eMedicine Specialties > Vascular Surgery > Medical Topics

Arteriovenous Malformations

Author: Steven L Lee, MD, Chief, Pediatric Surgery, Department of Surgery, Kaiser-Permanente, Los Angeles Medical Center
Coauthor(s): Devin P Puapong, MD, Fellow, Division of Pediatric Surgery, University of Oklahoma Health Sciences Center; Jeffrey J DuBois, MD, Consulting Staff, Division of Pediatric Surgery, Kaiser Permanente, North Sacramento Medical Center
Contributor Information and Disclosures

Updated: May 18, 2009

Introduction

Background

Vascular anomalies are among the most common congenital abnormalities observed in infants and children. Unfortunately, these lesions are also among the most confusing and misunderstood conditions, largely because of a history of inconsistent terminology used for classification. Commonly accepted names have been based on external appearance, such as strawberry nevus^1,2 cherry hemangioma, and port-wine stain,^3,4 or based on histology, such as capillary hemangioma, cavernous hemangioma,⁵ and arteriovenous fistula. However, lesions with a similar appearance may have markedly different growth patterns; conversely, lesions that are biologically identical may differ greatly in external appearance because of the location and depth of the lesion. Thus, the most clinically applicable and simplest classification scheme is based on the biological activity of the blood vessels contained in these lesions.

Pathophysiology

The varied origins of vascular tumors include true neoplastic growth, structural malformations, and hamartomatous transformations. The specific underlying biologic process forms the principal foundation of Mulliken and Glowacki's classification of this broad class of lesions.⁶

The rapidly progressive nature of hemangiomas intimates a neoplastic process; however, the precise point in fetal, embryonic, or postnatal development that gives rise to hemangiomas remains elusive. Whether hemangiomas represent embryonic mesodermal rests or arise de novo secondary to the activation of some angiogenic signaling is uncertain. The similarity between the proliferative phase of wound healing and the growth of hemangiomas suggests a prominent etiogenic role of disordered angiogenesis as the precipitating cause of hemangiomas. Furthermore, the increased numbers of mast cells in hemangiomas, through their production of heparin, influences the migration of capillary endothelial cells. Finally, the in vitro identification of selective steroid inhibition of angiogenesis through heparin binding supports the clinical experience of hastened regression with steroid therapy.

By comparison, vascular malformations represent abnormal embryonic and fetal morphogenesis during the retiform stage of development of endothelial channels (approximately day 48 of human embryogenesis). As such, these lesions are neither neoplastic nor proliferative; rather, they grow commensurate with the child. Vascular malformations are best characterized by their principal cell type, the degree of blood or lymph flow (which may influence clinical symptoms), and the structures involved. Coincident with their underlying dysmorphogenic nature, these lesions may involve elements of different vascular channels.

Frequency

United States

Hemangiomas are the most common benign tumor observed in infancy, occurring in approximately 10% of white infants. These lesions are observed more commonly in premature infants weighing less than 1000 grams (prevalence as high as 30%). Capillary vascular malformations occur in 3 per 1000 infants.

Mortality/Morbidity

• Hemangiomas: Complete involution occurs in 70-90% of patients; however, minor atrophic scars or residual ectatic vessels may remain. In the remaining 10-30% of patients, residual, baggy, atrophic skin; excess fibrofatty tissue; and even severe disfigurement may develop. Hemangiomas may also occur in areas where vital structures are compressed (see Complications).
• Vascular malformations: These lesions do not improve or resolve with time (see Complications).

Race

• Hemangiomas are less common in African American and Asian infants.

Sex

• The female-to-male ratio for hemangiomas is 3:1. The female-to-male ratio for vascular malformations is 1:1.

Age

• Hemangiomas: The infant is healthy but develops a red lesion during the first few weeks of life. The lesion continues to grow for 6-18 months and then reaches a plateau. Spontaneous involution occurs, which may last for a number of years.
• Vascular malformations: All are present at birth. The lesion grows proportionately with the child and is permanent.

Clinical

History

• Hemangioma
  • Parents often describe a small red dot appearing during the first few weeks of life. Initially, parents may mistake this lesion for a scratch that does not heal. The lesion then grows disproportionately fast compared with the child.
  • Hemangiomas exhibit spontaneous involution, but this process may continue for years. By the time the patients are aged 5 years, 50% of all hemangiomas resolve; by age 7 years, 70% resolve.
  • A residual skin deformity, such as excess fibrofatty tissue or cutaneous telangiectasia, may persist.
  • Those hemangiomas that show signs of involution by age 3 years have better cosmetic results, whereas lesions that are ulcerated always leave residual scars.
  • The head and neck area is involved in 60% of cases, followed by the trunk and then the extremities.
  • Multiple hemangiomas occur in as many as 20% of patients.
• Vascular malformations
  • These lesions always are present at birth. They may be subtle at first, but the color does not fade and often darkens.
  • The growth of vascular malformations is proportionate to the growth of the child and never extends beyond its initial boundaries.
  • Capillary vascular malformations (port-wine stain) roughly follow sensory nerve distribution.^3,4
  • Venous malformations may not be clinically evident at birth but become more evident as the child ages.
  • Aching pain has been associated with extremity lesions.
  • Patients typically have a strong family history of varicose veins.

Physical

• Hemangioma
  • Serial physical examinations reliably distinguish between hemangiomas and vascular malformations.
  • The key feature for hemangioma is disproportionate growth compared to the child.
  • Superficial hemangiomas are characterized by a bright strawberry-red pigmentation.
  • Deeper hemangiomas appear as purple- or blue-pigmented lesions.
  • Rapid growth occurs over the next 3-6 months.
  • Plateau and cessation of growth usually occur when patients are aged 6-18 months.
  • Involution occurs over years. Involution is often preceded by a graying appearance and softer tissue turgor of the lesion.
• Vascular malformations
  • Capillary vascular malformations are initially pale with normal overlying skin texture but may darken as the patient ages.
  • Nodularity and a darker purple pigmentation also may occur in adulthood because of increasing dilation of the dermal vessels.
  • Venous malformations become more evident as the child grows.
  • These malformations gradually dilate and may cause distortion of facial features.
• Arteriovenous malformations may appear similar to venous malformations. In addition, they may demonstrate increased warmth, an audible bruit, a palpable thrill, or visible pulsations. Hypertrophy of the involved limb or structure is more common with arteriovenous malformations than with simple venous malformations.

Causes

• Hemangioma
  • Hormonal influence is suggested by the 3:1 female-to-male ratio.
  • The mechanism by which angiogenesis is stimulated and then turned off is not known.
• Vascular malformations
  • Capillary vascular malformations possibly occur because of a lack of proper sympathetic vasomotor control.
  • Venous malformations are due to errors in development of the venous system and may result in hypoplasia, hyperplasia, and aplasia of the deep and superficial systems.

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