Management of Low-Flow Vascular Malformations

The goal of sclerotherapy is to obliterate abnormal channels by damaging the endothelium, thereby resulting in subsequent inflammation and fibrosis. Venous malformations (VMs) are caused by abnormal development of the vein wall, with thinning and asymmetric disruption of the smooth muscle layer of the vein in association with endothelial cell abnormalities. This results in progressive, often asymmetric, dilation of the affected channels. Associated absence or insufficiency of valves in the conducting veins contributes to swelling. Affected channels become progressively enlarged, and the resulting stagnation of blood causes thrombosis, swelling, and pain. Most VMs undergo a continuous cycle of spontaneous thrombosis and thrombolysis. Calcification of thrombi results in formation of phleboliths. Symptoms and signs include blue or purple cutaneous lesions, swelling with dependency or effort, pain, deformity, and consumption coagulopathy. Pulmonary embolism can occur, especially when the conducting venous channels are malformed.

The angioarchitecture of VMs includes focal ( Fig. 17.1 ), multifocal ( Fig. 17.2 ; also see Fig. e17.1 ), and diffuse forms ( Fig. 17.3 ; also see Fig. e17.2 ). The degree to which the lesion communicates with adjacent conducting veins is the key factor in planning treatment. VMs with minimal communication can be considered “sequestered,” whereas those with free drainage are confluent or “nonsequestered” (see Fig. 17.3 and Fig. e17.2 ). Focal lesions may be intramuscular, cutaneous, or mucosal and usually consist of collections of abnormal interconnecting channels or spaces that are sequestered or drain through fairly small channels to normal adjacent conducting veins. This type of lesion is characterized by focal pain or a sensation of fullness with dependency, after exercise, or on arising in the morning (due to stasis). These lesions are easily and effectively treated by injection of sclerosant.

Diffuse VMs involve multiple tissue layers, usually including muscle, subcutaneous fat, skin, and sometimes bone. In diffuse lesions, the malformed veins are nonsequestered and communicate directly with the main conducting veins, which are frequently also abnormal. Diffuse VMs are difficult to treat effectively because injected sclerosant can directly enter the circulation and potentially cause deep venous thrombosis, pulmonary embolism, or systemic effects of ethanol. Recanalization is also more likely than after sclerotherapy for nonsequestered lesions. Some patients with diffuse VMs have focal eccentric varices that can exert a considerable mass effect on adjacent structures. These varices can be obliterated by endovascular treatment.

Multifocal lesions are most commonly seen in familial forms of VM, including blue rubber bleb nevus syndrome (see Fig. 17.2 and Fig. e17.2 ), mucocutaneous familial VMs, glomuvenous malformation, and Maffucci syndrome.

Lymphatic malformations (LMs) result from regional maldevelopment of lymphatic channels and include cystic and channel-type anomalies. Cystic LMs are generally classified into three groups: microcystic (cystic components <1–2 cm diameter), macrocystic, and combined forms. Macrocystic lesions are most common in the neck, axilla, and pelvis ( Fig. 17.4 ). LMs are frequently combined with cutaneous capillary malformations (capillary-lymphatic malformations [CLMs]) and anomalies of conducting venous channels (LM with venous dilation, lymphatic-venous malformations, or capillary-lymphatic-venous malformations [CLVMs]). Generally, LMs manifest either as focal mass lesions (macrocystic) or as diffuse tissue swelling or overgrowth. Unlike VMs, they do not expand with the Valsalva maneuver but rather expand or swell intermittently, especially in association with systemic viral illness. Swelling can occur acutely as a result of infection or bleeding into the lesion. Bleeding is presumably due to either adjacent abnormal venous channels or rupture of small arteries, frequently seen in the septa. Sepsis is most frequently a problem with lesions close to the alimentary tract (e.g., face, pelvis). Cutaneous extensions of LMs are manifested as vesicles that may leak clear, bloody, or chylous fluid. Diffuse and multifocal LMs (generalized lymphatic anomaly) are composed of incompetent lymphatic channels, often associated with chylous reflux and leaks. Life-threatening chylothorax or chylous ascites may develop in patients with generalized lymphatic anomaly. Gorham syndrome (vanishing bone disease) is a type of CLM associated with increased osteoclastic activity and progressive osteolysis of affected bone, most often in the shoulder and pelvis.

