The Valsalva manoeuvre as a cardiovascular reflex test in healthy children and teenagers

The objective of this study was to determine whether the Valsalva manoeuvre is applicable as a test for neurocardiovascular control in healthy children and teenagers. Sixty-eight 6- to 16-year-old children and teenagers performed two Valsalva manoeuvres in the sitting position. They were instructed to maintain airway pressure (strain) for 15 s at 30 mmHg in the first and at 40 mmHg in the second manoeuvre. Finger arterial pressure and heart rate were monitored continuously. In three of the 68 subjects it was not possible to obtain a reliable blood pressure recording due to movements of the finger and/or hand. Only 10 subjects were able to reach a strain of 30 mmHg and to maintain this strain constant during 15 s; in the others the level or the duration of the strain varied substantially. Nine subjects kept strain at 40 mmHg during 15 s. With a Valsalva manoeuvre of 30 mmHg, control values of blood pressure and heart rate in the last 5 s prior to the manoeuvre increased in 11 subjects. Notwithstanding the large range in strainging (15–55 mmHg), on visual inspection blood pressure and heart rate responses known from studies in adults could be recognized in 57 of the 65 subjects. In the other eight subjects atypical heart rate responses were observed. Forty-four of the 65 subjects could perform a Valsalva manoeuvre with a higher airway pressure compared to the first manoeuvre: range 35–55 mmHg. The higher airway pressure resulted in more pronounced blood pressure and heart rate responses. There was no correlation between age and gender versus airway pressure. It was concluded that the Valsalva manoeuvre generated blood pressure responses as found in adults. Heart rate responses were sometimes atypical, and needed underlying blood pressure measurement for full interpretation. For quantitative analysis the test was hampered by the inability of the majority of our young subjects to produce the exact strain during the 15-s period. Qualitatively, however, the Valsalva manoeuvre seems applicable as a cardiovascular reflex test to assess neurocardiovascular control in children and teenagers.     

Influence of posture on cardiorespiratory reflexes in normal subjects and patients with diabetes mellitus

This study was designed to assess the effect of patient posture, either sitting or supine, on the results and diagnostic yield of tests of cardiorespiratory reflexes on 25 normal subject controls and 128 patients with diabetes mellitus. The heart rate changes during slow breathing at 6 per minute (R6) and during a Valsalva manoeuvre (highest heart rate during manoeuvre divided by lowest heart rate within 30 s after manoeuvre; Valsalva ratio) were measured from the electrocardiographic signal and tachometry. In control subjects, heart rate changes during slow breathing averaged 25.0 when sitting and 21.3 when supine (p < 0.01); Valsalva ratio averaged 1.90 and 1.83 (p > 0.2) respectively. In diabetic patients, mean values for heart rate changes during slow breathing were 6.1 and 5.1, and mean values for Valsalva ratio were 1.23 and 1.28 in sitting and supine postures respectively. According to our normal limits, heart rate changes during slow breathing was below normal in 109 patients tested when sitting and in 113 tested when supine, and Valsalva ratio was abnormal in 103 and 95 respectively. These results indicate that subject posture is an important variable of cardiorespiratory reflex testing, and should be standardized to allow comparisons of individual results.     

Evidence for cardiovascular autonomic nerve dysfunction in multiple sclerosis.

In 21 patients with multiple sclerosis and 20 healthy controls, the following tests of autonomic function were examined: (1) variation in heart rate during deep breathing, (2) the variations in heart rate and systolic blood pressure during a standardised Valsalva manoeuvre, (3) the changes in heart rate and systolic blood pressure during arm ergometry starting at 30 W with increments of 20 W every 3 min. In the control subjects the maximum variation in heart rate from inspiration to expiration was greater than 16 beat/min (range 17-43). In patients with multiple sclerosis, five had a maximum variation in heart rate of less than 13 beat/min which was considered as the lower limit of normal. The Valsalva ratio in the control subjects ranged from 1.33-3.24. Four patients had Valsalva ratios of less than 1.30. In patients with multiple sclerosis the heart rate and systolic blood pressure responses to exercise were attenuated significantly in four and seven subjects respectively. It is concluded that a significant number of patients with multiple sclerosis show evidence of autonomic dysfunction involving the cardiovascular system.     

