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Vascular and Interventional Radiology |
1 From the Division of Vascular and Interventional Radiology, St Luke's-Roosevelt Hospital Center, 1000 10th Ave, New York, NY 10019. From the 1997 RSNA scientific assembly. Received April 27, 1998; revision requested June 16; final revision received February 12, 1999; accepted March 24. Address reprint requests to S.G.C. (e-mail: scooper@slrhc.org).
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Abstract |
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MATERIALS AND METHODS: During a 4-month period, 79 patients presented with 126 episodes of graft occlusion. Percutaneous recanalization was performed by using the ATD (n = 57) or the modified PPT technique (n = 69). Evaluation included the technical success, complications, and primary patency rates.
RESULTS: Technical success was achieved in 93% (53 of 57) of the cases treated with the ATD and in 96% (66 of 69) of the cases treated with modified PPT (P = .70). Complications occurred in 6% (four of 69) of modified PPT procedures and 16% (nine of 57) of ATD procedures. This difference was not statistically significant (P = .08); however, there were significantly more local complications in the ATD group (P = .04). The primary patency rates at 30, 90, and 180 days were 65% and 65%, 36% and 50%, and 26% and 33% for modified PPT and ATD, respectively. Survival curves were found not to differ significantly (P = .49).
CONCLUSION: The ATD and modified PPT were similarly successful in the recanalization of thrombosed hemodialysis access grafts and achieved comparable primary patency rates. The higher rate of local complications and technical difficulties encountered with use of the 8-F ATD limit its usefulness for this indication.
Index terms: Angiography, 91.12 • Dialysis, shunts, 91.442, 91.457 • Grafts, interventional procedures, 91.1264, 91.1265, 91.1282, 91.442 • Grafts, stenosis or thrombosis, 91.751 • Thrombectomy, 91.1282 • Thrombolysis, 91.1264, 91.1265, 91.1282
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Introduction |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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A variety of alternatives to pulse-spray pharmacomechanical thrombolysis and infusion with urokinase have been described, including balloon declotting (6–9), thromboaspiration (10,11), pulse-spray thrombolysis with a saline solution containing heparin (12,13), and a growing list of mechanical thrombectomy devices (14–18). In August 1996, the Amplatz thrombectomy device ([ATD] Microvena, White Bear Lake, Minn) became the first mechanical thrombectomy device to receive approval from the Food and Drug Administration for use in hemodialysis access grafts. The purpose of this study was to compare our initial experience with the ATD versus the modified PPT technique.
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MATERIALS AND METHODS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Populations
Each patient's age, sex, cause of renal failure, and type and age of the graft were recorded (Table 1) (C.T.S.). Patients were treated with one technique or the other on the basis of the preference of the interventional radiologist performing the procedure. There were no identifiable patient or graft characteristics that swayed this decision.
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Specific to modified PPT.—A 5-F multisideslit pulse-spray infusion catheter (Angio-Dynamics, Glens Falls, NY) with appropriate length for each graft (5–20 cm available) was inserted toward the venous outflow. The tip of the catheter was positioned at the venous anastomosis.
In long loop grafts, the same type of infusion catheter was advanced through the second puncture site toward the arterial anastomosis. Care was taken to position the tip of this catheter near but not across the arterial anastomosis. In most of the straight or C-shaped grafts (18 of 25), the venous-directed catheter was inserted close to the arterial anastomosis, and the thrombolytic portion of the procedure was performed through this single catheter. In the remaining seven (28%) of 25 straight grafts, a second pulse-spray catheter was used.
A thrombolytic solution containing 250,000–500,000 IU of urokinase (Abbokinase; Abbott Laboratories, Abbott Park, Ill) and 3,000–4,000 U of heparin sodium (Elkins-Sinn, Cherry Hill, NJ), depending on the size and configuration of the graft, was prepared in a 10–20-mL solution with normal saline solution. Pulse-spray thrombolysis, with forceful injection of 0.3 mL of urokinase solution every 30 seconds through a 1-mL syringe, was completed during a period of 15–16 minutes.
Specific to the ATD.—After initial access in the graft was obtained as described, an 8-F sheath (Pinnacle Introducer; Medi-tech/Boston Scientific, Natick, Mass) was inserted to accommodate the device. The ATD has been described by several authors (16,19–22). The ATD was used toward the venous limb in all cases. Placement of a second 8-F sheath toward the arterial limb was performed in all of the long-loop configurations (25 of 43) and in six of the 18 straight or C-shape configured grafts for accommodation of the ATD. When the ATD was not used toward the arterial limb, a 5-F sheath (MTI One-Piece Introducer; Microtherapeutics, Irvine, Calif) was placed. Patients received 3,000–7,000 U of heparin sodium intravenously, depending on the duration of the procedure.
