Cold Face Test Research Articles

Does continuous positive airway pressure treatment affect autonomic nervous system in patients with severe obstructive sleep apnea?

ObjectiveThis study is aimed at evaluating whether Continuous Positive Airway Pressure treatment (CPAP) may affect autonomic nervous system (ANS) in male patients with severe obstructive sleep apnea (OSAS). MethodsWe compared autonomic symptoms of de novo severe OSAS patients, OSAS patients on chronic CPAP treatment and healthy controls, using the Scales for Outcome in Parkinson disease-Autonomic (SCOPA-AUT) questionnaire. All groups underwent cardiovascular function tests including head-up tilt test (HUTT), Valsalva maneuver, deep breathing, hand grip and cold face tests. Statistical significance was set at p < 0.05. ResultsTwelve de novo severe OSAS patients, 17 male OSAS on CPAP and 14 controls were studied. The mean SCOPA-AUT total score was significantly higher in de novo OSAS patients compared with controls. Regarding the distinct domains, both de novo OSAS and CPAP group had abnormalities in respect of controls in urinary sphere. In supine rest condition the baseline values of systolic blood pressure were significantly increased in untreated OSAS patients compared with controls, whereas the basal values of diastolic blood pressure were significantly higher in CPAP patients with respect to controls. After ten min of HUTT, diastolic blood pressure changes were significantly higher in controls compared to both OSAS groups. Untreated OSAS patients showed significant different responses at deep breathing compared to controls. Both OSAS groups had a significant reduction of reflex bradycardia at cold face test. ConclusionsOur study shows that both treated and untreated OSAS patients complain of subjective autonomic symptoms like other sleep disorders reinforcing the close relationship between sleep and autonomic activity. Furthermore, cardiovascular reflexes indicate a tendency to hypertension and a reduced sensitivity to stimuli during wakefulness even in OSA patients on CPAP treatment, suggesting potentially permanent autonomic function deficits.

Sympathetic vascular response to facial cooling is increased in flail phenotypes of amyotrophic lateral sclerosis

Objective: To assess cardiovascular responses to cold face test (CFT) in patients with classic-onset ALS (bulbar or limb onset, ALS-C) and in patients with flail arm and flail leg phenotypes (FA/FL). Methods: In 18 ALS-C, eight FA/FL patients and 10 age-matched controls we continuously monitored heart rate (HR), systolic (SBP), diastolic (DBP) and mean blood pressure (MBP) during two-minute baseline and one-minute cold stimulus application. HR and BP responses to CFT were calculated as differences between the peak responses and baseline values (dHR, dSBP, dDBP, dMBP), as percent changes from baseline (dHR%, dSBP%, dDBP%, dMBP%), and also latencies and durations of HR and BP responses were assessed (LatHR, tHR, LatBP, tBP). Results: There were no differences in baseline values of HR, SBP, DBP and MBP among ALS-C, FA/FL and controls (p > 0.05). A decrease in HR and increases in SBP, DBP and MBP were observed in all subjects (p < 0.05). However, in FA/FL, the magnitude of BP responses, i.e. dSBP, dSBP%, dDBP, dMBP, and dMBP% were significantly higher than in controls. Moreover, these BP responses occurred with a significantly shorter latency in FA/FL than in controls and ALS-C. Furthermore, duration of the BP changes was significantly longer in FA/FL than in ALS-C. In contrast, ALS-C patients had a significantly longer LatHR and shorter tHR than healthy persons. However, no significant differences were observed in dHR or dHR% among the three groups. Conclusions: Sympathetic vascular response to facial cooling is increased in flail phenotypes of ALS.

Cold Face Test-Induced Increases in Heart Rate Variability Are Abolished by Engagement in a Social Cognition Task

Abstract. The vagus nerve is a major constituent in the bidirectional relationship between the heart and the prefrontal cortex. This study investigated the role of the vagus in social cognition using the cold face test (facial cooling) to stimulate the vagus nerve and increase prefrontal inhibitory control. Heart Rate Variability (HRV) was measured to index parasympathetic outflow while social cognition ability was tested using the Reading the Mind in the Eyes Test (RMET). Healthy males (n = 25) completed the RMET under two conditions: with and without facial cooling. Results indicated that although facial cooling increased HRV at rest, there was no improvement in the RMET during the facial cooling condition. Interestingly, completing the RMET with facial cooling abolished this increase in HRV, suggesting interference along the vagal reflex arc. These results are consistent with the involvement of a common cortico-subcortical circuit in autonomic and cognitive processes, important for emotion recognition.

