Biological Maintenance of Distal Vein Arterialization

Abstract

Eleven weeks after surgery, a fine microvessel network was seen in the feet of patients with arteriosclerosis obliterans treated by distal vein arterialization. A possible mechanism for establishment of blood flow to, and biological maintenance of, the graft in the foot, in relation to oxygen consumption rate during walking was investigated, using Krogh’s tissue cylinder model. Our calculations showed that the increase in oxygen consumption rate of the muscle when patients walked would reduce the size of the oxygen front in the tissue cylinder, thus producing small, transient hypoxic regions in skeletal foot muscle. Such muscle hypoxia, although localized, could stimulate synthesis of vascular endothelial growth factor and facilitate angiogenesis in the grafted tissue. The architecture of fine microvessel networks observed in the foot by angiography seems consistent with this supposition and, moreover, suggests that the reinstatement of blood vessel networks in the foot tissues after grafting is supported by “normal” biological mechanisms.

Estimation of VO2 SM (Skeletal Muscle) from VO2WB (Whole Body)

The VO₂ SM has been described only partially, while the oxygen consumption rate for the human whole body and VO₂ WB at rest and during exercise have been well studied. For estimation of VO₂SM during slow and fast walks, numerical estimation was required from available data on VO₂WB during exercise. VO₂WB in a man weighing 70 kg is 250 ml min⁻¹ at rest, 700 ml min⁻¹ at a mild walk (4.0 km h⁻¹) and 1,400 ml min⁻¹ at a fast walk (5.6 km h⁻¹) [12]. The contribution of VO₂SM to the VO₂WB is 25 % at rest [13] and increases in proportion with the increase in work load of the whole body. Therefore, the following relation is given. VO₂SM ratio to VO₂WB (%)  =  25  +  (VO₂WB  –  250)  ⋅  (80  −  25)/(4,600  −  250). The contribution ratio of VO₂SM to VO₂ WB is 30.7 and 39.5 % for 4 km and 5.6 km h⁻¹ walks for 70 kg body weight, respectively. VO₂SM at rest  =  0.250  ×  250  =  62.5 ml min⁻¹  ×  70 kg⁻¹  =  0.00089 ml min⁻¹ g⁻¹, VO₂SM mild walk  =  0.307  ×  700  =  215 m  min⁻¹  ×  70 kg⁻¹  =  0.00307 ml min⁻¹ g⁻¹, and VO₂SM fast walk  =  0.395  ×  1,400  =  553 ml min⁻¹  ×  70 kg⁻¹  =  0.00790 ml min⁻¹ g⁻¹. Putting these values into the equation, the maximal oxygen diffusion fronts were roughly estimated.