Beat-to-beat heart rate (HR) and blood pressure were measured by the Finapres system in 44 healthy and 64 diabetic subjects in the at-rest condition. Autonomic control in diabetic subjects was assessed by the Ewing test. HR variability was explored by both linear and nonlinear methods. Linear methods used HR standard deviation and power spectrum. The percentage of the spectrum in the low frequencies was used to assess the sympathetic tone of the autonomic control. The nonlinear method used the "recurrence plot." This method explored long parallel subsequences in the HR time series. These sequences characterize the dependence of the HR dynamics on initial values. The HR standard deviation was reduced in the diabetic subjects compared with the healthy subjects (2.80 +/- 1.17 vs. 3.64 +/- 1.45 beats/min; P < 0.001). In the diabetic subjects, the HR standard deviation and the percentage of the spectrum in the low frequencies showed no correlations with the Ewing score (P > 0.10). In contrast, the longest length index was very strongly correlated to the Ewing score (r = -0.60; P < 0.0001). The results suggest that nonlinear methods might be powerful to explore the autonomic dysfunction in diabetic subjects.

The definition of hypertensive disorders in pregnancy is plagued by many difficulties, in part related to the limits of intermittent clinic readings of blood pressure. In order to better define the evolution of arterial blood pressure in normal subjects during normal pregnancy, casual and ambulatory (Spacelabs 90207, n = 22 or Diasys 200, n = 26) measurements of blood pressure were performed at gestational months 3, 6, and 9, in 48 normal women aged 18 to 39, both nulliparas (n = 19) and multiparas (n = 29). Ambulatory blood pressure levels were lowest in the first gestational trimester (24-hour mean: 104 +/- 8/63 +/- 6 mm Hg) and rose by a small increment during the last trimester (109 +/- 8/67 +/- 7 mm Hg at 8 months). Mean daytime ambulatory pressure was almost superimposable to clinic measurements at the three time points. A day-night variation in blood pressure level was detectable in all subjects at each recording. It is concluded that during normal pregnancy, ambulatory blood pressure levels were highest in the day and lowest at night at all gestational ages and increased only minimally before the ninth month. Reference values, as defined by the percentile distribution of daytime and nighttime systolic and diastolic blood pressure, may help define more precisely an alteration in the level and/or the circadian variation of arterial blood pressure during abnormal pregnancies.

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1. The forearm venous pressure-volume relationship was studied in 14 young men with borderline hypertension and in 16 control subjects of the same age and sex. Strain-gauge plethysmography was used to evaluate volume changes after slow increases and decreases in distention, in order to estimate the amplitude of the hysteresis curve. 2. Compared with normotensive control subjects, subjects with borderline hypertension had significantly higher values of blood pressure, heart rate and forearm blood flow. 3. Baseline forearm venous tone was slightly, but not significantly, increased in borderline hypertensive subjects (21.35 +/- 6.53 versus 18.75 +/- 5.95 mmHg ml-1 100 ml-1) and was significantly enhanced after a cold pressor test. The increase was no higher in the borderline hypertensive subjects than in the normotensive control subjects. 4. The area of the hysteresis curve was significantly decreased (7.58 +/- 3.58 versus 10.34 +/- 5.67 arbitrary units; P = 0.0092) as was the extent of isotonic relaxation (creep) (0.28 +/- 0.11 versus 0.39 +/- 0.22 ml/100 ml; P = 0.0098) in borderline hypertensive subjects compared with control subjects. Both parameters were unaffected by the cold pressor test. 5. The study suggests that the viscous component of the venous wall is altered in young patients with borderline hypertension, indicating intrinsic changes in vascular segments which are not exposed to increased intraluminal pressure.

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Beat-to-beat heart rate (HR) and blood pressure (BP) were measured by the Finapres system in 28 healthy subjects and 64 diabetic subjects. Autonomic controls in diabetic subjects were assessed by scoring 5 cardiovascular function tests (high score = abnormal control). The fractal dimension (FD) of HR (or SBP) was estimated as follows: Measuring the curve of 500 successive HRs with a rule of length L, one obtains N times L. The FD is the slope of the regression line of Log(N) versus Log(1/L) for different L. We found a lower FD of HR in diabetic subjects than in healthy subjects (1.35 +/- 0.10/1.44 +/- 0.09, p = 0.0002) and a similar FD of SBP in the 2 groups. In diabetic subjects, the FD of HR was negatively correlated with age (r = -0.27, p = 0.03), duration of diabetes (r = -0.33, p = 0.0078) and score of disautonomy (r = -0.43, p = 0.0007). So, heartbeat is more fractal in healthy status: a low fractal fluctuation is a sign of pathology.

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