% +/- 13%. Lesions 2.0 cm or more in length were five times more likely to have loss of patency than lesions smaller than 2.0 cm. The presence of at least one comorbid factor--diabetes, coronary artery disease, or peripheral vascular disease--was associated with nearly twice the risk of patency loss after any intervention. CONCLUSION: Despite modest primary patency rates in our experience, high assisted and secondary patency rates can be achieved with percutaneous intervention in native arteriovenous fistulas. These findings emphasize the need for close surveillance of native fistulas and a low threshold for diagnostic fistulography after initial intervention. The most detrimental determinant of outcome was lesion length > or =2 cm.

Aged↗
PubMed2002

Chemical ablation of hepatocellular carcinoma.

Chemical ablation with absolute ethanol is the most established technique of imaging-guided regional therapy for small hepatocellular carcinomas (HCCs), with long-term survival rates that rival those of surgical resection. In this article, the authors review patient selection criteria, techniques (including the one-shot approach of ethanol ablation for HCCs larger than 3 cm), complications, follow-up, and outcomes. The use of agents other than ethanol and the combination of chemical ablation with chemoembolization is also discussed.

Antineoplastic Agents↗
PubMed2002

Chemical-shift MR imaging of acetic acid during percutaneous chemical ablation therapy: preliminary work.

The purpose of this study was to test the hypothesis that chemical-shift magnetic resonance (MR) imaging may be used to map the distribution of acetic acid during percutaneous chemical ablation procedures. Chemical-shift MR imaging was performed with use of standard methods on a 1.5-T scanner. Phantom and ex-vivo data demonstrated focal increases in the observed signal in chemical-shift MR imaging that correlate well with the site of injection. Preliminary study in a patient with hepatoma revealed focal signal at the injection site. These preliminary results suggest that chemical-shift MR imaging may be used to visualize acetic acid distribution during percutaneous chemical ablation procedures.

Acetic Acid↗
PubMed2002

Serum bilirubin and early mortality after transjugular intrahepatic portosystemic shunts: results of a multivariate analysis.

PURPOSE: To examine the prognostic utility of the serum bilirubin level before transjugular intrahepatic portosystemic shunt (TIPS) creation as an independent predictor of 30-day mortality in patients who underwent TIPS creation for treatment of variceal hemorrhage. MATERIALS AND METHODS: Multiple covariates from a cohort of 220 consecutive patients undergoing TIPS creation were analyzed with use of univariate and multivariate logistic regression. These included pre-TIPS total bilirubin levels, modified Child-Pugh class, APACHE II score, intubation status, etiology of liver disease, and acute versus elective shunting. RESULTS: The mean pre-TIPS serum total bilirubin level was 3.2 mg/dL (range, 0.4-40.3 mg/dL). The bilirubin level was <3 mg/dL in 102 patients, > or = 3.0 mg/dL in 58, > or = 4.0 mg/dL in 34, and > or = 5.0 mg/dL in 27. Each 1.0-mg/dL increase in total bilirubin was associated with 40% greater odds of 30-day mortality (odds ratio = 1.4; 95% CI = 1.2-1.7). Using each threshold as its own referent, bilirubin levels at or greater than 3.0, 4.0, and 5.0 mg/dL stratified patients into increased odds of early death by 5.7, 9.7, and 19.2 times, respectively (all P <.001). A pre-TIPS APACHE II score of >18 increased the odds of early death by a factor of 5.6 (95% CI = 2.4-8.7); modified Child-Pugh class C (vs classes A and B combined) alone increased the odds by a factor of 8.1 (95% CI = 3.6-18.1). Only one of 20 patients (5%) with a pre-TIPS bilirubin level >6.0 mg/dL survived more than 30 days after TIPS creation. In acutely bleeding patients (n = 122) undergoing TIPS creation, bilirubin levels > or = 3.0, > or = 4.0, and > or = 5.0 mg/dL stratified patients into odds ratios of 4.4, 7.1, and 9.8, respectively, compared with 7.1, 13.2, and 9.2 for patients undergoing elective TIPS creation. Combining endotracheal intubation (n = 72) and bilirubin strata yielded mortality odds of 8.3, 12.5, and 20.8 compared with odds of 2.3, 4.6, and 11.2 in nonintubated patients. Combining alcoholic cirrhosis (n = 129) with bilirubin levels yielded mortality odds of 8.0, 10.6, and 18.0 compared with other etiologies of liver disease (odds ratios = 2.9, 7.3, and 22.7). CONCLUSION: An elevated pre-TIPS bilirubin level is a powerful independent predictor of 30-day mortality after TIPS creation with a 40% increased risk of death for each 1-mg/dL increase above 3.0 mg/dL. The predictive value of this criterion is increased in patients who undergo TIPS procedures electively. The magnitude of the effect on mortality is similar to that of APACHE II scores and modified Child-Pugh class but is simpler to ascertain.

