Linear and nonlinear interaction analyses of heart rate and blood pressure in pregnancy induced hypertension

Hypertensive pregnancy disorders have a deep impact on gestation and are a major cause of maternal and fetal mortality. This study was conducted to proof whether changes in the cardiovascular regulation in pregnancy induced hypertension (PIH) can be quantified by heart rate and blood pressure interaction analyses in comparison to healthy pregnancies (CON). Blood pressure recordings of 20 CON and 18 PIH patients were analysed. The measurements were performed under standardized resting conditions over a period of 30 minutes using the non-invasive Portapres M2 blood pressure monitor. For heart rate and blood pressure interaction analyses baroreflex sequence method, cross-correlation, cross-transinformation and joint symbolic dynamics were applied. Parameters derived from the sequence method (tslope; p<0,01, bslope; p<0,05) as well as from the joint symbolic dynamics (JSDsym and JSDdiam; p<0,05; JSDshannon; p<0,01) revealed significant differences between CON and PIH and were only slightly correlated (|r|<0.5) with each other. In contrast, no significant differences were found with the cross-transinformation and cross-correlation function techniques. In conclusion, heart rate and blood pressure interactions differ between CON and PIH. For the quantification of these alterations the sequence method and especially joint symbolic dynamics are suitable and might lead to an improved risk stratification during pregnancy.