Cryoablation: mechanism of action and devices

Cryoablation refers to all methods of destroying tissue by freezing. Cryoablation causes cellular damage, death, and necrosis of tissues by direct mechanisms, which cause cold-induced injury to cells, and indirect mechanisms, which cause changes to the cellular microenvironment and impair tissue viability. Cellular injury, both indirect and direct, can be influenced by four factors: cooling rate, target temperature, time at target temperature, and thawing rate. In this review, the authors describe the mechanisms of cellular injury that occur with cryoablation, the major advantages and disadvantages of cryoablation compared with other thermal ablation techniques, and the current commercially available cryoablation ablation systems.

Renal angiomyolipoma: long-term results after arterial embolization

PURPOSE

Selective arterial embolization of renal angiomyolipomas (AMLs) was performed to prevent hemorrhage in patients with AMLs larger than 4 cm. This study was conducted to evaluate the long-term efficacy of AML embolization.

MATERIALS AND METHODS

Nineteen patients underwent embolization for 30 renal AMLs between July 1991 and June 2002. Of these, 10 patients had tuberous sclerosis (TS) with multiple AMLs and nine patients had a solitary sporadic AML. Embolization was performed with use of ethanol mixed with iodized oil (Ethiodol) in 29 tumors; coils were used in addition to the ethanol/Ethiodol mixture in one case. All tumors were completely embolized according to angiographic criteria including vascular stasis and absence of arterial feeders. The efficacy of embolization was determined over a mean follow-up period of 51.5 months (range, 6-132 months). Recurrence was defined as an increase in tumor size of greater than 2 cm on follow-up imaging and/or recurrent symptoms that required repeat embolization. An institutional review board exemption was obtained to perform this retrospective study.

RESULTS

Embolization of the renal AMLs was technically successful in all 19 patients and for all 30 lesions. AML recurrence was noted in 31.6% of patients (n = 19) and for 30% of lesions overall (n = 9). Six of 10 patients in the TS group had AML recurrences. No recurrences occurred in the patients with sporadic AML. In the TS group of 10 patients, there was a total of 21 AMLs and the overall tumor recurrence rate was 42.9% (nine of 21). Six lesions in four patients had to be reembolized because of recurrent symptoms, including one hemorrhage, and three lesions in two patients required repeat embolization because of a greater than 2 cm increase in size. The median time interval from embolization to recurrence was 78.7 months (range, 13-132 months). Statistical testing with use of the Fisher exact test demonstrated that patients with TS were significantly more likely to develop recurrence than those without TS (P = .01).

CONCLUSIONS

Transarterial embolization is effective in preventing hemorrhage in patients with renal AMLs. However, long-term follow-up revealed a high AML recurrence rate in patients with TS. Lifelong surveillance for recurrence after AML embolization is essential in patients with TS.

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.

Experience with the Recovery Filter as a Retrievable Inferior Vena Cava Filter

PURPOSE

This study evaluates clinical experience with the Recovery filter as a retrievable inferior vena cava (IVC) filter.

MATERIALS AND METHODS

One hundred seven Recovery filters were placed in 106 patients with an initial clinical indication for temporary caval filtration. Patients were followed up to assess filter efficacy, complications, eventual need for filter removal, time to retrieval, and ability to remove the filter.

RESULTS

The patient cohort consisted of 62 men and 44 women with a mean age of 48 years (range, 18-90 y). Mean implantation time was 165 days. Indications for filter placement in patients with deep vein thrombosis (DVT) and/or pulmonary embolism (PE) included contraindication to anticoagulation (n = 33), complications of anticoagulation (n = 8), poor cardiopulmonary reserve (n = 6), large clot burden (n = 3), and PE while receiving anticoagulation (n = 1). Indications for filter placement in patients without proven PE or DVT included immobility after trauma (n = 35); recent intracranial hemorrhage, neurosurgery, or brain tumor (n = 18); and other surgical or invasive procedure (n = 3). Three patients (2.8%) had symptomatic PE after placement of the Recovery filter. No caval thromboses were detected. No symptomatic filter migrations occurred. Recovery filter removal was attempted in 15 of 106 patients (14%) at a mean of 150 days after placement. The Recovery filter was successfully retrieved in 14 of 15 patients (93%); one removal was unsuccessful at 210 days after placement. Ninety-two filters (87%) currently remain in place.

CONCLUSIONS

Although all the filters were placed with the intention of being removed, a large percentage of filters were not retrieved. The Recovery filter was safe and effective in preventing PE when used as a retrievable IVC filter.

