Automatic analysis of heart rate variation: II. Findings in patients attending an EMG laboratory

Autonomic dysfunction in the early stage of ALS with bulbar involvement

Our objective was to assess the autonomic function of ALS patients with and without bulbar signs to characterize dysautonomia in ALS disease. Standard autonomic tests and spectral analysis of heart rate variability (HRV), reflecting changes in the sympathovagal balance, were examined in 33 ALS patients (14 with bulbar signs) and 30 controls. Results showed that in the supine position, ALS patients had significantly lower total power and absolute values of high-frequency power indicating a depressed sinus arrhythmia. Patients with bulbar signs showed more marked autonomic alterations at rest. Tilting did not induce the expected increase in low-frequency and decrease in high-frequency power of HRV in all patients. No correlation was found between autonomic tests and clinical parameters. Our findings suggest an early subclinical involvement of the autonomic system in ALS, particularly affecting parasympathetic cardiac control. Patients with prominent bulbar signs show a more severe autonomic dysfunction under resting conditions.

Tactile direction discrimination and vibration detection in diabetic neuropathy

OBJECTIVE

To evaluate the clinical usefulness of quantitative testing of tactile direction discrimination (TDD) in patients with diabetic neuropathy.

MATERIALS AND METHODS

TDD and vibration detection were examined on the dorsum of the feet in 43 patients with type 1 diabetes mellitus and clinical signs and symptoms indicating mild neuropathy, and abnormal results for neurography, temperature detection, or heart rate variability. Test-retest examination of TDD was performed in nine of the patients.

RESULTS

Twenty-six of the patients had abnormal TDD (sensitivity 0.60) and 20 had abnormal vibration detection (sensitivity 0.46). Ten of the patients had abnormal TDD and normal vibration detection. Four of the patients had abnormal vibration detection and normal TDD. Test-retest examination of TDD showed a high degree of reproducibility (r = 0.87).

CONCLUSION

TDD seems more useful than vibration detection in examination of diabetic neuropathy.

COMPARATIVE NEUROPHYSIOLOGICAL STUDY FOR THE DIAGNOSIS OF MILD POLYNEUROPATHY IN PATIENTS WITH DIABETES MELLITUS AND GLUCOSE INTOLERANCE

This article evaluates diagnostic sensitivity of minimal F-wave latency, sural/radial amplitude ratio (SRAR), dorsal sural/radial amplitude ratio (DSRAR), sympathetic skin response (SSR), and R-R interval variability (RRIV) for detecting early polyneuropathy in patients with glucose intolerance and diabetic patients. F-wave latencies were more prolonged in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). SRAR was lower, SSR latency was more prolonged, and RRIV was lower in diabetic patients with abnormal nerve conduction studies than healty controls (p < .001). SSR latency was more prolonged and RRIV was lower in diabetic patients with normal nerve conduction studies than healty controls (p < .01, p < .05, respectively). DSRAR was lower in diabetic patients with normal and abnormal nerve conduction studies than control subjects (p < .001). DSRAR was also lower in patients with glucose intolerance than control subjects (p < .01). DSRAR was the most sensitive and specific test in either of diabetic patients with normal nerve conduction studies (sensitivity 66%, specificity 90%) and diabetic patients with abnormal nerve conduction studies (sensitivity 100%, specificity 90%). DSRAR is the most reliable method for detection of early nerve pathology. Patients with glucose intolerance might have subclinical neuropathy that can be demonstrated with DSRAR analysis.

R-R Interval Variation and Sympathetic Skin Response in Fibromyalgia

BACKGROUND

This study proposed to assess the autonomic nervous system (ANS) functions in fibromyalgia (FM) by using two electrophysiological tests, sympathetic skin response (SSR) and the heart rate variability named R-R interval variation (RRIV).

METHODS

Sympathetic skin response and RRIV were studied in 29 female patients with FM and 22 healthy age-matched female controls. R-R interval variation at rest (R%), during deep breathing (D%), the difference between D% and R% (D-R) and the ratio of D-R% (D/R) were determined. Pain threshold was measured using a mechanical algometer.

