Congenital vascular malformations(CVMs) constitute some of the most difficult diagnostic and therapeutic enigma that can be encountered in the practice of medicine. The clinical presentations are extremely protean and can range from an asymptomatic birthmark to fulminant life-threatening congestive heart failure. CVMs were first treated by surgeons. Complete extirpation of an CVM proved very difficult and extremely hazardous necessitating suboptimal partial resections. Partial resection could cause an initial good clinical response, but with time the patient's presenting symptoms recurred or worsened at follow-up. As catheter delivery systems and embolic agents improved, embolotherapy has emerged as primary mode of therapy in the management of CVMs.

A. Interlacing blood spaces in the primitive mesenchyme differentiate into a primitive capillary network(stage 1) B. Primitive capillary coalesce into large plexiform structures(stage 2) C. Disappearance of primitive elements and the appearance of mature vascular stems and capillary beds(stage 3) D. Focal failure of the developmental sequence with the persistence of primitive vascular structures, resulting in a CVM. Most pediatric hemangiomas are not present at birth, clinically manifest within the first month of life, and exhibit a rapid growth phase in the first month of life, and exhibit a rapid growth phase in the first year. More than 90% of pediatric hemangiomas spontaneously regress to near complete resolution by five to seven years of age. CVMs are vascular lesions that are present at birth and grow commensurately with the child. Trauma, surgery, hormonal influences caused by birth control pills, and hormonal swings during puberty and pregnancy may cause the lesion to expand hemodynamically. CVMs can be classified as high-flow (arteriovenous malformations;AVM and arteriovenous fistulae;AVF) and low flow (venous malformations;VM, lymphatic malformations;LM, and mixed lesions) malformations.

A. Venography Venography may be required in VM. This allows visualization of the abnormal venous vascular elements filled by retrograde venous injection, which may be opacified incompletely with angiography alone. B. Angiography Baseline angiography is used for planing treatment and comparison with follow-up studies to determine the efficacy of therapy of AVM and AVF. C. Color Doppler Imaging(CDI) CDI is an essential tool in the diagnostic workup of AVM and AVF. Accurate measurements of flow volumes and resistive indexes can be helpful in the initial evaluation and also are important noninvasive parameters for follow-up after therapy. High-flow CVMs are characterized as enlarged in-flow arteries and dilated draining veins. Spectral analysis of the in-flow arterial feeders demonstrates low S/D ratio, resistive index. D. MRI MRI has replaced CT in the evaluation of CVMs. MR easily distinguishes between high-flow CVMs and low-flow CVMs, and the relationship to adjacent anatomic structures, such as muscles, nerves, and organs, is easily determined. High-flow lesions demonstrate a signal void on most sequences and enlarged feeding arteries and draining veins. Low-flow CVMs have a characteristic signal intensity that is greater than skeletal muscle on both T1- and T2-weighted images, but is less than subcutaneous fat on T1 images and greater than fat on T2 images. At follow-up, MR can accurately determine residual areas of CVMs as well as those areas that have been treated. E. Whole Blood Pool Scintigraphy Whole blood pool scintigraphy with 99m-Tc-RBC is an essential tool in diagnostic workup of VM, AVM, and AVF. CVMs except lymphatic malformation are always demonstrated as hot uptake lesions at whole blood pool scintigraphy. Accurate measurements of uptake in the lesion are helpful in the initial evaluation and also are important noninvasive and cheap tools for follow-up after therapy.

Absolute indications : hemorrhage, secondary ischemic complications, and congestive heart failure from arteriovenous shunting. Relative Indications : pain, functional impairment, and cosmetic deformity, including limb asymmetry associated with extremity lesions.

