RR-variation: the autonomic test of choice in diabetes

Electrodiagnostic assessment of the autonomic nervous system: A consensus statement endorsed by the American Autonomic Society, American Academy of Neurology, and the International Federation of Clinical Neurophysiology

Evaluation of disorders of the autonomic nervous system is both an art and a science, calling upon the physician's most astute clinical skills as well as knowledge of autonomic neurology and physiology. Over the last three decades, the development of noninvasive clinical tests that assess the function of autonomic nerves, the validation and standardization of these tests, and the growth of a large body of literature characterizing test results in patients with autonomic disorders have equipped clinical practice further with a valuable set of objective tools to assist diagnosis and prognosis. This review, based on current evidence, outlines an international expert consensus set of recommendations to guide clinical electrodiagnostic autonomic testing. Grading and localization of autonomic deficits incorporates scores from sympathetic cardiovascular adrenergic, parasympathetic cardiovagal, and sudomotor testing, as no single test alone is sufficient to diagnose the degree or distribution of autonomic failure. The composite autonomic severity score (CASS) is a useful score of autonomic failure that is normalized for age and gender. Valid indications for autonomic testing include generalized autonomic failure, regional or selective system syndromes of autonomic impairment, peripheral autonomic neuropathy and ganglionopathy, small fiber neuropathy, orthostatic hypotension, orthostatic intolerance, syncope, neurodegenerative disorders, autonomic hyperactivity, and anhidrosis.

Simplified Diagnosis of Cardiovascular Autonomic Neuropathy in Type 2 Diabetes Using Ewing's Battery

AIM

To find a potential simplification of the established Ewing's battery for the diagnosis of cardiovascular autonomic neuropathy (CAN) in type 2 diabetes (T2D).

METHODS

We included 152 patients (92 men) with mean age 64.51 ± 7.85 years and median diabetes duration of 12 years. Ewing's battery was used as the gold standard for the diagnosis of CAN. Against this, we compared the results from each test and their combinations.

RESULTS

The 30:15 ratio exhibited the best diagnostic performance (AUC = 0.817, 95% CI: 0.730-0.903, p < 0.001), with 96% sensitivity, 65% specificity, and 94% negative predictive value (NPV). The corresponding values for the Valsalva ratio (VR) were 62%, 92%, and 85%, respectively. The 30:15 ratio was the strongest independent predictor of neuropathy in multivariate regression analysis; low levels yielded an odds ratio (OR) of 21.14 for CAN. The rise in diastolic blood pressure and the expiration/inspiration/VR ratio (E/I/VR) were also identified as independent predictors of CAN, with 9.45 and 10.79 ORs, respectively.

CONCLUSIONS

The 30:15 ratio has the best diagnostic accuracy, primarily in the exclusion of CAN, by virtue of its very high sensitivity and NPV. If this ratio is positive for CAN, the VR, the rise in diastolic blood pressure, and the E/I/VR may be useful to increase diagnostic accuracy. This procedure is a simplified diagnostic approach that merits further evaluation to enable wider screening for CAN.

Insulin resistance is independently associated with peripheral and autonomic neuropathy in Korean type 2 diabetic patients

In addition to chronic hyperglycemia, insulin resistance itself has been proposed to cause a diabetic neuropathy. We evaluated the role of insulin resistance in the pathogenesis of peripheral and autonomic neuropathy in patients with type 2 diabetes. Eighty-six patients with type 2 diabetes were evaluated for the anthropometric and biochemical profiles, and Kitt value was calculated from insulin tolerance test to assess the insulin resistance. Various autonomic function tests, nerve conduction velocity, and quantitative sensory tests were performed to assess autonomic and peripheral neuropathy. In univariate analysis, both autonomic and peripheral neuropathy were significantly associated with glycemic exposure index (GE index), HDL-cholesterol, duration of DM, and Kitt value. In stepwise linear regression analysis, GE index was an independent predictor of autonomic and peripheral neuropathy (β = 0.643, P < 0.001; β = 0.207, P = 0.013, respectively), and Kitt value was also an independent factor for the autonomic and peripheral neuropathy (β = - 0.306, P < 0.001; β = - 0.329, P < 0.001, respectively). Low HDL-cholesterol increased the odds ratio for peripheral neuropathy. Insulin resistance is independently associated with peripheral and autonomic neuropathy in Korean Type 2 diabetic patients along with hyperglycemia and HDL-cholesterol.

Dysfunction of pre- and post-operative cardiac autonomic nervous system in elderly patients with diabetes mellitus

The pre- and post-operative cardiac autonomic nervous functions were compared in elderly, non-cardiac surgery patients with diabetes mellitus (DM) and without diabetes mellitus (NDM). A group of 30 unpremedicated elderly patients scheduled to undergo elective non-cardiac surgery were studied, including 15 DM patients and 15 NDM patients. Each component of heart rate variability (HRV) analysis in the frequency domain was monitored with Holter during the nights of the day before and on 1st and 2nd day after operation. After surgery, total power (TP), high frequency (HF), low frequency (LF) and very low frequency (VLF) significantly decreased as compared to the baseline values before operation in both groups (p<0.05). The LF/HF ratio was significantly changed in DM group but did not change in NDM group. On the 2nd postoperative day, TP, HF, LF and VLF in DM group were further decreased as compared to those on the 1st postoperative day and were significantly lower than those in NDM group (p<0.01 or 0.05), but these indices in NDM group did not show significant decreases. Surgery induced the cardiac autonomic nervous dysfunction in elderly patients not only with DM but also without diabetes. On the 2nd postoperative day, the disturbances of cardiac autonomic nervous activity were more sever in DM patients, compared to the 1st postoperative day, but was not significantly more sever than in the NDM patients.

Wavelet analysis of autonomic outflow of normal subjects on head-up tilt, cold pressor test, Valsalva manoeuvre and deep breathing

Non-invasive autonomic evaluation has used fast Fourier transform (FFT) to assign a range of low (LF) and high frequencies (HF) as markers of sympathetic and parasympathetic influences, respectively. However, FFT cannot be applied to brief transient phenomena, such as those observed on performing autonomic tests where the acute changes of cardiovascular signals (blood pressure and heart rate) that represent the first and most important stage of the autonomic performance towards a new state of equilibrium occur. Wavelet analysis has been proposed as a method to overcome and complement information taken exclusively in the frequency domain. With discrete wavelet transform (DWT), a time-frequency analysis can be done, allowing the visualization in time of the contribution of LF and HF to the observed changes of a particular signal. In this study, we evaluate with wavelets the acute changes in R-R intervals and systolic blood pressure that are observed in normal subjects during four classical autonomic tests: head-up tilt (HUT), cold pressor test (CPT), deep breathing (DB) and Valsalva manoeuvre (VM). Continuous monitoring of ECG and blood presure was performed. Also LF, HF and LF/HF were calculated. Consistent with previous interpretations, data showed an increase of sympathetic activity in HUT, CPT and VM. On DB, results reflected an increase in parasympathetic activity and frequencies. In conclusion, when compared with FFT, wavelet analysis allows the evaluation of autonomic variability during short and non-stationary periods of time and may constitute a useful advance in the assessment of autonomic function in both physiological and pathological conditions.

Sympathetic sudomotor disturbance in early type 1 diabetes mellitus is linked to lipid peroxidation

The present study was performed to determine whether increased lipid peroxidation, as assessed from malondialdehyde (MDA) excretion, is associated with deterioration in peripheral nerve function in early type 1 diabetes mellitus. These parameters were measured annually for 3 years in 36 patients who entered the study less than 2 years after the diagnosis of diabetes. Malondialdehyde excretion was 1.51 +/- 0.20 micromol/g creatinine in the controls, and 2.43 +/- 0.21, 2.39 +/- 0.22, and 1.93 +/- 0.21 micromol/g creatinine at the first, second, and third evaluations, respectively (P < .005). The increased MDA was seen only in the female participants. Malondialdehyde excretion was increased in those with high vs low hemoglobin Alc across all years (P < .05). Malondialdehyde excretion correlated negatively with sudomotor function below the waist. The mean sweat production from the 3 evaluations correlated with mean MDA excretion across all years in the proximal leg (r = -0.42, P < .005) and distal leg (r = -0.40, P < .01). Below the waist, sweating correlated with MDA (r = -0.40, P < .01) as did total sweat (r = -0.38, P < .01). The response amplitudes of the peroneal nerves correlated negatively with MDA excretion (for the mean values at the second 2 evaluations, P < .005, r = -0.45). Tests of sensory function correlated inconsistently with MDA excretion. In summary, lipid peroxidation, as assessed from malondialdehyde excretion, is associated with sudomotor dysfunction in early diabetes.