Magnetic resonance imaging (MRI) is the best technique to confirm the diagnosis and extent of low-flow vascular malformations. VMs and LMs are hyperintense on fluid-sensitive sequences and do not have fast-flow components on gradient-recalled echo sequences. VMs enhance inhomogeneously, whereas LMs typically show minimal or rim enhancement. Arteriography is not routinely necessary.

Indications

Endovascular or percutaneous treatment is warranted in patients with significant symptomatology not well controlled by conservative treatment. For VMs, standard nonoperative treatment includes use of graded elastic compression garments (for limbs) and aspirin or anticoagulation. Indications for invasive treatment include pain secondary to swelling, a mass effect resulting in functional impairment (e.g., interference with ambulation, breathing, swallowing, speech), and disfigurement. For macrocystic LMs, sclerotherapy is now the preferred treatment over resection. Indications include pain, recurrent infection or bleeding, and a significant mass effect in the presence of macrocysts on imaging.

Contraindications

Pulmonary hypertension and atrial septal defects are contraindications to sclerotherapy for VMs unless the malformation is completely sequestered from the venous circulation. Relative contraindications include diffuse involvement of a closed space, such as the orbit or a muscle compartment (because of the risk of compartment syndrome), confluent or nonsequestered VMs, and severe consumption coagulopathy. The latter can often be corrected or improved with use of anticoagulants for 2 weeks before treatment. In patients with vascular malformations involving or adjacent to the airway, precautions for airway protection must be taken. Patients who have had cardiovascular complications from ethanol should not receive this agent again. Those with lesion-related neuropathy may be made worse by sclerotherapy.

Equipment

Low-flow vascular malformations are best treated in an angiography suite with road-mapping capability and anesthesia support. Ultrasound equipment with high-frequency probes and sterile probe covers and gel is useful. An automated tourniquet system with sterile cuffs is important for control of flow in some VMs of the limbs. Sclerosants include 95% to 98% ethanol, 3% sodium tetradecyl sulfate (STS), morrhuate sodium, ethanolamine, and bleomycin for VMs, and doxycycline, OK-432, bleomycin, or ethanol for LMs. Ethiodol or Lipiodol can be used to opacify sclerosants with minimal dilution. An agent that combines ethanol and ethyl cellulose for greater viscosity has been developed but is not yet clinically available. Useful needles include angiocatheters, 21-gauge single-wall needles, and 25- and 27-gauge butterfly needles. Plastic connecting tubes and three-way stopcocks are useful for hand-injected imaging. If oily contrast medium is used, plastic stopcocks must be checked for compatibility (see Fig. e17.2 ).

Fig. e17.1, Long-term outcome after ethanol sclerotherapy of massive focal nonconfluent venous malformation (VM). (A) Axial short T1 inversion recovery (STIR) image of pelvis in an infant who was unable to sit shows intramuscular and subcutaneous VM without dilated regional veins. (B) Radiograph taken after injection of contrast medium shows interconnecting blood-filled spaces without obvious drainage. Patient underwent several sclerotherapy sessions with ethanol. (C) Axial STIR image of pelvis at 15 years of age shows excellent persistent response to sclerotherapy. (D) Roadmap image of contrast injection before sclerotherapy at 15 years of age shows a lobulated lesion without venous drainage.

$Fig. e17.2, Sclerotherapy of a confluent venous malformation (VM) of chest wall. The patient, an adolescent boy, complained of severe pain in the wall of the right side of the chest. Axial (A) and coronal (B) short T1 inversion recovery images of thorax demonstrate extensive VM involving right ribs, intercostal muscles, and subcutaneous tissues. Note dilated intercostal veins. (C) Coronal computed tomography image, bone window, shows rib involvement. Pathologic fracture was identified on another image. (D) Sonographic image shows large channels in multiple tissue layers making up malformation. (E) Percutaneous venogram shows one of large venous sacs draining into dysplastic intercostal veins. (F) Percutaneous venogram in another space after endovenous laser therapy (EVLT) shows persistent drainage into large intercostal vein. (G) Percutaneous injection to dilute N -butyl-2-cyanoacrylate (NBCA) to close venous outflow. (H) Injection of 3% sodium tetradecyl sulfate foam in same compartment demonstrates retention of sclerosant within saccular part of malformation, without filling draining vein. (I) Radiograph taken after treatment of several compartments, using a combination of EVLT, outflow occlusion with NBCA, and foam sclerotherapy.$