6. Neurophysiological methods of autonomic nervous system testing in multiple sclerosis

Autonomic dysfunction (AD) is commonly seen in patients with multiple sclerosis (MS). The most common manifestations of AD in MS patients include bladder or bowel dysfunction, impairment of sexual performance, pupillomotor or sweating alterations and orthostatic hypotension. Furthermore, AD is supposed to be related to fatigue. The incidence and severity of the symptoms related to AD correlated with the degree of disability. The lifetime prevalence of autonomic impairment reaches up to 80 % in MS population. Besides medical history and validated questionnaires, neurophysiological testing of cardiovascular and sudomotor functions are most commonly used for evaluation of autonomic nervous system impairment in MS patients. Of the cardiovascular tests, analysis of heart-rate variability in the time- and frequency-domain has repeatedly been published as a suitable method for evaluation of cardiovascular autonomic nervous system status in MS patients (the latter being mainly represented by spectral analysis of heart-rate variability). Autonomic challenge manoeuvres (suited for activation of sympathetic or parasympathetic nervous system) are also frequently used for this purpose and comprise Valsalva manoeuvre, deep metronomic breathing, response to active standing, sustained handgrip test, cold pressor test or cold face test. Furthermore, orthostatic challenge testing represented by head-up tilting (besides above mentioned active standing) can be useful in MS patients. Sudomotor functions in MS are most frequently tested using the sympathetic skin response (mainly because of wide availability of testing equipment), which seems to be less sensitive comparing cardiovascular tests. The availability of other testing methods, which may be used for the sweating evaluation (thermoregulatory sweat test, quantitative sudomotor axon reflex or similar tests) is lower, but they seem to have higher sensitivity in evaluation of sudomotor dysfunction in multiple sclerosis.

Noninvasive Assessment of Autonomic Cardiovascular Activity in Patients With Inappropriate Sinus Tachycardia

Inappropriate sinus tachycardia (IST) is a clinical syndrome characterized by excessive resting heart rate (HR) or disproportional HR increase during exercise. The etiology of IST has not been fully elucidated and remains controversial. The aim of the present study was to assess autonomic function by means of noninvasive tests and commonly available electrocardiographic methods in a series of consecutive patients with symptomatic IST. Twenty-four patients (37 ± 12 years; 20 women) with IST were enrolled. Six cardiovascular reflex tests were performed: (1) HR variation during slow deep breathing, (2) 30-to-15 ratio during active standing, (3) blood pressure response to standing, (4) cold face test, (5) Valsalva maneuver, and (6) blood pressure response to sustained handgrip. Intrinsic HR was calculated and compared with HR after pharmacologic denervation. Additionally, spontaneous baroreflex sensitivity and 24-hour HR variability indices were analyzed. In IST patients, intrinsic HR was significantly higher compared with control subjects. Most cardiovascular autonomic tests revealed abnormal or borderline results, particularly those reflecting mainly parasympathetic function. The spontaneous baroreflex gain was significantly reduced in IST patients. After controlled orthostatic stress and during Valsalva maneuver, impaired baroreflex function was observed. The sympathovagal balance from HR variability was preserved, but altered activity in both bands of frequency domain analysis was recorded. In conclusion, IST is a heterogenic syndrome with enhanced sinus node automaticity modulated by complex alterations of autonomic tone.

Examination of cardiovascular and peripheral autonomic function in the ICU: a pilot study

Critical illness may affect the autonomic nervous system. Decreased cardiovascular autonomic function measured by heart rate variability (HRV) has been reported in critically ill patients but limited information exists about other autonomic functions. The cold face test (CFT) and skin wrinkle test (SWT) have never been investigated in critically ill patients. Feasibility and safety of the CFT and SWT were investigated in critically ill patients. polyneuropathy, autonomic neuropathy, admission after stroke, spinal cord injury or cardiac arrest. For the CFT, a cold pack was applied to the forehead to measure the maximal increase in RR interval. The simulated SWT was used and wrinkling was assessed on a five-point scale. HRV was investigated using power spectral analysis of continuous 5-min ECG recordings. Twelve critically ill patients were included (mean age 54). No adverse effects for the CFT and SWT were noted. The CFT could be performed in 10 patients and showed an abnormal response in 9. The SWT could be performed in 11 patients; results were abnormal in 6. HRV analysis showed decreased HRV in all patients. CFT and HRV responses were correlated with each other, no correlation was found between SWT and CFT or HRV results. The CFT and SWT are feasible and safe in critically ill patients. Cardiovascular dysfunction may be more prevalent in critical illness than peripheral sympathetic dysfunction. Influence of confounders and further validation of these tests needs to be investigated.

