Reduction In Sympathetic Activity Research Articles

Rem sleep brady-arrhythmias: An indication to pacemaker implantation?

Important adjustments in the autonomic nervous system occur during sleep. Bradycardia, due to increased vagal tone, and hypotension, caused by reduction of sympathetic activity, may occur during non rapid eye movement (REM) sleep (NREM). Increased sympathetic activity, causing increased heart rate, is conversely a feature of phasic REM sleep. During REM sleep, sinus arrests and atrioventricular (AV) blocks unrelated to apnea or hypopnea have been described. These arrhythmias are very rare and only a few cases have been reported in the literature. Following an ECG performed for other reasons, two patients with no history of sleep complaints nor symptoms of heart failure or heart attack were referred to our center for nocturnal brady-arrhythmias. 24h ECG Holter recorded several episodes of brady-arrhythmia with sinus arrest in the first patients and brady-arrhythmias with complete AV block in the second patient. In both patients, episodes of brady-arrhythmia were prevalent in the second part of the night. Nocturnal polysomnography (PSG) demonstrated that episodes occurred only during REM sleep, particularly during phasic events. Treatment with pacemaker was considered only for the patient with complete AV blocks. These types of brady-arrhythmias are usually detected accidentally due to their lack of symptoms. It has been suggested that in some patients they may lead to sudden unexpected death. Thus, the identification of predisposing factors is mandatory in order to prevent potentially dangerous arrhythmic events.

Effects of tiotropium on sympathetic activation during exercise in stable chronic obstructive pulmonary disease patients

BackgroundTiotropium partially relieves exertional dyspnea and reduces the risk of congestive heart failure in chronic obstructive pulmonary disease (COPD) patients. However, its effect on the sympathetic activation response to exercise is unknown.AimsThis study aimed to determine whether tiotropium use results in a sustained reduction in sympathetic activation during exercise.MethodsWe conducted a 12-week, open-label (treatments: tiotropium 18 μg or oxitropium 0.2 mg × 3 mg), crossover study in 17 COPD patients. Treatment order was randomized across subjects. The subjects underwent a pulmonary function test and two modes of cardiopulmonary exercise (constant work rate and incremental exercise) testing using a cycle ergometer, with measurement of arterial catecholamines after each treatment period.ResultsForced expiratory volume in 1 second and forced vital capacity were significantly larger in the tiotropium treatment group. In constant exercise testing, exercise endurance time was longer, with improvement in dyspnea during exercise and reduction in dynamic hyperinflation in the tiotropium treatment group. Similarly, in incremental exercise testing, exercise time, carbon dioxide production, and minute ventilation at peak exercise were significantly higher in the tiotropium treatment group. Plasma norepinephrine concentrations and dyspnea intensity were also lower during submaximal isotime exercise and throughout the incremental workload exercise in the tiotropium treatment group.ConclusionTiotropium suppressed the increase of sympathetic activation during exercise at the end of the 6-week treatment, as compared with the effect of oxipropium. This effect might be attributed to improvement in lung function and exercise capacity and reduction in exertional dyspnea, which were associated with decreases in respiratory frequency and heart rate and reduced progression of arterial acidosis.

Effect of yogic bellows on cardiovascular autonomic reactivity.

Context:Yoga is an ancient science, which originated in India. Pranayama has been assigned a very important role in yogic system of exercises. It is known that regular practice of breathing exercises (pranayama) increases parasympathetic tone, decreases sympathetic activity, and improves cardiovascular functions. Different types of breathing exercises alter autonomic balance for good by either decrease in sympathetic or increase in parasympathetic activity. Mukh Bhastrika (yogic bellows), a type of pranayama breathing when practiced alone, has demonstrated increase in sympathetic activity and load on heart, but when practiced along with other types of pranayama has showed improved cardiac performance.Aim:The present study was conducted to evaluate the effect of long term practice of fast pranayama (Mukh Bhastrika) on autonomic balance on individuals with stable cardiac function.Settings and Design:This interventional study was conducted in the department of physiology.Materials and Methods:50 healthy male subjects of 18 - 25 years age group, fulfilling the inclusion and exclusion criteria underwent Mukh Bhastrika training for 12 weeks. Cardiovascular autonomic reactivity tests were performed before and after the training.Statistical Analysis Used:The parameters were analyzed by Student t test.Results:This study showed an increase in parasympathetic activity i.e., reduced basal heart rate, increase in valsalva ratio and deep breathing difference in heart rate; and reduction in sympathetic activity i.e., reduction in fall of systolic blood pressure on posture variation.Conclusion:It can be concluded that Mukh Bhastrika has beneficial effect on cardiac autonomic reactivity, if practiced for a longer duration.

