Classification of congenital vascular malformations. Hamburg, 1988
A. Malformation typ e
Predominantly arterial malformation
Predominantly venous malformation
Predominantly lymphatic malformation
Predominantly arteriovenous malformation
Combined vascular malformation
B. Anatomical form (embryological subtype)
Extratruncular form
– Infiltrative, diffuse
– Limited, localized
Truncular form
– Aplasia or obstruction: hypoplasia, aplasia, hyperplasia, stenosis, membrane
– Dilation: localized (aneurysm), diffuse (ectasia)
Table 34.2
Revised Hamburg classification of vascular malformations
Affected vascular system segment | Anatomic forms |
|---|---|
Arterial malformations | Truncular forms Aplasia or obstruction Dilatation Extratruncular forms Infiltrating Limited |
Venous malformations | Truncular forms Aplasia or obstruction Dilatation Extratruncular forms Infiltrating Limited |
Arteriovenous malformations (with shunt) | Truncular forms Deep AV fistula Superficial AV fistula Extratruncular forms Infiltrating Limited |
Capillary malformations | |
Lymphatic malformations | Truncular forms Aplasia or obstruction Dilatation Extratruncular forms Infiltrating Limited |
Combined vascular malformations | Truncular forms Arterial and venous Hemolymphatic Extratruncular forms Infiltrating hemolymphatic Limited hemolymphatic |
Although relatively rare, congenital vascular malformation and fistulae can present a diagnostic challenge even in the hands of an experienced clinician or vascular technologists. Testing should focus on both arteriovenous hemodynamics using both duplex ultrasound and indirect physiologic testing modalities. Interpretation should address changes in artery and venous flow compared to the normal contralateral limb. The effect of high-volume arterial flow on venous hemodynamics and distal limb perfusion should be determined. In general, the noninvasive vascular diagnostic laboratory (VDL) can provide useful hemodynamic information for clinical decision-making information regarding the correlation of altered anatomy and physiology with patient symptoms and signs. Application of VDL testing is limited to the extremities since other imaging modalities are used to assess AVMs involving the head and trunk.
Initial Evaluation
Evaluation of the patient with a suspected congenital vascular anomaly begins with a complete history and physical examination with the most common symptoms being extremity pain and/or swelling. Typically, the patient presenting for VDL testing has the diagnosis established by the referring physician. The physical examination often can exclude the presence of a vascular malformation without direct ultrasound imaging. Most clinically significant arteriovenous malformations (AVMs) will present in childhood when a vascular birthmark, localized skin color change, overlying varicose veins, other prominent blood vessels, or, occasionally, a distinct vascular mass or tumor or enlargement of the limb (increase in length or girth) has gained the attention of a parent or a patient. It is important to point out that the classic triad of birthmark, varicose veins, and limb enlargement, associated with these anomalies, is not present in many cases. Sziylagyi et al. studied 82 patients with angiographically proven congenital vascular anomalies and AVFs, and only 57% of them demonstrated this classic triad [6].
Occasionally, it is difficult to establish a definitive conclusion with the history and physical exam, and the clinician must await further symptoms, clinical findings, or diagnostic tests before establishing a clear diagnosis. It is clear that optimal management of these conditions requires follow-up on the patients for years at times.
Birthmarks in childhood can represent true hemangiomatous lesions , and others can be superficial vascular anomalies, i.e., cutaneous capillary or superficial venous malformations, which are still commonly referred to as “ cavernous malformations .” Differentiating between these two entities and true sentinel lesions is extremely important in early childhood and usually can be done on clinical grounds alone, based upon their time of appearance, their growth rate, or lack of growth with time. Intervention is unnecessary with the former lesions. Juvenile hemangiomas may be found to have high-flow characteristics on ultrasound. Importantly, juvenile hemangiomas are true tumors, with a rapid endothelial turnover, which characteristically are discovered shortly after birth, undergo rapid early growth then spontaneously involute, usually between 2 and 8 years of age, whereas true vascular malformations, including cavernous malformations, and “sentinel” lesions overlying an arteriovenous malformation (AVM) are present at birth and characteristically maintain the same size relative to the growing child. Juvenile hemangiomas may leave an inelastic scar after involuting, but this can be dealt with later, as necessary.
Four fundamental questions would need to be answered before a prognosis and/or a treatment plan could be provided to the patient and his/her parents. Does a vascular anomaly exist? If it does, what is its location? Anatomically, what is its extent? Hemodynamically, what is its extent and effect?
With today’s technology, all these questions can be answered with noninvasive diagnostic modalities while reserving invasive studies such as venography or arteriography to intervention and treatment.
