11.1  Commentary

A false aneurysm after catheterization is suspected when there is a hematoma, especially an enlarging one, at the puncture site hours or days after the procedure. There is often significant ecchymosis of the overlying skin. There may be a bruit, but a continuous bruit is usually associated with an arteriovenous fistula. There may be pain or neuralgia, and the site is often tender. A pulsatile mass is usually palpable, but a simple hematoma overlying thearterymaygivethesameimpression.Onlyaminorityoffalseaneurysmsarediagnosed­ unequivocally by physical examination. The diagnosis of a femoral false aneurysm has become very easy with duplex ultrasound. [Q1: B]

The incidence of postcatheterization femoral false aneurysms varies from less than 0.5% to more than 5%.1 Some of the factors that increase the likelihood of false aneurysm formation include larger sheaths, longer procedure times, multiple catheter exchanges, and periand postprocedure anticoagulation. Puncture of the superficial femoral or deep femoral artery instead of the CFA is found to be associated with higher rates of false aneurysm formation. Direct manual compression after catheter removal is better than compression devices, such as the FemoStop or C-clamp. Patient characteristics that may increase the likelihood of false aneurysm formation include atherosclerosis of the punctured artery, obesity and hypertension. [Q2: B, C, D]

The potential complications of untreated false aneurysms are well known. Rupture is the most dramatic and life-threatening complication. Compression of surrounding tissues can cause pain, neuropathy, venous thrombosis, and necrosis of the overlying skin. Thrombosis of, or embolisation into, the femoral artery may occur. Infection of these false aneurysms is less common. Because of these potential outcomes, early surgical repair had been advocated in the past. However, in the 1990s, several series showed that the majority of small false aneurysms will develop spontaneous thrombosis.2–4 It is less likely to occur forlargerfalseaneurysmsorinpatientswhoareonanticoagulants.[Q3:C,D]Thrombosis may occur within days, or it may take weeks. Once thrombosis occurs, the false aneurysm is then a simple hematoma that gets resorbed slowly over time. The defect in the artery heals uneventfully in most cases.

In 1991, Fellmeth et al.5 described the method of UGCR of postcatheterization femoral false aneurysms and arteriovenous fistulas. The ultrasound transducer is used to apply downward pressure on the neck of the false aneurysm to arrest flow. Pressure is maintained until the blood in the aneurysm becomes thrombosed. After the introduction of UGCR, numerous reports were published verifying the efficacy and overall safety of this proce- dure.6–9 The typical success rate was between 60% and 90%. There were only a few published complications, including thrombosis of the underlying artery or the femoral vein from the compression, rupture during compression, rupture after successful compression, skinnecrosiscausedbyprolongedpressureontheskin,andvasovagalreactions.Therefore, UGCR was shown to be a good alternative to surgical repair or observation, and most centers made it the initial treatment method.

There are several disadvantages to the procedure. It is time-consuming, requiring an average of 30–60 min of compression. In most hands, the results are significantly poorer

for patients on anticoagulants.10 The recurrence rate is about 4–11%, but it is as high as 20% for anticoagulated patients.6 About 10% of patients cannot be treated with UGCR because they have false aneurysms that are not compressible or cannot be compressed without also collapsing the underlying artery, which would increase the chance of arterial thrombosis. For most patients, the compression is painful, and intravenous sedation or analgesia is often necessary. Some patients have required epidural or general anesthesia to allow compression. Applying compression is also very uncomfortable for the operator.

[Q4: B, C]

Various endovascular treatments have been described for false aneurysms that have failed compression. They usually require catheterization of the feeding artery or false aneurysm from a remote access site. Embolisation coils can be used to occlude the neck or to fill the cavity of the false aneurysm.11,12 Stent grafts can be placed in the femoral artery to exclude the false aneurysm, but late occlusion of the grafts is not uncommon.13 They certainly should not be the initial method of treatment. However, for false aneurysms arising from other, less easily accessible arteries, these techniques may have a role.

Because of the shortcomings of UGCR, we developed a new method of treating false aneurysms with ultrasound-guided thrombin injection.14,15 Thrombin causes the cleavage of fibrinogen into fibrin, which then polymerises into a solid. It is the final product of the coagulation cascade, and this reaction occurs naturally whenever blood clots. Thrombin has been used topically for many years to control surface bleeding in the operating room. Ourtechniqueisasfollows:Theultrasoundtransduceriscenteredoverthefalseaneurysm. Thrombin at a concentration of 1,000 U/mL is placed into a small syringe, and a 22G spinal needle is attached. The needle is inserted at an angle into the false aneurysm along the same plane as the transducer, and the tip is positioned near the center of the false aneurysm. About 0.5 mL thrombin solution is injected slowly into the false aneurysm. Within seconds, thrombosis of the false aneurysm is seen. The procedure is not painful, and patientsdonotrequireanyanalgesiaorsedation.Weallowpatientstogetoutofbedimmediately after treatment, and outpatients are sent home soon after the procedure.

So far, we have had great success with this procedure. We have treated 165 false aneurysms. Most (149) developed after groin puncture. There were also false aneurysms in six brachial, three subclavian, two radial, two tibial, one distal SFA, and one superficial temporal arteries, and in one arm arteriovenous fistula. Forty-seven patients were anticoagulated at the time of thrombin injection. It was initially successful in 161 of 165 patients. The other four (all femoral) had partial thrombosis. One of these had complete thrombosis 3 days later when brought back for repeat injection. Three had surgical repair. There were early recurrences in twelve patients who had initial successful thrombin injection. Seven were reinjected successfully at the time the recurrence was diagnosed. One had spontaneous thrombosis several days after recurrence was identified. Four had surgical repair. Overall, only 7 of 165 required surgical repair. There were three complications. A brachial artery false aneurysm had injection of thrombin directly into its neck, which caused thrombosis of the brachial artery. A femoral false aneurysm had a relatively large volume of thrombin injected and developed a thombus in the posterior tibial artery. Both of these thromboses resolved after intravenous heparin. A femoral false aneurysm with a short neck that was about 10 mm wide had partial thrombosis of the aneurysm. Further injection was not able to thrombose the remaining cavity but instead caused a tail of thrombus to

form in the SFA. The patient underwent surgical thrombectomy and repair of the aneurysm. [Q5: D]

Our results show that intra-arterial thrombosis after thrombin injection is uncommon. The high concentration of thrombin results in almost immediate conversion of the solution into a solid (thrombus) when it mixes with relatively stagnant blood. Since the neck of the false aneurysm is usually much narrower than the aneurysm cavity, the thrombus cannot enter the artery. As long as the volume of the thrombin injected does not approach or exceed the volume of the false aneurysm, which may result in forcing some of the solution out of the cavity, then the risk of native artery thrombosis should be small. It is likely to be higher when the neck is very wide. Other complications that have been reported include single cases of anaphylaxis16 and prolonged urticaria.17 [Q6: A, B, C] Repeated exposure to bovine thrombin can also lead to development of antibodies to bovine factor V, which may cross-react with autogenous factor V, causing hemorrhagic complications.18 Recently available recombinant human thrombin should be similarly effective in treating false aneurysms with fewer immunologic complications.19

Many others have also had good results with this procedure. In the largest series, the success rate is around 96% and the complication rate less than 2% (Table 11.1). Given its simplicity, efficacy, and safety, ultrasound-guided thrombin injection should be considered the initial treatment of choice for postcatheterization false aneurysms.

References

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