Sympathetic nervous system activity after gastric bypass surgery

The effect of gastric bypass surgery (GBS) on MSNA and the relationship between MSNA and NE in these individuals has not been well described. We measured MSNA in subjects who were 38±5 months post surgery (GBS, BMI= 28±0.8 kg/m2, N=10) and in lean (L, BMI= 23±0.4 kg/m2, N=13), and obese (O, BMI= 39±1.0 kg/m2, N=13) control subjects. MSNA (bursts/min) trended to be lower in GBS (15.0±3.2) and L (17.2±3.2) compared with O (24.3±2.8), although this difference was not significant (P=0.08). Similarly, there was trend for NE to be lower in GBS (88.9±31.9) compared with both L (180.1±28.0) and O (182.3±28.0) but again this was not significant (P=0.06). A weak relationship was present between NE and MSNA for all subjects (R2=0.15, P<0.05). There was a trend for this relationship to be stronger in L (R2=0.40, P=0.07) and also O (R2=0.32, P=0.06) but there was clearly no relationship in GBS (R2=0.03, P=0.63). This preliminary data indicates that a reduction in sympathetic activity probably occurs after GBS. This is likely due to weight loss as MSNA was significantly related to weight (R2=0.22, P<0.01). However, the relationship between MSNA and NE is not present after GBS due to markedly lower NE levels. Based on this preliminary data it does not appear that plasma NE should be used a measure of sympathetic activity after GBS. Supported by Mayo Clinic and NIH Grant Numbers K23 DK82424 (TC) and UL1 RR024150 (Mayo Clinic).

Impact of shock wave lithotripsy on heart rate variability in patients with urolithiasis

The physiological response of the cardiac autonomic nervous system during shock wave lithotripsy (SWL) remains unclear. Heart rate variability (HRV) is an index of cardiac autonomic balance. This study aimed to analyze HRV during SWL in patients with urolithiasis. Electrocardiograms of patients who underwent SWL were obtained. Recordings were obtained before and after SWL. For each time point, the recordings were obtained continuously for 6 min, after which R wave-to-R wave (RR) intervals were extracted. The time digital sequence derived from RR intervals was the HRV signal. Time-domain analysis revealed that the mean of RR intervals (MRR) and standard deviation of normal beat-to-normal beat (NN) intervals (SDNN), but not the square root of the mean squared difference of successive NNs (RMSSD) or triangular interpolation of NN intervals (TINN), significantly increased during SWL. The increase in SDNN persisted after SWL but MRR returned to the initial level. Frequency-domain analysis revealed that very low frequency (VLF), low frequency (LF), and LF/high frequency (HF) ratio significantly increased after SWL, while there was no statistically significant difference in HF. Thus, the patients had significantly high MRR and SDNN during SWL and significantly high SDNN, VLF, LF, and LF/HF ratio after SWL. SWL could alter the functioning of the cardiac autonomic nervous system, resulting in reduction in sympathetic activity and increase in parasympathetic activity. Further studies with larger samples are required to confirm these findings and understand the underlying mechanisms.

Sustained suppression of sympathetic activity and arterial pressure during chronic activation of the carotid baroreflex

Following sinoaortic denervation, which eliminates arterial baroreceptor input into the brain, there are slowly developing adaptations that abolish initial sympathetic activation and hypertension. In comparison, electrical stimulation of the carotid sinus for 1 wk produces sustained reductions in sympathetic activity and arterial pressure. However, whether compensations occur subsequently to diminish these responses is unclear. Therefore, we determined whether there are important central and/or peripheral adaptations that diminish the sympathoinhibitory and blood pressure-lowering effects of more sustained carotid sinus stimulation. To this end, we measured whole body plasma norepinephrine spillover and alpha(1)-adrenergic vascular reactivity in six dogs over a 3-wk period of baroreflex activation. During the first week of baroreflex activation, there was an approximately 45% decrease in plasma norepinephrine spillover, along with reductions in mean arterial pressure and heart rate of approximately 20 mmHg and 15 beats/min, respectively; additionally, plasma renin activity did not increase. Most importantly, these responses during week 1 were largely sustained throughout the 3 wk of baroreflex activation. Acute pressor responses to alpha-adrenergic stimulation during ganglionic blockade were similar throughout the study, indicating no compensatory increases in adrenergic vascular reactivity. These findings indicate that the sympathoinhibition and lowering of blood pressure and heart rate induced by chronic activation of the carotid baroreflex are not diminished by adaptations in the brain and peripheral circulation. Furthermore, by providing evidence that baroreflexes have long-term effects on sympathetic activity and arterial pressure, they present a perspective that is opposite from studies of sinoaortic denervation.