Impaired baroreflex function in temporal lobe epilepsy

Changes of cardiovascular function are frequent in temporal lobe epilepsy (TLE). The baroreflex - the most important reflex for cardiovascular stability - has not been studied systematically in TLE. We evaluated cardiovascular variability and baroreflex function in TLE. In 22 TLE patients and 20 controls, we continuously monitored heart rate (HR) and blood pressure (BP). Time-domain parameters were derived from recordings at rest and from standard cardiovascular reflex tests. Spectral analysis determined sympathetic and parasympathetic modulation of HR and BP in the low (LF-power) and high frequency range (HF-power). We calculated the relative LF- and HF-powers of HR in relation to the sum of LF- and HF-powers. LF/HF-ratio of HR was assessed as a parameter of sympatheticovagal balance. LF-transfer function gain between BP and HR determined baroreflex function.Time-domain parameters did not differ between TLE patients and controls. Spectral analysis showed decreased absolute LF- and HF-powers but increased relative LF-power and LF/HF-ratio of HR in TLE. LF-transfer function gain between BP and HR was reduced in TLE (p<0.05). The reduction of absolute LF- and HF-powers indicates decreased total autonomic variability in TLE. However, increased relative LF-power and LF/HF-ratio of HR in TLE show a relative increase of sympathetic tone. Most importantly, we demonstrate an impaired baroreflex function in TLE. These cardiovascular autonomic abnormalities may contribute to cardiac arrhythmia in TLE.

Endothelial dysfunction and exercise performance in lone atrial fibrillation or associated with hypertension or diabetes: different results with cardioversion

Endothelial dysfunction and underperfusion of exercising muscle contribute to exercise intolerance, hyperventilation, and breathlessness in atrial fibrillation (AF). Cardioversion (CV) improves endothelial function and exercise performance. We examined whether CV is equally beneficial in diabetes and hypertension, diseases that cause endothelial dysfunction and are often associated with AF. Cardiopulmonary exercise and pulmonary and endothelial (brachial artery flow-mediated dilation) function were tested before and after CV in patients with AF alone ( n = 18, group 1) or AF with hypertension ( n = 19, group 2) or diabetes ( n = 19, group 3). Compared with group 1, peak exercise workload, O2 consumption (V̇o2), O2 pulse, aerobic efficiency (ΔV̇o2/ΔWR), and ratio of brachial diameter changes to flow changes (Δ D/ΔF) were reduced in group 2 and, to a greater extent, in group 3; exercise ventilation efficiency (V̇e/V̇co2 slope) and dead space-to-tidal volume ratio (Vd/Vt) were similar among groups. CV had less effect on peak workload (+7% vs. +18%), peak V̇o2 (+12% vs. +17%), O2 pulse (+33% vs. +50%), ΔV̇o2/ΔWR (+7% vs. +12%), V̇e/V̇co2 slope (−6% vs. −12%), Δ D/ΔF (+7% vs. +10%), and breathlessness (Borg scale) in group 2 than in group 1 and was ineffective in group 3. The antioxidant vitamin C, tested in eight additional patients in each cohort, improved flow-mediated dilation in groups 1 and 2 before, but not after, CV and was ineffective in group 3, suggesting that the oxidative injury is least in lone AF, greater in hypertension with AF, and greater still in diabetes with AF. Comorbidities that impair endothelial activity worsen endothelial dysfunction and exercise intolerance in AF. The advantages of CV appear to be inversely related to the extent of the underlying oxidative injury.

Quantitative studies of autonomic function

Dysfunction of the peripheral and central autonomic nervous system is common in many neurological and general medical diseases. The quantitative assessment of sympathetic and parasympathetic function is essential to confirm the diagnosis of autonomic failure, to provide the basis for follow-up examinations, and potentially to monitor successful treatment. Various procedures have been described as useful tools to quantify autonomic dysfunction. The most important tests evaluate cardiovascular and sudomotor autonomic function. In this review, we therefore focus on standard tests of cardiovascular and sudomotor function such as heart-rate variability at rest and during deep breathing, active standing, and the Valsalva maneuver, and on the sympathetic skin response. These tests are widely used for routine clinical evaluation in patients with peripheral neuropathies. Refined methods of studying heart-rate variability, baroreflex testing, and detailed measures of sweat output are mostly used for research purposes. In this context, we describe the spectral analysis of slow modulation of heart rate or blood pressure, reflecting sympathetic and parasympathetic influences, and consider various approaches to baroreflex testing, the thermoregulatory sweat test, and the quantitative sudomotor axon reflex test. Finally, we discuss microneurography as a technique of direct recording of muscle sympathetic nerve activity.

Aberrant parasympathetic and hemodynamic function distinguishes a subgroup of psychologically distressed individuals with asymptomatic type-I diabetes mellitus

In a previous study, a subgroup of asymptomatic insulin-dependent diabetic individuals (termed IDDM-2) were identified on the basis of diminished parasympathetic cardiac input and elevated heart rate at rest. When compared to another group of asymptomatic IDDM participants (termed IDDM-1), and a nondiabetic healthy control group, the IDDM-2 group displayed elevated blood pressure, supported by elevated total peripheral resistance. Measures of psychological regulation were also taken in this study, and form the basis of this article, which examined whether these IDDM-2 patients differed from the other two groups on these measures. The possible role of glycemic control, IDDM duration, and number of somatic complaints among group differences in psychological regulation was also examined. The IDDM-2 group reported increased psychological distress, as reflected by increased dysphoric or depressive symptoms, trait anxiety, perceived stress, and cynical hostility, as well as decreased optimism and interpersonal, but not family, social support. Glycemic control did not account for any of the group differences in psychological regulation. However, group differences in dysphoria and anxiety were accounted for by differences in somatic complaints, whereas differences in interpersonal social support were accounted for by IDDM duration. Moreover, none of the variables investigated accounted for the diminished optimism of the IDDM-2 group. Therefore, in individuals with IDDM, who would otherwise be considered, after medical examination, as no different from other asymptomatic IDDM individuals, the combination of diminished parasympathetic cardiac input and elevated heart rate was associated with aberrant alterations of both hemodynamic and psychological functioning; the increased psychological distress in these individuals may be influenced, in part, by increased diabetes duration and number of somatic symptoms.

Association of cardiac autonomic neuropathy and microalbuminuria in non-insulin-dependent diabetes mellitus

OBJECTIVE

To evaluate the relationship between microalbuminuria and autonomic neuropathy in diabetes mellitus.

METHODS

A consecutive series of 151 patients with non-insulin-dependent diabetes mellitus underwent assessment in a single medical practice during a 3 1/2-year period for the presence of microalbuminuria and cardiac autonomic neuropathy. On the basis of microalbuminuria, the patients were categorized into two groups for comparison.

RESULTS

Of the overall group of 151 patients, 91 had increased urinary albumin (50 mg/L or more), and 60 had normal albumin excretion (20 mg/L or less). Cardiac autonomic neuropathy was detected in 54% of the former group and 35% of the latter group. Thus, the presence of microalbuminuria was highly associated with cardiac autonomic neuropathy (results of chi2 analysis were significant at 2.3%). Other factors--duration of diabetes, blood pressure, and serum cholesterol and creatinine levels--did not differ between the two study groups.

CONCLUSION

Results of this study indicate that the incidence of cardiac autonomic neuropathy is higher in those patients with increased urinary albumin levels than in those with normal excretion of albumin.

Autonomic activity in trauma patients based on variability of heart rate and respiratory rate

OBJECTIVE

To evaluate the effects of sympathetic and parasympathetic nervous system activity on the heart rate and other hemodynamic variables in acute emergency patients with mild to moderately severe trauma.

DESIGN

Clinical study.

SETTING

Level 1 university-run trauma service.

PATIENTS

Fourteen trauma patients studied immediately after admission to the emergency department.

INTERVENTIONS

We measured heart rate and respiratory rate variability by spectral analysis in the early period of mildly to moderately injured patients and compared the patterns of the low- (Lfa) and high-frequency (Hfa) areas of variability.

