Aortic function in patients during intra-aortic balloon pumping determinedby the pressure-diameter relation

Objective: The physiologic basis for the hemodynamic and clinical improveme nt achieved by the use of intra-aortic balloon pumping in patients with car diogenic shock has not been clarified in all its aspects. This study evalua ted the possible contribution of pump-induced alterations of aortic mechani cs to the overall benefit gained by the implementation of this therapeutic modality in patients with acute heart failure of ischemic origin. Methods: The aortic pressure-diameter relation was obtained by use of an intravascul ar catheter for aortic diameter measurements developed in our institution a nd previously validated, simultaneously with a catheter-tip micromanometer for aortic pressure measurements at the same aortic level. Aortic function indices were compared before and during intra-aortic balloon pumping in 12 patients with cardiogenic shock. Results: Intra-aortic balloon pumping incr eased cardiac index and aortic distensibility by 24% and 30%, respectively, and reduced myocardial oxygen demand by 31% (P < .001 for all alterations) . Energy loss caused by aortic wall viscosity increased ba 207% (P < .001), The aortic diameter augmentation index increased by 68% (P < .001); the ao rtic pressure augmentation index decreased by 117% (P < .001). Linear regre ssion analysis showed that cardiac index and myocardial oxygen demand were related with the aortic stiffness constant both before and during intra-aor tic balloon pumping. Conclusions: During intra-aortic balloon pumping, aort ic distensibility was improved, and wave reflection from the arterial perip hery was reduced. The relationship between cardiac index and myocardial oxy gen demand and aortic stiffness suggests that improvement of the elastic pr operties of the aorta was an important mechanism by which intraaortic ballo on pumping improved circulatory function.