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| Pseudoaneurysm by Brandie James |
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Abstract
A pseudoaneurysm is a fibrous containment of arterial contents after the arterial wall has been disrupted. There are several causes that amy produce a pseudoaneurysm, the most common being penetrating trauma. False aneurysms can be diagnosed clinically and sonographically. Treatment methods offered include surgery, Ultrasound Guided Compression Repair, and Ultrasound Guided Thrombin Injection. Results are overall positive, but vary with each method being used. |
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Key Words
pseudoaneurysm, PSA, UGCR, Thrombin-injection, False aneurysm |
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Introduction
A pseudoaneurysm, also termed a false aneurysm, is a leakage of blood from an artery into the surrounding tissue with persistent communication between the originating artery and the terminating blood filled cavity. The leakage can result from an artery being punctured during a diagnostic test such as a cardiac catheterization or an arteriogram, but may also occur in a surgical graft. Some pseudoaneurysms resolve themselves while others require repair to prevent hemorrhage, an uncontrolled leak, by ultrasound guided compression repair or thrombin injection, and even surgical treatment.
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Body
A false aneurysm is a contained rupture through all three layers, intima, media and adventica, of the arterial wall. The wall of the pseudoaneursym is composed of fibrous tissue. When these exist for a prolonged period of time, the surrounding tissue may mature and have resemblance to the arterial wall. Although there are many sites where a pseudoaneurysm may occur, the most common site is the common femoral artery.
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Numerous factors are responsible for the development of a false aneurysm. Pseudoaneurysms result from 0.5 to 2% of procedures which require catheter puncture of the femoral artery, or at the anastomoses of arterial bypass grafts/ dialysis access fistulas or following direct trauma to the artery. They may also result from arterial wall infection or even an overaggressive endarterectomy. Another risk factor for their development may be deeply lying arteries due to body habitus. Pseudoaneurysms are most often seen after cardiac catheterization. An experienced drug abuser who has exhausted other access sites and have an injection error wherein the artery is entered rather than the vein may also cause a pseudoaneurysm. They are seen more frequently in patients who are anti-coagulated, are on anti-platelet medications, or in whom large caliber catheters were used. Low arterial entries during angiography may also predispose to this complication. |
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Diagnosis of a pseudoaneurysm can be detected by physical examination or sonographically. Two essentials of a clinical diagnosis would be a pulsatile femoral mass and back pain (in case of retroperitoneal false aneurysm). Since pseudoaneurysms are acute expansions they are often moderately tender. It is often possible for an experienced examiner to distinguish this lesion on physical examination from a bland, simple hematoma through which a normal femoral pulse is transmitted, in that the pseudoaneurysm is pulsatile in a radial fashion when the lateral edges of a lesion are palpated between the fingers. The diagnosis of a retroperitoneal false aneurysm is more difficult; therefore, patients are more likely to present with symptoms of back pain as the retroperitoneal false aneurysm enlarges or ruptures. When a femoral pseudoaneurysm is diagnosed, a search for others should be undertaken. Most femoral artery aneurysms are bilateral, and around 15% to 20% will have associated aortic false aneurysms
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A more accurate and definitive diagnosis can be obtained by ultrasound imaging. The diagnostic accuracy of duplex sonography is above 95% for pseudoaneurysms. Pseudoaneurysms are cystic structures on gray scale images and can be easily mistaken for cyst. They will tend to have some thrombus deposition within them. Color Doppler-imaging reveals an almost classic appearance of swirling motion or color “ying-yang” sign of blood in the perivascular mass. When examining a pseudoaneurysm, the sonographer should always evaluate the presence and location of false aneurysm. A measurement should be obtained in anteroposterior and transverse planes. The position of the connecting tract, or neck, should be identified and measured. The waveforms within the pseudoaneurysm have varied appearances depending on the location of the Doppler gate. The duplex sonographic finding of a “to-and-fro” waveform is typically detected in the flow channel between the perivascular collection and the native vessel. The “to” component is due to blood entering during systole as expansion occurs in the pseudoaneurysm. Often, a high-velocity scale is needed for detection since the flow in the channel is of a very high velocity. The “fro” component is seen during diastole as the blood stored in the cavity is ejected back into the artery. The “fro” component is more prominent if the pseudoaneurysm expands efficiently and if there is a wide pulse pressure between systole and diastole.