Prevalence and treatment of cephalic arch stenosis in dysfunctional autogenous hemodialysis fistulas

PURPOSE

Cephalic arch stenosis (CAS) is a recently recognized cause of dysfunction in autogenous hemodialysis fistulas. The prevalence of this lesion among dysfunctional autogenous fistulas is described, as are outcomes after percutaneous therapy.

MATERIALS AND METHODS

A cohort of 177 dysfunctional autogenous fistulas treated over a 48-month period was retrospectively analyzed for the presence of CAS. Of these, 116 (66%) were radiocephalic fistulas and 61 (34%) were brachiocephalic fistulas. CAS was identified in 26 fistulas among 24 patients. Fifty dilations and three stent placements in the cephalic arch were performed. Surveillance was conducted after percutaneous therapy by means of ultrasound dilution technique and measurement of dialysis flow rates. Patency rates were estimated with use of the Kaplan-Meier method. No patients were lost to follow-up.

RESULTS

The prevalence of CAS was 15% (26 of 177). There was a significant difference in the prevalence of CAS between brachiocephalic and radiocephalic fistulas (39% vs 2%; P <.001). High-pressure noncompliant balloon catheters were required in 29 of 50 dilations (58%) to efface the lesion. Primary patency rates (+/-SE) at 3, 6, and 12 months were 76% +/- 8, 42% +/- 10, and 23% +/- 9, respectively. Primary assisted patency rates (+/-SE) at 3, 6, and 12 months were 96% +/- 4, 83% +/- 8, and 75% +/- 10. Complications occurred in three cases (6%). A major complication with rupture of the cephalic arch resulted in thrombosis and fistula loss (n = 1); two minor complications of cephalic arch rupture were salvaged with placement of a Wallstent (n = 1) or prolonged balloon inflation (n = 1).

CONCLUSIONS

CAS is common among failing brachiocephalic arteriovenous fistulas. With aggressive percutaneous intervention and surveillance, favorable primary assisted patency rates can be achieved.

Complications of hepatic chemoembolization

Transarterial hepatic chemoembolization continues to evolve as an integral therapy for unresectable primary and secondary liver tumors. Despite relatively low morbidity, major complications may be seen. This article provides an overview of the spectrum of vascular and nonvascular complications related to this therapy.

Chemoembolization and bland embolization of neuroendocrine tumor metastases to the liver

PURPOSE

To assess the toxicity and efficacy of chemoembolization and bland embolization in patients with neuroendocrine tumor metastases to the liver.

MATERIALS AND METHODS

A total of 67 patients underwent 219 embolization procedures: 23 patients received primarily bland embolization with PVA with or without iodized oil and 44 primarily received chemoembolization with cisplatin, doxorubicin, mitomycin-C, iodized oil, and polyvinyl alcohol. Clinical, laboratory, and imaging follow-up was performed 1 month after completion of therapy and every 3 months thereafter. Patients with disease relapse were treated again when feasible. Toxicity was assessed according to National Cancer Institute Common Toxicity Criteria for Adverse Events, version 3.0. Efficacy was assessed by clinical and morphologic response. Time to progression (TTP), time to treatment failure, and survival were estimated by Kaplan-Meier analysis.

RESULTS

Ten of 67 patients (15%) were lost to follow-up. The mortality rate at 30 days was 1.4%. Toxicities of grade 3 or worse in severity occurred after 25% of chemoembolization procedures and 22% of bland embolization procedures (odds ratio, 1.2; 95% CI, 0.4-4.0). Mean length of stay was 1.5 day in both groups. Rates of freedom from progression at 1, 2, and 3 years were 49%, 49%, and 35% after chemoembolization and 0%, 0%, and 0% after bland embolization (log-rank test, P = .16). Among the subgroup with carcinoid tumors, the proportions without progression were 65%, 65%, and 52% after chemoembolization and 0%, 0%, and 0% after bland embolization (log-rank test, P = .08). Patients treated with chemoembolization and bland embolization experienced symptomatic relief for means of 15 and 7.5 months, respectively (P = .14). Survival rates at 1, 3, and 5 years after therapy were 86%, 67%, and 50%, respectively, after chemoembolization and 68%, 46%, and 33%, respectively, after bland embolization (log-rank test, P = .18).

CONCLUSIONS

Chemoembolization was not associated with a higher degree of toxicity than bland embolization. Chemoembolization demonstrated trends toward improvement in TTP, symptom control, and survival. Based on these results, a multicenter prospective randomized trial is warranted.

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.

Transplant renal artery stenosis: outcome after percutaneous intervention

PURPOSE

To assess the outcome of percutaneous transluminal angioplasty (PTA) and stent placement as the primary treatment for transplant renal artery stenosis (TRAS).