Spectral analysis of heart rate variability reveals an enhanced sympathetic activity in narcolepsy with cataplexy

ObjectiveTo test the autonomic control of cardiovascular reflexes and heart rate variability (HRV) at rest and during orthostatic stress in narcolepsy with cataplexy (NC).MethodsTen NC patients with a hypocretin deficit and 18 control subjects underwent head-up tilt test (HUTT), Valsalva manoeuvre, deep breathing and cold face under controlled laboratory conditions. Heart rate variability (HRV) was analysed during supine rest and HUTT considering the normalized unit of LF and HF power (LFnu; HFnu), using autoregressive (AR) and fast Fourier transform (FFT) algorithms.ResultsCardiovascular changes during HUTT, Valsalva manoeuvre, deep breathing, isometric handgrip and cold face were normal and comparable in the two groups. AR and FFT analysis showed an increased LF/HF ratio in NC patients during supine rest. As expected, LFnu increased and HFnu decreased in the control group during HUTT, but did not change in narcoleptics being comparable to values in the supine condition.ConclusionsNC patients showed an increased sympathetic drive on heart rate (HR) in the supine condition that did not further increase during HUTT.SignificanceThese results suggest the proper functioning of cardiovascular reflexes in NC but support an impairment of HR modulation at rest in favour of an enhanced sympathetic activity.     

The effect of indomethacin on the circulatory and plasma noradrenaline responses to cold pressor testing in normal subjects

Prostaglandins may alter neuronal noradrenaline release or vascular responsiveness to sympathoexcitation. The purpose of this study was to determine if indomethacin, a prostaglandin synthesis inhibitor, influences the sympathetic and circulatory adjustments to a commonly utilized laboratory stressor in the clinical assessment of autonomic function, the cold pressor test. Venous plasma noradrenaline levels (n = 8), mean arterial pressure and heart rate (n = 10) were measured in healthy male subjects during immersion of the non-dominant hand in cold water (1°C) for 90 s. The subjects were given either placebo or indomethacin (100 mg) in a double-blind manner. The order of administration was counterbalanced and a 1 week period was given for systemic clearance of the drug. The absolute level of mean arterial pressure was elevated during the resting control period after indomethacin treatment (88 in placebo vs. 92 mmHg in indomethacin). Both heart rate and venous plasma noradrenaline levels were similar between trials during the resting control period. Mean arterial pressure and heart rate increased similarly during cold pressor testing in both indomethacin and placebo. Venous plasma noradrenaline levels increased during cold pressor testing 162 ± 39 vs. 200 ± 69 pg/ml in indomethacin vs. placebo (p > 0.05), respectively. In addition, perceived pain (peak level = 7 ± 1 vs. 6 ± 1 units; indomethacin vs. placebo, respectively) was not different between the trials. These results suggest that administration of indomethacin in a maximal single therapeutic dose, does not affect the sympathetic nervous system or circulatory responsiveness to cold pressor testing. It may not be necessary to discontinue indomethacin prior to autonomic function testing.     

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.     

Comparison of autonomic function using Valsalva ratio and 30:15 postural ratio prior to and after haemodialysis treatment

In published studies of chronic haemodialysis patients, the frequency of autonomic dysfunction varies widely. One reason for the variation may be the time of testing with respect to time of dialysis. The current study tests the hypothesis that autonomic function — as measured by heart rate responses to the Valsalva manoeuvre (Valsalva ratio) and 30:15 electrocardiogram (ECG) R—R interval to upright posture (postural ratio) — is different when patients are above dry weight (predialysis) than when they are at or below dry weight (postdialysis). The study also reviews available literature to analyze other factors that may affect the results of autonomic testing in this population. A total of 25 chronic haemodialysis patients underwent standard Valsalva and 30:15 R—R interval postural autonomic testing prior to and after haemodialysis. In addition, pre- and postdialysis orthostatic responses were measured and compared with a control population. The 30:15 ratio increased after dialysis (p = 0.001). The Valsalva ratio did not change with dialysis. Out of 25 subjects, seven had an abnormal 30:15 ratio prior to dialysis decreasing to two out of 25 patients postdialysis (p < 0.03). Orthostatic responses predialysis did not differ from those in the control group. Review of the literature shows great variability in definition of normal Valsalva and postural (30:15 R—R interval) ratios. Diabetic patients in the current and prior studies were more likely to have abnormal responses. In conclusion, the prevalence of autonomic dysfunction in chronic dialysis patients as determined by Valsalva and 30:15 ECG postural ratios may be influenced by the following factors: when subjects are studied with respect to their dialysis treatment; the number of subjects with diabetes; and the cut-off point used to define abnormal test results. Abnormal Valsalva ratios are less frequent when measured postdialysis.     