RESULTS

R-R interval variation at rest (R%) and D/R did not show significant difference between patients and controls, whereas D% and D-R were significantly lower in patients compared to controls. SSR latencies of patients' hands and feet had no significant difference compared to controls' hand and feet SSR latencies. SSR latencies of patients' hands correlated significantly with control point score, total myalgic score, Hamilton Anxiety Rating Scale (HARS) and Hamilton Depression Rating Scale. Sympathetic skin response latencies of patients' feet correlated only with HARS.

CONCLUSIONS

Analysis of heart rate variability may be useful and complementary to clinical examination in patients with symptoms of dysfunction in cardiovascular reflex pathways.

Chronological changes of sympathetic outflow to muscles in amyotrophic lateral sclerosis

To confirm correlations between muscle sympathetic nerve activity (MSNA) and patients' chronological data, we selected 40 consecutive patients with sporadic amyotrophic lateral sclerosis (ALS) recorded by similar methods. MSNA at rest was quantified as the number of sympathetic bursts per 100 heartbeats and as the value expressed as a percentage of the predicted value based on control data. Twelve patients who underwent recordings of MSNA twice at intervals of 6 months or more showed marked decreases in MSNA amplitudes and frequencies between examinations. There was a slightly positive correlation between the frequency of MSNA and age, though younger patients exhibited higher values of MSNA than older patients. The standardized value of MSNA correlated negatively with disease duration and disability levels (p<0.01, 0.05, respectively), but several patients with duration shorter than 12 months showed low values of MSNA. Twelve patients who underwent repeated recordings of MSNA showed a significant decrease in the mean standardized value of MSNA (102.6+/-24.9%) at the second examination, compared to the value (114.3+/-18.9%) at the first one. In ALS, sympathetic outflow to muscles tends to increase initially and then decrease with increasing age and duration. This pattern may be similar to chronological changes at motor neurons.

R-R interval variation and the sympathetic skin response in the assessment of the autonomic nervous system in leprosy patients

OBJECTIVES

The aim of this study was to evaluate possible autonomic nervous system (ANS) dysfunction in leprosy patients with the sympathetic skin response (SSR) and the heart rate (R-R) interval variation (RRIV) measurements which are easy and reliable methods for evaluation of autonomic functions.

MATERIAL AND METHODS

We studied 37 lepromatous leprosy patients (mean age: 38 +/- 17 years, range 23-62 years, 20 females and 17 males) and 35 age-matched healthy subjects (mean age: 34.19 +/- 12.74 years, range 24-48 years, 20 females and 15 males). Non-invasive bedside tests (orthostatic test, Valsalva ratio), R-R interval variation (RRIV) during at rest and deep breathing, the SSR latency and amplitude from both palms, and nerve conduction parameters were studied in all the subjects.

RESULTS

The mean values of RRIV in leprosy patients during at rest [mean RRIV in patients, 17.42 +/- 8.64% vs controls, 22.71 +/- 3.77% (P < 0.05)] and during deep breathing [mean RRIV in patients, 21.64 +/- 9.08% vs controls, 30.70 +/- 5.99% (P < 0.005)] was significantly lower compared with the controls. The mean latency of SSR in leprosy patients [mean SSR latency in patients, 1.72 +/- 1.13 ms vs controls, 1.30 +/- 0.41 ms (P < 0.05)] was significantly prolonged compared with the controls. The mean amplitude of SSR in leprosy patients [mean SSR amplitude in patients, 0.54 +/- 0.57 microV vs controls, 1.02 +/- 0.56 microV (P > 0.05)] was smaller compared with the controls, but this difference was not significant. The mean Valsalva ratio in leprosy patients [mean in patients, 1.11 +/- 0.13 vs controls, 1.16 +/- 0.07 (P > 0.05)] was smaller compared with the controls, but not statistically significant. The mean difference of systolic and diastolic blood pressure between supine rest and during standing in leprosy patients were higher compared with the controls [mean systolic pressure in patients, 7 +/- 6 mmHg vs controls, 6 +/- 8 mmHg (P > 0.05) and mean diastolic pressure in patients, 3 +/- 3 mmHg vs controls, 3 +/- 2 mmHg (P > 0.05)], but they did not reach statistical significance. Furthermore, lower RRIV and the prolonged SSR latencies in leprosy patients were closely correlated to some parameters of sensorimotor nerve conduction and each other [median nerve distal latency and RRIV, r = -0.67 (P < 0.05), ulnar nerve distal latency and RRIV, r = -0.59 (P < 0.05), RRIV and SSR latency, r = -0.33 (P < 0.02)]. These data indicate that leprosy patients have the functional abnormalities of ANS.

