Arterial pressure pulsation during nonpulsatile biventricular bypass experiments: possible idioperipheral pulsation.

During nonpulsatile biventricular bypass (NPBVB) experiments, regular fluctuations of arterial pressure were observed in all five long-term animals whose ventricles were fibrillated. Analysis of the characteristics of this fluctuation was performed retrospectively. The pulse pressure of this fluctuation increased gradually after the first 2 weeks. They were 6.7, 7.6, 10.2, and 12.4 mm Hg on the fortieth, sixtieth, eightieth, and ninetieth postoperative day, respectively, in the animal surviving for 99 days. Cycle rate was generally high for the first 40 days, and then decreased to approximately 40 cycles/min in calves alive for greater than 90 days. The beat rate of these arterial pressure fluctuations was lower than atrial but similar to respiratory cycle rates. However, no flow fluctuations were observed in conjunction with the arterial pressure oscillations. Therefore, neither atrial contractions nor the mechanical effects of respiration were causing the pressure pulsations. Though further investigations are necessary, it is highly suggestive that this phenomenon was derived from the vasomotor center and can be called "idioperipheral pulsation." It is conceivable that the NPBVB animals adapted to the nonpulsatile condition by adding active pulsatile components of their own to maintain adequate peripheral circulation.