No abstract

Diabetic autonomic dysfunction, even when not yet manifest, is associated with a high risk of mortality [1±11] which makes its early identification clinically important. In the early eighties Ewing and co-workers [1,12] validated a battery of laboratory tests for identification of autonomic abnormalities in patients with diabetes mellitus. These tests consist in the measurement of the heart rate changes induced by manouvers such as deep breathing, Valsalva and standing which engage reflexes that alter vagal and sympathetic modulation of the heart [13±17]. They further consist in the measurement of the blood pressure responses to standing, cold pressure test and hand-grip exercise which allow assessment of sympathetic modulation of systemic vascular resistance [15±19].Although useful for the identification of a diabetic-dependent damage of autonomic cardiovascular Diabetologia (1997) Summary Diabetic autonomic dysfunction is associated with a high risk of mortality which makes its early identification clinically important. The aim of our study was to compare the detection of autonomic dysfunction provided by classical laboratory autonomic function tests with that obtained through computer assessment of the spontaneous sensitivity of the baroreceptor-heart rate reflex (BRS) by time domain and frequency domain techniques. In 20 normotensive diabetic patients (mean age ± SD 41.9 ± 8.1 years) with no evidence of autonomic dysfunction on laboratory autonomic testing (D0) blood pressure (BP) and ECG were continuously monitored over 15 min in the supine position. BRS was assessed as the slope of the regression line between spontaneous increases or reductions in systolic BP and linearly related lengthening or shortening in RR interval over sequences of at least 4 consecutive beats (sequence method), or as the squared ratio between RR interval and systolic BP spectral powers around 0.1 Hz. We compared the results with those of 32 age-matched normotensive diabetic patients with abnormal autonomic function tests (D1) and with those of 24 healthy age-matched control subjects with normal autonomic function tests (C). Compared to C, BRS was markedly less in D1 when assessed by both the slope of the two types of sequences (data pooled) and by the spectral method (±71.3 % and ±60.2 % respectively, both p < 0.01). However, BRS was consistently although somewhat less markedly reduced in D0, the reduction being clearly evident for all the estimates (±57.0 % and ±43.5 %, both p < 0.01). The effects were more evident than those obtained by the simple quantification of the RR interval variability. These data suggest that time and frequency domain estimates of spontaneous BRS allow earlier detection of diabetic autonomic dysfunction than classical laboratory autonomic tests. The estimates can be obtained by short non-invasive recording of the BP and RR interval signals in the supine patient, i. e. under conditions suitable for routine outpatient evaluation. [Diabetologia (1997

The aim of our study was to assess whether the Finapres device is able to accurately monitor not only average blood pressure values but also blood pressure variability. To examine this issue, we analyzed 30-minute recordings of finger and intra-arterial pressure simultaneously obtained at rest in 14 patients. We compared systolic blood pressure, diastolic blood pressure, mean arterial pressure, pulse interval (the reciprocal of heart rate), overall variability (standard deviation), and specific time-domain and frequency-domain components. Systolic blood pressure, diastolic blood pressure, mean arterial pressure, and pulse interval spectral powers were computed by fast Fourier transform over three frequency bands: low frequency (0.025 to 0.07 Hz), midfrequency (0.07 to 0.14 Hz), and high frequency (0.14 to 0.35 Hz). The coherence, ie, the degree of association between blood pressure and pulse interval powers obtained by the two techniques, was also assessed. Standard deviations of diastolic blood pressure, mean arterial pressure, and pulse interval were similar when assessed from the two recordings, whereas standard deviation of systolic blood pressure was overestimated by analysis of finger pressure recordings. All powers of diastolic blood pressure and mean arterial pressure and high-frequency powers of systolic blood pressure estimated from analysis of finger blood pressure tracings were superimposable to those obtained by analyzing invasive recordings. Low-frequency and midfrequency powers of intra-arterial systolic blood pressure were significantly overestimated by the analysis of finger blood pressure tracings (+13.7±4.4 mmHg 2 , P<.01, and +2J±0.9 mm Hg 2 , P<.05). Finger and intra-arterial systolic blood pressure, diastolic blood pressure, mean arterial pressure, and pulse interval powers showed a high coherence in the frequency range considered (0.025 to 0.35 Hz). The coherence of all blood pressure powers became smaller for frequencies greater than 0.35 Hz and lower than 0.025 Hz. The number and slope of hypertensionbradycardia (+pulse interval/+systolic blood pressure) and hypotension-tachycardia (-pulse interval/ -systolic blood pressure) sequences assessed by time-domain analysis of both recordings were similar. Thus, specific frequency-domain and time-domain components of blood pressure and pulse interval variability seem to be properly assessed by finger blood pressure recordings in most cases, although low-frequency oscillations of systolic blood pressure appear to be magnified by finger blood pressure tracings. (Hypertension 1993;22:26-33) KEY WORDS • blood pressure monitors • spectrum analysis • pressoreceptors • blood pressure determination C omputer analysis of blood pressure variability provides information on the mechanisms regulating blood pressure in humans. This analysis relies on the standard deviation or the variation coefficient calculated from prolonged monitoring periods.1 It also makes use of complex methods to identify blood pressure variations in the time and frequency domains,...