Differential responses of the insular cortex gyri to autonomic challenges

Determining insular functional topography is essential for assessing autonomic consequences of neural injury. We examined that topography in the five major insular cortex gyri to three autonomic challenges, the Valsalva, hand grip, and foot cold pressor, using functional magnetic resonance imaging (fMRI) procedures. Fifty-seven healthy subjects (age ± std: 47 ± 9 years) performed four 18 s Valsalva maneuvers (30 mm Hg load pressure), four hand grip challenges (16 s at 80% effort), and a foot cold pressor (60 s, 4°C), with fMRI scans recorded every 2 s. Signal trends were compared across gyri using repeated measures ANOVA. Significantly (P<0.05) higher signals in left anterior versus posterior gyri appeared during Valsalva strain, and in the first 4 s of recovery. The right anterior gyri showed sustained higher signals up to 2 s post-challenge, relative to posterior gyri, with sub-gyral differentiation. Left anterior gyri signals were higher than posterior areas during the hand grip challenge. All right anterior gyri showed increased signals over posterior up to 12 s post-challenge, with decline in the most-anterior gyrus from 10 to 24 s during recovery. The left three anterior gyri showed relatively lower signals only during the 90 s recovery of the cold pressor, while the two most-anterior right gyri signals increased only during the stimulus. More-differentiated representation of autonomic signals appear in the anterior right insula for the Valsalva maneuver, a bilateral, more-posterior signal representation for hand grip, and preferentially right-sided, anterior-posterior representation for the cold pressor. The functional organization of the insular cortex is gyri-specific to unique autonomic challenges.     

Impaired autonomic control of heart interval changes to Valsalva manoeuvre in Chagas' disease without overt manifestation

BACKGROUND: In the apparent indeterminate form of Chagas' disease, which lacks any overt clinical, electrocardiographic, and radiological manifestations of organ damage, lesions of the intrinsic autonomic innervation of heart are not striking features and evidences for cardiac autonomic dysfunction are elusive and conflicting. OBJECTIVE: To evaluate the cardiac autonomic modulation based on Valsalva manoeuvre-associated heart interval variation in Chagas' disease subjects with apparent indeterminate form. SUBJECTS AND METHODS: We examined 36 outpatient volunteers aged 15-51 years old (median: 36.5), in comparison with 52 healthy control individuals aged 17-49 years old (median: 29) (p<0.001). Each subject sequentially performed in the supine position three to four manoeuvres at an intra-oral pressure of 40 mm Hg during 20 s, under continuous DII lead electrocardiographic registration, and rate- and time-dependent indices of Valsalva manoeuvre-associated R-R interval variation were obtained. The t-test or the Mann-Whitney test was employed to compare the data between the groups. RESULTS: No correlation was found between every index and age for the control group (p=0.39-0.71). The chagasic group presented similar basal to phase IV median increment (relative bradycardia) (23.7% vs. 22.7%; p = 0.63) and smaller basal to phase III median decrement of R-R interval (relative tachycardia) (-31.7% vs. - 35%; p=0.02) in comparison to the control group, respectively. The median Valsalva ratio showed a tendency for reduction in chagasics (1.78 vs. 1.90; p = 0.08). Prolonged median time (14.2 vs. 10.3 s; p < 0.001) and slowed median velocity (5.1%/s vs. 8.9%/s; p < 0.001) of the phases III-IV bradycardia were also observed in chagasic group. The majority (58.3%) of the chagasics presented exclusively at least one depressed, and 8.3% presented at least one enhanced index of rate- and/or time-dependent heart interval responses beyond the 25th or 75th control percentiles, and 27.8% presented at least one depressed and other enhanced index, while 5.6% showed all indices within the control interquartile range. All the indices outside the 25th or 75th control percentiles were noted in 13.9% of chagasics. CONCLUSION: Chagas' disease subjects without overt manifestations presented variable and subtle depression and less frequent enhancement or normality of the rate- and time-dependent tachycardia and bradycardia reflex responses related to Valsalva manoeuvre, which demonstrates distinct patterns of finely disturbed cardiac sinus parasympathetic and sympathetic modulation, probably due to inflammatory or autoimmunological damage of intrinsic innervation and/or to autoantibodies-induced derangement in neurotransmitter receptors.     