After modified PPT or use of ATD.—Reevaluation of the graft and the venous anastomosis was performed by means of hand injection of dilute contrast material with digital spot imaging (Integris V3000; Philips Medical Systems, Best, the Netherlands). The infusion catheter (modified PPT) or the ATD was exchanged for a high-pressure balloon (Ultrathin Diamond or Blue Max; Medi-tech/Boston Scientific) to perform balloon angioplasty at the venous anastomosis. Balloon size was 6–9 mm, depending on the size of the outflow vein. Balloon pressures of 15-22 atm typically were achieved. The results of angioplasty were evaluated angiographically (Integris V3000), and repeat dilation was performed, if necessary.
Reestablishment of arterial inflow was then performed. A 3- or 4-F balloon embolectomy catheter (Baxter, Irvine, Calif; Applied Medical, Laguna Hills, Calif) was inserted through the arterially directed introducer sheath and advanced through the arterial anastomosis to the inflow artery. The balloon was inflated and retracted into the graft to the tip of the arterial sheath to dislodge the arterial plug. If no thrill was palpable at this point, it was usually owing to impaction of the arterial plug at the level of the crossing sheaths. This was treated by means of maceration with the venous-directed balloon.
Angiographic evaluation of the arterial anastomosis and the entire graft subsequently was performed. Small amounts of residual thrombus within the graft were macerated with the angioplasty balloon. Flow-limiting intragraft stenoses were treated by means of balloon angioplasty. Residual adherent thrombus at the arterial anastomosis was treated with a repeated embolectomy maneuver as described. If this failed, balloon angioplasty with a 4–7-mm balloon was performed. Balloon size was selected on the basis of the diameter of the inflow artery.
Reevaluation of the graft to document patency was performed at this point and included reevaluation of the venous anastomosis. Redilation with prolonged inflation or larger balloon diameter, only if the outflow vein could accommodate it, was performed in cases with recoil or recurrent stenosis of the venous anastomosis. Stent placement was considered if there was persistent residual or flow-restricting stenosis at the venous anastomosis. Additional stenoses identified in the final angiographic evaluation of the graft and venous outflow to the central veins also were treated with use of percutaneous balloon angioplasty and stent placement as needed, through the venous directed access in the graft.
Definitions
"Technical success" was defined as restored graft patency with at least one successful dialysis session either immediately following treatment or on the following day.
"Primary patency" was defined as the time between the initial therapeutic procedure and the subsequent intervention or graft failure. In patients who underwent both techniques for treatment of different episodes of occlusion, each procedure was considered a starting point for the calculation of patency in each group.
Statistical Analysis
Comparison was made between the two groups with respect to technical success rates, complication rates, and the primary patency rates and survival curves (23–26). Follow-up with review of the angiographic data and radiology reports, medical records, and direct communication with the hemodialysis centers was obtained to determine patency.
The success rates and complication rates for the ATD and modified PPT were compared statistically by means of the two-sided Fisher exact test. A P value of less than .05 was considered to indicate a statistically significant difference.
Kaplan-Meier survival curves were used to describe the distribution of time until failure for the ATD and modified PPT treatment groups. Technical failures in each group were included in the patency calculations. A 6-month primary patency was used to determine whether the survival curves crossed at all during this period. The interval used was 30 days. The log-rank, or Mantel-Haenszel, test was performed to statistically compare the two survival curves, and a P value of less than .05 indicated significance.
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RESULTS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Technical success was achieved in 66 (96%)of the 69 cases in which modified PPT was used and in 53 (93%) of the 57 cases in which the ATD was used. The difference in technical success between the two techniques in this study was found not to be statistically significant (P = .70).
Three technical failures (4%) in the modified PPT group were attributed to ventricular fibrillation, which resulted in death in one patient; reaction to contrast material, which resulted in acute parotitis in the second patient; and uncorrectable arterial inflow disease in the third patient. Four technical failures (7%) were recorded with use of the ATD and were the result of pulmonary edema or fluid overload, severe resistant intragraft stenosis, large arterial pseudoaneurysm with diseased native brachial artery, and recurrent thrombosis in a patient in whom use of heparin was contraindicated.