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| There are several complications of pseudoaneurysms. These masses can gradually or abruptly increase in size. Some large pseudoaneurysms can compress a nerve sufficient to cause neuralgia, or an adjacent vein, which can reduce venous outflow from the extremity. They may also cause a distal embolization, or even go on to rupture. Arterial punctures can result also in arteriovenous fistulas, which may be separate from, or in association, with a pseudoaneurysm. |
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| Treatment of pseudoaneurysms should be individualized according to the characteristics and severity of the lesion as well as the patient’s status. Studies have shown that as many as 89% of untreated pseudoaneurysms resolve in 5 to 90 days. However, no Duplex criteria has been shown clearly to be useful in predicting which pseudoaneurysms will resolve without treatment. Pseudoaneurysms that are very large or expanding, especially in patients who require ongoing anticoagulation, should be treated. For symptomatic pseudoaneurysms, Duplex- guided compression therapy or thrombin injection can be safely done. Atypical or deep pseudoaneurysm configurations or pseudoaneurysms that have not responded to compression therapy or thrombin injection may require surgical repair. |
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| Duplex- guided compression therapy has proved effective for treating pseudoaneurysms. During ultrasound guided compression repair, the neck ,or tract, of the pseudoaneurysm is compressed by an ultrasound transducer until there is no blood flow detected in the pathway. Compressions, only lasting up to one hour, are usually applied in ten minute time intervals . Color flow imaging confirms compression of the neck and patency of the artery and vein. During the 1990s, this method alone was the initial treatment of choice for pseudoaneurysms. However, there are several disadvantages to this technique, including patient and technologist discomfort and long procedure times. It is more difficult with atypical or non-compressible pseudoaneurysms or when patients need to remain anticoagulated. Absolute contraindications are skin necrosis and signs of local infection. |
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More recently, since 1996, Duplex guided thrombin injection has been shown to be safe and effective. During Thrombin-Injectiuon a needle is used to inject a small amount of thrombin into the pseudoaneurysm causing immediate thrombosis. Several methods of thrombin injection are used. Thrombin injection with a 21- gauge needle is most commonly used on conjunction with saline injection to visualize the tip of the needle; however, scoring the needle or injecting a small amount of thrombin from the needle tip may also aide in visualization. Variations in the technique include thrombin dose, single or double syringes, and monitoring of the patient. Patients typically receive 500 to 1000 units of bovine thrombin after the echogenic needle is visualized within the cavity. Most injections occur in a monitored setting, and at least two personnel are present to allow visualization and injection of the pseudoanurysm. There are several potential benefits to this technique. The rapid thrombosis of the pseudoaneurysm is tolerated more by the patient than the often long and painful compression time associated with compression therapy. It also avoids technologist discomfort and prolongs use of ultrasound equipment. In addition, success rates may be superior to compression, decreasing the need for repeating study, treatment, or surgical intervention. Contraindications are similar to those for compression therapy, and pseudoaneurysm with skin necrosis or signs of local infection are best treated surgically. Compression and thrombin injection are not recommended for pseudoaneurysm associated with by-pass grafts because there is likely to be an underlying defect in the graft that will require surgical repair.
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Conclusion
Pseudoaneurysms are a disruption of all three arterial walls usually caused by a penetrating trauma. They are diagnosed clinically and easily with ultrasound Color Duplex proving a swirling motion within the cystic mass. Ultrasound is also used in treatment options including ultrasound- guided compression and ultrasound- guided thrombin injection. Within the past century, diagnosis and treatment options for pseudoaneurysms have greatly improved with the use of ultrasound.
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Resources
Ernst, Calvin B M.D. and James C. Stanley, M.D, eds. Current Therapy in Vascular Surgery. St.Louis: Mosby, 1995.
Dean, Richard H. and James S.T. Yao, eds. Current Diagnosis and Treatment In Vascular Surgery. Boston; Appleton & Lange,1995.
Kurtz, Alfred B. and William D. Middleton. Ultrasound: The Requisites. New York: Mosby, 1996.
Polak, Joseph F. Peripheral Vascular Songraphy. Baltimore: Williams &Wilkins,1992.
Rumack, Carol M.Wilson, Stephanie R. and Charboneau, William J. Diagnostic Ultrasound 2nd ed. Philadelphia: Mosby, 1998.
Strandness, Jr. M.D. D. Eugene Duplex Scanning inVascular Disorders.Philadelphia; Lippincott Williams & Wilkins.2002.
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Created by: Brandie James on September 19,2002:)
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Copyright CVTC 2003. All Rights Reserved.