Examination of the autonomic nervous system in the ICU: a pilot study

The most widely used test for autonomic dysfunction in the ICU is the heart rate variability (HRV) test [1]. HRV is thought to be a very sensitive but less specific test [1]. Several other tests are available. For this pilot study we have investigated the ability of two tests, the skin wrinkle test (SWT), a test for postganglionic sympathetic function, and the cold face test (CFT), a reflex slowing heart rate after cold application to the forehead, to detect autonomic dysfunction in critically ill patients alongside the HRV.

Heart rate reduction and autonomic response in young adults following different vagal maneuvers

ObjectiveVagal maneuvers can cause a bradycardiac response with a reciprocal increase in parasympathetic outflow and reduction of sympathetic tone. Heart rate variability (HRV) analysis is useful in the evaluation of the autonomic nervous system. The present study investigated the magnitude of heart rate (HR) reduction and autonomic response in healthy young adults following three vagal maneuvers: carotid sinus massage (CSM), the cold face test (CFT), and the Valsalva maneuver (VM). Materials and MethodsA prospective study was conducted in 50 healthy volunteers between 21 and 35 years old who completed CSM, the CFT, and the VM in random order. Before and after each test, the RR intervals were recorded by electrocardiography for 5min to analyze variability in the time and frequency domains, and to monitor changes in the HR, blood pressure (BP), and body temperature (BT). ResultsAfter each test, HR, BP, and BT significantly decreased compared with values at rest (all p values < 0.05). The mean HR during CSM, the CFT, and the VM significantly decreased by 4.0%, 3.2%, and 2.3%, respectively, revealing that CSM most potently induced HR reduction. Significantly increased variance of the RR (VAR) indicated that CSM, the CFT, and the VM induced cardiac autonomic function (p=0.001, p=0.009, and p=0.009, respectively). Although not all of these changes were statistically significant, increased power of the normalized low-frequency component (LF%), decreased power of the normalized high-frequency component (HF%), and an increased LF/HF ratio suggested relative sympathetic enhancement. Only the VM had significant effects on sympathovagal balance in the LF%, HF%, and LF/HF (p=0.006, p=0.004, and p=0.006, respectively). ConclusionOf the three maneuvers, CSM had the greatest effects on HR reduction, while only the VM had significant effects on sympathovagal modulation. Although accurate assessment of vagal activity was not available from spectral analysis of HRV, the increases in VAR, LF%, and LF/HF, and decrease in HF% observed in this study suggest that increases in cardiac autonomic activities and sympathetic dominance occur as compensatory responses to HR reduction in a 5-min window following vagal maneuvers. More research is required to determine whether CSM is a superior initial nonpharmacologic treatment for supraventricular tachyarrhythmia in a young population if there are no contraindications.

Reproducibility of sympathetic response to cold face test: Comparison with three other pressor stimuli

Background/Aims: Is the adrenergic component of the cold face test (CFT) reproducible? We compared reproducibility of blood pressure (BP) response of CFT with that of cold pressor test (CPT), Valsalva maneuver (VM), and isometric hand-grip test (IHG).

Association between Cold Face Test‐induced vagal inhibition and cortisol response to acute stress

Low vagal function is related to several disorders. One possible underlying mechanism linking the vagus nerve and disorders is the HPA axis. Thirty-three healthy male subjects participated in a stress task, while heart rate (HR), respiratory sinus arrhythmia (RSA), salivary cortisol, and mood were assessed. Vagal function was determined using baseline, stress-induced inhibition, and Cold Face Test (CFT)-induced stimulation. The stress task induced a significant increase in cortisol and HR, a decrease in RSA, and a worsening of mood. A linear regression model with the time from CFT onset until maximum bradycardia as the independent variable explained 17.9% of the total variance in cortisol in response to the stressor (mood: 36.5%). The results indicate that a faster CFT response is associated with reduced cortisol increase and enhanced mood after acute stress. Our data support an inverse relationship between vagal function and the HPA axis.

