Effects of intra-aortic counterpulsation on aortic wall energetics and damping: in vivo experiments.

Intra-aortic balloon pumping (IABP) could modify the arterial biomechanics; however, its effects on arterial wall properties have not been fully explored. This dynamical study was designed to characterize the pressure-dependent and smooth muscle-dependent effects of IABP on aortic wall energetics in an in vivo animal model. Intra-aortic balloon pumping (1:2) was performed in six anesthetized sheep in which aortic pressure and diameter signals were measured in basal, augmented (during balloon inflation), and assisted (postaugmented) beats. Energy dissipation values in augmented and assisted beats were significantly higher than those observed in basal state (p < 0.05). Assisted beats showed a significant increase of wall damping with respect to basal and augmented beats (p < 0.05). Intra-aortic balloon pumping resulted in a significant increase of pulse wave velocity (p < 0.05) in augmented beats with respect to basal state (6.3 +/- 0.8 vs. 5.2 +/- 0.5 m x s(-1)); whereas values observed in assisted beats were significantly (p < 0.05) lower than those observed in augmented beats (4.9 +/- 0.5 vs. 6.3 +/- 0.8 m x s(-1)). Our findings show that IABP determined the pressure and smooth muscle-dependent changes in arterial wall energetics and damping properties in this animal model.