Discerning aortic waves during intra-aortic balloon pumping and their relation to benefits of counterpulsation in humans.

An explanation of the mechanisms leading to the beneficial hemodynamic effects of the intra-aortic balloon pump (IABP) is lacking. We hypothesized that inflation and deflation of the balloon would generate a compression (BCW) and an expansion (BEW) wave, respectively, which, when analyzed with wave intensity analysis, could be used to explain the hemodynamic benefits of IABP support. Simultaneous ascending aortic pressure (P(ao)) and flow rate (Q(ao)) were recorded in 25 patients during control conditions and with IABP support of 1:1 and 1:2. Diastolic aortic pressure augmentation (P(aug)) and end-diastolic aortic pressure (ED P(ao)) reduction were calculated from P(ao). Energies of the BCW and BEW were obtained by integrating the wave intensity contour over time. P(aug) was 19.1 mmHg (SD 13.6) during 1:2 support. During 1:1 support significantly higher P(aug) of 21.1 mmHg (SD 13.4) was achieved (P < 0.001). ED P(ao) decreased from 50.9 mmHg (SD 15.1) to 43.9 mmHg (SD 15.7) (P < 0.0001) during 1:1 assistance and the decrease was not statistically different with 1:2. During 1:1 support the energy of BCW was correlated positively to P(aug) (r = 0.83, P < 0.0001) and energy of the BEW correlated negatively to ED P(ao) (r = 0.78, P < 0.005); these relationships were not statistically different during 1:2. In conclusion, the energies of the BCW and BEW are directly related to P(aug) and ED P(ao), which are the conventional hemodynamic parameters indicating IABP benefits. These findings imply a cause and effect mechanism between the energies of BCW and BEW, and IABP hemodynamic effects.