CONCLUSION

We conclude that combined use of these two tests, both of which can be easily and rapidly performed in the electromyogram (EMG) laboratory using standard equipment, allows separate testing of parasympathetic and sympathetic function, and are very sensitive methods in assessing of ANS function in peripheral neuropathy in leprosy patients.

Cardiac sympathetic denervation in early stages of amyotrophic lateral sclerosis demonstrated by 123I-MIBG-SPECT

Involvement of the autonomic cardiac nervous system in early stages of amyotrophic lateral sclerosis (ALS) was evaluated in 40 patients. I-123-metaiodobenzylguanidine-single photon emission computed tomography (MIBG-SPECT) and heart rate variability (HRV) yielded information about sympathetic and parasympathetic innervation of the heart. MIBG-SPECT is a sensitive diagnostic method for demonstration of early cardiac sympathetic denervation. Both sympathetic and parasympathetic dysfunction was observed in 16 (40%) out of 40 patients. Mean cardiac MIBG uptake as demonstrated by the heart/mediastinum ratio was significantly reduced in all ALS patients in comparison with controls (P<0.01). The global MIBG-SPECT score was clearly abnormal in 29% and slightly abnormal in 22% of patients. HRV was diminished in 6 of 38 patients, 4 of whom having an abnormal MIBG-SPECT score as well. The presented results indicate that ALS patients with mild to moderate impairment may have evidence of postganglionic sympathetic adrenergic cardiac or cardiovagal denervation. To our knowledge, this is the first study indicating possible postganglionic sympathetic denervation in ALS. The original concept of ALS as an isolated degeneration of motor neurons seems to extend to a more widespread understanding of the disease which possibly represents different entities.

Normative data of sympathetic skin response and RR interval variation in Turkish children

Sympathetic skin response (SSR) and RR interval variation (RRIV) are used commonly for the assessment of sympathetic and parasympathetic nervous system function, respectively. We determined the normal values of SSR and RRIV in 23 (14 females, nine males) Turkish children aged 5 to 14 (mean 9.86, SD 2.48) years. SSR was recorded on the hands and feet during the electrical stimulation of both median and posterior tibial nerves, respectively. Similar response was elicited on both feet during the stimulation of the right median nerve. RRIV testing was performed during rest on the supine position and deep inspiration at a frequency of 6 times/min. The SSR was elicited in all children. The mean SSR latencies recorded on the feet during the stimulation of median or posterior tibial nerve were significantly more prolonged than those recorded at the hands (P < 0.001). There was no significant difference between the mean latencies of SSR recorded at the ipsilateral and contralateral palms or soles. The mean latencies recorded at the sole during stimulation of the median nerve were not significantly different compared to those that recorded at the sole during the posterior tibial nerve (P > 0.05). The SSR amplitudes were not assessed because of great variability and rapid habituation. The mean RRIV (46.54+/-11.29%) during deep breathing was significantly increased as compared to that (35.90+/-10.63%) during rest (P < 0.003). As a result, SSR and RRIV are preferred non-invasive tests for evaluation of autonomic nervous system in children. The SSR is useful and reliable if it is obtained in the optimum technical conditions. Further research is necessary to establish strict criteria for abnormality.