Nutritional status and autonomic nervous system function

Autonomic function was studied in 20 undernourished subjects without medical or neurologic disease (aged 20 to 66 years, mean age 36) and compared to 30 well nourished subjects (age 20 to 65 years, mean age 40). Anthropometric measurements were performed (height, weight, triceps skinfold thickness, arm muscle circumference). The Valsalva manoeuvre and the immediate heart rate response to lying down test (S/L) were performed to study autonomic functions. The Valsalva ratio was 1.56 +/- 0.29 for controls and 1.66 +/- 0.34 for undernourished subjects (p greater than 0.1). The S/L ratio showed a significant difference (p less than 0.001) between controls (1.278 +/- 0.13) and undernourished subjects (1.06 +/- 0.07).     

Cardiovascular responses to various autonomic tests in males and females

The results of cardiovascular autonomic reflex tests on 224 healthy, randomly selected subjects were analysed to study possible sex differences in the autonomic responses. The heart rate response to the Valsalva manoeuvre (Valsalva ratio) was greater in females over 50 years than in males of the same age (1.58 ± 0.34 vs. 1.44 ± 0.30,p < 0.05). The heart rate response to deep breathing (E/I ratio) was higher in females under 50 years than in males under 50 years (1.37 ± 0.17 vs. 1.34 ± 0.18,p < 0.001). The diastolic blood pressure response to isometric handgrip was higher in males under 50 years than in females of the same age (p < 0.05). Although there were sex differences in the magnitude of the responses, the effect of age was similar in males and females and accelerated attenuation of the autonomic responses could not be demonstrated with increasing age. It can be concluded that significant sex differences exist in cardiovascular autonomic responses. The implication of such differences need consideration.     

Autonomic cardiovascular reflexes in pregnancy. A longitudinal study

Cardiovascular reflexes were studied in 22 healthy women before they were pregnant, once during each pregnancy trimester and after delivery to evaluate the effect of pregnancy on autonomic control of haemodynamics. The Valsalva manoeuvre, the deep breathing test, the orthostatic test and the isometric handgrip test were used to assess changes in autonomic nervous function. We found that pregnancy altered the heart rate response in the Valsalva manoeuvre, the deep breathing test and the orthostatic tests. The deep breathing difference (p = 0.03) and max/min ratio (p = 0.03) decreased in pregnancy, whereas standing heart rate increased (p < 0.0001). Both the systolic and diastolic blood pressure increased after standing up during pregnancy. The circulatory responses to isometric exercise were not affected by pregnancy. The results show that parasympathetic respon-siveness is decreased in pregnancy and that it returns to normal after delivery.     

The cold face test: A non-baroreflex mediated test of cardiac vagal function

Application of cold to the face evokes potent bradycardia and a pressor response, similar to the diving reflex. However, the role of the baroreceptors in this response is unclear. Ten healthy controls and two patients with baroreflex impairment were recruited. A cold face test (CFT) was induced by the application of three cold packs (0.5°C) to the face. Heart rate (ECG), blood pressure (Finapres) and skin temperature (forehead electrode) were recorded continuously. All data were analyzed using unpaired Students t-tests, and expressed as mean ± SD. In all controls, CFT induced bradycardia. The mean onset latency was 5.6 ± 4.6 s, and the maximal bradycardia was seen at 35.8 ± 15.8 s. Systolic blood pressure increased in eight controls, with a mean onset latency of 18.8 ± 16.6 s and a peak rise at 38.7 ± 22.7 s. In the controls, bradycardia preceded the pressor response. The heart rate and blood pressure changes during CFT had a longer latency than baroreflex evoked responses. Moreover, one subject had bradycardia despite a fall in blood pressure. The two patients had abnormal Valsalva ratios and no change in heart rate during tilt, indicating impairment of the baroreflex. However, both their heart rate and blood pressure responses to CFT were normal. These data are further evidence of the limited role of the baroreflex in the autonomic responses to CFT. They suggest that the CFT may be of use in assessing the integrity of the efferent cardiovascular autonomic pathways in patients with suspected baroreflex impairment.     

Is autonomic nervous system involved in restless legs syndrome during wakefulness?

