Multiresolution Analysis of Heart Rate Variability as Investigational Tool in Experimental Fetal Cardiac Surgery

Abstract

Multiresolution analysis of heart rate variability derived from aortic blood pressure, acquired before and after (30 and 60 min) experimental fetal cardiac bypass performed on five ewe's fetuses, was used to investigate the physiological response to an invasive clinical approach. Tachograms were implemented and analyzed by wavelet transform in order to verify the existence of a quantitative relationship between arterial blood gases and time series in the very-low (0.021<f<0.084 Hz) and low (0.084<f<0.337 Hz) frequency band. Multiresolution analysis showed an average decreasing trend from basal condition for all the fetuses investigated in the very-low frequency band, while an opposite trend was highlighted in the low frequency band: this resulting behavior could be related to the temporal evolution of blood gas data. Finally, a slight decrease of sympatho-vagal balance was monitored 30 min after the cardiac bypass was discontinued compared to basal condition. Multiresolution analysis could give more insights on fetal hypoxemia and could also represent a minimally invasive monitoring tool to limit the damage to the fetoplacental unit during experimental fetal cardiac surgery.