APACHE↗
PubMed2002

Procedural success and patency after percutaneous treatment of thrombosed autogenous arteriovenous dialysis fistulas.

PURPOSE: To retrospectively evaluate success and midterm patency after percutaneous thrombectomy, lytic therapy, and angioplasty for thrombosed autogenous arteriovenous dialysis fistulas. MATERIALS AND METHODS: From March 1996 to September 2001, 24 patients with 25 fistulas presented with 30 episodes of thrombosis of their autogenous fistulas, including 19 forearm radiocephalic fistulas in 18 patients and six upper arm brachiocephalic fistulas in six patients. Patients presented for percutaneous therapy within 48 hours of fistula thrombosis, with the exception of one patient who presented 7 days after thrombosis. Lytic therapy with urokinase or recombinant tissue plasminogen activator (rt-PA) was administered as a bolus into the fistula in 24 cases, with the exception of one case in which a 16-hour infusion of rt-PA was initiated. A mechanical thrombectomy device was used in a single case. Balloon thrombectomy was performed for residual clot. Angioplasty was performed at the arterial inflow, fistula, and outflow veins as required for identified areas of stenosis and/or maceration of thrombus. RESULTS: Clinical success was achieved in 73% of cases (22 of 30). All patients were followed for a maximum of 66 months (mean, 12 mo). Primary patency rates were 36% at 3 months (95% CI, 18%-54%), 28% at 6 months (95% CI, 12%-46%), and 24% at 1 year (95% CI, 10%-42%). The assisted primary patency rate was 40% (95% CI, 21%-58%) at 3 months and stabilized at 32% at 6 months (95% CI, 15%-50%). The secondary patency rate stabilized at 3 months at 44% (95% CI, 24%-62%) for 15 months. Patency rates after clot removal were not significantly different between upper and lower arm fistulas (P =.14). Total observation time of the cohort of 25 fistulas was 296 months. The complication rate was 7% (two of 30), with one major complication and one minor complication. CONCLUSION: Salvage of function after percutaneous clot removal from autogenous fistulas involves a steep learning curve initially and is possible with 3-month patency rates that approximate Kidney Disease Outcomes Quality Initiative recommendations for clot removal from polytetrafluoroethylene grafts.

Adult↗
PubMed2002

Treatment of type 2 endoleaks after endovascular repair of abdominal aortic aneurysms: comparison of transarterial and translumbar techniques.

