Arterialized venous flaps: Control of afferent arterial flow and implications for survival [Lembi venosi arterializzati: Possibilita di controllo del flusso arterioso afferente ed implicazioni sulla sopravvivenza]

In arterialized venous flpas (AVF), arterial blood reaches the flap through a vein which is anastomosed with an arterial vessel. Venous drainage comes about through one or more afferent veins. An essential requirement for this type of flap is that the arterial blood, which passes through the venous tree by inverted flow, is able to reach the capillary bed and hence the tissues, in order to ensure oxygenation and nutriment. Despite the theoretical assumptions, however, the survival of these flaps (with the exception of those described to repair minor tissue loss in the hand) is not in practice comparable to that of standard axial flaps. Their use in clinical practice has therefore been highly conditioned by the risk of failure. In particular, it has been observed that, in experimental AVF models, after termino-lateral arteriovenous anastomosis, without any other technical adjustments, the flow of arterial blood through the vein, normally able to stand low pressure levels, gave rise to excessive dilatation and consequently a hyperflow of blood. Since this was not sufficiently drained by the actual venous system, stasis ensued, to the detriment of flap survival. We have therefore designed an experimental model composed of a rectangular abdominal flap based solely on superficial epigastric veins, one of which has been anastomosed with the femoral artery, that has in turn been joined upstream of the anastomosis. This technique produces reverse arterial flow, at lower pressure through the arterialized venous tree. Flaps raised in this way have shown good survival and vitality, which has been compared with that of classis, nonreverse AVF and standard axial flaps. Another control group was composed of AVF in which arteriovenous anastomosis was performed 72 hours prior to the flap being raised (AVF with delay). The good survival of reverse AVF suggests that modulating arterial flow may reduce the problems related to stasis and ensure greater reliability of AVF raised in a single invertion rather than with delay. On the other hand, it now seems ascertained that the delay in this type of flap ensures good reliability, as demonstrated by positive outcomes recently achieved in clinical practice. Further studies are, however, warranted which better clarify the phenomena consequent to arterialization of the venous tree, at both hemodynamic and structural and ultrastructural level.