Estimation of timing errors for the intraaortic balloon pump use in pediatric patients

The use of the intraaortic balloon pump (IABP) for managing acute left ventricular failure in pediatric patients is less successful than in adults. It is often reported that rapid pediatric heart rates make accurate timing difficult to achieve. Traditional IABP theory requires that the balloon inflate during diastole (after aortic valve closure), for optimum coronary pressure and flow augmentation, and deflate just before the next systole for optimal ventricular afterload reduction. Errors in timing balloon inflation and deflation may result in the reduced IABP efficacy seen in children. To investigate timing errors when using the traditional IABP inflation and deflation markers in pediatric patients, six patients (age, 2.2 +/- 1.4 years; weight, 11.5 +/- 3.9 kg) were studied intraoperatively. Radial artery pressure (RAP) waveforms from a standard, fluid-filled pressure monitoring system were recorded on an FM data tape recorder simultaneously with high-fidelity, aortic root pressure waveforms, aortic root flow waveforms, and M-mode echocardiography. For each patient a sequence of five recorded waveforms was analyzed. The mean +/- standard deviation of the time delay between aortic root and RAP markers and percentage delay of the corresponding part of the cardiac cycle were determined. When compared with aortic roof waveforms, the RAP waveform consistently showed a delay in the IABP timing markers. A 107 +/- 23 msec (53 +/- 11%) delay in diastolic inflation and a 92 +/- 11 msec (40 +/- 4%) delay in presystolic deflation was found. If IABP timing to the RAP markers were to be used, the delay in IABP inflation would result in reduced diastolic augmentation, and the delay in IABP deflation into the systolic period would increase afterload. M-mode echocardiography provided timing markers that were identical to those provided by high-fidelity aortic root pressure waveforms. The combined effect of these delays on IABP function could substantially reduce the efficacy of the IABP in pediatric patients, indicating the need for more accurate indices for IABP timing in this patient group.