OBJECTIVE: The exact significance of collateral endoleaks is unknown and a topic of great debate. Because of this uncertainty, some physicians choose to watch and wait while others aggressively treat these leaks. The purpose of this investigation was the evaluation of the efficacy of the two techniques used in the treatment of collateral endoleaks that occur after endovascular aneurysm repair. METHODS: Patients with 33 angiographically proven type 2 endoleaks underwent treatment with either transarterial inferior mesenteric artery embolization (n = 20) or direct translumbar embolization (n = 13) during an 18-month period. Embolization success was defined as resolution of endoleak on all subsequent computed tomography angiogram results. The likelihood of embolization failure between the two treatments was expressed as a risk ratio and was compared with Fisher exact test. RESULTS: Sixteen of 20 transarterial inferior mesenteric artery embolizations (80%) failed with recanalization of the original endoleak cavity over time. A single failure (8%) in the direct translumbar embolization group occurred in a patient in whom a new attachment site leak developed. The remaining 12 translumbar endoleak embolizations (92%) were successful and durable, with a median follow-up period of 254 days. The patients who underwent transarterial inferior mesenteric artery embolization were significantly more likely to have persistent endoleak than were the patients who underwent treatment with direct translumbar embolization (risk ratio, 4.6; 95% confidence interval, 1.9 to 11.2; P =.0001). CONCLUSION: The transarterial embolization of inferior mesenteric arteries for the repair of type 2 endoleaks is ineffective and should not be performed. Direct translumbar embolization of the endoleak is effective in the elimination of type 2 leaks and should be the therapy of choice when aggressive endoleak management is indicated.

Aortic Aneurysm, Abdominal↗
PubMed2002

Arterial port catheter system placement using a translumbar aortic route.

RATIONALE AND OBJECTIVES: Implantable ports for arterial infusion hold promise in a growing number of clinical applications, including regional chemotherapy and gene therapy. Percutaneous placement of arterial infusion ports has been described clinically; however, existing sites of access pose unique anatomic challenges. The feasibility of translumbar aortic placement of a port-catheter system for long-term arterial infusion was assessed. MATERIALS AND METHODS: Eight swine underwent placement of a percutaneously implantable arterial port-catheter system using a translumbar aortic approach for catheter placement. The tip of the catheter was positioned in the left or right hepatic artery and the port reservoir implanted in the paraspinal subcutaneous tissues. Patency and position of the port-catheter system were assessed at 7 to 10 days and 28 days. The insertion procedure was modified in two animals by introducing tissue adhesive around the catheter to prevent dislodgment. RESULTS: Immediate technical success was achieved in 6 of 8 animals (75%). Catheters were dislodged into the aorta in two animals on the day of the procedure, extravascular in four animals and intra-aortic in one animal by day 10. One animal died at 21 days of sepsis. The port-catheter systems remained functional at 28 days with catheters positioned within the left or right hepatic artery in three animals, including two animals in which the catheter had been fixated within the paraspinal soft tissues with tissue adhesive. CONCLUSIONS: A translumbar aortic route for percutaneous placement of arterial infusion port-catheter systems is feasible in swine and holds potential as an ancillary access site in a clinical setting if the obstacle of catheter fixation can be overcome.

Animals↗
PubMed2002

Access flow monitoring of patients with native vessel arteriovenous fistulae and previous angioplasty.

Screening strategies based on measurement of access blood flow (Qa) allow detection and angioplasty of subclinical stenosis in native vessel arteriovenous (AV) fistulae. However, little is known about the efficacy of Qa measurements for detecting recurrent stenoses in fistulae and that of angioplasty for correcting them. A total of 303 patients were studied over 30 mo; 69 (23%) of these had stenoses, of whom 53 underwent angioplasty. Of those undergoing angioplasty, 30 patients had 46 episodes of recurrent positive studies and underwent repeat fistulography. In 31 of these episodes (19 patients), stenosis was again identified and treated successfully with angioplasty. Overall positive predictive values for stenosis were similar in first and subsequent episodes of stenosis (71% versus 67%), and angioplasty was associated with sustained increases in Qa for both first and subsequent episodes. Assisted patency in fistulae that required repeat angioplasty was 87% (median follow-up 10 mo after the second angioplasty). In conclusion, Qa is effective for detecting first and subsequent lesions in patients with AV fistulae, and angioplasty of first or subsequent lesions is associated with sustained increments in Qa. Continued screening after correction of first stenoses appears reasonable, because of both the frequency of recurrent stenosis and the success of repeat intervention.