The Relationship between Heart Rate Variability and Serum Cytokines in Chronic Chagasic Patients with Persistent Parasitemia

Persistent parasitemia, immunological, and autonomic nervous system impairments may play an important role in the evolution and clinical outcome of the chronic phase of Chagas' disease by triggering functional cardiovascular changes. Three groups were evaluated: 17 chronic chagasic patients with the indeterminate form (IChD), 12 chronic chagasic patients with cardiac forms (ChHD), and 29 individuals as a healthy control group. Parasitemia was assessed by polymerase chain reaction; hemoculture, heart rate variability by linear and nonlinear methods, and interleukin (IL)-1β, IL-4, IL-6, IL-10, IL-12, IL-13, IL-17, and tumor necrosis factor-α, and interferon (IFN)-γ serum cytokines were assessed by enzyme-linked immune assay. Twenty-nine chronic chagasic patients were positive for parasitemia (17 IChD and 12 ChHD). Heart rate variability parameters in baseline condition and after cold face test were significantly decreased in chagasic patients compared to controls. Tilt tests showed no alteration. However, using nonlinear indices, ChHD patients presented lower values compared to IChD and controls. Differences in the expression of serum cytokines were observed between chagasic patients and controls. However, among the groups, ChHD presented higher median values of IL-10 and lower of IFN-γ compared to IChD. Both chagasic groups present an autonomic impairment using linear methods. The nonlinear methods revealed that the ChHD group had a higher cardiovascular risk. Serum cytokine concentrations between chagasic patients were similar. However, ChHD showed higher concentrations of IL-10 and lower of IFN-γ, suggesting some established process of immune regulation.

Heart rate variability in chronic Chagas patients before and after treatment with benznidazole

Background There is no consensus regarding large-scale use of benznidazole to treat Chagas disease, because of its toxicity and low efficacy during the chronic phase. Objectives To evaluate heart rate variability in chronic Chagas patients before and after treatment with benznidazole. Methods Twenty-one Chagas patients with positive blood cultures and/or PCR received benznidazole (5 mg/kg twice daily for 60 days) and were matched for age and gender with 24 Chagas individuals with negative blood cultures, as controls. R–R intervals were assessed in time and frequency domains using an autoregressive algorithm under three different conditions: baseline, cold face and active tilt tests. Power spectral densities in low and high-frequency bands were estimated in absolute and normalized units. Data were expressed as mean ± SD or medians (lower and upper quartiles). Groups were compared using non-paired or paired Student's T, Mann–Whitney or Wilcoxon tests, as required. The significance level was 5%. Results The groups were comparable regarding age, gender and clinical disease forms. There were no differences in temporal and spectral indices between groups in baseline and cold face tests. Treated patients presented significantly lower tachycardic responses in mean R–R intervals during the active tilt test ( p = 0.0200) than controls did. Genetic characterization of T. cruzi isolates from treated group samples showed that 100% belonged to genotype II. Conclusion For the first time in the medical literature, we detected sympathetic impairment during the active tilt test in chronic Chagas patients treated with benznidazole. This finding may be partially explained by benznidazole neurotoxicity.

Cold face test in persons with spinal cord injury: age versus inactivity

Persons with spinal cord injury (SCI) reflect a model of precocious aging and inactivity; as such, these individuals manifest well-appreciated cardiovascular abnormalities. We aimed to determine the influence of inactivity in persons with SCI, and the influence of age in healthy controls, on cardiovascular autonomic responses to the cold face test (CFT). Subjects recruited (n = 42) included 18 controls: 10 young (25 +/- 2 years) and 8 old (50 +/- 6 years), and 24 subjects with chronic SCI: 17 with tetraplegia (C3-C8 44 +/- 7 years) and 7 with paraplegia (T5-T10 36 +/- 8 years). Heart rate (HR) and blood pressure were collected continuously: 2-min pre-CFT, 1-min CFT and 2-min post-CFT. Time-frequency (wavelet) analysis of HR (HFln) was used as an estimate of vagal cardiac modulation. The HR response to the CFT differed significantly among the SCI group (4.1 +/- 8.8 bpm) and the young (-7.7 +/- 5.9 bpm; P \ 0.001) and old (-6.8 +/- 10.7 bpm; P \ 0.01). The HFln response was reduced in the SCI (0.01 +/- 1.59) as compared with the young controls (1.50 +/- 1.50; P \ 0.05), but was not different from the old controls (0.69 +/- 1.39). The bradycardia did not differ among the young and old controls; however, the vagal response was attenuated in the old compared with the young. These data suggest that age does not significantly alter the heart rate response to the CFT, but attenuates the vagal response. In the SCI group, the paradoxical heart rate response to facial cooling and the lack of vagal activation suggest that abnormal autonomic cardiovascular reflexive control may result from profound inactivity and/or from the spinal cord injury per se.

