Endovascular Therapy for Arteriovenous Malformation

Transcription

1 Endovascular Therapy for Arteriovenous Malformation Wayne F. Yakes, MD Vascular malformations involving the spinal cord are technically challenging clinical entities to diagnosis and ultimately treat. Our experience in treating over 400 such lesions involving diverse anatomic locations is presented here. Experience dictates that treatment aims at cure rather than palliation. Our results and treatment modality are discussed here. Introduction. Vascular malformations constitute some of the most difficult diagnostic and therapeutic enigmas that can be encountered in the practice of medicine. The clinical presentations are extremely protean and can range from an asymptomatic birthmark to fulminate life-threatening congestive heart failure. Attributing any of these extremely varied symptoms that a patient may present with to a vascular malformation can be challenging to the most experienced clinician. Compounding this problem is the extreme rarity of these lesions. If a clinician sees one patient every several years it is extremely difficult to gain a learning curve to diagnose and how to optimally manage them. Typically, these patients bounce from clinician to clinician only to experience disappointing outcomes, complications, and recurrence or worsening of their presenting symptoms. Based on the landmark research of Mulliken, et al,1-4 a rational classification of pediatric hemangioma and vascular malformations has evolved that should be incorporated into everyone s modern clinical practice. This classification system based on endothelial cell characteristics has removed much of the confusion in terminology that is present in the literature today. Once all clinicians understand and utilize this important classification system, ambiguity and confusion will be removed and all clinicians will speak a common language. Vascular malformations are lesions that present at birth and grow commensurately with the child. Trauma, surgery, hormonal influences caused by birth control pills, puberty, and pregnancy may cause the lesion to expand and grow hemodynamically. Vascular malformations at the histologic level demonstrate no endothelial cell proliferation, contain large vascular channels lined by flat endothelium, have a unilamellar basement membrane, do not incorporate tritiated thymidine into endothelial cells, and have normal mast cell counts. They may be formed from any combination of arterial, capillary, venous, or lymphatic elements with or without direct arterial venous shunts. Vascular malformations are true structural anomalies resulting from incomplete resorption of primitive blood vessels. Work-up of a vascular malformation includes a thorough physical examination with history. Appropriate issues are the time of occurrence of the initial symptoms and

2 whether it was present at birth. Were there issues with regards to hormonal influences? Does the patient have a Nicoladoni-Branham test (whether reflex bradycardia occurs with an inflow arterial occlusion)? Color Doppler imaging is an essential tool in the work up of vascular malformations, particularly with high-flow lesions. Color Doppler imaging is also an important non-invasive method for following patients undergoing treatment. MR has proven to be invaluable in the initial diagnosis and the follow-up management of patients with vascular malformations in all anatomic locations. It is able to distinguish between high-flow and low-flow lesions. Further, it is able to determine the efficacy of therapy at long-term follow up. High-flow lesions include congenital arterial venous malformations, arteriovenous fistula, and acquired vascular lesions as well. Low-flow lesions include venous malformations, lymphatic malformations, capillary venous malformations, and mixed lesions. After the diagnosis is established, the next hurdle is to determine whether therapy is warranted. A vascular malformation team should be in place even though the Interventional Radiologist does primarily plan and direct patient s care. According to D. Emerick Szilagyi, MD, former editor for the Journal of Vascular Surgery,... with few exceptions, their (vascular malformations) cure by surgical means is impossible. We intuitively thought that the only answer of a surgeon to the problem of disfiguring, often noisome, and occasionally disabling blemishes and masses, prone to cause bleeding, pain, or other unpleasantness, was to attack them with vigor and with the determination of eradicating them. The results of this attempt at radical treatment were disappointing. 5 Indeed, of 82 patients seen in this patient series, only 18 were even deemed operable with no therapy offered to the remaining patients. Of the 18 patients operated upon, 10 were improved, 2 remained unchanged, and 6 were worse at follow up. This patient series points to the enormity of the problem posed by vascular malformations. They are best treated in centers where these patients are seen regularly. The Interventional Radiologist who occasionally evaluates a patient every year or so will have difficulty gaining a significant learning curve or have enough experience to manage these challenging lesions. All too frequently, the patient ultimately pays for the Interventional Radiologist s initial enthusiasm, inexperience, folly, and lack of necessary clinical back up. For optimal treatment, a vascular malformation team should be in place. Headed by the Interventional Radiologist, the various surgical and medical specialties function together much like a tumor board team of specialists. When patients are seen and treated regularly, experience can be gained, rational decisions can be made, and patient care is optimized. It cannot be emphasized enough that, as a group, vascular malformations pose one of the most difficult challenges in the practice of medicine. A cavalier approach will always lead to significant complications and dismal patient outcomes. In our treatment of over 400 patients, the vast majority of our patients undergo general anesthesia. In addition, in selected cases, additional Swan-Ganz line

