Circulating mechanism of the "pure" venous flap: direct observation of microcirculation.
The circulating mechanism of the "pure" venous flap was studied via venography and direct observation of the microcirculation through transparent ear chambers and ear edges in a rabbit model. The flap, without arterial inflow, survived with normal hair growth and wound healing. Renewed blood circulation occurred 3 to 5 hr after transfer There were two typical flow patterns in the venules: one was a shaking movement with high frequency and short range; the other was a pendulum-like movement with low frequency and long range. The former was related to heart rate, while the later was not. The pendulum-like movement was the main flow responsible for perfusion of capillaries. Blood flow in the capillaries occurred 1 to 2 hr later than that in the venules. The pendulum-like flow perfused the capillaries in two ways: one was in the direction of venules to capillaries and then back to venules along the same route; the other was from venules to arterioles through arteriovenous shunts and then to capillaries. The first type of perfusion was gradually replaced by the second 2 days after transfer. There were extensive venous plexus flows in the flap, which lasted more than 4 weeks after transfer. Revascularized vessels ultimately supplied blood to the flap. The dynamic energy for the movement of blood at an early post-transfer stage was probably due to spontaneous venomotion.