Classification of Peripheral Arteriovenous and Venous Malformations



Classification of Peripheral Arteriovenous and Venous Malformations



J. Leonel Villavicencio


The three vascular systems—arterial, venous, and lymphatic—form miles of a complex seamless network of intricate vessels with specific vital physiologic functions. They intertwine, twist, and cross in different directions, continuously moving large volumes of blood and lymph. They are automatically separated from one another at birth. However, owing to obscure genetic derangements, distorted errors result in vascular malformations. After birth, these systems can maintain their fetal characteristics and produce diffuse or circumscribed clusters of vessels where arteries and veins are still connected, mixing arterial with venous blood (arteriovenous shunts) or mixed venous and lymphatic vessels as occurs in cases of malformations of venolymphatic predominance such as Klippel–Treanaunay syndrome.


The understanding of congenital vascular malformations has constituted a formidable challenge. Efforts of classification have contributed to confusion among physicians who are often bewildered by the bizarre and often grotesque presentation of congenital vascular anomalies. In 1863, and based on anatomic and pathological features (anatomopathological classification), the German pathologist Rudolf Virchow called all vascular anomalies “angiomas” and divided them into simplex, cavernosum, and racemosum. Virchow’s classification exerted a strong influence in the field of vascular anomalies during the 19th and 20th centuries.


In 1974, the Italian surgeon Edmondo Malan published the scholarly monograph Vascular Malformations (Angiodysplasias), in which he described his experience in the study and management of 535 patients with vascular malformations. Based on embryologic studies he called them angiomas (Greek angios, “vessel,” and oma, “tumor”) and classified them into predominantly venous (localized and diffuse); predominantly arterial (arterial atresia, aneurysms); predominantly arteriovenous (localized and diffuse), predominantly lymphatic: localized (cystic hygroma) or diffuse (lymphedema); and mixed malformations with arterial, venous, and lymphatic components.


Malan also considered that angiodysplasias may be either localized to an area or diffuse, involving entire extremities or the entire body. He apologized for not having included congenital lymphatic anomalies as a single isolated entity. An important observation in his classification was the introduction of the concept of “the pathological predominance of one vascular system over the others and that invariably there is a certain amount of arteriovenous leakage or shunting through arteriovenous micro-malformations.” This astute observation, made in the early 1960s, was later confirmed by the Austrian investigator H. Partsch, who injected a radioactive isotope into the arterial system and detected it in the lungs of nearly 10% of a group of patients with venolymphatic malformations such as the Klippel–Trenaunay syndrome.


The cellular growth behavior in vascular anomalies in infancy and childhood were defined by Mulliken and Glowacki in 1975. Surgical specimens were examined by autoradiography, histochemistry, and electron microscopy. Based on cell kinetic studies, vascular anomalies or birthmarks, as Mulliken labeled them, were classified as hemangiomas where there was hyperplasia and rapid endothelial activity and as malformations where cells had a normal turnover.


This latter classification has a clinical correlation as well as a biologic basis. Owing to their active endothelial activity, hemangiomas usually grow quickly and sometimes alarmingly during the first months of life, only to gradually decrease their activity, fading during the following years of life until they eventually partially or completely disappear.


Malformations are defined as lesions that usually are present at birth and remain with the patient, growing at the same rate as the patient does. This classification may be called biologic because the endothelial cellular behavior reflects on the clinical manifestations of the anomaly. This classification was the cornerstone of the International Society for the Study of Vascular Anomalies (ISSVA) classification of 1996.


Because of the complex nature of the diseases making up the spectrum of congenital vascular malformations, there have been many classifications trying to shed light into the intricate clinical presentations of these diseases. It took many more years and many more attempts at classification to understand the importance of the endothelium. Terms such as endothelioma, angioendothelioma, and hemangiopericytoma began to appear in the literature, confusing already-confused clinicians. For these reasons, a group of dedicated physicians met during the 7th International Workshop on Vascular Malformations held in Hamburg, Germany, in 1988. The result was a consensus classification known as the Hamburg Classification (Table 1). It was considered a working classification subject to further modifications. It did not include capillary malformations because at the time this type of vascular anomaly was not considered clinically significant and was considered equivalent to other vascular malformations. Capillary malformations were later included in the Denver consensus meeting in 1992 and the Seoul consensus meeting of 1996.


Tags:
Aug 25, 2016 | Posted by in CARDIOLOGY | Comments Off on Classification of Peripheral Arteriovenous and Venous Malformations

Full access? Get Clinical Tree
Get Clinical Tree app for offline access