MEASUREMENTS AND MAIN RESULTS

The Lfa is the area under the spectral analysis curve within the frequency range of 0.04-0.10 Hz. This area reflects primarily the tone of the sympathetic nervous system as mediated by the cardiac nerve. The respiratory area or Hfa is a 0.12 Hz-wide frequency range centered around the fundamental respiratory frequency defined by the peak mode of the respiratory power spectrum. It is indicative of vagal outflow reflecting parasympathetic nervous system activity. The Lfa/Hfa, or "L/R ratio," reflects the balance between the sympathetic and parasympathetic nervous systems. The hemodynamic effects of bursts of autonomic activity in response to injury were explored by heart rate and respiratory rate variability measured with non-invasive hemodynamic monitoring consisting of bioimpedance cardiac output, heart rate, and mean arterial pressure to measure cardiac function and transcutaneous oxygen (PtcO2) to reflect tissue perfusion. During sudden surges of autonomic activity, we described increased heart rate variability reflecting increased Lfa and to a lesser degree to Hfa. Slightly later there was increased heart rate, mean arterial pressure, and cardiac index but decreased tissue perfusion indicated by the decreased PtcO2/FIO2 ratio.

CONCLUSIONS

Surges in autonomic activity in the period immediately after emergency department admission of trauma patients were associated with pronounced increases in cardiac index, mean arterial pressure, and heart rate and reduced tissue oxygenation.

Effect of treatment with losartan on cardiovascular autonomic and large sensory nerve fiber function in individuals with diabetes mellitus: a 1-year randomized, controlled trial

This study evaluated the effect of losartan, an angiotensin II receptor antagonist, on cardiovascular autonomic function and large sensory nerve fiber function in individuals with diabetes mellitus. In a double-blind placebo-controlled trial, individuals were randomly assigned to treatment with a daily oral dose of 50-mg losartan (n=24) or placebo (n=20) for 12 months. Tests of cardiovascular autonomic function (i.e., RR-variation during deep breathing and the Valsalva maneuver) and of large sensory nerve fiber function (i.e., vibratory thresholds) were measured at baseline and at 12 months. No significant difference at baseline was found for duration of diabetes, glycemic control, blood pressure, or body mass index (BMI) between the two groups. After 12 months, the decline in RR-variation that occurs over time appeared to be less for those taking losartan. There was, however, no statistically significant change in the results for any of the tests of cardiovascular autonomic function or vibratory thresholds between the groups. Multivariate analyses in the losartan study group revealed an independent association of duration of diabetes, change in (reduced) systolic blood pressure (SBP), and improved vibratory thresholds. This association was particularly noted for women. Pharmacologic agents may affect cardiovascular autonomic function by favorable or detrimental changes in the electrophysiology of the heart. The results of this study indicate that, although losartan may have slowed the normal decline in RR-variation, it did not result in any significant improvement in cardiovascular autonomic nerve fiber function. An association of vibratory thresholds and SBP was observed.

Sympathetic vasomotor response of the radial artery in patients with diabetic foot syndrome

OBJECTIVE

Neurophysiological assessment of the peripheral autonomic system is characterized by various limitations. An alternative approach to laser Doppler and venous plethymography is the assessment of the sympathetic vasomotor response of the radial artery obtained by continuous wave Doppler sonography. Nomogram data have been established and demonstrate the temporary disappearance of diastolic flow after coughing or deep inspiration.

RESEARCH DESIGN AND METHODS

We assessed the sympathetic vasomotor response in 25 patients (mean age 64 years, range 43-76) with diabetic foot syndrome. The Doppler data were correlated with nerve conduction studies of the median and peroneal nerve, the extent of radiologically diagnosed media sclerosis, and compared with nomogram values (n = 41).

RESULTS

Although similar mean flow velocities were found under baseline conditions, the flow pattern was characterized by higher pulsatility in the diabetic group (resistance index [RI] 1.1 vs. 0.7). No significant difference in RI was observed after coughing. The latency of onset of the response was prolonged (2.1 vs. 1.5 s), while the duration of the response did not differ (18 vs. 15 s). Only the nerve conduction velocity of the peroneal nerve correlated inversely with the RI. The extent of radiologically proven calcification tended to correlate with the pulsatility of the baseline signal and the response latencies.

CONCLUSIONS

The data obtained by this study suggest the concurrent existence of reduced vessel elasticity due to media sclerosis and dysfunction of the autonomic vasomotor system.

Corticotropin-releasing factor modulates cardiovascular and pupillary autonomic reflexes in man: is there a link to inflammation-induced autonomic nervous hyperreflexia?

In two recent studies, we found autonomic nervous hyperreflexia in subjects with chronic inflammatory diseases, particularly, in those subjects with higher degrees of systemic inflammation. Since corticotropin-releasing factor (CRF) is induced by inflammatory stimuli and acts within the brain to change neuroendocrine and autonomic activity, we investigated CRF modulation of standard autonomic nervous reflexes. Fifteen healthy subjects were administered 100 microg CRF i.v., which led to a short-term increase of heart rate (p < 0.001) and a decrease in systolic and diastolic blood pressure (p < 0.050). These changes were accompanied by a reduction in heart rate variation at rest (p = 0.010) and during the respiratory sinus arrhythmia test (p = 0.019), and a reduction of pupillary latency time (p = 0.038). In further 21 normal subjects we studied the effect of prednisolone treatment on autonomic nervous function (100 mg/d during three days --> CRF reduction), which resulted in an increase of heart rate (p < 0.001), increase of heart rate variation during the respiratory sinus arrhythmia test (p < 0.001), increase in pupillary latency time (p = 0.012), a increase in maximal pupillary area (p = 0.002), and a decrease in diastolic blood pressure (p = 0.002). In conclusion, induction of a low central CRF content by prednisolone leads to a marked hyperreflexia in respiratory sinus arrhythmia and hyporeflexia in the latency time test. It is obvious that CRF can regulate autonomic reflexes. Possibly, central CRF status may also influence autonomic reflexes during chronic inflammation due to chronically changed central CRF concentration.

Obesity is not a confounding factor for performing autonomic function tests in individuals with diabetes mellitus

AIM

Cardiovascular autonomic neuropathy is a serious complication of diabetes mellitus. Previous studies have revealed conflicting results with regard to the role of obesity and its effect on the performance of tests (e.g. RR-variation during deep breathing) for the determination of the presence of cardiovascular autonomic dysfunction. The objective of this study was to determine if obesity affects the performance and the reproducibility of autonomic function tests.

METHODS

This cross-sectional study included 159 diabetic individuals. Autonomic function tests included: RR-variation during deep breathing and the Valsalva ratio. These tests were assessed using the ANS2000 ECG Monitor and Respiration Pacer. RR-variation was measured by vector analysis (i.e. mean circular resultant, MCR). Reproducibility of the autonomic function tests was assessed by determining the coefficient of variation (CV) on repeat testing.

RESULTS

Using cut-off points to describe normal weight (body mass index (b.m.i.) < or = 25 kg/m(2)), overweight (b.m.i. 25.01-30 kg/m(2)), obese (b.m.i. 30.01-40 kg/m(2)), and morbidly obese (b.m.i. > or = 40.1 kg/m(2)), no difference was found for the MCR, Valsalva ratio, CV of the MCR, or CV of the Valsalva ratio among the various weight levels for individuals with type 1 or type 2 diabetes.

CONCLUSIONS

The results of this study indicate that obesity is not a confounding factor in the performance of autonomic function tests. Likewise, the reproducibility of autonomic function testing is not affected by obesity. Assessment of autonomic function is important for obese and non-obese individuals given that reduced RR-variation is associated with exercise intolerance, intraoperative cardiovascular lability and increased risk of mortality.

Effect of non-insulin-dependent diabetes mellitus on pulmonary function and exercise tolerance in chronic congestive heart failure

In chronic congestive heart failure (CHF), backward effects of left ventricular dysfunction alter pulmonary volumes and gas diffusion. Some of these disorders are detected in some patients with diabetes mellitus, possibly due to a microangiopathic process and nonenzymatic glycosylation of lung tissue proteins. We explored the possibility that coexistence of non-insulin-dependent diabetes mellitus (NIDDM) may potentiate the deterioration of lung function in CHF. In 20 normoglycemic patients (group 1) and in 20 patients with NIDDM (group 2), with New York Heart Association class II to III CHF due to idiopathic or ischemic cardiac disease, and in 20 controls (groups were age- and gender-matched), we investigated cardiac function, pulmonary volumes, carbon monoxide diffusion (DL(CO)) and its alveolar-capillary membrane (D(M)) subcomponent, oxygen uptake and dead space-to-tidal volume ratio (pVD/VT) at peak exercise (individualized ramp test), and slope of ventilation-to-carbon dioxide production ratio (VE/VCO(2)) during exercise. Although, compared with reference subjects, both patient groups had similar variations in left ventricular diastolic volume, ejection fraction, and pulmonary wedge pressure; in group 2 lung volumes, DL(CO), D(M), and oxygen uptake were significantly more reduced; in this group there was no overlap of individual results of DL(CO) and D(M) with those in controls; VE/VCO(2) slope and pVD/VT also were significantly increased, and inversely correlated with D(M). Thus, coexistence of NIDDM makes pulmonary dysfunction worse in CHF, and significantly enhances exercise intolerance.