Spectral analysis of heart rate and blood pressure in Guillain-Barré patients with respiratory failure

The clinical value of heart rate and blood pressure variation (HRV and BPV) spectra was assessed in 11 consecutive patients with Guillain-Barré syndrome (GBS) on artificial ventilation. Their HRV and BPV spectra were compared with those from 28 control intensive care unit (ICU) patients without peripheral nerve disorders. ICU controls had low respiratory HRV during controlled ventilation. If present, it was closely related to, but smaller than BPV, suggesting baroreceptor reflex mediation. Respiratory HRV similar to that of healthy controls was observed only in ICU controls with significant spontaneous ventilation. HRV was prominent in a subgroup of GBS patients who suffered from bradycardia or sinus arrest, whereas GBS patients without episodic bradycardia only exceptionally had respiratory HRV. Interpretation of HRV during artificial ventilation cannot be extrapolated from experience with spontaneously breathing subjects. In contrast to diabetic neuropathy, not loss, but preservation of respiratory HRV was ominous in artificially ventilated GBS patients. A pattern of prominent broad respiratory HRV peaks and narrow BPV peaks occurred only in GBS and forebode sinus arrest.

AAEM minimonograph #48: autonomic nervous system testing

The autonomic nervous system maintains internal homeostasis by regulating cardiovascular, thermoregulatory, gastrointestinal, genitourinary, exocrine, and pupillary function. Testing and quantifying autonomic nervous system function is an important but difficult area of clinical neurophysiology. Tests of parasympathetic cardiovagal regulation include heart rate analysis during standing (the 30:15 ratio), heart rate variation with deep breathing, and the Valsalva ratio. Tests of sympathetic adrenergic vascular regulation include blood pressure analysis while standing, the Valsalva maneuver, sustained handgrip, mental stress, and cold water immersion. Tests of sympathetic cholinergic sudomotor function include the sympathetic skin response, quantitative sudomotor axon reflex test, sweat box testing, and quantification of sweat imprints. Pupil function is tested pharmacologically and with pupiilographic techniques. Tests of gastrointestinal and genitourinary function do not satisfactorily isolate autonomic regulation from their other functions. The available tests have various sensitivities and ease of administration. They are typically administered in a battery of multiple tests, which improves sensitivity and reliability, and allows probing of various autonomic functions.

Electrophysiological tests of autonomic function in patients with idiopathic autonomic failure syndromes

Three electrophysiological tests of autonomic function were performed in patients with autonomic nervous system dysfunction to define test sensitivities and specificities. The skin sympathetic response, Valsalva ratio, and heart rate variation with deep breathing were studied in 10 patients with multiple system atrophy (MSA) and in 7 patients with pure (also called progressive or primary) autonomic failure (PAF); control subjects were 17 normal individuals of similar age. Thirteen patients had abnormal skin sympathetic responses, and 16 had abnormal Valsalva ratios. Fourteen patients had an abnormal variation of the heart rate with deep breathing. Taking the three tests together, binary logistic regression for distinguishing between patients and normal subjects correctly classified 91% of the 33 individuals for whom there were complete data with sensitivity of 88% and specificity of 94%. However, only 69% of the patients could be correctly classified by a logistic regression for discriminating between MSA and PAF. Electromyography (EMG) studies showed that 7 of 8 patients with MSA but only 2 of 7 patients with PAF (both multiparous women) had denervation of the rectal sphincter muscle. The EMG study is, therefore, valuable in men, but has a high false positive rate in women, probably because of pudendal nerve injury from parturition.

Increased sympathetic outflow to muscles in patients with amyotrophic lateral sclerosis: a comparison with other neuromuscular patients

We investigated the effects of muscle loss and limitation of daily activities on sympathetic outflow to muscles by measuring muscle sympathetic nerve activity (MSNA) in 12 patients with amyotrophic lateral sclerosis (ALS) as compared with other 15 neuromuscular patients (controls). The burst incidence of MSNA at rest was significantly higher in patients with ALS, even in elderly patients, compared with controls (p < 0.01). There were no differences in the level of disability, heart rate or blood pressure at rest between two groups. Blood pressure and MSNA were less changed by head-up tilting in patients with ALS compared with controls. MSNA of ALS was not correlated with the disability score, PaO2, PaCO2, forced vital capacity, the disease duration or prognosis. MSNA at rest was increased in ALS patients, regardless of the severity of muscle loss or disability. It might be suggested that autonomic motor neurons seem to become affected by the same pathologic process that kills motor neurons.

