Angiographic Evaluation of Arteriovenous Shunting in Peripheral Vascular Diseases

Abstract

Although arteriovenous anastomoses (AVA) were first described over a century ago (4, 11), their physiologic significance and in particular, their role in vascular diseases still remain ill-defined. Situated proximal to the capillary network, the AVA usually remain completely closed, but in the presence of increased capillary resistance they open up, dilate, and shunt the arterial blood into the venous system (Fig. 1). Usually the shortcircuiting function of the anastomoses is only temporary and lasts as long as the persisting impediment in the capillary bed. Under these circumstances, their action is that of a safety valve. Their clinical role in vascular diseases, although suspected for some time, was not demonstrated until the early part of 1950, and then mostly by a few European investigators (1, 6, 7, 9, 10). Serial arteriography was primarily instrumental in renewing interest in the role of AVA in clinical disorders. Under normal conditions their demonstration directly by arteriography is practically impossible. Presence of AVA is assumed always in directly when there is premature visualization of veins. The factors governing the interplay between the capillary bed and the AVA are poorly defined. A better understanding of such factors may be helpful in the management of the vascular disturbances secondary to arteriovenous shunting. The present investigation was undertaken to evaluate the role of arteriovenous anastomoses in the genesis of some peripheral vascular disorders of the lower extremity. Methods and Material This study is based on 593 femoral arteriographic examinations performed in 410 patients. The angiographic technic was essentially that described previously by one of the authors (2, 3). General anesthesia was administered in almost all cases. In only a few rare instances was local anesthesia employed instead. Irrespective of the type of anesthesia, preanesthetic medications were comprised of a hypodermic injection of meperidine hydrochloride (Demerol) (100 mg), atropine sulfate (0.43 mg) or ethyl phenothiazine hydrochloride (Phenergan) (25 mg), and secobarbital (Seconal) (100 mg) administered one hour prior to the procedure. The actual anesthesia consisted of intravenous injection of thiopental sodium (Pentothal), halothane (Fluothane), and nitrous oxide. These anesthetics were supplemented by oxygen and succinylcholine chloride (Anectine), the latter being administered thirty to sixty seconds immediately preceding the injection of the contrast medium. The total average duration of the anesthesia ranged from fifteen to twenty minutes. The actual technic included a percu taneous puncture of the common femoral artery with a No. 17 gauge spinal needle with a short bevel, directed cephalad. In about 25 per cent of the cases, simultaneous bilateral arteriography was carried out. The contrast medium employed was 50 per cent sodium diatrizoate (Hypaque), injected manually in all instances. Thirty milliliters were necessary for good visualization of the entire lower extremity.