Angioplasty, Balloon↗
PubMed2002

Is routine micropuncture access necessary for percutaneous nephrostomy? A randomized trial.

OBJECTIVE: To compare the micropuncture technique and the conventional large-bore needle approach for renal access. METHODS: From July 1999 to July 2000, patients referred to interventional radiology for emergent or elective percutaneous nephrostomy with normal coagulation profiles were considered for the study. Nephrostomy procedures were performed using a micropuncture system or large-bore needle for collecting system access; 24 nephrostomy procedures were randomized to each group using permuted blocks and opaque sealed envelopes. Gross hematuria, quantitative urine red blood cell counts, pain scores and procedural success were compared between the 2 groups. RESULTS: There was a small difference in the incidence of gross hematuria between the large-bore needle and micropuncture groups (12 [50%] v. 8 [33%] patients), but this difference was not statistically significant. Quantitative urine red blood cell counts obtained immediately after and 24 hours after nephrostomy placement showed no significant differences. Significantly fewer needle passes were required for access in the large-bore needle group than the micropuncture group (1.7 v. 2.8, p = 0.01), and mean procedure duration was 7 minutes longer in the micropuncture group, although this difference was not significant. No differences in pain scores or procedure success were seen. CONCLUSION: Percutaneous nephrostomy performed with a micropuncture system in patients with normal coagulation profiles does not significantly decrease organ bleeding or pain. More needle passes and manipulations are required, which may increase procedure duration. The additional costs of routine micropuncture access for percutaneous nephrostomy are not supported by this study.

Aged↗
PubMedDate not supplied

Predicting infected bile among patients undergoing percutaneous cholecystostomy.

PURPOSE: Patients may not achieve a clinical benefit after percutaneous cholecystostomy due to the inherent difficulty in identifying patients who truly have infected gallbladders. We attempted to identify imaging and biochemical parameters which would help to predict which patients have infected gallbladders. METHODS: A retrospective review was performed of 52 patients undergoing percutaneous cholecystostomy for clinical suspicion of acute cholecystitis in whom bile culture results were available. Multiple imaging and biochemical variables were examined alone and in combination as predictors of infected bile, using logistic regression. RESULTS: Of the 52 patients, 25 (48%) had infected bile. Organisms cultured included Enterococcus, Enterobacter, Klebsiella, Pseudomonas, E. coli, Citrobacter and Candida. No biochemical parameters were significantly predictive of infected bile; white blood cell count >15,000 was weakly associated with greater odds of infected bile (odds ratio 2.0, p = NS). The presence of gallstones, sludge, gallbladder wall thickening and pericholecystic fluid by ultrasound or CT were not predictive of infected bile, alone or in combination, although a trend was observed among patients with CT findings of acute cholecystitis toward a higher 30-day mortality. Radionuclide scans were performed in 31% of patients; all were positive and 66% of these patients had infected bile. Since no patient who underwent a radionuclide scan had a negative study, this variable could not be entered into the regression model due to collinearity. CONCLUSION: No single CT or ultrasound imaging variable was predictive of infected bile, and only a weak association of white blood cell count with infected bile was seen. No other biochemical parameters had any association with infected bile. The ability of radionuclide scanning to predict infected bile was higher than that of ultrasound or CT. This study illustrates the continued challenge to identify bacterial cholecystitis among patients referred for percutaneous cholecystostomy.

Adult↗
PubMedDate not supplied

Patency of Wallstents placed at the venous anastomosis of dialysis grafts for salvage of angioplasty-induced rupture.

