EFFECTS OF INTRA-AORTIC BALLOON PUMPING DURING RIGHT VENTRICULAR INFLOW OBSTRUCTION IN THE NEWBORN LAMB

Abstract

The intra-aortic balloon pump (IABP), while effective in adults, could be limited in effectiveness in infants because of differences in coronary dynamics, central vascular impedence, heart rate, and the hemodynamic indications for its use. One potential indication is the decreased cardiac output (CO) secondary to right ventricular inflow obstruction (RVIO). In 6 young lambs, catheters were placed in the vena cava, left atrium, coronary sinus, aorta, and pulmonary artery. An IABP was advanced via the femoral artery to the thoracic aorta. RVIO was produced by inflating a Foley catheter in the right atrium, reducing CO by 50%. Studies were performed at rest, rest + IABP, RVIO, and RVIO + IABP. Regional blood flows were measured by the microsphere method. During resting studies, the IABP did not alter CO, heart rate, aortic pressures, systemic or myocardial O2 consumption (VO2) or O2 transport, or regional blood flows. During RVIO, aortic and left atrial pressures decreased, vena caval pressure doubled, and systemic and myocardial VO2 and O2 delivery decreased. Blood flow and O2 delivery to all organs decreased. The IABP had no significant effect on any of these parameters. In conclusion, although the IABP does not interfere with resting hemodynamics or regional blood flows, there is no evidence for its effectiveness in clinical situations where CO is decreased because of RVIO. The utility of the IABP may be affected by the etiology of the reduction in CO, or by the presence of a normal coronary vascular bed.