A. Ethanol Ethanol induce thrombosis by denaturing blood proteins, dehydrating vascular endothelial cells and precipitating their protoplasm, denuding the vascular wall totally of endothelial cells, and segmentally fracturing the vascular wall to the level of the internal elastic lamina. The combination of all these factors causes an acute thrombosis. Alcohol embolotherapy of large complex vascular malformations should be staged for several reasons. First, a single embolization procedure may require several hours in itself, and contrast limits can be exceeded in a lengthy procedure. Moreover, serial embolotherapy reduces the risk of too extensive embolization, thereby decreasing the risk of tissue necrosis, lesion rupture, or potential complications of post-thrombosis edema. The maximum volume of ethanol used in treating patients with CVMs rarely exceeds 0.5-1.0 ml/kg body weight. Total dose exceeding these doses can lead to ethanol toxicity. B. Anesthesia With the use of intravascular ethanol, pain control is a significant problem. Anesthesiologists can aid in solving this problem and determine whether general anesthesia or intravenous sedation is required for the procedure. In patients with large AVM and AVF, as opposed to small lesions and VM, Swan-Ganz and arterial line monitoring should be performed. Pulmonary artery pressures are consistently monitored during the injection of absolute ethanol. Ethanol reaching the pulmonary artery through AVM nidus or AVF may cause precapillary spasm, pulmonary arterial hypertension, and then cardiopulmonary collapse. Once pulmonary artery pressures begin to rise, it is best to wait and not inject any more ethanol until the pulmonary pressures begin to normalize. If pulmonary artery pressures become pathologically high, the infusion of nitroglycerin, or prostaglandin E1 through the Swan-Ganz line can lower the intrapulmonary pressures. C. Arteriovenous Malformations(AVM) (Fig. 2) Detailed arteriography is performed to determine the angioarchitecture of the AVM. In treating AVMs, superselective catheter placement is absolutely essential. If the patients have had prior therapy(surgical ligation, partial resection, intraarterial coil placement, tissue adhesives embolization) or superselection is not possible, direct puncture techniques should be used. Inflow occlusion using balloon catheter, blood pressure cuff, tourniquet is not always required to induce vascular stasis to maximize the thrombogenic properties of ethanol. Inflow occlusion can reduce the total amount of ethanol, but increase the risk of complications such as tissue necrosis or proximal embolization. Multi-directional arteriograms must be performed to determine exactly the flow characteristics of the AVM and anatomy of normal vascular structure so that an appropriate volume and rate of ethanol injection may be determined. After ethanol injection, wait for 10-15 min, then arteriograms should be performed to determine if therapy is complete or further embolization is required. The amount of ethanol used in each procedure is tailored to the flow-volume characteristics of the individual lesion. After the procedure and recovery from anesthesia, patients are sent to the ICU. Postoperative management consists of steroid, anti-acid medication, fluids, and pain control.

A,B. Angiogram shows dilated feeding arteries and infiltrative arteriovenous malformations (arrows) with early dilated draining veins (arrow heads) at left foot. Note multiple small intravascular coils which were inserted at other hospital. C,D. Follow-up angiogram after several sessions of ethanol embolotherapy by intra-arterial approach or direct puncture of arteriovenous malformations shows markedly reduced arteriovenous malformations.

D. Venous Malformations(Fig. 3) Direct-puncture angiogram is performed to asses the adequacy of position for ethanol injection. Ethanol embolotherapy is directed against the abnormal venous malformed elements. If venous occlusion is desirable to prevent unwanted outflow of ethanol into normal venous structures, extrinsic tourniquets, pneumatic blood pressure cuffs, and manual digital compression can be utilized. The amount of ethanol used is equal to the flow-volume characteristics of the venous malformation compartment. Not all patients requires total obliteration of their malformation to achieve a symptomatic improvement.

A. MRI of T2-WI with fat suppression shows intramuscular venous malformations at calf area as high signal intensity lesions. B. Five sessions of ethanol embolotherapy were performed by direct puncture of venous malformations (arrows). C. Follow-up MRI shows reduced volume of venous malformations. But further several sessions of ethanol embolotherapy are necessary to treat residual lesions.

