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Original Report |
1 Department of Radiology, St. Luke's-Roosevelt Hospital Center, 1000 Tenth
Ave., New York, NY 10019.
2 ProHealth Care Associates, 2800 Marcus Ave., Lake Success, NY 11042.
Received February 4, 2002;
accepted after revision August 28, 2002.
Address correspondence to S. G. Cooper.
Abstract
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CONCLUSION. Pulse-spray pharmacomechanical thrombolysis with tissue plasminogen activator is an effective method for percutaneous recanalization of thrombosed hemodialysis access grafts with results similar to other percutaneous techniques.
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Tissue plasminogen activator ([t-PA] Alteplase; Genentech, South San Francisco, CA), which has been shown to be effective as a percutaneous, catheter-directed thrombolytic agent in the treatment of peripheral arterial occlusive disease, is increasingly being applied to applications for which urokinase was routinely used. Few recent reports, however, have been published regarding the use of t-PA in the treatment of thrombosed hemodialysis access sites [2, 7, 8], with only one study [2] involving pulse-spray administration.
This article reports a pilot study in the treatment of hemodialysis graft thrombosis by pulse-spray pharmacomechanical thrombolysis with t-PA. The goal of this study was to assess a simple, rapid protocol for hemodialysis graft recanalization with evaluation of success, procedure time, and 90-day patency.
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Technique
In all patients, the modified pulse-spray technique
[2,
9] was used, and all procedures
were performed by the same operator. The grafts were initially accessed near
the arterial anastomosis in an antegrade direction, and after evaluation of
the venous outflow tract, a single 5-French infusion catheter (Unifuse;
AngioDynamics, Glens Falls, NY) was inserted. The infusion length of the
catheter, over which multiple side slits were distributed, was selected on the
basis of the length of the graft and the presence of outflow vein thrombus
(Fig. 1A,
1B,
1C). A solution containing 1 mg
of t-PA per 5 or 10 mL of 0.9% saline solution was administered in a
pulse-spray fashion. The Pulse Spray Injector (AngioDynamics) was used to
automatically deliver 0.3–0.5 mL of solution every 20–30 sec to
yield an average dose of 2.0 mg over a mean period of 16 min.
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The concentration, pulse volume, pulse interval, and total volume were varied within a narrow range to allow differences in catheter length and clot burden. Completed administration of the selected dose was the end point for thrombolysis. Heparin sodium was not administered as an adjunct to thrombolysis. Subsequently, contrast material was slowly injected into the graft through the Unifuse infusion catheter. The amount of thrombus in the graft was subjectively estimated, both before and after thrombolysis, by visual determination of relative contrast opacification versus intraluminal filling defect. The degree of thrombolysis was calculated by comparison of the preand postthrombolysis appearances.
The infusion catheter was exchanged for a 6-French sheath, and percutaneous balloon angioplasty was performed at the venous anastomosis. High-pressure balloons (Centurion, C. R. Bard, Covington, GA; Blue Max, Boston Scientific/Med-iTech, Watertown, MA; 6- to 10-mm diameters) were routinely used and were typically inflated to 15–20 atm) of pressure. Improved luminal diameter was confirmed by injection of contrast material with digital spot imaging. Angioplasty sites were considered adequately dilated when they were shown angiographically to have minimal or mild residual stenosis, as determined visually.
Grafts were then accessed in the venous limb in a retrograde direction, and a 5-French sheath was placed. The arterial plug was displaced with a 4-French balloon thrombectomy catheter (Applied Medical, Laguna Hills, CA). After restoration of antegrade flow through the graft, digital subtraction angiography was performed to evaluate the entire arteriovenous shunt system. Residual thrombus within the graft was macerated with either the embolectomy balloon or the angioplasty balloon, and additional sites of stenosis were treated as indicated. Adjunctive interventions and complications were recorded for each patient. Sheaths were removed and hemostasis was achieved by manual compression in most patients. One patient with chronic central vein occlusion that could not be successfully crossed had purse-string sutures placed. Another patient had one purse-string suture placed after 75 min of compression failed to achieve hemostasis. Procedure times were calculated from the time of the first puncture to the time at which the sheaths were removed. Time to hemostasis was not included in total procedure time because there was considerable variability among the techniques used. Compression was generally applied by a resident and fellow trainees, who may have elected to compress access sites either simultaneously or one at a time. Follow-up for patency was obtained by contact with patients, hemodialysis centers, and referring nephrologists.
Technical success was defined as restoration of graft patency with a palpable thrill. Clinical success was defined as technical success plus at least one successful dialysis session. Primary patency was considered the time between thrombolysis and subsequent intervention or graft failure. Life-table analysis of patency data was performed and a survival curve was generated using Stata 5.0 software (Stata, College Station, TX). The one technical failure was included in the life-table analysis.
Patient and Graft Data
Of the 17 patients enrolled, 10 were men and seven were women. The average
age for all patients was 63.1 years, with an age range from 35 to 84 years.
The average age for men was 61.0 years (range, 46–78 years); and the
average age for women was 66.1 years (range, 35–84 years). There were 12
C-shaped grafts, three loop configurations, and two straight grafts. Thirteen
of the grafts were located in the upper arm (12 left and one right), three in
the forearm (all left), and one in the thigh (right). The approximate age of
the graft was known in 14 of the 17 and ranged from 1.5 weeks to 4.5 years
(mean, 18.4 months). Nine (53%) of the 17 grafts had a prior episode of
thrombosis an average of 154 days (range, 14–454 days) earlier.