Diagnosis and treatment of diabetic autonomic neuropathy

Diabetic autonomic neuropathy (DAN) is associated with a markedly reduced quality of life and poor prognosis. The manifestations of DAN cause multiple symptoms and involve the 1) cardiovascular system: resting tachycardia, reduced heart rate variability and circadian rhythm of heart rate and blood pressure, painless myocardial ischemia/infarction, orthostatic hypotension, exercise intolerance, perioperative instability, sudden death; 2) respiratory system: reduced ventilatory drive to hypercapnia/hypoxemia, sleep apnea; 3) gastrointestinal tract: esophageal motor dysfunction, diabetic gastroparesis, gallbladder atony, diabetic enteropathy, colonic hypomotility, anorectal dysfunction; and 4) genitourinary tract: diabetic cystopathy, erectile dysfunction. Treatment is based on four cornerstones: 1) causal treatment aimed at near-normoglycemia; 2) treatment based on pathogenetic mechanisms; 3) symptomatic treatment; and 4) avoidance of risk factors and complications. Pharmacologic treatment of symptomatic DAN may be difficult, due to limited efficacy and frequent adverse reactions. First-line treatments include midodrine for orthostatic hypotension, prokinetic drugs for gastroparesis, broad-spectrum antibiotics for diabetic diarrhea, and sildenafil for erectile dysfunction. Prior to an adequate symptomatic treatment a thorough risk-benefit estimate, aimed at maintaining the patient's quality of life, is required.

Cardiac responses to insulin-induced hypoglycemia in nondiabetic and intensively treated type 1 diabetic patients

Insulin-induced hypoglycemia occurs commonly in intensively treated patients with type 1 diabetes, but the cardiovascular consequences of hypoglycemia in these patients are not known. We studied left ventricular systolic [left ventricular ejection fraction (LVEF)] and diastolic [peak filling rate (PFR)] function by equilibrium radionuclide angiography during insulin infusion (12 pmol. kg(-1). min(-1)) under either hypoglycemic (approximately 2.8 mmol/l) or euglycemic (approximately 5 mmol/l) conditions in intensively treated patients with type 1 diabetes and healthy nondiabetic subjects (n = 9 for each). During hypoglycemic hyperinsulinemia, there were significant increases in LVEF (DeltaLVEF = 11 +/- 2%) and PFR [DeltaPFR = 0.88 +/- 0.18 end diastolic volume (EDV)/s] in diabetic subjects as well as in the nondiabetic group (DeltaLVEF = 13 +/- 2%; DeltaPFR = 0.79 +/- 0.17 EDV/s). The increases in LVEF and PFR were comparable overall but occurred earlier in the nondiabetic group. A blunted increase in plasma catecholamine, cortisol, and glucagon concentrations occurred in response to hypoglycemia in the diabetic subjects. During euglycemic hyperinsulinemia, LVEF also increased in both the diabetic (DeltaLVEF = 7 +/- 1%) and nondiabetic (DeltaLVEF = 4 +/- 2%) groups, but PFR increased only in the diabetic group. In the comparison of the responses to hypoglycemic and euglycemic hyperinsulinemia, only the nondiabetic group had greater augmentation of LVEF, PFR, and cardiac output in the hypoglycemic study (P < 0.05 for each). Thus intensively treated type 1 diabetic patients demonstrate delayed augmentation of ventricular function during moderate insulin-induced hypoglycemia. Although diabetic subjects have a more pronounced cardiac response to hyperinsulinemia per se than nondiabetic subjects, their response to hypoglycemia is blunted.

The heartbeat-evoked brain potential in patients suffering from diabetic neuropathy and in healthy control persons

OBJECTIVES

Neurotransmission from the heart to the brain results in a heartbeat evoked potential (HEP). This potential appears as a positive waveform ranging from 250 to 600 ms after the onset of ventricular contraction. Only limited information exists as to what extent the HEP is sensitive to a dysfunction in cardio-afferent pathways. Thus, the HEP was studied in patients with autonomic diabetic neuropathy.

METHODS

Twenty-five patients and a healthy control group of equal size participated. The HEP was obtained as the average over 1200 EEG sweeps (18 channels) sampled contingent upon the onset of ventricular contraction. A heartbeat attention task and a distraction task were employed. Patients answered a questionnaire pertaining to the frequency of subjective symptoms related to diabetic neuropathy.

RESULTS

The HEP amplitude at frontal, central and temporal locations was significantly diminished in patients in the latency range of 280-330 ms. A significant correlation was found between the questionnaire score of subjective autonomic symptoms and the reduction in the HEP.

CONCLUSIONS

We conclude that the HEP is sensitive to a comparably moderate abnormality in nerve function. Furthermore, we assume that the processing of subjective symptoms of the disease and the generation of the HEP share some common neuronal pathways.

Redistribution of sudomotor responses is an early sign of sympathetic dysfunction in type 1 diabetes

Patients with diabetic neuropathy typically have decreased sweating in the feet but excessive sweating in the upper body. Previous studies of sudomotor function in diabetes have included patients with longstanding disease. The present study was designed to test for the early presence of sudomotor dysfunction and to characterize its relation to glycemic control and other aspects of peripheral nerve function. A total of 37 patients (10 males, 27 females) enrolled in a longitudinal study, in which autonomic function was evaluated annually for 3 years. Patients enrolled 2-22 months after the diagnosis of type 1 diabetes. Forty-one age- and sex-matched healthy control subjects were also studied. Sweat production in response to acetylcholine stimulation was dramatically increased in the forearm at the time of the first evaluation (1.67 +/- 0.24 micro/cm2 in the diabetic patients vs. 1.04 +/- 0.14 microl/cm2 in the control subjects, P < 0.05). Likewise, the ratio of sweating in the forearm to sweating below the waist was higher in the diabetic patients (0.553 +/- 0.07 microl/cm2) than in the control subjects (0.385 +/- 0.04 microl/cm2, P < 0.05). Forearm sweat was negatively associated with the renin-toprorenin ratio and vanillylmandelic acid (VMA) excretion (P < 0.025), tests of sympathetic nerve function. The ratio of sweating in the forearm to sweating in the foot was likewise increased in diabetic patients with poor glycemic control. We interpret this redistribution of sudomotor responses to be indicative of sympathetic nerve injury and conclude 1) that the sympathetic nervous system is especially vulnerable to the adverse effects of chronic hyperglycemia and 2) that sympathetic dysfunction can be detected very early in type 1 diabetes.

Antibodies to glutamic acid decarboxylase and peripheral nerve function in type 1 diabetes

Autoimmune mechanisms have been implicated in the pathophysiology of diabetic neuropathy. We studied the association between glutamic acid decarboxylase (GAD65) and islet cell (IA-2) autoantibodies as well as autoantibodies to the autonomic nervous system and peripheral nerve function in recent onset type 1 diabetes. Thirty-seven patients (27 females and 10 males) enrolled 2-22 months after diagnosis. Humoral factors, glycemic control, and peripheral nerve function were measured annually for 3 yr. Patients with high GAD65Ab had worse glycemic control and higher insulin requirements. Patients with high GAD65Ab had slower motor nerve conduction velocities in the median, ulnar, and peroneal nerves (P < 0.025 for each nerve). The mean motor nerve conduction velocity Z scores at the time of the third evaluation was 0.341 +/- 0.25 for the low GAD65Ab patients and -0.600 +/- 0.25 for the high GAD65Ab patients (P < 0.01). Similar differences between the low and high GAD65Ab groups were observed for F wave latencies, thermal threshold detection, and cardiovascular autonomic function. The composite peripheral nerve function Z scores in the low GAD65Ab patients were 0.62 +/- 11, 0.71 +/- 0.19, and 0.21 +/- 0.14 at the first, second, and third evaluations, significantly different from those in the high GAD65Ab patients in whom they were -0.35 +/- 0.15, -0.46 +/- 0.18, and -0.42 +/- 0.16 (P < 0.001). In summary, GAD65Ab in patients with recent onset type 1 diabetes are associated with worse glycemic control and slightly worse peripheral nerve function. Although the latter remained within normal limits and none of the patients had clinical neuropathy, the GAD65Ab-related differences in composite peripheral nerve function were highly significant (P < 0.001) and could not be attributed to GAD65Ab-related differences in glycemic control.

