Change of complex and periodic heart rate dynamics with change of pulmonary artery pressure in infants with left-to-right shunt lesion.

We studied how complex and periodic heart rate dynamic changed as pulmonary artery pressure elevated in 32 infants with ventricular septal defect. In addition, we tested the possibility that the dynamical change could be used to predict the pulmonary artery pressure noninvasively. During cardiac catheterization, mean pulmonary artery pressure was measured and, at the same time, 5-min segments of continuous electrocardiographic recording was stored into computer files. High- (>0.15 hertz) and low- (0.03-0.15 hertz) frequency components of heart rate variability were computed using spectral analysis. The overall complexity of heart rate time series was quantified by its approximate entropy. Pulmonary hypertensive infants (mean pulmonary artery pressure >20 mm Hg, n=17) have significantly lower low- (p<0.05) and high- (p<0.05) frequency power and lower approximate entropy (p<0.0001) than pulmonary normotensive infants (mean pulmonary artery pressure < or =20 mm Hg, n=15). The mean pulmonary artery pressure is significantly correlated not with the spectral powers but with the approximate entropy (r=-0.71, p=0.0001). It can be concluded that, in infants, pulmonary hypertension induced by left- to-right shunt lesions suppresses both periodic and complex heart rate oscillation and that mean pulmonary artery pressure can be predicted by calculating the approximate entropy of heart rate variability.