Reduced coronary flow reserve and parasympathetic dysfunction in patients with cardiovascular syndrome X

Although cardiovascular syndrome X was described many years ago, its causes are still unclear. Many studies have addressed the autonomic function, whereas others have investigated the coronary reserve. The purpose of this study was to investigate the correlations between parasympathetic dysfunction and coronary flow reserve deficiency. Eleven consecutive women suffering from cardiovascular syndrome X were enrolled in the study. All the patients underwent the analysis of heart rate and blood pressure variability, the cold face test and noninvasive evaluation of the coronary flow reserve by transthoracic echocardiography. Comparison was made with healthy volunteers. Seven patients (64%) showed vagal impairment in the analysis of heart rate and blood pressure variability and a pathological response to the cold face test, whereas four patients (36%) did not show significant differences from the control group. In these three groups, patients with and without vagal impairment and controls, there was a difference in the mean diastolic coronary velocity reserve (1.94+/-0.48; 3.73+/-0.95, 2.88+/-0.55, P=0.0005) and in maximal diastolic velocity reserve (2.00+/-0.48, 3.26+/-0.64, 2.65+/-0.57, P=0.0047). Post-hoc analysis demonstrated that the mean and maximal diastolic velocity reserves of the patients with vagal impairment seemed to be reduced compared with those of the other groups (P<0.05), which were similar. This study confirmed that syndrome X patients represent a heterogeneous group. More than half of the patients exhibited vagal dysfunction. In these patients, coronary flow reserve was abnormal compared with controls and other syndrome X patients without vagal impairment.

Effects of magnesium infusion on hemodynamic and autonomic changes in healthy volunteers

Background: Magnesium has been used for treatments and preventions of various situations, such as cardiovascular disease and pre-eclampsia. And it also used for decreasing demands of anesthetics and analgesics during anesthesia. Activity of autonomic nervous system has important roles for homeostasis of cardiovascular system, and its dysfunction affects mortality and morbidity. Because there are few reports about effects of magnesium infusion on autonomic nervous system, we investigated effects of magnesium infusion on hemodynamic and autonomic changes using variable autonomic function tests in healthy volunteers. Methods: Hemodynamic parameters, heart rate variability, blood pressure variability, and baroreflex sensitivity were evaluated before and after magnesium infusion of 30 mg/kg during 20 min in twenty healthy volunteers. Cold face test, valsalva maneuver were also performed before and after magnesium infusion. Results: Low-frequency components of blood pressure variability decreased after magnesium infusion (P = 0.026). There were no significant differences in blood pressure, heart rate, cardiac output, stroke volume, total peripheral resistance, heart rate variablility and baroreflex sensitivity between before and after magnesium infusion. Increases of diastolic blood pressure during cold face test decreased significantly after magnesium infusion (P = 0.022). In addition, no significant hemodynamic and autonomic changes were found during valsalva maneuver. Conclusions: Central sympathetic vasomotor tone decreased after magnesium infusion of 30 mg/kg during 20 min in healthy volunteers. However, it had no effects on parasympathetic system and baroreflex sensitivity. (Korean J Anesthesiol 2008; 55: 691~9)

Effect of deep brain stimulation of the posterior hypothalamic area on the cardiovascular system in chronic cluster headache patients

The objective of this study was to determine the cardiovascular effects of chronic stimulation of the posterior hypothalamic area (PHA) in cluster headache (CH) patients. Systolic and diastolic blood pressure (SBP, DBP), cardiac output, total peripheral resistance (TPR), heart rate (HR) and breathing were monitored at supine rest and during head-up tilt test (HUTT), Valsalva manoeuvre, deep breathing, cold face test and isometric handgrip in eight drug-resistant chronic CH patients who underwent monolateral electrode implantation in the PHA for therapeutic purposes. Autoregressive power spectral analysis (PSA) of HR variability (HRV) was calculated at rest and during HUTT. Each subject was studied before surgery (condition A) and after chronic deep brain stimulation (DBS) of PHA (condition B). Baseline SBP, DBP, HR and cardiovascular reflexes were normal and similar in both conditions. With respect to condition A, DBP, TPR and the LF/HF obtained from the PSA of HRV were significantly (P < 0.05) increased during HUTT in condition B. In conclusion, chronic DBS of the PHA in chronic CH patients is associated with an enhanced sympathoexcitatory drive on the cardiovascular system during HUTT.

