Contractions of postmortem human saphenous veins perfused with pulsatile flow

Summary

The aim of this study was to evaluate the contractions of postmortem human saphenous veins under pulsatile flow conditions as a simulation of coronary-aortic bypass graft (CABG) surgery. Twenty-five cylindrical specimens of veins, obtained from 20 cadavers several hours after death, were mounted in a pulsatile flow system with a pulse rate of 80/min and a mean flow rate of 7 ml/min at various perfusion pressures. Prostaglandin F_2α(PGF_2α) was then applied to the outer physiological salt solution at a concentration of 3×10⁻⁶ mol. Of the 25 veins, 18 (72%) contracted and seven did not. Contractions were observed at a mean perfusion pressure of less than 60 mmHg but not at higher pressures. Three contraction patterns were observed: One caused pressure gradients between the proximal and distal sites of the vein and showed periodic contractions (P); one showed only tonic contractions (T); the other showed pulse pressure increase without developing the pressure gradients (PP). The incidences of P, T, and PP in the 18 instances of contraction were 50%, 33%, and 17%, respectively. Repeated applications of PGF_2α to the same vein with the same and/or increased perfusion pressure caused changes of pattern in the direction of P to T, to PP, and to no response, whereas decreasing perfusion pressure caused the patterns to change in the reverse direction. The pressure gradients that developed in veins showing P and T patterns correlated well with the mean perfusion pressure (r=0.68,P<0.01). The predisposing factors for the contractions seemed to be a shorter interval between the time of death and the start of the experiment, smaller diameter of the vein, and a mean perfusion pressure of less than 60 mmHg.