E. A-V Fistulae(AVF) Congenital and post-traumatic AVF are similar to AVMs in that they are high-flow vascular malformations. AVF is characterized by an artery connected to a draining vein without an intervening capillary bed. The natural history of AVF can be extremely varied. AVF can remain clinically silent. If the shunt through an AVF is large, hemodynamic consequences such as cardiomegaly, increased cardiac output, and intermittent bouts of congestive heart failure can occur. Vascular steal alone may cause ischemic symptoms in the tissues or organs to the AVF as well. Treatment of AVF requires complete occlusion of the AV connection. Surgical ligation are not only futile, they remove possible vascular access routes for endovascular ablative therapy. Various vascular occlusive devices, such as spring coil, detachable balloons, PVA, and tissue adhesives(IBCA) have been successful in occluding AVF. Recanalization and recurrences have been reported with the use of IBCA, and detachable balloons. Ethanol has proven extremely successful in closing renal AVF, and recurrent peripheral and neural axis AVF. F. Follow-up All patients exhibited focal swelling in the area of treated procedure. Most patients had the majority of the swelling resolved by 2 weeks. In those patients with toe, foot/ankle, and/or leg malformations, the time until the swelling resolved could last up to 3 weeks. After serial therapy, MR, Whole blood-pool scintigraphy , and/or CDI are used to document the efficacy of the therapy. CDI spectral analysis gives accurate information in treated and untreated AVM and AVF.

In patients with CVMs, complication rates greater than 10% must be expected. Complication rates are related to the tissue that are being embolized. Nontarget embolization with ethanol will lead to tissue necrosis as capillary beds of normal arteries will be totally destroyed. Therefore, it is essential that superselective catheter positioning be achieved before ethanol can be used. Venous thrombosis, skin blister, injury to adjacent muscle or other tissue is possible. Motor or sensory nerve injuries may occur as well by the swelling. Bleeding is an uncommon complication. Hematuria by the intravascular hemolysis effect of ethanol is observed more than 10% of patients. It resolved spontaneously without any problem.

When it is clear that CVMs must be treated, then embolotherapy should be employed first, whether or not surgery is contemplated. In unresectable CVMs, embolotherapy is the only therapeutic alternative. Alcohol is superior to many embolic agents because it is easy to use and induces an intense thrombosis to the level of the smallest-caliber vessels. To optimally manage these patients, a dedicated team(interventional radiologist, surgeon, anesthesiologist) should be in place.

1. Behnia R. Systemic effects of absolute alcohol embolization in a patient with a congenital arteriovenous malformation of the lower extremity. Anesth Analg 1995;80:415-417 2. Yakes WF, Parker SH, Gibson MD, Haas DK, Pevsner P, Carter TE. Alcohol embolotherapy of vascular malformations. Semin in Intervent Radiol 1989;6(3) : 146-161 3. Yakes WF, Haas DK, Parker SH, et al. symptomatic vascular malformations: ethanol embolotherapy. Radiology 1989;170:1059-1066 4. Yakes WF, Luethke JM, Merland JJ, et al. Ethanol embolization of arteriovenous fistulas: a primary mode of therapy. JVIR 1990;1:89-96 5. Finn MC, Glowacki J, Mulliken JB. Congenital vascular lesions: clinical application of a new classification. J Pediatr Surg 1983;18:894-900 6. Yakes WF. Extremity venous malformations: diagnosis and management. Semin in Intervent Radiol 1994;11(4):332-339 7. Yakes WF, Rossi P, Odink H. How I do it : Arteriovenous malformation management. Cardiovasc Intervent Radiol 1996;19:65-71 8. Rak KM, Yakes WF, Ray RL, et al. MR imaging of sympto-matic peripheral vascular malformations. AJR 1986;159:107-112 9. Doppman JL, pevsner P. Embolization of arteriovenous malformations by direct oercutaneous puncture. AJR 1983;140:773-778