Reduction of Sympathetic Activity via Adrenal-targeted GRK2 Gene Deletion Attenuates Heart Failure Progression and Improves Cardiac Function after Myocardial Infarction

Chronic heart failure (HF) is characterized by sympathetic overactivity and enhanced circulating catecholamines (CAs), which significantly increase HF morbidity and mortality. We recently reported that adrenal G protein-coupled receptor kinase 2 (GRK2) is up-regulated in chronic HF, leading to enhanced CA release via desensitization/down-regulation of the chromaffin cell alpha(2)-adrenergic receptors that normally inhibit CA secretion. We also showed that adrenal GRK2 inhibition decreases circulating CAs and improves cardiac inotropic reserve and function. Herein, we hypothesized that adrenal-targeted GRK2 gene deletion before the onset of HF might be beneficial by reducing sympathetic activation. To specifically delete GRK2 in the chromaffin cells of the adrenal gland, we crossed PNMTCre mice, expressing Cre recombinase under the chromaffin cell-specific phenylethanolamine N-methyltransferase (PNMT) gene promoter, with floxedGRK2 mice. After confirming a significant ( approximately 50%) reduction of adrenal GRK2 mRNA and protein levels, the PNMT-driven GRK2 knock-out (KO) offspring underwent myocardial infarction (MI) to induce HF. At 4 weeks post-MI, plasma levels of both norepinephrine and epinephrine were reduced in PNMT-driven GRK2 KO, compared with control mice, suggesting markedly reduced post-MI sympathetic activation. This translated in PNMT-driven GRK2 KO mice into improved cardiac function and dimensions as well as amelioration of abnormal cardiac beta-adrenergic receptor signaling at 4 weeks post-MI. Thus, adrenal-targeted GRK2 gene KO decreases circulating CAs, leading to improved cardiac function and beta-adrenergic reserve in post-MI HF. GRK2 inhibition in the adrenal gland might represent a novel sympatholytic strategy that can aid in blocking HF progression.

Influence of a peat bath series on heart rate variability (HRV) measures of patients with prolapse of the nucleus pulposus during an inpatient orthopaedic rehabilitation

Introduction Peat baths are used in rehabilitation medicine to treat, e.g. pain syndromes. The resulting increase of the central body temperature by 1–1.5 °C is a substantial stress for the cardiovascular system. The aim of the study was to investigate adaptive reactions of patients on a series of peat baths in a rehabilitative setting by means of HRV. Methods Cardiovascular healthy, non-smoking patients (19 female, 10 male, 18–55 years) with lumbar prolapse of the nucleus pulposus were exposed to a series of 6 peat baths (40.5 °C) during an inpatient orthopaedic rehabilitation of 3 weeks. RR-intervals were determined by a 24 h ECG (Ela medical ® , SORIN GROUP, France) to calculate HRV-parameters during the first and sixth measuring period. Each measuring period consisted of a recumbent rest V1, (respectively V6), a 20 min peat bath M1 (resp. M6) and a subsequent 20 min recumbent phase N1 (resp. N6). The high-frequency (HF) spectrum of HRV reflects parasympathetic nervous activity; the low frequency spectrum (LF) and the ratio LF/HF represent sympathetic activity. Results The comparison of the two measuring periods did not show significant differences for HF, LF/HF and heart rate (HR). The percentage of LF in V6 was reduced compared to V1 ( p p Conclusions The decrease of LF during rest (V1 vs. V6) could be interpreted as a reduction of sympathetic activity, which is a cumulative effect of the rehabilitation programme performed during the preceding 3 weeks. Comparable results are known from studies of sports medicine, supporting our results. In contrast, a training effect of the 6 peat baths on the cardiovascular healthy patients could not be demonstrated, as HR, HF and LF/HF were not changed significantly.

Effects of Antihypertensive Drugs and Exercise Training on Insulin Sensitivity in Spontaneously Hypertensive Rats

