Time and frequency domain estimates of spontaneous baroreflex sensitivity provide early detection of autonomic dysfunction in diabetes mellitus

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

Glycemic Control, Hand Activity, and Complexity of Biological Signals in Diabetes Mellitus

“…Moreover, we also uncovered the large-scales MCAE between ECG R-R intervals and PPG pulse amplitudes of left index finger decreased in the same manner in type 2 diabetes [31]. Several studies have shown that as compared with those free of diabetes, diabetic patients with cardiac or peripheral autonomic neuropathy related to poor glycemic control and sedentary status have lower baroreflex sensitivity [32,33]. The impaired short-term cardiovascular control in diabetes mellitus may be caused by the functional or structural impairment of nerve fibers of the autonomic nervous system innervating the heart and blood vessels [34].…”

Early autonomic dysfunction in type 1 diabetes: a reversible disorder?

“…Essentially, these previous findings were replicated here by: (1) showing a lower global HRV (assessed by the SD of RR interval); (2) the relative increase in the lowfrequency components; (3) the relative and absolute reduction in the high-frequency components of HRV; and (4) the higher low-frequency:high-frequency ratio, as assessed by spectral analysis. It is of note that reduced BRS was found to be a sensitive marker of autonomic cardiovascular dysregulation in a population of type 1 diabetic patients with a wide range of age and diabetes duration [10] and that such a reduction in BRS has furthermore been repeatedly reported by different studies in type 1 and type 2 diabetic patients [9,11,12,15]. Our findings also support these previous data, but, importantly, do so even in the absence of clinical complications or in the absence of alterations in the autonomic function tests.…”

“…A high prevalence of CAN, reduced HRV and blunted spontaneous BRS in patients with type 1 as well as in patients with type 2 diabetes have been reported previously [9][10][11][12][13][14][15]. It is of note that the tests used allow early detection of abnormalities in the autonomic nervous system.…”

Measures of cardiovascular autonomic nervous function: agreement, reproducibility, and reference values in middle age and elderly subjects

“…In addition, heart-rate variability (HRV) and, more recently, the sensitivity of spontaneous baroreflex control of the heart rate (baroreflex sensitivity, BRS), have been used to assess autonomic dysfunction as well. It has been proposed that these measures might be even more sensitive than the Ewing battery [4,5,6,7].…”

“…Autonomic function has been reported to decrease in relation to age [8,9,10,11,12,13] and to differ between men and women [9,14,15]. Furthermore, diabetic patients have lower values on the Ewing battery [3,16,17,18,19], of the spectral analysis of HRV [4,16,20,21], and have a low BRS [5,22] in comparison with normal glucose tolerant control subjects. Besides their application in the assessment of cardiovascular autonomic function in diabetic patients, HRV and BRS are used in cardiology for risk stratification after myocardial infarction.…”