MATERIALS AND METHODS

A retrospective review of PTA and stent placement procedures performed for TRAS from April 1997 to July 2003 was conducted. Reviewed parameters included technical success, date of transplantation, dates of percutaneous intervention, mean arterial blood pressure, number of blood pressure medications, and serum creatinine level before and after intervention. Twenty-one interventions were performed in 18 allografts. The primary clinical indication for imaging and treatment was increased creatinine level in 12 allografts and hypertension in six allografts. Patency rates were estimated with use of the Kaplan-Meier method.

RESULTS

The technical success rate of PTA/stent placement was 100% and the clinical success rate was 94% (17 of 18 allografts). Thirteen interventions involved PTA alone, with eight combined PTA and stent insertions. The mean preintervention serum creatinine level among 12 allografts presenting with elevated creatinine levels was 2.8 mg/dL +/- 1.4 (SD), compared with a 1-month postintervention mean of 2.2 mg/dL +/- 0.7 (P = .03). Of six allografts that presented with hypertension, significant improvement was seen between the preintervention and 1-month postintervention mean systolic (174 mm Hg vs 135 mm Hg, P = .003) and diastolic (99 mm Hg vs 82 mm Hg, P = .02) pressures. These patients required a mean of 2.3 medications for blood pressure control before intervention, compared with a mean of 1.0 medications at 1 month after intervention (P = .002). Primary patency rates at 3, 6, and 12 months (+/-95% CI) were 94% +/- 6%, 72% +/- 12%, and 72% +/- 12%, respectively. Secondary patency rates at 3, 6, and 12 months (+/-95 CI) were 100%, 85% +/- 10%, and 85% +/- 10%, respectively. Mean follow-up time was 27 months. Of the eight allografts that underwent stent placement, all eight remained patent at last follow-up (mean, 18.3 months +/- 9.2). One major complication of a puncture site pseudoaneurysm occurred (5%).

CONCLUSION

Primary treatment of TRAS with PTA with or without stent placement has good intermediate-term patency and is associated with significant early improvement in blood pressure and creatinine level.

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.

Use of CT Angiography to Classify Endoleaks after Endovascular Repair of Abdominal Aortic Aneurysms

PURPOSE

Accurate endoleak detection and classification is critical for the follow-up of patients who have undergone endovascular aneurysm repair (EVAR). This determination is often made with computed tomography angiography (CTA). This investigation was performed to determine the accuracy of CTA in the classification of endoleaks in patients who have undergone EVAR.

MATERIALS AND METHODS

Thirty-six patients with endoleaks underwent both CTA and conventional contrast digital subtraction angiography (DSA) to determine endoleak etiology. Two independent radiologists determined the source of the endoleak based on a retrospective review of the CTA. The results of the CTA-based endoleak classification were compared to the reference standard, contrast DSA.

RESULTS

There was agreement regarding endoleak classification between CTA and DSA on 86% of the patients (31 of 36 patients). Correlation between the CTA reading of the two readers was 94% (34 of 36 patients), yielding a kappa statistic of 0.8. In three patients, the CTA reading incorrectly classified endoleaks as type 2 when the endoleaks were actually type 1 endoleaks on DSA. One patient was incorrectly classified as having a type 1 endoleak on CTA when it was a type 2 endoleak on DSA. Finally, one patient had a type 1 endoleak on DSA that was incorrectly classified as a type 3 endoleak on CTA. The change in CTA endoleak classification based on the DSA resulted in a significant change in patient management in four of the 36 patients (11%).

CONCLUSIONS

Endoleak classification based on CTA correlates fairly well with DSA findings. However, optimal endoleak management requires performance of selective angiograms with DSA to classify endoleaks that are detected on CTA.

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.

Percutaneous transhepatic venous access for hemodialysis

Percutaneous transhepatic venous access is an option for hemodialysis patients who have exhausted more traditional sites of venous access. Thirty-six transhepatic dialysis catheters were placed in 12 patients. The mean time of the catheters in situ was 24.3 days. Twenty-one catheters were replaced or removed because of catheter thrombosis, yielding a catheter thrombosis rate of 2.40 per 100 catheter-days. The line sepsis rate was 0.22 per 100 catheter-days. Poor patency rates were seen because of a high rate of late thrombosis. Transhepatic dialysis catheters should only be used as a last resort unless limitations of catheter thrombosis can be overcome.

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.

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.

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.

Embolization of Type 2 Endoleaks after Endovascular Repair of Abdominal Aortic Aneurysms with Use of Cyanoacrylate with or without Coils

Translumbar embolization was used to treat 11 type 2 endoleaks in nine patients with the liquid embolic agent n-butyl cyanoacrylate (NBCA). Nine of the embolizations were performed with a combination of stainless-steel coils and NBCAJ and the other two were performed with NBCA alone. There was complete occlusion on initial computed tomographic (CT) angiography in six of nine patients (66%), including the two cases treated with NBCA alone. Persistent endoleak on initial CT angiography occurred in three of nine patients (33%). Two of these patients underwent successful repeated embolization with NBCA. Aneurysm size remained unchanged in four patients (44%), decreased in four patients (44%), and increased in one patient (11%). No complications occurred. Initial results with the use of NBCA for endoleak embolization are encouraging.

