Effect of vascular augmentation on the haemodynamics and survival area in a rat abdominal perforator flap model

A major drawback of the DIEP flap is the compromised venous drainage in the distal area, which is the rationale behind the creation of additional venous anastomoses for better flap survival. Although venous congestion is defined as an increase in the venous pressure, the effect of vascular augmentation on the venous pressure has not been elucidated. We investigated the effects of arterial supercharge and venous superdrainage on the venous pressure and the flap survival area in a rat abdominal perforator flap model. An abdominal perforator flap was raised in each of 30 Wistar rats, with the contralateral superficial inferior epigastric artery (SIEA) and vein (SIEV) isolated for pressure measurements. The changes in the SIEV pressure were recorded while proximal sites of these vessels were opened and closed. Thereafter, the animals were divided into three groups: a control group (n=10, both the SIEA and SIEV were ligated), an enhanced arterial inflow (EAI) group (n=10, the SIEA was left intact) and a supplemental venous outflow (SVO) group (n=10, the SIEV was left intact). The flap survival area was determined 7 days after surgery. The SIEV pressure without vascular augmentation was only 13.2+/-5.9 mm Hg. Compared with the control group, the flap survival area was significantly larger in the EAI group, but not in the SVO group. An extremely high venous pressure was noted when the SIEA was opened and the SIEV was occluded, but there was great variation among the individual animals (range: 21.2-79.6 mm Hg). The necrotic area in the EAI group correlated well with the SIEV pressure (r=0.861). These findings indicate that the major factor contributing to distal necrosis in this rat perforator flap model is arterial insufficiency rather than venous congestion. The results suggest that, as long as the arterial inflow is secure, the venous pressure is a reliable parameter for deciding the necessity of venous superdrainage.