Venous anastomoses were dilated in 66 (96%) of the 69 cases in which modified PPT was used and in 56 (98%) of the 57 cases in which the ATD was used. All sites of stenosis treated by means of percutaneous balloon angioplasty are shown in Table 2. Endovascular stent placement was used to treat percutaneous balloon angioplasty failure, postangioplasty extravasation, central venous occlusion, and, rarely, resistant intraluminal defects (Table 3). The groups were similar in the number of angioplasties performed (P = .81) and in the number of lesions requiring stent placement (P = .19). Intragraft stents were deployed near, but not across, the arterial anastomosis in two patients in the ATD group to treat adherent thrombus that did not respond to repeated balloon embolectomy maneuvers and prolonged percutaneous balloon angioplasty. Both of these grafts were restored successfully.
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Nine (16%) complications occurred during the 57 procedures in which the ATD was used. There were four cases of arterial emboli (7%) that were detected as filling defects or abrupt cutoff within the native artery (Fig 2a). In two of four of these cases, the device was not used toward the arterial limb. Two of these cases had no clinical manifestation, whereas in the other two cases patient symptoms included hand coldness, numbness, or pain. Emboli were successfully retrieved by using an embolectomy balloon (Baxter) in two cases and an occlusion balloon (Medi-tech/Boston Scientific) over a Glidewire (Terumo, Tokyo, Japan) in the other two (Fig 2b, 2c).
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The difference in overall complication rates between the two techniques (16% for the ATD and 6% for modified PPT) was found not to be statistically significant (P = .08), although a trend was evident. When considering local complications only, excluding reaction to contrast material, respiratory distress, and cardiac arrhythmia, there were significantly more complications in the ATD group (P = .04).
Several technical difficulties were noted during the use of the ATD related to its size and design specifications. Because the device has a blunt tip and does not track over a wire, it was difficult to steer the device around angles, tortuous segments, and curves. The sudden transition between the delicate shaft of the device and the relatively heavy handle often requires more than one person to keep the device constantly aligned. Malfunction and breakage of the device occurred in seven (12%) of 57 cases. In two of these cases, a second device was used to complete the procedure. The 8-F introducer sheath required for introduction of the ATD can be occlusive within the graft (Fig 4a, 4b), as already noted by other authors (16), especially when crossing the opposite sheath (Fig 4b, 4c). This can create difficulty in maneuvering the device and may necessitate added manipulations.
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DISCUSSION |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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The technical success rates (ATD, 93%; modified PPT, 96%) are comparable in the two groups and are similar to the success rates reported for hemodialysis graft recanalization by means of various percutaneous methods. Uflacker et al (16) reported an 89% (17 of 19) success rate with the ATD, which is slightly higher than the 83% (15 of 18) success rate of surgical thrombectomy in the same study. Trerotola et al (17), in their study comparing the Arrow-Trerotola percutaneous thrombolytic device to pulse-spray thrombolysis, reported 95% success rates in each group (61 of 64 and 55 of 58, respectively).
Technical success with use of pulse-spray thrombolysis with urokinase was achieved by Valji et al (1) in 91% (259 of 284) and by Cooper et al (4) in 96.4% of their cases. Beathard et al (12,13) reported success in 93% (51 of 55) to 95% (1,123 of 1,176) of their procedures in which pulse-spray delivery of a saline solution containing heparin was used. Cynamon et al (5) reported a 94% (17 of 18) success rate with the "lyse and wait" technique. Balloon-assisted hemodialysis graft mechanical thrombolysis was reported by Trerotola et al (6), Soulen et al (8), and Sharafuddin et al (10) as successful in 94% (32 of 34), 86% (74 of 86), and 90% (18 of 20) of cases, respectively. Turmel-Rodrigues et al (11) were able to achieve 100% success in 43 cases by using a manual thromboaspiration technique.
Our calculated primary patency rates for the ATD of 65%, 50%, and 33% at 30, 90, and 180 days, respectively, are comparable to multiple other reported results for which alternative percutaneous techniques were used (1,4,11,12). In comparison with modified PPT in this study (Table 4, Fig 1), there was some divergence in survival curves at 90 and 120 days; however, the early and late parts of the curves are virtually identical, and log-rank test results showed no statistical difference between the curves.
Although the trend toward a higher overall complication rate in the ATD group did not achieve statistical significance, there was a significant increase in local complications. An unusually high occurrence rate of arterial emboli (7%) was seen during use of the ATD (Fig 2), whereas no arterial embolic event was seen with modified PPT in this study. The occurrence rate of arterial emboli with use of modified PPT and pulse-spray thrombolysis reported in the literature (1,4) is 1%–2%. The increased occurrence rate we experienced with the ATD may be the result of the large sheath volume displacing thrombus on insertion, or, alternatively, it may be related to the blunt metal cap pushing thrombus on advancement toward the arterial anastomosis. This second theory cannot explain two of the events in which the ATD was not advanced toward the arterial limb. The occurrence of arterial emboli in our series was equally distributed throughout the 57 ATD cases chronologically and cannot be attributed to a learning curve.