The effect of initial shunt outflow position on patency of transjugular intrahepatic portosystemic shunts

PURPOSE

It has been suggested that initial stent position in transjugular intrahepatic portosystemic shunts (TIPS) with relation to hepatic venous outflow is an important determinant of shunt patency. It was hypothesized that TIPS with the stent-implanted segments terminating in the hepatic vein (HV) have shorter primary unassisted shunt patency durations than TIPS with the stent-implanted segments extending to the hepatocaval junction.

MATERIALS AND METHODS

A consecutive group of 107 patients who underwent TIPS creation for variceal bleeding were retrospectively identified, and the angiographic images during initial TIPS creation were reviewed independently by two observers who were blinded to outcome. Primary unassisted patency was estimated in group A (TIPS terminating in the HV; n = 47) and group B (TIPS terminating at the hepatocaval junction; n = 60) with the Kaplan-Meier method, and the two groups were compared with the log-rank test. Patients who had less than 30 days of follow-up were excluded from the analysis.

RESULTS

Among all 107 patients, primary unassisted patency rates at 3, 6, and 12 months were 91% +/- 4%, 74% +/- 6%, and 49% +/- 6%. TIPS were classified into group A or group B with high interobserver agreement (Cohen kappa = 0.98). At 12 months, the primary unassisted patency rate among the patients in group A was 36% +/- 10%, compared with 58% +/- 8% among the patients in group B (P =.017, log-rank test). Patients in group A were twice as likely to lose patency than patients in group B (95% CI of odds ratio, 1.2-4.5). Thirty-day mortality was similar between groups (15% vs 12%; P =.13).

CONCLUSION

Initial stent position within the hepatic venous outflow is predictive of shunt patency, with TIPS extending to the hepatocaval junction having a longer lifespan than shunts terminating in the HV.

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.

Direct intrahepatic portocaval shunt

The direct intrahepatic portacaval shunt (DIPS) is a modification of the TIPS procedure, using intravascular ultrasound-guidance, combined with fluoroscopy. The DIPS procedure was initially conceived to increase the durability of shunt patency and extend the spectrum of patients with portal hypertension for whom endovascular portocaval shunting can be performed. The DIPS procedure involves intravascular ultrasound-guided puncture from the inferior vena cava to the portal vein through the caudate lobe of the liver. The shunt is completed with a polytetrafluoroethylene-covered stent graft. This article describes the indications, technique, and outcomes of the DIPS procedure to enable the interventional radiologist currently experienced with TIPS to incorporate this procedure into their practice.

Risk of Intrauterine Infectious Complications after Uterine Artery Embolization

PURPOSE

To identify risk factors for the development of intrauterine infection following uterine artery embolization.

MATERIALS AND METHODS

A retrospective review of uterine artery embolizations (UAE) performed for the treatment of symptomatic fibroids from January 2000 to July 2003 was conducted. With logistic regression and the Fisher exact test, multiple variables were analyzed as predictors for intrauterine infectious complications requiring medical and/or surgical therapy, including the use of preprocedural antibiotics, embolic agent used, quantity of embolic material, location of fibroids (submucosal, nonsubmucosal), and size and location of the dominant fibroid.

RESULTS

A total of 414 UAE procedures were performed in 410 patients with a technical success rate of 99%. Average age of the patient cohort was 42.8 years (SD, 5.8 years). One hundred forty-eight patients (36.1%) had submucosal fibroids or fibroids projecting submucosally, 262 patients (63.9%) had nonsubmucosal fibroids. Intrauterine infectious complications requiring intravenous antibiotic therapy and/or surgery occurred in five patients (1.2%). A total of five infectious complications requiring therapy occurred in the submucosal group (3.4%) and none in the nonsubmucosal group. Patients within the submucosal group were more likely to develop intrauterine infectious complications than patients with nonsubmucosal fibroids based on univariate analysis (P = .006) but with logistic regression, the association was not significant (P = .079). No significant difference with embolic agent, quantity of embolic particles, use of preprocedure antibiotics, or size of or location of the dominant fibroid was found.

CONCLUSION

No specific risk factor for intrauterine infection following UAE was identified in this study. Infection after UAE is rare and appears to be a sporadic occurrence. Nevertheless, close surveillance is warranted in all women following UAE given the potential morbidity of this complication.

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.