Decreased prorenin processing develops before autonomic dysfunction in type 1 diabetes

It is well documented that diabetic patients with chronic complications have decreased renin secretion and elevations in the renin precursor prorenin. It is uncertain, however, whether the abnormal processing of prorenin is reflective of microvascular disease, hypertension, or autonomic neuropathy. Dechaux et al. (Transplant Proc. 18:1598-1599, 1986) observed abnormalities in prorenin processing in uncomplicated diabetes and suggested that it was the result of subclinical autonomic neuropathy. To test this hypothesis, we measured renin, prorenin, and autonomic function in early type 1 diabetes at a time when there is little or no microvascular disease or hypervolemia. Thirty-seven patients (10 males, 27 females) enrolled 2-22 months after diagnosis in a longitudinal study in which renin, prorenin, and autonomic function were measured annually for 3 years. Forty-one age-matched control subjects were also studied. PRA in the diabetic patients at the time of the second and third evaluations was 1.71 +/- 0.24 ng angiotensin I/mL x h and 1.67 +/- 0.24 ng angiotensin I/mL x h, respectively, significantly lower (P < 0.05) than that of the control subjects in whom PRA was 2.96 +/- 0.38 ng angiotensin I/mL x h. Prorenin was not different in the diabetic patients in comparison with controls. The renin to prorenin ratio in the diabetic patients at the time of the first, second, and third evaluations was 0.260 +/- 0.03, 0.235 +/- 0.05, and 0.227 0.05, respectively, significantly lower (P < 0.01) than in control subjects in whom the renin to prorenin ratio was 0.475 +/- 0.08. Despite this, at the time of the first and second evaluations, there was no evidence of autonomic dysfunction and no correlation between any test of autonomic function and the renin to prorenin ratio. At the time of the third evaluation, however, the intermediate frequency (0.04-0.15 Hz) power spectra while patients were supine (an index of sympathetic modulation of heart rate variability) showed a highly significant (P < .001) correlation with the renin to prorenin ratio. High frequency (0.15-0.40 Hz) spectra from supine patients at the third evaluation also correlated with the renin to prorenin ratio (P < 0.01). We conclude abnormal processing of prorenin develops in diabetic patients prior to microvascular disease, even before the first evidence of autonomic dysfunction. Although the latter may play a contributory role, additional as yet unidentified mechanisms seem to interrupt the processing of prorenin in early diabetes.

Autonomic dysfunction and hyperdynamic circulation in cirrhosis with ascites

Patients with advanced cirrhosis frequently show hemodynamic abnormalities. Autonomic dysfunction (AD) is also common and, owing to the importance of autonomic function in cardiovascular homeostasis, it may be involved in the pathogenesis of the hyperdynamic circulation. We, therefore, evaluated the hemodynamic status and autonomic function in 30 patients with cirrhosis, most of them with an advanced stage of the disease. Autonomic function was assessed with 7 cardiovascular tests exploring the vagal or sympathetic function. Each test was scored from 1 to 3 (normal, borderline, altered). Cardiac index (CI) was measured by an echocardiogram. Twenty-four (80%) patients showed an AD, this being definite in 14 (47%) patients. A vagal dysfunction (VD) was found in 19 patients (63%), this being definite in 11 patients (37%), and a sympathetic dysfunction (SD) in 7 patients (definite in 3 [10%] patients). The patients with AD showed a faster heart rate (P =.021), lower indicized peripheral vascular resistance (P =.013), and increased CI (P =.004) than patients without AD whereas mean arterial pressure did not differ. Similar results were seen by grouping patients according to the VD. AD score was directly correlated with heart rate (r = 0.53; P =.002) and CI (r = 0.45; P =. 016), and inversely correlated with peripheral vascular resistance (r = 0.46; P =.013). Even closer correlations were found with vagal score. AD (mainly VD) may be involved in the pathogenesis of the hyperdynamic circulatory syndrome of patients with advanced cirrhosis.

Changes in clinical measures of autonomic nervous system function related to cancer chemotherapy-induced nausea

Individual cancer patients differ in their nausea/vomiting response to chemotherapy. It is not known why patients receiving the same chemotherapy have different severity of side effects. Several lines of research implicate the autonomic nervous system (ANS) in the development of chemotherapy-induced nausea. We examined the association between autonomic reactivity and the level of nausea experienced following chemotherapy in 20 patients with ovarian cancer treated with cisplatin or carboplatin who received the same antiemetic. We applied eight common non-invasive clinical tests of autonomic function prior to inpatient chemotherapy treatment, 2 h after treatment and again 24 h following treatment. Two hours after chemotherapy and before any nausea was reported by the patients, the nine patients who subsequently experienced high levels of nausea had a greater overall percentage of abnormal clinical ANS tests than the 11 patients who subsequently developed low levels of nausea (P < 0.01). Twenty-four hours after treatment, the overall number of abnormal autonomic tests remained non-significantly higher than at the pretreatment baseline for the high nausea group. Demographic and clinical characteristics were not related to chemotherapy-induced nausea in this sample. Autonomic reactivity appears to be related to the development of nausea following chemotherapy. Further investigation of ANS involvement in chemotherapy-induced nausea could increase understanding of nausea etiology and potentially lead to the prediction of susceptible patients.

The perception of safe driving ability during hypoglycemia in patients with type 1 diabetes mellitus

PURPOSE

Insulin-induced hypoglycemia and its sequelae of cognitive impairment may place patients with type 1 diabetes at risk when driving and when making decisions about driving. Little is known about the factors that influence judgments of safe driving ability during hypoglycemia in these patients.

PATIENTS AND METHODS

Thirty men and 30 women with uncomplicated type 1 diabetes (age [mean +/- SD] 33 +/- 9 years, duration 9 +/- 3 years, hemoglobin A1c level 8.7% +/- 1.0%) underwent a stepped hypoglycemic insulin clamp. Serum glucose levels were reduced from 120 mg/dL to 80, 70, 60, 50, and then 40 mg/dL during 190 minutes. At each glucose plateau, patients completed a symptom questionnaire and neuropsychological test, estimated their glucose level, and reported whether they could drive safely.

RESULTS

The proportion of patients judging that they could drive safely decreased as serum glucose levels decreased from 70% at 120 mg/dL to 22% at 40 mg/dL. Men and middle-aged patients were more likely to consider it safe to drive during hypoglycemia than women and those under 25 years of age. Those who were symptomatic and those who recognized hypoglycemia were less likely to report safe driving ability during hypoglycemia. Most patients who were cognitively impaired appeared to recognize this and reported that they could not drive safely at a serum glucose level of 40 mg/dL.

CONCLUSIONS

Adults with type 1 diabetes need educational reinforcement of safe driving habits, particularly to check glucose levels before driving. Glucose levels less than 70 mg/dL should be treated before driving. This information is as important for middle-aged, experienced drivers as it is for younger, inexperienced drivers.

Cardiovascular autonomic dysfunction and hemodynamic response to anesthetic induction in patients with coronary artery disease and diabetes mellitus

Autonomic neuropathy is a major complication of diabetes mellitus and is reported to be associated with increased perioperative hemodynamic instability. We investigated the relationship between autonomic dysfunction and hemodynamic response to anesthetic induction in diabetic and nondiabetic patients with coronary artery disease. We studied 60 patients scheduled for coronary artery surgery, 30 suffering from diabetes mellitus. Preoperative evaluation included traditional cardiovascular autonomic function tests (coefficient of variation of 150 beat-to-beat intervals in heart rate at rest, heart rate response to deep breathing, and heart rate and arterial blood pressure response to standing), spectral analysis of blood pressure and heart rate variability (HRV), and the computation of spontaneous baroreflex sensitivity. After premedication with clorazepate, anesthesia was induced with sufentanil (0.5 microg/kg), etomidate (0.1-0.2 mg/kg), and vecuronium (0.1 mg/kg). Heart rate and blood pressure before anesthetic induction and before and after tracheal intubation were compared between groups. Autonomic function tests, spectral analysis of HRV, and spontaneous baroreflex sensitivity revealed significant differences between patient groups. Most diabetic patients (n = 23) had one or more abnormal test results, in contrast to most nondiabetic patients, who did not show signs of autonomic neuropathy (n = 23). There was no relationship between cardiovascular autonomic function and hemodynamic behavior during anesthetic induction. The blood pressure response to anesthetic induction was not different between patient groups, even when comparing the subgroups with and without abnormal autonomic function tests. These findings indicate that increased hemodynamic instability during anesthetic induction is not obligatory in patients with diabetes mellitus and autonomic dysfunction.