3 monitoring and arterial line may be necessary. Pulmonary artery pressures are constantly monitored during the injection of absolute ethanol. During a procedure we rarely treat patients with greater than 0.5 ml/kg body weight total dose. Depending on how to access the nidus of the high-flow or low-flow lesion will determine if transvascular approaches or direct percutaneous puncture approaches will be utilized. In our practice, patients are treated with 98% ethyl alcohol as the embolic agent. This is our preferred agent of choice. As has been published by several authors, the use of Ethibloc, glue, coils, PVA, etc, is palliative at best. 6 In fact, many authors have reported, not only an incomplete treatment, but also recanalization at follow up.6-9 Our approach is to treat AVM s in a curative fashion, not a palliative fashion. The main reason recanalizations and neovascular recruitment phenomenon occur in AVM management is that all embolic agents do not completely destroy the endothelial cells of the AVM. Only sclerosants, in particular the sclerosant ethanol, does it the best. The endothelial cell, when it is intact during thrombosis, senses decreased oxygen tension and sends out an angiogenesis factor which stimulates neovascular formation. Further, it sends out chemotactic factors that cause a cellular infiltration to carry debris from the vascular channels. Once this occurs, the endothelial cell re-endothelializes and recanalization occurs. With the use of ethanol, the endothelial cell is denuded from the vascular wall, its protoplasm is precipitated, and there is a fracture in the vascular wall to the level of the internal elastic lamina. Because of this destruction of the endothelial cell, the permanence encountered by ethanol in treating vascular malformations is almost routine In over 400 patients, we have been able to cure peripheral arteriovenous malformations at long-term follow up in excess of 2 years and greater than 80% of the time. In arteriovenous fistula, that are congenital and not traumatic, the cure rate at the same mean follow up, is 100%. In acquired arteriovenous fistula, we re able to cure approximately 90% of the time at 2-year mean follow up. The low-flow lesions also demonstrate permanent occlusion at long- term follow up. In the world s published literature, the cure rate for brain AVM with endovascular approaches is less than 5%, and of those that are cured, it is almost always in the Spetzler-Martin grading scale of 1 to 2. The higher-grade lesions, grade 3 to 5, are almost never cured by endovascular means and require additional neurosurgery or surgical extraction to achieve cure. In the series of Frizzel and Frazier, who did a review of the last 35 years of all embolization papers published of brain AVM, a cure rate of 5% was noted.24 In our first paper utilizing ethanol as the embolic agent to treat brain AVM, our cure rate was 47%.25 Currently, our rate is greater than 60% in patients with brain AVM Grade 3, Grade 4, and Grade 5. Conclusion. Thus, we conclude that, at long-term follow up, cure of vascular malformations is a distinct possibility. Acceptable complication rates can occur with the use of ethanol. Patients are best treated in centers that manage these patients regularly. In the endovascular management of vascular malformations, ethanol demonstrates a level of permanence that is seldom encountered by other agents.

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5 14. Yakes WF, Haas DK, Parker SH, et al. Symptomatic vascular malformations: Ethanol embolotherapy. Radiology. 1989; 170: Yakes WF, Parker SH, Gibson MD, et al. Alcohol embolotherapy of vascular malformations. Semin Intervent Radiol. 1989; 6: Yakes WF, Luethke JM, Parker SH, et al. Ethanol embolization of vascular malformations. RadioGraphics. 1990; 10: Yakes WF, Luethke JM, Merland JJ, et al. Ethanol embolization of arteriovenous fistulas: a primary mode of therapy. JVIR. 1990;1: Yakes WF, Rossi P, Odink H. How I do it: Ateriovenous malformation management. CVIR. 1996;19: Yakes WF. Discussion of sclerotherapy of head and neck venous malformations. Plast Reconstr Surg. 1999;104: Berenguer B, Burrows PE, Zurakowski D, Mulliken JB. Sclerotherapy of carniofacial venous malformations: complications and results. Plast Reconstr Surg. 1999;104: Berthelsen B, Fogdestam I, Svendsen P. Venous malformation in the face and neck: radiologic diagnosis and treatment with absolute ethanol. Acta Radiol Diag (Stockh.). 1986;27: Svendsen P, Wikholm G, et al. Installation of alcohol into venous malformations of the head and neck. Scand J Plast Reconstr Surg Hand Surg. 1994; 28: Mourao GS, Hodes JE, Gobin YP, Casasco A, Aymard A, Merland JJ. Curative treatment of scalp arteriovenous fistulas by direct puncture and embolization with absolute alcohol. J Neurosurg. 1991; 75: Frizzel RT, Fisher WS. Cure, morbidity, and mortality associated with embolization of brain AVM s: a review of 1246 in 32 series over a 35-year period. Neurosurgery. 1995; 37: Yakes WF, Krauth L, Ecklund J, et al. Ethanol endovascular management of brain AVMs; initial results. Neurosurgery ;40: