Change in vasoconstrictive function during prolonged nonpulsatile left heart bypass

We investigated changes in vasoconstrictive function accompanying prolonged nonpulsatile left heart bypass (NLHB). After 2-week pulsatile left heart b ypass (PLHB) in 11 goats, NLHB was conducted for another 4 weeks (Group N) in 6 goats. In the other 5 goats. PLHB was continued for another 4 weeks (G roup P). Systemic vascular resistance at rest (rSVR) was measured on the la st days of the second and sixth postoperative week (W2 and W6. respectively ). Subsequently. phenylephrine was injected, and the maximum values (SVRmax ) and the maximum increasing change in SVR (Delta SVR) were measured. No si gnificant difference was observed in rSVR between groups at W2 or W6. The S VRmax and the Delta SVR at W2 were consistent in both groups. However, at W 6, the SVRmax and the Delta SVR of Group N were significantly lower than th ose of Group P. In conclusion, prolonged NLHB caused a significant decrease in the SVR response to phenylephrine. indicating a dimunition of vasoconst rictive function.