IMPLICATIONS

This study indicates that increased hemodynamic instability during anesthetic induction is not obligatory in patients with coronary artery disease and autonomic dysfunction.

Regression and progression of cardiac sympathetic dysinnervation complicating diabetes: an assessment by C-11 hydroxyephedrine and positron emission tomography

Cardiovascular denervation complicating diabetes has been implicated in sudden cardiac death potentially by altering myocardial electrical stability and impairing myocardial blood flow. Scintigraphic evaluation of cardiac sympathetic integrity has frequently demonstrated deficits in distal left ventricular (LV) sympathetic innervation in asymptomatic diabetic subjects without abnormalities on cardiovascular reflex testing. However, the clinical significance and subsequent fate of these small regional defects is unknown. This study reports the results of a prospective observational study in which positron emission tomography (PET) with (-)-[11C]-meta-hydroxyephedrine ([11C]-HED) was used to evaluate the effects of glycemic control on the progression of small regional LV [11C]-HED retention deficits in 11 insulin-dependent diabetic subjects over a period of 3 years. The subjects were divided into two groups based on attained glycemic control during this period: group A contained six subjects with good glycemic control (individual mean HbA1c <8%), and group B contained five subjects with poor glycemic control (individual mean HbAlc > or =8%). Changes in regional [11C]-HED retention were compared with reference values obtained from 10 healthy aged-matched nondiabetic subjects. At baseline, abnormalities of [11C]-HED retention affected 7.3%+/-1.4% and 9.9%+/-6.6% of the LV in group A and B subjects, respectively, with maximal deficits of LV [ C]-HED retention involving the distal myocardial segments. At the final assessment in group A, the extent of the deficits in [11C]-HED retention decreased to involve only 1.7%+/-0.7% of LV (P<.05 v. baseline scan), with significant increases in [11C]-HED retention occurring in both the distal and proximal myocardial segments. In contrast, in group B with poor glycemic control, the extent of [11C]-HED deficits increased to involve 34%+/-3.5% of the LV (P<.01 v. baseline), with retention of [11C]-HED significantly decreasing in the distal segments ([11C]-HED retention index, 0.066+/-0.003 v. 0.057+/-0.002, P<.05, at baseline and final assessment, respectively). Poor glycemic control was associated with increased heterogeneity of LV [11C]-HED retention, since three of five group B subjects developed abnormally increased [11C]-HED retention in the proximal myocardial segments. In conclusion, defects in LV sympathetic innervation can regress or progress in diabetic subjects achieving good or poor glycemic control, respectively. In diabetic subjects with early cardiovascular denervation, institution of good glycemic control may prevent the development of myocardial sympathetic dysinnervation and enhanced cardiac risk.

Autonomic dysfunction in patients with achalasia of the oesophagus

It has been suggested that achalasia is associated with extraoesophageal sympathetic and parasympathetic dysfunction. In a prospective study we applied conventional ultrasonography and duplex sonography to investigate basal and postprandial peak systolic velocity (PSV), pulsatility index (PI) and resistance index (RI) of superior mesenteric artery and PSV of portal vein in nine patients with achalasia and 10 healthy controls (study I). In addition, in eight of these patients autonomic nervous function was investigated by pupillary function tests as well as cardiovascular reflex tests and compared with eight age- and sex-matched controls (study II). The results indicated that postprandial increase of PSV in the superior mesenteric artery was significantly lower, and postprandial decrease of PI and RI significantly higher in achalasia compared to healthy controls. In contrast, postprandial increase of PSV in the portal vein was not significantly different between both groups. Autonomic function tests revealed significant lower maximal pupillary contraction and redilatation velocities, significantly lower heart rate variation during orthostasis, deep respiration test and Valsalva manoeuvre in achalasia compared to controls. It is concluded that achalasia is associated with extraoesophageal autonomic nervous dysfunction that involves cardiovascular and pupillary function as well as regulation of mesenteric arterial blood flow.

Abnormal oxygen uptake kinetic responses in women with type II diabetes mellitus

Persons with type II diabetes mellitus (DM), even without cardiovascular complications have a decreased maximal oxygen consumption (VO2 max) and submaximal oxygen consumption (VO2) during graded exercise compared with healthy controls. We evaluated the hypothesis that change in the rate of VO2 in response to the onset of constant-load exercise (measured by VO2-uptake kinetics) was slowed in persons with type II DM. Ten premenopausal women with uncomplicated type II DM, 10 overweight, nondiabetic women, and 10 lean, nondiabetic women had a VO2 max test. On two separate occasions, subjects performed 7-min bouts of constant-load bicycle exercise at workloads below and above the lactate threshold to enable measurements of VO2 kinetics and heart rate kinetics (measuring rate of heart rate rise). VO2 max was reduced in subjects with type II DM compared with both lean and overweight controls (P < 0.05). Subjects with type II DM had slower VO2 and heart rate kinetics than did controls at constant workloads below the lactate threshold. The data suggest a notable abnormality in the cardiopulmonary response at the onset of exercise in people with type II DM. The findings may reflect impaired cardiac responses to exercise, although an additional defect in skeletal muscle oxygen diffusion or mitochondrial oxygen utilization is also possible.

Effect of aldose reductase inhibition on cardiovascular reflex tests in patients with definite diabetic autonomic neuropathy over a period of 2 years

The potential of the aldose reductase inhibitor tolrestat to ameliorate definite diabetic autonomic neuropathy (DAN), as defined by standard cardiovascular autonomic function tests, was evaluated in 35 patients over a period of 2 years, with repeated measurements at 3-month intervals. The effect of tolrestat (200 mg a day) was compared with that of placebo on 35 controls with diabetes mellitus, of similar age, gender, and glycemic control. In the placebo group, a significant deterioration of the indices, with the exception of Valsalva ratio, was recorded, while tolrestat induced a significant beneficial change in the values of most standard cardiovascular reflex tests, in comparison to baseline and placebo. The deep breathing tests (expiration-inspiration ratio, standard deviation, and mean circular resultant of R-R intervals), postural index, and postural hypotension were favorably affected. Three of 35 patients on tolrestat (8.6%) developed high transaminases levels (more than threefold the upper normal limit) and were withdrawn from the study. In conclusion, tolrestat improved autonomic nervous system function in patients with definite DAN, in comparison to baseline and placebo. The clinical importance of this finding needs further investigation.

Scintigraphic assessment of regionalized defects in myocardial sympathetic innervation and blood flow regulation in diabetic patients with autonomic neuropathy

OBJECTIVES

This study sought to evaluate whether regional sympathetic myocardial denervation in diabetes is associated with abnormal myocardial blood flow under rest and adenosine-stimulated conditions.

BACKGROUND

Diabetic autonomic neuropathy (DAN) has been invoked as a cause of unexplained sudden cardiac death, potentially by altering electrical stability or impairing myocardial blood flow, or both. The effects of denervation on cardiac blood flow in diabetes are unknown.

METHODS

We studied 14 diabetic subjects (7 without DAN, 7 with advanced DAN) and 13 nondiabetic control subjects without known coronary artery disease. Positron emission tomography using carbon-11 hydroxyephedrine was used to characterize left ventricular cardiac sympathetic innervation and nitrogen-13 ammonia to measure myocardial blood flow at rest and after intravenous administration of adenosine (140 microg/kg body weight per min).

RESULTS

Persistent sympathetic left ventricular proximal wall innervation was observed, even in advanced neuropathy. Rest myocardial blood flow was higher in the neuropathic subjects (109 +/- 29 ml/100 g per min) than in either the nondiabetic (69 +/- 8 ml/100 g per min, p < 0.01) or the nonneuropathic diabetic subjects (79 +/- 23 ml/100 g per min, p < 0.05). During adenosine infusion, global left ventricular myocardial blood flow was significantly less in the neuropathic subjects (204 +/- 73 ml/100 g per min) than in the nonneuropathic diabetic group (324 +/- 135 ml/100 g per min, p < 0.05). Coronary flow reserve was also decreased in the neuropathic subjects, who achieved only 46% (p < 0.01) and 44% (p < 0.01) of the values measured in nondiabetic and nonneuropathic diabetic subjects, respectively. Assessment of the myocardial innervation/blood flow relation during adenosine infusion showed that myocardial blood flow in neuropathic subjects was virtually identical to that in nonneuropathic diabetic subjects in the distal denervated myocardium but was 43% (p < 0.05) lower than that in the nonneuropathic diabetic subjects in the proximal innervated segments.