Technique

Vascular Malformations

Anatomy and Approach

Sclerotherapy is performed by direct percutaneous cannulation of vascular channels, usually with a simple needle. Previously obtained MRIs are used to determine the location and extent of the lesion and are available in the procedure room to help plan the percutaneous access. Sonographic guidance of needle placement is useful (see Fig. 17.1B ). MRI guidance is feasible and may be advantageous for deep lesions not easily seen with sonography. Small localized lesions can be injected with detergent sclerosants under regional anesthesia. Patients with extensive VMs and those undergoing ethanol sclerotherapy are anesthetized and pretreated with corticosteroids, and have a Foley catheter placed. Patients undergoing sclerotherapy for VMs must be kept well hydrated to compensate for the hemolysis caused by the sclerosant.

Technical Aspects

Affected limbs are widely prepared to permit observation of the skin and placement of a peripheral intravenous cannula and tourniquet or other occlusion device.

Compression of proximal veins is useful to distend the malformation before cannulation. The abnormal channels or spaces are cannulated with a needle after localization by either palpation or sonography. After obtaining blood return, contrast medium is injected into the lesion, followed by sclerosant. The process is repeated until the selected components of the malformation are all injected.

Contrast medium is injected, usually with imaging by digital subtraction radiography, to exclude arterial cannulation or extravasation, assess the nature of the lesion and its drainage, determine how much of the lesion is accessed, and calculate how much liquid is necessary to displace the blood into the draining vein. If possible, blood is displaced from the malformation. The appropriate sclerosant drug is then injected. The initial volume injected is less than the amount of contrast medium required to opacify the draining vein. Ethanol should not be used in lesions adjacent to major nerves or cutaneous lesions or in confluent or nonsequestered venous channels without some form of outflow control. The total volume of ethanol injected in one session should be less than 0.5 mL/kg or 40 mL. The volume of 3% STS should be kept below 0.5 mL/kg or 20 mL per session. STS can be diluted with normal saline (e.g., 0.5%–1% STS) for injection into cutaneous lesions.

Sclerosing agents may be opacified for fluoroscopic guidance. Detergent sclerosants can be mixed with either oily or water-soluble liquid contrast. Oily contrast medium (Ethiodol or Lipiodol) added in a 1:10 to 3:10 ratio (contrast to sclerosant) results in minimal dilution and, when combined with detergent sclerosant and air mixed through a three-way stopcock, produces relatively stable foam. The injection of opacified sclerosant should be observed by fluoroscopic subtraction (road map); injection must be stopped if extravasation or arterial penetration is seen. Once the sclerosant reaches a small outflow vein, injection should be stopped for a few minutes to allow occlusion of the outflow. Additional opacified sclerosant is injected until the lesion is completely filled as shown by fluoroscopy. With nonopacified sclerosant, roadmap imaging shows washout of previously injected contrast or negative opacification (see Fig. 17.1F ). Control of minor documented venous drainage to minimize egress of sclerosant can be accomplished in the head and neck by manual compression, and in the limbs by manual compression or tourniquets. A sterile automated orthopedic tourniquet inflated to a pressure less than mean arterial pressure can be used in the limbs. In lesions with significant venous drainage (confluent VMs), permanent outflow occlusion—accomplished by placing coils or tissue adhesive at sites of communication between the malformation and adjacent conducting veins—is useful in retaining the sclerosant in the VM and minimizing the risk for pulmonary embolism or cardiovascular reaction to the sclerosant (see Fig. e17.2 ). When sclerosing VMs of the extremities, a peripheral intravenous line should be placed in the affected limb to document venous patency before and after treatment and to infuse heparinized saline during sclerotherapy.

Sclerotherapy for superficial vascular malformations is performed with unopacified (sometimes diluted) sclerosant, with observation of skin color rather than the fluoroscopic image. The injection must be terminated when ischemic changes such as pallor or duskiness become evident. Applying cold sterile saline onto the surface of the skin to induce local vasoconstriction seems to minimize damage.

A double-needle technique in which a venous channel is cannulated with two needles, one for injection and one to release blood and excess sclerosant, has been proposed for added safety (see Fig. 17.3 ).

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