Assessment of baroreceptor-cardiac reflex sensitivity using time domain analysis in patients with IDDM and the relation to left ventricular mass index

Abstract

Summary Autonomic dysfunction in insulin-dependent diabetic (IDDM) patients has been associated with abnormalities of left ventricular function and an increased risk of sudden death. A group of 30 patients with IDDM and 30 age, sex and blood pressure matched control subjects underwent traditional tests of autonomic function. In addition, baroreceptor-cardiac reflex sensitivity (BRS) was assessed using time domain (sequence) analysis of systolic blood pressure and pulse interval data recorded non-invasively using the Finapres beat-to-beat blood pressure recording system. 'Up BRS' sequences-increases in systolic blood pressure associated with lengthening of R-R interval, and 'down BRS' sequences-decreases in systolic blood pressure associated with shortening of R-R interval were identified and BRS calculated from the regression of systolic blood pressure on R-R interval for all sequences. We also assessed heart rate variability using power spectral analysis and, after expressing components of the spectrum in normalised units, assessed sympathovagal balance from the ratio of low to high frequency powers. IDDM subjects underwent 2-D echocardiography to assess left ventricular mass index. Standard tests of autonomic function revealed no differences between IDDM patients and control subjects, but dramatic reductions in baroreceptor-cardiac reflex sensitivity were detected in IDDM patients. 'Up BRS' when supine was 11.2 ± 1.5 ms/mmHg (mean ± SEM) compared with 20.4 ± 1.95 in control subjects (p < 0.003) and when standing was 4.1 ± 1.9 vs 7.6 ± 2.7 ms/mmHg (p < 0.001). Down BRS when supine was 11.5 ± 1.2 vs 22 ± 2.6 (p < 0.001) and standing was 4.4 ± 1.9 vs 7.3 ± 2.5 ms/ mmHg (p < 0.003). There were significant relations between impairment of the baroreflex and duration of diabetes (p < 0.001) and poor glycaemic control (p < 0.001). From a fast Fourier transformation of supine heart rate data and using a band width of 0.05-0.15 Hz as low-frequency and 0.2-0.35 Hz as high frequency total spectral power of R-R interval variability was significantly reduced in the IDDM group for both low-frequency (473 ± 62.8 vs 746.6 ± 77.6 ms 2 p = 0.002) and high frequency bands 125.2 ± 12.9 vs 459.3 ± 89.8 ms 2 p < 0.0001. When the absolute powers were expressed in normalised units the ratio of low frequency to high frequency power (a measure of sympathovagal balance) was significantly increased in the IDDM group (2.9 ± 0.53 vs 4.6 ± 0.55, p < 0.002 supine: 3.8 ± 0.49 vs 6.6 ± 0.55, p < 0.001 standing). Thus, time domain analysis of baroreceptor-cardiac reflex sensitivity detects autonomic dysfunction more frequently in IDDM patients than conventional tests. Impaired BRS is associated with an increased left ventricular mass index and this abnormality may have a role in the increased incidence of sudden death seen in young IDDM patients. [Diabetologia (1996[Diabetologia ( ) 39: 1385[Diabetologia ( -1391

Effect of hypoxia on heart rate variability and baroreflex sensitivity during hypoglycemia in type 1 diabetes mellitus

“…Reduced HRV is indicative of impaired vagal control and altered sympathovagal balance, and is an independent predictor of sudden arrhythmic death and cardiovascular mortality [14]. Measures of HRV have repeatedly been shown to be impaired in patients with type 1 diabetes [9, 15, 17, 32, 34] and recently our group found these impairments are worsened during acute hypoglycemia [16]. Impairments in HRV, and specifically vagal tone, will increase the risk of ventricular arrhythmias and cardiovascular mortality in this clinical population [3, 27].…”

“…Statistical significance was determined a priori at the α=0.05 level. The number of subjects (n=13) was selected a priori by a power test equation with α=0.05 and power=0.80, using differences in BRS from previously published research in patients with type 1 diabetes mellitus [32]. Furthermore, post hoc analysis showed 13 subjects provided 77% power to detect a difference in BRS.…”

Evaluation of Baroreflex Sensitivity by the Sequence Method Using Blood Pressure Oscillations and R–R Interval Changes during Deep Respiration

“…In our study, baroreflex sensitivity obtained by the sequence method at rest significantly correlated with that obtained by the Valsalva maneuver in healthy volunteers and patients with Parkinson’s disease. However, baroreflex sensitivity could not be measured in some patients with autonomic dysfunction [14]because there was no significant correlation between systolic blood pressure and R–R intervals owing to very small fluctuations in systolic blood pressure at rest.…”

“…Therefore, baroreceptor sensitivity may be evaluated on the basis of fluctuations in blood pressure and associated changes in R–R interval. Several authors have referred to this technique as the sequence method [7, 13, 14]. However, baroreflex sensitivities cannot be measured by the sequence method in some patients with autonomic dysfunction at rest because fluctuations in blood pressure are too small and lack significant correlation with changes in R–R intervals [15].…”

Hemodynamic and autonomic response to acute hemorrhage in streptozotocin-induced diabetic rats

“…In diabetic patients with CAN, this compensation mechanism may not work adequately because some evidence suggests that both the sympathetic and parasympathetic nervous system are impaired in patients with insulin-dependent diabetes mellitus [1,10,11]. However, little is known about autonomic and hemodynamic responses to acute hemorrhage in diabetic patients with CAN.…”