CONCLUSIONS

DAN is associated with altered myocardial blood flow, with regions of persistent sympathetic innervation exhibiting the greatest deficits of vasodilator reserve. Future studies are required to evaluate the etiology of these abnormalities and to evaluate the contribution of the persistent islands of innervation to sudden cardiac death complicating diabetes.

The effect of intensive diabetes therapy on measures of autonomic nervous system function in the Diabetes Control and Complications Trial (DCCT)

In the Diabetes Control and Complications Trial (DCCT), 1441 insulin-dependent diabetic patients in the primary prevention and secondary intervention cohorts were randomly assigned to either conventional or intensive therapy and followed for up to 9 years. Baseline and biennial measurements of autonomic function (R-R variation, Valsalva ratio, and postural testing) as well as quarterly assessment of autonomic symptoms were performed throughout the trial. There were no differences at baseline between patients randomized to intensive vs conventional therapy. In general, autonomic abnormalities increased during the trial; however, R-R variation was less abnormal in the intensively treated secondary intervention (7% with abnormal results at 4-6 years) compared with the conventionally treated group (14% with abnormal results, p = 0.004) and in the combined cohorts (5% of intensive treatment subjects with abnormal results vs 9% of conventional treatment subjects, p = 0.0017). There were few abnormal Valsalva ratios or postural tests at baseline or during the trial. No significant difference in Valsalva ratio or postural tests occurred between the intensive and conventional treatment groups. Both the R-R variation and the Valsalva ratio had significantly greater slopes of decline over time in the patients randomized to conventional therapy (1.48 points per year and 0.015 per year, respectively) compared to those randomized to intensive therapy (0.912 points per year and 0.0025 per year). Of the symptoms related to autonomic function, only incomplete bladder emptying was significantly more common in the conventional group. In summary, the DCCT documented that intensive therapy can slow the progression and the development of abnormal autonomic tests.

Association of autonomic nervous hyperreflexia and systemic inflammation in patients with Crohn's disease and ulcerative colitis

The autonomic nervous system modulates gastrointestinal motility, secretion and mucosal immunity. Its dysfunction may be of pathogenetic importance in inflammatory bowel disease (IBD). This study aimed at investigating the autonomic nervous function in patients with IBD. Forty-seven patients with IBD, 28 with Crohn's disease (CD) and 19 with ulcerative colitis (UC), were investigated by means of 5 cardiovascular and 2 pupillary standardized autonomic nervous function tests. In CD and UC, cardiovascular autonomic neuropathy was very rare (0%, 5%), whereas pupillary autonomic neuropathy was more prevalent (21%, 21%). In contrast to autonomic neuropathy, overall cardiovascular (CD: 29%, UC: 26%) and pupillary autonomic hyperreflexia (46%, 37%) were found more often. Patients with CD and UC demonstrated elevated percentiles in the respiratory sinus arrhythmia test as compared to controls (RSA: 82.3 +/- 3.9%, 80.0 +/- 5.9%, controls: 50.0% +/- 1.5%, p < 0.0001). CD patients with, as compared to patients without, RSA hyperreflexia had significantly higher CDAIs (p < 0.001), increased erythrocyte sedimentation rates (p < 0.005) and more often extraintestinal disease manifestations (p < 0.001). UC patients with, as compared to patients without, pupillary latency time hyperreflexia had lower hemoglobin (p < 0.05), lower albumin (p < 0.01) and increased erythrocyte sedimentation rates (p < 0.05). Autonomic hyperreflexia was significantly associated with more severe inflammation and systemic disease in IBD. Hyperreflexia may be a response to inflammation or a pathogenetic element that drives mucosal inflammation.

[Cardiovascular and pupillary autonomic and somatosensory neuropathy in chronic diseases with autoimmune phenomena. A comparative study of patients with Crohn disease, ulcerative colitis, systemic lupus erythematosus, progressive systemic sclerosis and type I diabetes mellitus]

BACKGROUND

During the last years, examination of autonomic nervous function and of autonomic neuropathy has attracted attention not only in diabetes mellitus research but also in other areas of internal medicine. However, patients with various chronic diseases with autoimmune phenomenons have never been investigated in a comparative study with standardized examination techniques. Hence, the aim of the study was to examine the prevalence and the severity of autonomic neuropathy in patients with the following chronic diseases.

PATIENTS AND METHODS

We investigated 28 patients with Crohn's disease (CD: age: 32.4 +/- 2.0 y), 17 patients with ulcerative colitis (UC: 39.7 +/- 3.6 y), 39 patients with systemic lupus erythematosus (SLE: 34.9 +/- 2.0 y), 38 patients with progressive systemic sclerosis (pSS; 51.5 +/- 2.4 y) and 65 patients with insulin-dependent diabetes mellitus (IDDM: 35.5 +/- 1.6 y). Cardiovascular autonomic (cANP), pupillary autonomic (pANP), and sensorimotor (ssNP) neuropathy were assessed by standardized techniques.

RESULTS

Prevalence rates for cANP, pANP and ssNP were found to be 0%, 19%, and 7% in CD, 6%, 25%, and 18% in UC, 5%, 29%, and 10% in SLE, 11%, 16%, and 32% in pSS, and 26%, 66%, and 29% in IDDM, respectively.

CONCLUSION

The study demonstrated patients with IDDM to have the highest prevalence rates of cANP and pANP. Patients with other chronic diseases, particularly SLE, pSS and UC, had high prevalence rates of pANP. This may be due to alterations of structures of the central nervous system in these patients. cANP was rare in patients with inflammatory bowel disease and ssNP was found very often in patients with pSS, probably due to local fibrotic lesions. The various disease groups differ in the pattern and severity of autonomic and sensorimotor neuropathy, which indicates that different structures and neuropathogenic mechanisms may be involved.

Decreased sympatho-adrenal activity in diabetic patients with autonomic dysfunction following mental stress

The sympathetic nervous system is of major importance in the regulation of numerous physiological functions. While it is clearly established that there is a decreased noradrenergic status in people with autonomic neuropathy, the epinephrine secretion is much more controversial. Basal and mental stress-stimulated plasma catecholamine levels were measured in 42 diabetic patients with and without pathological cardiovascular function tests and in 13 healthy, non-diabetic control subjects. In addition, the excretion of catecholamines was measured in a 24 h urine collection and compared with the stress stimulated plasma levels. During mental stress exposure a diminished epinephrine secretion was found in diabetic patients with autonomic neuropathy compared with diabetic patients without neuropathy and the healthy control group (p < 0.05: respectively). The decreased epinephrine response to mental stress was strongly correlated with a diminished urinary excretion of this "neurotransmitter' (r = 0.46; p < 0.01). Diabetic patients suffering from cardiovascular autonomic neuropathy exhibit a diminished sympatho-adrenal response following mental stress exposure. Both measurement of urinary and mental stress stimulated plasma epinephrine levels following mental stress provide reliable information regarding sympatho-adrenal activity in diabetic patients.

Botulinum toxin: influence on respiratory heart rate variation

Remote adverse effects of local intramuscular botulinum toxin were investigated in a prospective follow-up study. Twenty-six patients with spasmodic torticollis were examined (18 women, eight men, 45 +/- 13 years). Respiratory heart rate variation (HRV) was investigated by a computerized method. Different parameters were recorded (beats per minute, coefficient of variation, root mean square successive difference (RMSSD), spectral analysis, difference and quotient between maximum and minimum RR intervals, mean circular resultant). After one intramuscular injection of 12.5 ng botulinum toxin (Porton Products Ltd., England), no significant influence on HRV was seen. After the second injection, a significant attenuation was seen of four parameters (coefficient of variation, Rmax - Rmin, Rmax divided by Rmin, mean circular resultant) that lasted up to several months. No clinically manifest remote side effects and no cardiac arrhythmia were seen for several months of botulinum toxin treatment. Our investigation proves an effect of local intramuscular botulinum toxin on autonomic cardiac innervation.