Three episodes of dissection within the graft were documented in the ATD group. We believe this phenomenon is related to direct pseudointimal trauma caused by the blunt tip of the ATD coming into contact with the graft wall (Fig 3). This contention is supported by the results of an article (22) about extraction of myointimal tissue fragments from the impeller and housing mechanism of the ATD after mechanical thrombolysis of clotted hemodialysis grafts. One case of intimal dissection occurred during modified PPT. This patient underwent a procedure with the ATD 9 days earlier. This raises the possibility that the pseudointimal injury may have occurred during the earlier procedure and became evident only after recurrent thrombosis and subsequent thrombolysis.
We noted a high occurrence rate of arterial plugs that were resistant to standard balloon embolectomy maneuvers in the ATD group (30%) and that required maceration with an angioplasty balloon, as compared with rates with modified PPT in our study (16%) and in series reported in the literature (1,4) in which a pharmacomechanical thrombolysis technique was used (10%–19%). The concept of "softening" of the arterial plug thrombus by means of treatment with urokinase with a resultant better response to the balloon embolectomy maneuver has been proposed but never proved. It is of interest to note, however, that in other studies, in which no urokinase was used for mechanical declotting, balloon angioplasty at the arterial anastomosis was necessary in 29%–40% of cases (6,10).
Two particularly resistant adherent plugs in the ATD group were treated by means of placing short Wallstents near the arterial anastomosis. In both of these cases, the patients had multiple prior failed grafts and had undergone numerous surgical revisions on the current graft. Consequently, the surgeons wanted to avoid further surgical intervention and urged a more aggressive attempt at percutaneous salvage.
Technical difficulties encountered during the use of the ATD were, in part, the result of the large size of the introducer sheath necessary to accommodate the ATD. We believe that this is likely the major single disadvantage of the 8-F device. Since our data were acquired, Microvena has released a 6-F version of the ATD. Although the smaller version overcomes many of the difficulties caused by the size of the 8-F device, we experienced persistent problems with device breakage and reduced vortex size and power, which, in our opinion, have prevented widespread acceptance of this product.
In summary, the ATD was successful in restoring patency in a large percentage of thrombosed hemodialysis access grafts. The initial results and primary patency rates are comparable to those for both modified PPT and the alternative percutaneous radiologic procedures found in the literature. We are concerned with the higher rate of local complications. This, in conjunction with the technical difficulties we experienced, has discouraged us from using the device on a regular basis in the treatment of thrombosed hemodialysis access grafts. We believe that the ATD has potential benefit as an alternative method of treatment; however, further technical improvements are needed to achieve a more durable smaller size, better steerability, and potential use over a guide wire. With these improvements, a prospective randomized clinical trial may be undertaken to evaluate the device further.
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Acknowledgments |
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Footnotes |
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Abbreviations: ATD = Amplatz thrombectomy device PPT = pulse-spray pharmacomechanical thrombolysis
Author contributions: Guarantors of integrity of entire study, C.T.S., S.G.C., I.S.; study concepts and design, I.S., S.G.C., C.T.S.; definition of intellectual content, S.G.C., I.S., C.T.S.; literature research, C.T.S., S.G.C.; clinical studies, all authors; data acquisition, C.T.S., I.S., S.G.C., A.I., S.W.; data analysis, S.G.C., C.T.S.; statistical analysis, S.G.C., C.T.S.; manuscript preparation, C.T.S., S.G.C.; manuscript editing, S.G.C.; manuscript review, I.S., R.I.P., A.I., S.W.
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References |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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This article has been cited by other articles:
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  L. Turmel-Rodrigues Stenosis and thrombosis in haemodialysis fistulae and grafts: the radiologist's point of view Nephrol. Dial. Transplant., February 1, 2004; 19(2): 306 - 308. [Full Text] [PDF]
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 S. G. Cooper Pulse-Spray Thrombolysis of Thrombosed Hemodialysis Grafts with Tissue Plasminogen Activator Am. J. Roentgenol., April 1, 2003; 180(4): 1063 - 1066. [Abstract] [Full Text] [PDF]
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L. Turmel-Rodrigues, J. Pengloan, S. Baudin, D. Testou, M. Abaza, G. Dahdah, A. Mouton, and D. Blanchard Treatment of stenosis and thrombosis in haemodialysis fistulas and grafts by interventional radiology Nephrol. Dial. Transplant., December 1, 2000; 15(12): 2029 - 2036. [Abstract] [Full Text] [PDF]
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