Assessment of cardiovascular reactivity by fractal and recurrence quantification analysis of heart rate and pulse transit time.

Methods used for the assessment of cardiovascular reactivity are flawed by nonlinear dynamics of the cardiovascular responses to stimuli. In an attempt to address this issue, we utilized a short postural challenge, recorded beat-to-beat heart rate (HR) and pulse transit time (PTT), assessed the data by fractal and recurrence quantification analysis, and processed the obtained variables by multivariate statistics. A 10-min supine phase of the head-up tilt test was followed by recording 600 cardiac cycles on tilt, that is, 5-10 min. Three groups of patients were studied, each including 20 subjects matched for age and gender--healthy subjects, patients with essential hypertension (HT), and patients with chronic fatigue syndrome (CFS). The latter group was studied on account of the well-known dysautonomia of CFS patients, which served as contrast against the cardiovascular reactivity of the healthy population. A total of 52 variables of the HR and PTT were determined in each subject. The multivariate model identified the best predictors for the assessment of reactivity of healthy subjects vs CFS. Based on these predictors, the "Fractal & Recurrence Analysis-based Score" (FRAS) was calculated: FRAS=76.2+0.04*HR-supine-DET -12.9*HR-tilt-R/L -0.31*HR-tilt-s.d. -19.27*PTT-tilt-R/L -9.42*PTT-tilt-WAVE. The median values and IQR of FRAS in the groups were: healthy=-1.85 (IQR 1.89), hypertensives=+0.52 (IQR 5.78), and CFS=-24.2 (5.34) (HT vs healthy subjects: P=0.0036; HT vs CFS: P<0.0001). Since the FRAS differed significantly between the three groups, it appears likely that the FRAS may recognize phenotypes of cardiovascular reactivity.

Fluorescein angiography in hypertensive pregnancies.

A retrospective study in two university hospitals investigating retinal changes in pregnancies complicated by hypertension, seldom revealed retinal vascular changes in pre-eclamptic toxemia. Fluorescein angiography was performed on 16 severe pre-eclamptic toxemias and 14 chronic hypertension pregnancies. Normal caliber retinal vessels and normal filling time, with no subretinal or subepithelium leakage, was found in all pre-eclamptic toxemic patients. Four out of the 14 chronic hypertensive patients showed signs of mild hypertensive retinopathy. A review of the literature on fluorescein angiography in pregnancy showed that vascular changes in pre-eclamptic toxemia are choroidal rather than retinal.