ObjectiveTo investigate cardiovascular autonomic function in patients with restless leg syndrome (RLS) by means of cardiovascular reflexes and heart rate variability (HRV) during wakefulness.MethodsTwelve RLS patients and 14 controls underwent cardiovascular function tests including head-up tilt test (HUTT), Valsalva maneuver, deep breathing, hand grip, and cold face. HRV analysis was performed in the frequency domain using both autoregressive (AR) and fast Fourier transform algorithms in rest supine condition and during HUTT.ResultsThere was a significant increase in systolic blood pressure values in supine rest condition and a trend toward a lower Valsalva ratio in RLS patients with respect to controls. The significant and physiological changes of HRV at HUTT detected in healthy subjects were not found in RLS patients.ConclusionRLS patients exhibit a tendency toward hypertension, reduced amplitude of both sympathetic and parasympathetic responses at HUTT, as well as blunted parasympathetic drive to blood pressure changes. These findings, if confirmed by more controlled studies, might support the hypothesis of autonomic nervous system involvement during wakefulness and consequently an enhanced cardiovascular risk in RLS.     

Skin blood flow and autonomic reactivity in human poikilothermia

Autonomic reactivity is pivotal in maintaining a constant body core temperature. Skin vasomotor reflexes and cardiovascular reactivity were investigated in four women (aged 28–37 years) with acquired poikilothermia, during steady-state spontaneous hypothermia (rectal temperature (T_r)=33.7 ± 1.0°C [mean ±SD]) and steady-state normothermia (T_r=36.7 ± 0.3°C), as well as in 12 normothermic control subjects. Baseline finger temperature (T_f) during hypothermia was significantly lower than during normothermia (T_f=32.4 ± 1.2 compared with 36.2 ±0.3°C, respectively), and than in the controls (T_f=34.8 ±0.8°C). No significant differences in baseline skin blood flow and forearm blood flow were found between subjects during hypothermia or normothermia and controls, suggesting a failure of sympathetic drive to counter-regulate hypothermia in the subjects. Skin vasoconstrictor responses to the contralateral cooling test and neck cooling test were markedly attenuated in three subjects, and to the finger cooling test in two subjects, during normothermia compared with hypothermia. Blood presure responses to the Valsalva manoeuvre and head-up tilting were normal in all subjects, whereas the heart rate response to head-up tilting was blunted in three subjects during hypothermia. The responses of blood pressure and forearm blood flow to the cold pressor test in the subjects during both thermal conditions were comparable with the controls. We conclude that in our subjects, without generalized autonomic failure, poikilothermia has to be attributed predominantly to disorders of the central thermoregulatory pathways. Our findings during hypothermia and normothermia indicate that variations in core and skin temperature significantly affect skin vasomotor reactivity.     

Autonomic neuropathy and prolongation of QT interval in human immunodeficiency virus infection

Autonomic neuropathy has been reported in human immunodeficiency virus positive (HIV+) patients. Since alterations in cardiac innervation may determine QT interval prolongation, this interval was studied in a group of HIV+ subjects to evaluate if it is prolonged and to compare this measurement with other diagnostic tests for autonomic neuropathy. Fifty-seven HIV+ and 23 human immunodeficiency virus negative (HIV–) subjects were studied. Autonomic function was tested by noninvasive cardiovascular reflex tests, and the QT interval on the electrocardiogram was measured at rest, at maximum tachycardia during Valsalva manoeuvre, and afterwards at maximum bradycardia. QT intervals were corrected for heart rate according to Bazzett's formula (QTc). Autonomic neuropathy was found in 37 HIV+ subjects: 25 had moderate autonomic neuropathy (HIV+/mAN) and twelve had severe autonomic neuropathy (HIV+/sAN). The 23 HIV– and 20 HIV+ (HIV+/AN–) patients did not have autonomic neuropathy. QTc intervals were significantly longer in HIV+/sAN and HIV+/mAN than in HIV– at rest; in HIV+/sAN than in HIV– at maximum tachycardia; in HIV+/sAN and HIV+/mAN than in HIV+, in HIV+/sAN and HIV+/mAN than in HIV+/AN– and in HIV+/sAN than in HIV+/mAN at maximum bradycardia. QTc was 440 ms in 24 out of 37 (64.8%) patients with autonomic neuropathy and in five out of 20 (25%) HIV+/AN– patients (sensitivity 65%, specificity 75%). A significant correlation was observed between scores of autonomic involvement and QTc interval prolongation. This study confirms that the QTc measurement is a reliable parameter indicating the presence of autonomic neuropathy. Since QT prolongation may determine ventricular arrhythmias, such patients must be followed because they may be at increased risk of sudden death.     