PURPOSE: To retrospectively evaluate the patency of Wallstents placed at the venous anastomosis of polytetraflouroethylene (PTFE) hemodialysis grafts to preserve function following angioplasty-induced rupture. METHODS: The charts of all patients who underwent percutaneous angioplasty of functioning hemodialysis PTFE grafts between September 1997 and September 2001 were retrospectively reviewed. A total of 414 angioplasties were performed. Nine cases of rupture at the venous anastomosis managed with stent placement were identified (7 women, 2 men). Two grafts were loop grafts, seven grafts were straight grafts. All stents placed were Wallstents; six stents were 8 x 40 mm, the remaining three were 8 x 20 mm, 8 x 60 mm and 10 x 42 mm. Average follow-up was 13 months. RESULTS: Technical and clinical success of stent placement was 100%. The primary patency rates (+/- SE) of stents placed at the venous anastomosis were 88% (12%) at 30 days, 63% (17%) at 90 days, 33% (18%) at 180 days and 17% (15%) at 360 days. The secondary patency rates (+/- SE) were 89% (11%) at 90 days, 76% (15%) at 180 days and 69% (23%) (6 stents patent) at 360 days. During follow-up, one graft was removed because of infection, one patient died and another was lost to follow-up. A single minor complication of a puncture site hematoma occurred (11%) with no major complications. CONCLUSIONS: This small retrospective series suggests that Wallstent placement following angioplasty-induced venous anastomotic rupture is effective for preserving dialyzable flow in hemodialysis grafts. Patency is comparable to that of stents placed for reasons other than rupture.

Aged↗
PubMedDate not supplied

Pulmonary hypertension among end-stage renal failure patients following hemodialysis access thrombectomy.

PURPOSE: Percutaneous hemodialysis thrombectomy causes subclinical pulmonary emboli without short-term clinical consequence; the long-term effects on the pulmonary arterial vasculature are unknown. We compared the prevalence of pulmonary hypertension between patients who underwent one or more hemodialysis access thrombectomy procedures with controls without prior thrombectomy. METHODS: A retrospective case-control study was performed. Cases (n = 88) had undergone one or more hemodialysis graft thrombectomy procedures, with subsequent echocardiography during routine investigation of comorbid cardiovascular disease. Cases were compared with controls without end-stage renal disease (ESRD) (n = 100, group 1), and controls with ESRD but no prior thrombectomy procedures (n = 117, group 2). The presence and velocity of tricuspid regurgitation on echocardiography was used to determine the prevalence and grade of pulmonary hypertension; these were compared between cases and controls using the chi-square test and logistic regression. RESULTS: The prevalence of pulmonary hypertension among cases was 52% (46/88), consisting of mild, moderate and severe in 26% (n = 23), 10% (n = 9) and 16% (n = 14), respectively. Prevalence of pulmonary hypertension among group 1 controls was 26% (26/100), consisting of mild, moderate and severe pulmonary hypertension in 14%, 5% and 7%, respectively. Cases had 2.7 times greater odds of having pulmonary hypertension than group 1 controls (p = 0.002). The prevalence of pulmonary hypertension among group 2 controls was 42% (49/117), consisting of mild, moderate and severe pulmonary arterial hypertension in 25% (n = 49), 10% (n = 12) and 4% (n = 5), respectively. Cases were slightly more likely to have pulmonary hypertension than group 2 controls (OR = 1.5), although this failed to reach statistical significance (p = 0.14). CONCLUSION: Prior hemodialysis access thrombectomy does not appear to be a risk factor for pulmonary arterial hypertension. Patients with ESRD are more likely to have pulmonary hypertension.

Arteriovenous Shunt, Surgical↗
PubMedDate not supplied

Treating intractable venous stenosis: present and future therapy.

The widespread use of percutaneous angioplasty for venous stenoses has lengthened the functional life span of hemodialysis access, while preserving precious venous capital. A subset of dialysis patients with dysfunctional access sites will harbor stenoses which are intractable, in that they fail to respond to conventional balloon angioplasty or recur in the weeks following angioplasty. This editorial discusses various endovascular approaches to the management of intractable venous stenosis as well as promising future therapies.

Angioplasty, Balloon↗