Diagnostic Evaluation
Basic Considerations
There are a few considerations that dictate how noninvasive VDL methods can be applied in diagnosing vascular anomalies. First, a basic understanding of the hemodynamic characteristics caused by vascular anomalies is paramount in order to appropriately utilize these diagnostic modalities. Second, the diagnostic capabilities and limitations of each different test must be understood when applying them. Physiologic VDL tests gauge the changes in pressure, volume, or velocity associated with a peripherally located vascular anomaly. They do not visualize the AVM or AVF as duplex ultrasound imaging would. On the other hand, physiologic VDL tests can assess the hemodynamic significance of a lesion, which duplex ultrasound cannot. Third, most of these studies have common limitations, for example, they are primarily qualitative and can be used for assessing peripherally located (extremity) vascular anomalies only. Fourth, a clinician should keep in mind that congenital and acquired AVFs differ significantly in their anatomic localization. Congenital AVFs are rarely isolated lesions; they occur more in clusters within major arterial distribution but can be even more diffuse in location and involve an entire limb segment. If they are too extensive, the VDL modalities might be capable of encompassing the entire lesion. Finally, diagnostic goals can vary considerably in different clinical settings, and this significantly affects the application of the tests. Appropriately sized cuffs will be needed for very young patients.
The diagnostic goal might be as simple as trying to determine the presence or absence of an AVM or AVF. Beyond their presence, which might be clinically obvious, the relative magnitude of an AVM or AVF’s hemodynamic significance should be evaluated. The lesion’s overall effect on the peripheral circulation should be gauged (Fig. 34.1).
Fig. 34.1
Schematic depiction of the effect of the presence of anomalous arteriovenous connection (fistulas or malformations)
This chapter will focus on presenting the various noninvasive diagnostic modalities, which a clinician in their armamentarium to appropriately diagnose, assess, and plan a management approach for patients presenting vascular anomalies. As mentioned previously, the first basic question is whether a vascular anomaly exists or not. These vascular diagnostic techniques, if used appropriately, can be valuable in ruling in or out the presence of an AVM or AVF in patients presenting with atypical varicose veins and/or birthmark, with or without limb enlargement.
Vascular Diagnostic Laboratory-Based Imaging
These involve segmental limb pressure assessment, segmental plethysmography, spectral waveform analysis, and duplex scanning. Before discussing each of these modalities, it is paramount that we understand how AVMs and/or AVFs can affect the hemodynamics of circulation in an extremity and thus affect ultrasound evaluation.
Generally speaking, an AVF represents an anomalous connection between the artery and a vein which can be a micro-AVF or a larger AVF. An AVM is a collection of anomalous micro-AV fistulas. Vascular anomalies, whether they are AVMs or AVFs, are congenital anomalies in which the anatomic defect shunts arterial blood to the venous system to varying degrees. If the connection is hemodynamically significant enough, it would lead to arterial steal when the arterial pressure decreases distally because of a substantial diversion of blood flow leading to symptoms of ischemia. These changes can be assessed with plethysmography evaluating volume changes (reflecting increased pulsatility) and duplex evaluating flow velocity (with or without flow turbulence).
Reduction of mean pressure across a vascular anomaly is largest when there is a large fistula with small or poorly developed arterial collaterals. On the other hand, if the AVF is small and/or arterial collaterals are well developed, the anomaly’s effect on circulation in this limb might be minimal. AVMs containing a number of micro-AVFs can, in combination, have the same hemodynamic significance as a single large AVF. The magnitude of arterial pressure drop across a vascular anomaly could therefore provide a fair assessment of its hemodynamic importance. A large hemodynamically significant AVF or AVM can produce substantial pressure swings, perceived as increased pulsatility, which are reflected in volume changes seen with plethysmographic evaluation of the limb [7, 8].
To understand the velocity changes associated with vascular anomalies, one must first understand what the circulation flow patterns are in a non-affected extremity. In a normal resting extremity, circulation is characterized with a low-flow, high-resistance state, which changes to a high-flow, low-resistance state during exercise. In contrast the circulation pattern, in an extremity with a hemodynamically significant vascular anomaly, is characterized with a high-flow, low-resistance pattern at rest. It is important to emphasize that although the VDL studies assess variables of pressure, flow volume, and velocity, the greatest value is in interpreting them in comparison with the normal non-affected contralateral extremity.
Segmental Limb Pressures
Segmental limb pressures are noninvasive techniques, which measure segmental systolic blood pressures along the extremity. They provide a simple, fairly accurate, reproducible, and painless assessment of blood flow through the extremity. Multiple segment cuffs can be used to detect and localize AVMs. This is particularly helpful when being compared to the cuffs at the same location along the contralateral extremity.
A vascular anomaly with hemodynamically significant impact on the blood flow to the extremity will reduce the mean pressure in the affected limb at the level and distal AVM. These cuffs measure the systolic and not the mean pressure.
Nonetheless, in an affected limb, pressure swings between systolic and diastolic pressures are increased. The systolic pressure might be elevated proximal to or at the level of the vascular anomaly. These systolic pressure elevations can be best appreciated when comparing the suspected limb to the opposite limb pressures. Compared to the contralateral limb, cuffs at or above a hemodynamically significant AVM will usually record higher systolic pressure measurement, and those below the AVM will record a normal or lower systolic pressure. The decreased pressure distal to the vascular anomaly represents a detectable degree of distal steal and pressure drop. Such differences between equivalent limb segment pressures, not within the measurement variability range, represent a hemodynamically significant AVM.
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