Measurement of heart rate variations: influencing factors, normal values and diagnostic impact on diabetic autonomic neuropathy

Different methods of heart rate variation (HRV) measurement are recommended to assess disturbances of cardiovascular reflexes in autonomic polyneuropathies. Influencing factors on the E/I-ratio, HRV variations during Valsalva's maneuver, and change of position from lying down to standing up, as well as age, gender, time of day and satiety were investigated in healthy volunteers. Normal values were then calculated and a total of 100 diabetics with clinically manifest neuropathy of different stages (N0 = 8, N1 = 15, N2a = 24, N2b = 28, N3 = 25), 26 of whom were insulin-dependent and 74 non-insulin-dependent, were examined. Apart from clinical examination, nerve conduction velocity (NCV) measurement of five nerves as well as amplitude measurement of evoked sensory and motor action potentials was performed. No significant influence of the time of day the test was performed could be found. Test reproducibility was good, day-to-day differences did not reach a significant level. This was also true for the test results before and after food intake. Gender-correlated test result differences could not be proven. Statistical analysis showed significant differences between the overall group of diabetics and controls. The difference was most accentuated in the E/I ratio. The further developed the clinical picture of neuropathy, the more pathological were the results obtained in different tests. The results suggest that most changes leading to pathological values of NCV and HRV occur in a clinical stage in which no, or only very slight, clinical signs give evidence of diabetic neuropathy (N0-N1). Therefore, these examinations should, especially, be performed in diabetics with no, or only slight, clinical signs of neuropathy in order to reveal those patients with neuropathic disturbances at an initial stage.

Identifying delirious states and autonomic cardiovascular dysfunction associated with amitriptyline treatment by standardized analysis of heart rate

Ninety-one patients treated with amitriptyline and 60 normal control subjects underwent a standardized heart rate analysis in supine posture. Tests included the determination of time- and frequency-derived measurements of heart rate variability. The patients differed significantly from the control subjects in all parameters investigated. Two-thirds of the patients treated with a tricyclic antidepressant (TCA) reached values that met the criteria for cardiovascular autonomic neuropathy. Our results provide evidence that heart rate analysis might be a more sensitive tool in diagnosing amitriptyline-associated anticholinergic delirium than determination of TCA plasma levels. Further research is needed to elucidate what implications the TCA-associated alteration of autonomic cardiovascular function might have for patients.

Cognitive function in patients with insulin-dependent diabetes mellitus during hyperglycemia and hypoglycemia

BACKGROUND

To determine the impact of glycemic control, gender, and other relevant parameters on cognitive function during exposure to different blood glucose levels in patients with insulin-dependent diabetes mellitus (IDDM), we examined neuropsychologic function during experimentally induced periods of hyperglycemia and hypoglycemia.

METHODS

We studied 20 men and 22 women, aged 18 to 44 years, with IDDM duration of 3 to 14 years and HbA1 values ranging from 5.8% to 18.0% (nondiabetic range 5.4% to 7.4%). We used a controlled experimental setting involving tests of sensory perceptual processing, simple motor abilities, attention, learning and memory, language, and spatial and constructional abilities at plasma glucose levels of 2.2, 5.6, 8.9, 14.4, and 21.1 mmol/L. Patients were blind to the glucose level. Tests used at each glucose level included reaction time (simple and choice), digit vigilance, trail making part B, word recall, digit sequence learning, and verbal fluency.

RESULTS

All aspects of neuropsychologic function were diminished at 2.2 mmol/L when compared with basal levels of performance at 8.9 mmol/L, whereas no alterations were observed at 14.4 or 21.1 mmol/L. Tests involving associative learning, attention, and mental flexibility were the most affected during hypoglycemia. Glycemic control was not correlated with neuropsychologic function at any glucose level. Women demonstrated less of an impairment in neuropsychologic function than men at 2.2 mmol/L.

CONCLUSIONS

Cognitive function in IDDM patients was generally well-preserved even at substantially elevated blood glucose levels. Deficits in all relevant areas of cognitive function occurred during hypoglycemia (2.2 mmol/L), irrespective of prior glycemic control, and women with IDDM were less cognitively impaired than men with IDDM during hypoglycemia.

Autonomic nerve dysfunction in patients with bolus-specific esophageal dysmotility

The pathogenetic mechanisms causing esophageal dysmotility is not well understood. We examined 13 patients with solid bolus dysphagia in a radiologic barium study including the swallowing of a 14-mm tablet. In all 13 patients the tablet was caught in the proximal or midesophagus. In 8 patients, the entrapment was associated with symptoms (Group 1) whereas in 5 patients (Group 2), no symptoms were reported. All 13 patients together with a control group of 56 healthy, nondysphagic subjects were tested for autonomic nerve function. Autonomic nerve function tests included registration of electrocardiographic R-R interval variation during deep breathing test (E/I ratio), a test of parasympathetic, vagal, nerve function. The results showed that the E/I ratio was significantly lower in patients with symptoms of bolus-specific esophageal dysmotility (-2,19 [1.76]) (median [interquartile range]) compared with patients without symptoms (0.05 [2, 87], p = 0.0192) and controls (-0.25 [1.26], p = 0.0009). In conclusion, symptomatic bolus-specific esophageal dysmotility is associated with vagal nerve dysfunction.

The influence of the type, duration, severity and levodopa treatment of Parkinson's disease on cardiovascular autonomic responses

The influence of the type, duration, severity and levodopa treatment of Parkinson's disease on autonomic involvement has been assessed. The Valsalva manoeuvre, deep breathing, handgrip and orthostatic tests were performed in 50 patients with Parkinson's disease and in a control group of 30 healthy subjects. No attempt was made to classify further patients with parkinsonian features into groups such as the Shy-Drager syndrome or multiple system atrophy. All test results were significantly smaller in patients than in healthy subjects. The diastolic pressure increase during handgrip was significantly smaller in akinetic-rigid than in tremor-akinetic-rigid type patients. The Valsalva ratio and orthostatic test results were significantly smaller in patients with longer duration than in those with shorter duration of disease. All test results except those of the orthostatic test were significantly smaller in patients with the more severe form than in those with the less severe form of disease. Comparing test results of levodopa-treated and -untreated patients no significant differences were found. Our studies in parkinsonian patients suggest that (1) sympathetic impairment is more pronounced in akinetic-rigid than in tremor-akinetic-rigid type patients; (2) sympathetic impairment occurs early, whereas parasympathetic impairment develops later; (3) sympathetic and parasympathetic impairment parallels the severity of disease; (4) orthostatic parameters are more duration-sensitive than severity-sensitive; (5) chronic levodopa treatment does not markedly influence cardiovascular autonomic responses.

Assessment of diabetic neuropathy: definition of norm and discrimination of abnormal nerve function

One hundred one normal subjects and 46 patients were investigated. Various objective and subjective tests for polyneuropathies were compared. Motor and sensory nerve conduction velocities are the most sensitive tests. In normals, age hardly influenced nerve conduction velocities. This is believed to be a result of the strict exclusion criteria. Diagnostic sensitivity is also high with the vibration fork test and with vibratometry at the big toe. Results with the method of limits are as reliable and sensitive as more cumbersome techniques, such as the titration method and the forced choice method. Thermal thresholds and cardiovascular tests are less sensitive. The most correct overall classification is attained with a combination of tests reflecting the function of different nerve fiber classes in the peripheral and autonomic nervous systems.

A comparison of cardiovascular reflex tests and spectral analysis of heart rate variability in healthy subjects

Determination of whether results of cardiovascular reflex tests and spectral analysis of heart rate variability are age dependent and whether there is correlation between results of both, cardiovascular reflex tests (the Valsalva manoeuvre, deep breathing test, handgrip test, cold face stimulus test, orthostatic test) and spectral analysis of heart rate variability were performed on 83 healthy volunteers of both genders, aged 21 to 70 years. We found that results of all heart rate based tests and results of spectral analysis decreased with aging, while results of blood pressure based tests did not. Parasympathetic activity predominated in younger subjects, while in older subjects sympathetic activity was dominant. Valsalva, deep breathing, and orthostatic ratios correlated with integrals of amplitude spectra in the standing posture and deep breathing and cold face stimulus ratios with integrals of amplitude spectra in the supine posture, whereas blood pressure changes during handgrip and orthostatic test did not correlate with integrals of the amplitude spectra. These findings suggest that tests based on heart rate may be more sensitive than tests based on blood pressure changes. This study supports the use of spectral analysis as an additional clinical test of autonomic nervous system function and stresses the importance of age in the evaluation of the results of autonomic nervous system function testing.