Cardiovascular reflexes and autonomic dysfunction in parkinson's disease

Summary Cardiovascular reflexes were analysed in a group of 20 patients suffering from Parkinson's disease and in 12 age-matched healthy subjects, in order to ascertain the incidence and degree of autonomic dysfunction. The following were measured: heart rate variation during normal breathing, postural change (30/15 ratio) and during the Valsalva manoeuvre; blood pressure variation after standing. These measurements were taken at least 12 h after therapy had been withdrawn and were repeated after therapy had been resumed. Significant changes in the different heart rate variation indices were found in the parkinsonian patients which correlated with the duration and severity of the extrapyramidal symptomatology. After standing the patients showed a significant drop in blood pressure, when compared respectively with their base values and with the response in controls. Anticholinergic drugs had no significant effect on the heart rate variation indices, whereas antiparkinsonian therapy seems to have contributed to the drop in blood pressure after standing.     

Stimulation of sympathetic activity by carbon dioxide in patients with autonomic failure compared to normal subjects

In vivo studies selectively assessing preganglionic and central autonomic nervous system activity in patients with autonomic failure have so far been limited to testing pituitary function. In animal experiments carbon dioxide (CO₂) selectively stimulates central sympathetic nuclei in the ventrolateral medulla and preganglionic sympathetic neurons in the cervical trunk. This central stimulation seems to overrule less pronounced peripheral vasodilatatory effects. This study addressed the question of whether hypercapnea is a suitable challenge procedure to test preganglionic and central autonomic activity in healthy subjects and in patients with autonomic failure of preganglionic and central origin. Seven patients with multiple system atrophy (MSA) and 30 age-matched healthy volunteers underwent a protocol including a Valsalva manoeuvre (VM) under normo- and hypercapnic conditions and exposure to hypercapnea under supine resting conditions. Blood pressure (BP), heart rate (HR) and end-tidal CO₂ partial pressure were measured continuously and non-invasively. In normal controls hypercapnea induced significantly higher BP values in phases II, IIe, III and IV of the VM compared to the normocapnic VM and a significant increase in BP during steady-state supine exposure compared to normocapnic baseline. HR increased significantly only after 40 s of steady-state hypercapnea during the latter challenge. In patients with MSA and autonomic failure, in whom a predominantly preganglionic lesion of the autonomic nervous system is established, no significant effects of hypercapnea on the cardiovascular parameters were found. Although this non-invasive challenge procedure cannot differentiate between pre- and postganglionic autonomic failure, exposure to hypercapnea enables the investigation of efferent autonomic activity to vasoconstrictors generated from autonomic centres in the brainstem and cervical trunk.     

Cardiovascular reflex responses in cluster headache patients: basal autonomic alterations

To investigate the involvement of the autonomic nervous system in Cluster Headache (CH) patients, we compared the cardiovascular reflex responses in a group of CH subjects and a group of controls. We considered five tests: 1) deep breathing test (DB); 2) lying to standing test; 3) heart rate response to Valsalva manoeuvre; 4) blood pressure response to standing; 5) blood pressure response to sustained handgrip. Our data confirm an autonomic dysfunction in CH, particularly regarding the parasympathetic system. Alternative interpretations of these results are discussed.     

Neurogenic forearm vasodilatation during contralateral isometric exercise is attenuated in diabetes mellitus

The responses in heart rate, blood pressure and blood flow in the resting forearm during contralateral isometric handgrip were investigated together with the respiratory sinus arrhythmia (measured during standardized breathing frequency and depth), and the heart rate response to a Valsalva manoeuvre in 20 patients with insulin-dependent diabetes and clinical signs of a peripheral neuropathy. The respiratory sinus arrhythmia and the Valsalva ratio were attenuated in the patients compared to age-matched controls, indicating reduced vagal function. Also the responses to handgrip were reduced. The blood flow increase in the resting forearm upon handgrip was correlated with both the respiratory sinus arrhythmia and the Valsalva ratio, supporting neurogenic mediation of the flow response and indicating a reduction in sympathetic as well as vagal function in diabetes autonomic neuropathy.