Decreased heart rate variability in amyotrophic lateral sclerosis

Autoregressive spectral analysis of heart rate variability (HRV) was performed in 29 patients with amyotrophic lateral sclerosis (ALS) and 33 age-matched healthy subjects to evaluate the involvement of the autonomic nervous system. HRV analysis provides a means to recognize low (LF) and high (HF) frequency components, respectively mediated by sympathetic and parasympathetic heart control. An increase in the mean heart rate at rest (P < 0.001), a decrease in standard deviation of R-R interval as well as in PNN50 (P < 0.001), and an increase in the LF/HF component ratio (P < 0.01) were found in the ALS patients, indicating a vagal-sympathetic imbalance. These alterations were not related to the clinical features and to the duration of the disease. Our results suggest a subclinical involvement of the autonomic nervous system in ALS, particularly affecting parasympathetic cardiovascular control.

Sympathetic skin response and R-R interval variation in Parkinson's disease

We investigated autonomic function in patients with idiopathic Parkinson's disease (PD) by measuring sympathetic skin response (SSR) and R-R interval variation (RRIV). Sixty-two PD patients and 62 age-matched normal subjects were recruited. Abnormal SSR was noted in nine (14.5%) PD patients, including three in Stage II, three in Stage III, and three in Stage IV, but not in Stage I patients or normal subjects. Four of these nine patients had postural hypotension. Abnormal SSR was correlated with duration of illness and impotence. In PD patients, abnormal SSR may be due to intermediolateral column dysfunction. After logarithmic transformation and age adjustment, 19 (31.6%) of 60 PD patients had abnormal RRIV during rest and deep breathing. Abnormal RRIV was not related to staging or duration of illness. Patients with constipation had significantly lower RRIV, indicating parasympathetic dysfunction. RRIV was not affected by acute or chronic L-dopa treatment. The agreement between RRIV and SSR in PD patients was poor (kappa = -0.07). It appears that abnormal SSR, but not RRIV, may be associated with more autonomic disturbances in PD patients.

Microneurographic analysis of muscle sympathetic nerve activity in amyotrophic lateral sclerosis

Muscle sympathetic nerve activity by (microneurograph) blood pressure and heart rate has been studied in patients with amyotrophic lateral sclerosis and in age-matched normal subjects (controls) at rest and during head-up tilt. Muscle sympathetic nerve activity in amyotrophic lateral sclerosis patients was significantly increased at rest unlike controls. There was no correlation between muscle sympathetic nerve activity and age in the patients with amyotrophic lateral sclerosis. Elevated muscle sympathetic nerve activity was present mainly in younger patients. There were no differences between blood pressure or heart rate in either group at rest or during head-up tilt in amyotrophic lateral sclerosis. The increase in muscle sympathetic nerve activity following tilt in the amyotrophic lateral sclerosis patients was less than in the controls, but they had no postural hypotension. The possible reasons for this observation of increased muscle sympathetic nerve activity at rest in amyotrophic lateral sclerosis are discussed.

X-linked bulbospinal muscular atrophy (Kennedy's syndrome): a report of three cases

Two cases of X-linked bulbo-spinal muscular atrophy and one sporadic case with the same clinical features are presented. All three cases were extensively studied by electrophysiological methods. One of the patients showed some transient weakness, which was partly improved by pyridostigmin. In this patient the Decrement test and jitter revealed a mild degree of motor-end plate dysfunction. Clinical and electrophysiological findings obtained from all three patients suggest that in Kennedy syndrome cell bodies of group IA muscle afferents are also affected selectively, with other peripheral afferents.

Cardiovascular reflexes in Parkinson's disease: effect of domperidone and apomorphine

Cardiovascular reflexes were evaluated in 18 patients with idiopathic Parkinson's disease who had a Hoehn & Yahr score of III-IV. The effect of apomorphine and domperidone on blood pressure, heart rate, R-R interval variation, and the Valsalva ratio were studied. Autonomic dysfunction was not found in the patients and there were no differences between subgroups of patients on different treatments. Apomorphine altered cardiovascular reflexes to a greater degree in patients who received the drug for the first time than in chronically treated patients. The changes were antagonized by domperidone, a peripheral dopamine receptor antagonist. Apomorphine treated patients who were receiving long-term domperidone had similar abnormalities of cardiovascular reflexes to those who had been able to withdraw it.