All arteriovenous malformations (AVMs) are potentially limb threatening and may be life threatening. An early, aggressive approach to AVMs is warranted to reduce and prevent the immediate risk of bleeding and the long-term risks of cardiac failure and gangrene.
Current AVM management, based on a multidisciplinary approach, can minimize morbidity and reduce recurrence by adopting a proper combination of the surgical therapy and embolo/sclerotherapy. Embolo/sclerotherapy in this context is an adjunctive therapy for conventional surgical resection, and its use has expanded the role of surgical therapy in AVM management. Treatment strategies should be based on achieving a positive balance between subsequent morbidity and treatment gain. The importance of the careful assessment of a treatment strategy before therapy is instituted cannot be overemphasized. Amputation should not be excluded, but rather treated as the last option, especially when the AVM is in an extremity and is complicated by life-threatening bleeding/sepsis and total functional loss.
Classical surgical therapy for AVM management fulfills a different role in contemporary AVM management, and it is now viewed as an aspect of total care management that also incorporates various nonsurgical therapies.
AVMs are a relatively uncommon type of congenital vascular malformation (CVM). AVMs represent a subgroup of various CVMs. They are characterized by their complicated anatomic, pathologic, physiologic, embryologic, and hemodynamic characteristics, with high morbidity and recurrence.
The majority of AVMs belong to the extratruncular (ET) form and originate from the residual remnants of developmental arrest during an early stage of embryonic life. They behave aggressively as a primitive CVM type and show a tendency to progress destructively. They retain the evolutional potential for growth. This is often represented clinically by recurrence. In contrast, the truncular (T) form of AVM, which develops at a later stage of embryogenesis, lacks this characteristic. The ET form is totally unpredictable. Various stimulations such as injury, surgical intervention, or systemic hormone effects can result in explosive growth. Improper treatment can stimulate dormant AVMs to grow rapidly. Recurrence and unbridled growth are the trademarks of AVMs. The ET form of AVM has a high recurrence rate because of its origin, from mesenchymal cells (angioblasts) at an early stage of embryogenesis.
The primary effects of an AVM lesion are compression and erosion of surrounding tissues. However, secondary hemodynamic effects due to potential arterial steal phenomena are generally more serious. These hemodynamic effects are more prominent in the T form, and depend on the degree and extent of the arteriovenous (AV) shunting associated with the lesion. In the extreme, the heart will be affected, causing high-output cardiac failure. Shunting can affect peripheral tissues with the spectrum of changes from distal ischemia to gangrene. Venous stasis dermatitis and ulcer or gangrene can be caused by venous hypertension.
The management of AVMs is the most challenging of the various CVMs: i.e., venous malformations (VMs), lymphatic malformations (LMs), hemolymphatic malformations (HLMs), and capillary malformations (CMs). (See
Table 76-1.)
Diagnosis
A precise diagnosis of the AVM, either an ET or T form, or a combined (ET and T) form based on the Hamburg classification (
Table 76-1), is of key importance in the management of AVMs. Once the lesion is confirmed as pure AVM and not a combined CVM, the accurate assessments of the extents and degrees of its hemodynamic (circulatory) and nonhemodynamic (anatomic) involvement can begin.
Various combinations of newly developed noninvasive or minimally invasive tests based on new diagnostic technologies (
Table 76-2) are now able to provide a precise diagnosis of the AVM, differentiating them from other CVMs. A combination of an MR image study, duplex ultrasonography, and Tc-99m red blood cell (RBC) whole body blood pool scintigraphy (WBBPS) is used for general CVM evaluation. Transarterial lung perfusion scintigraphy (TLPS) using Tc-99m macroaggregated albumin is also included when the lesion is located in an extremity, as it allows the shunting volume to the lung through the nidus of the AVM to be determined quantitatively. TLPS is extremely useful not only for detecting gross (macro)/micro AV (arteriovenous) shunting lesions in the extremities, but also for following the physiologic effects of the lesion.
CT-contrast studies with 3-D reconstruction can be added when the MRI does not adequately define the extent of the lesion and its involvement with surrounding structures. These are determinations that are crucial for treatment strategy. Once a diagnosis of an AVM has been established, subsequent treatment is decided upon based on local and systemic indications. Arteriographic evaluation is added at this stage, usually as a roadmap prior to treatment.
Treatment Strategy
AVMs, in contrast to other types of CVMs, should be considered for early intervention, either surgically or by embolo/sclerotherapy to arrest further progress and/or to eliminate the lesion. Because AVMs are potentially life- and limb-threatening lesions, an aggressive approach is recommended, wherever and whenever possible, regardless of the age of the patient and the extent or degree of the lesion. This approach is more aggressive than that taken in cases of other less potentially dangerous CVM lesions (e.g., VM, LM, or HLM).
The multidisciplinary CVM management team should decide whether to treat the lesion based on a minimum of at least two indications of those described in
Table 76-3. It should select the proper timings and safe treatment intervals and decide upon the treatment modalities for the primary lesion and its secondary consequences.