Cold face test: adrenergic phase

The cold face test (CFT) evokes reflex bradycardia and pressor responses. Bradycardia has been used to assess vagal function. This study evaluated two aspects of physiology and clinical applicability of the pressor response. During constant monitoring of blood pressure (Finapres) and heart rate (EKG), CFT was induced by the application of three cold packs (0.5 degrees C) to the face for 1 min. Group 1: Latencies of systolic blood pressure (SBP) and heart rate (HR) response to the CFT were recorded in 10 normal subjects. Group 2: CFT was performed in eight normal subjects after cholinergic blockade with atropine (0.03 mg/kg body weight intravenously). Group 3: Four patients with baroreflex failure and five patients with pure autonomic failure were subjected to CFT. In Group 1, mean latency of CFT-induced SBP rise (mean +/- SD) (13.8 +/- 16.6 s) was longer than that of bradycardia (5.6 +/- 4.6 s). In Group 2, bradycardia was abolished in all subjects and SBP was unaffected after atropine administration. In Group 3, patients with baroreflex failure demonstrated normal HR and SBP responses to CFT. In the pure autonomic failure patients, bradycardia was absent and SBP response was either absent or subnormal. The adrenergic phase of the CFT is independent of the cholinergic phase (bradycardia) and baroreceptors. Rise in SBP is useful in evaluating the integrity of the efferent sympathetic pathway with baroreflex failure. Absence of SBP rise in response to the CFT may be of diagnostic value in detecting the sympathetic component of pure autonomic failure.

Cardiac autonomic function in chagasic elderly patients in an endemic area: A time and frequency domain analysis approach

Chagas' disease is a common cause of cardiac autonomic impairment. In an endemic area there is a predominance of the indeterminate form and the number of elderly individuals committed by the disease is increasing. This study aimed to investigate the profile of heart rate variability (HRV) in elderly chagasic patients. 28 aged chagasic (CH), 28 non-chagasic (NC) aged individuals and 28 adults between 20 and 40 years old (YG) were studied. R–R intervals were assessed in time and frequency domains applying an autoregressive algorithm. There was no difference regarding temporal and spectral indices among the elderly groups in baseline. The values of the variance in CH, NC and YG individuals were 891.80, 283.60, 2557.00, showing a reduction of the total HRV in the aged groups when compared to the young control ( p < 0.001). During the cold face test, the pNN50 response was significantly different only in the young group ( p < 0.001). The temporal and spectral indices were not different among the elderly groups. The percentile changes of the R–R intervals induced by the tilt test in CH, NC and YG were respectively − 7.04%, − 9.35%, − 15.81%, being significantly higher in the young individuals ( p < 0.001). There was no difference regarding the percentile changes of the temporal and spectral indices between CH and NC elderly patients. The cardiac autonomic function assessed by HRV parameters presented no differences among the elderly individuals (CH and NC) living in an endemic area.

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 degrees 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.

Power Spectral Analysis of Heart Rate Variability in HIV‐Infected and AIDS Patients

In HIV-infected patients the risks for cardiovascular disease are multifactorial. Autonomic dysfunction has been detected in the early phase of HIV infection as well as in AIDS patients with advanced cardiomyopathy. Forty AIDS patients receiving highly active antiretroviral therapy (HAART), 40 HIV+ naïve of HAART, and 40 control subjects were studied. Computerized analysis of heart rate variability was performed using an analog to digital converter. R-R intervals were obtained from a standard ECG, recorded in DII lead in supine rest and after the cold-face and tilt tests. The series of R-R intervals were assessed in time and frequency domains using an autoregressive algorithm. There was no difference regarding to mean values of R-R intervals and variance in baseline. The normalized power of the low-frequency (LF) component and the low-frequency/high-frequency (HF) ratio (LF/HF) was significantly decreased in the HIV group. Responses of normalized HF and LF/HF ratio during the cold-face test were significantly decreased in the HIV group, as compared to the control. During the tilt test, a higher augmentation of normalized LF and the LF/HF ratio was observed in the HIV group compared with the control. The AIDS group was similar to the control in baseline and after cold-face and tilt tests. The HIV group presented in baseline conditions, a shift of cardiac sympathovagal balance, an exacerbated response of the LF component during the tilt test, and an ineffective cardiac vagal response to the cold-face test suggesting sympathetic and parasympathetic dysfunction. AIDS patients receiving HAART did not present these autonomic alterations.