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Procedure times ranged from 50 to 123 min (with a mean of 80.6 ± 18.8 min and a median of 79 min). Hemostasis times ranged from 10 to 75 min (with an average of 35 min).
Procedural Results
Technical and clinical success was achieved in 16 (94%) of 17 procedures.
The single failure occurred in a left upper arm C-shaped graft in which
pulse-spray thrombolysis was initially successful, but rethrombosis of the
graft and the adjacent outflow tract occurred before completion of the
procedure. Mechanical thrombolysis was then successfully performed with the
Arrow-Trerotola device (Arrow International, Reading, PA). No complications
were recorded in this series of procedures. No local or distant hemorrhage was
encountered.
Successfully treated grafts remained patent for a mean of 72 days. Primary patency, as calculated by the Kaplan-Meier method, was 71% at 30 days and 47% at 90 days, as illustrated in Table 1.
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Mean (81 min) and median (79 min) procedure times were comparable to those previously reported in the literature for percutaneous mechanical and pharmacomechanical techniques [2, 4, 5]. Although time to hemostasis would seem to be an important consideration in comparing pharmacologic versus nonpharmacologic methods, average hemostasis times have not been previously documented. Our mean hemostasis time of 35 min may have been more the result of the compression techniques used than of any other variable.
To our knowledge, little concrete data exist in the literature on which the selection of an optimal dose for pulse-spray thrombolysis in the treatment of thrombosed hemodialysis access grafts can be based. The few existing reports of pulse-spray thrombolysis with t-PA in the treatment of peripheral arterial occlusive disease are not relevant for an application in which practitioners have come to expect total procedure times of 1–2 hr and considerably shorter thrombolysis times. A review of the literature found only a few English language reports on the use of t-PA for hemodialysis graft thrombolysis. Two recent studies evaluated thrombolysis with t-PA by the lyse and wait technique. Falk et al. [7] reported 42 procedures using a 2-mg dose of t-PA and a mean overall procedure time of 106 min. Vogel et al. [8] used a 4-mg dose of t-PA in 20 patients, with a mean procedure time of 39 min. Valji et al. [2], in their report on pulse-spray thrombolysis in 284 instances of hemodialysis graft thrombosis, mentioned the use of t-PA in 23 procedures. Those authors used a solution containing 0.5 mg/mL and delivered a mean of 7.1 mg of t-PA over an average of 32 min. The results for these 23 procedures were not reported separately from the remainder of the patients, who were treated with urokinase.
This study sought to make the t-PA pulsespray protocol as similar to the widely accepted urokinase-based protocols [2, 9] as possible. A pulse volume of 0.3–0.5 mL was maintained every 20–30 sec for a total delivery volume of 10 mL. Choosing a t-PA dose that is equivalent to 250,000 U of urokinase was less straightforward. A dose of approximately 2 mg was arbitrarily selected. Although this dose is lower than that described previously [2], experimental evidence suggests that the dose of t-PA can be further reduced by a factor of 10 [11].
The generation of a high-pressure pulse has typically relied on forceful hand injection with a 1-mL syringe. The pulse-spray injector was designed to automate the pulse generation process so that each pulse is identical in volume, timing, and pressure. Froelich et al. [12] showed, in an in vitro model, that pulse delivery with the pulse-spray injector provided a highly significant improvement (p < 0.001) in the speed and homogeneity of thrombus dissolution when compared with the conventional manual technique.
The cost of a single vial of t-PA (list price, $1100/50-mg vial) was a prohibitive factor in the use of t-PA for hemodialysis graft thrombolysis when urokinase became unavailable in 1998. Since that time, many hospitals began reconstituting and fractionating 50-mg vials into individual 2- or 4-mg doses. Currently, 2-mg-dose vials are available.
Experience has shown that the incidence of distant hemorrhage with locally administered, short-duration thrombolytic therapy with urokinase, as in pulse-spray thrombolysis, is negligible [2, 3, 4, 5, 6, 9, 10]. Similarly, a short, locally administered, low-dose regimen of t-PA could reasonably be expected to have an acceptable safety profile. Although no hemorrhagic complications were experienced, the study population was small, and larger studies would be required to definitively assess the safety profile of pulse-spray thrombolysis with t-PA.
In conclusion, pulse-spray pharmacomechanical thrombolysis with t-PA can be an effective method for efficient percutaneous recanalization of thrombosed hemodialysis access grafts. Although the originally described pulse-spray thrombolysis technique has been refined over the past decade and a number of pulse-spray variations have been described, there has been little scientific analysis of the optimal pulse volume, frequency of pulsing, concentration of thrombolytic agent, and duration of administration. Experimental protocols designed to optimize these individual factors involved in pulse generation are the next logical step in the evolution of pulse-spray thrombolysis. With a "new" thrombolytic agent for pulse-spray thrombolysis and the availability of the pulse-spray injector, it may be possible to improve the pulse-spray thrombolysis technique to enhance the effectiveness and cost efficiency of thrombolysis for restoration of thrombosed hemodialysis access grafts.
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