We examined the effects of antihypertensive drugs, exercise training, and combinations thereof on insulin sensitivity (IS), and the association between this relation and sympathetic activity, muscle fiber composition, and capillary density in spontaneously hypertensive rats (SHR). Six-week-old male SHR were allocated to 7 groups: a control group (C), and groups treated with azelnidipine (Aze) (a calcium channel blocker), olmesartan (Olm) (an angiotensin II type 1 receptor blocker), exercise training (Exe), and combinations of drugs and exercise training (Aze+Exe, Olm+Exe, and Olm+Aze+Exe). At age 18 weeks, IS and sympathetic activity were evaluated by an euglycemic hyperinsulinemic glucose clamp technique and power spectral analysis of systolic blood pressure, respectively. After the experiments, capillary density and muscle fiber composition in soleus muscle were examined. Aze or Exe alone significantly increased IS associated with a significant reduction in sympathetic activity. Olm alone tended to increase IS with little change in sympathetic activity. Aze, Olm, or Exe significantly increased the capillary density and percentage of insulin-sensitive type I fiber. A combination of Aze and Exe or a combination of Olm and Exe tended to increase IS compared with each drug therapy alone. There were significant correlations between IS and sympathetic activity, capillary density, and the percentage of type I fiber in all the rats. We found that Aze improved IS more substantially compared with Olm in SHR. We also found that Aze, Olm, Exe, and combinations thereof improved IS, probably through the modulation of sympathetic activity or capillarity and muscle fiber type in skeletal muscles.

How Does Successful Off-Pump Pulmonary Vein Isolation for Paroxysmal Atrial Fibrillation Influence Heart Rate Variability and Autonomic Activity?

: Surgical pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF) blocks trigger stimulation from PVs and partially disconnects the atria from sympathetic and parasympathetic neural stimulation. This study describes long-term changes in heart rate variability (HRV) and autonomic activity (AA) after successful bipolar radiofrequency PVI. : Twenty-seven patients who underwent coronary artery bypass grafting and successful (defined as stable sinus rhythm for 1 year) off-pump bipolar radiofrequency PVI for PAF were prospectively followed 3, 6, and 12 months after surgery including 24 hours Holter electrocardiogram. The following HRV and AA parameters were calculated: mean NN-interval, SD of NN-intervals, SD of averaged NN-intervals, root mean square of successive differences, low frequency (LF) power (0.04-0.15 Hz; a parameter specific for sympathetic activity), high frequency (HF) power (0.15-0.4 Hz; a parameter specific for parasympathetic activity), and the LF:HF ratio. : Preoperatively, high HRV and AA parameters were recorded. In 3-, 6-, and 12-month time, a progressive reduction of HRV and AA was observed, reaching significance after 12 months. Respective rates before surgery and 12 months after it were: for SD of averaged NN-intervals (122.4 ± 113; 80.5 ± 42 milliseconds; P = 0.046), for root mean square of successive differences (79.2 ± 93; 45 ± 20 milliseconds; P = 0.04). The LF:HF ratios were 1.22 and 0.73 before and 12 months after surgery, respectively. The statistically significant continuous reduction in LF:HF ratio (P = 0.02) is suggestive of a progressive parasympathetic dominance 12 months after surgery. : Successful PVI for PAF results in HRV and sympathetic activity reduction with preoperative sympathetic dominance and oncoming vagal dominance after 1 year from surgery. Despite preoperative sympathetic dominance, successful PVI for PAF results in HRV and a reduction in sympathetic activity with emerging parasympathetic dominance 12 months after surgery.

Prolonged Activation of the Baroreflex Abolishes Obesity-Induced Hypertension

Prolonged electrical activation of the carotid baroreflex produces sustained reductions in sympathetic activity and arterial pressure in normotensive dogs. The main goal of this study was to assess the influence of prolonged baroreflex activation on arterial pressure and neurohormonal responses in 6 dogs with obesity-induced hypertension. After control measurements, the diet was supplemented with cooked beef fat for 6 weeks, whereas sodium intake was held constant. After 4 weeks of the high-fat diet, there were increments in body weight from 25.8+/-0.7 to 38.6+/-1.0 kg, mean arterial pressure from 97+/-2 to 110+/-3 mm Hg, heart rate from 67+/-3 to 91+/-4 bpm, and plasma norepinephrine concentration from 141+/-35 to 280+/-52 pg/mL. Plasma glucose and insulin concentrations were elevated, but increases in plasma renin activity during the initial weeks of the high-fat diet were not sustained. During week 5, baroreflex activation resulted in sustained reductions in mean arterial pressure, heart rate, and plasma norepinephrine concentration; at the end of week 5, these values were 87+/-2 mm Hg, 77+/-4 bpm, and 166+/-45 pg/mL, respectively. These suppressed values returned to week 4 levels during a 7-day recovery period after baroreflex activation. There were no changes in plasma glucose or insulin concentrations, or plasma renin activity during prolonged baroreflex activation. These findings indicate that baroreflex activation can chronically suppress the sympathoexcitation associated with obesity and abolish the attendant hypertension while having no effect on hyperinsulinemia or hyperglycemia.

Autonomic modulation of heart rate of young and postmenopausal women undergoing estrogen therapy

The aim of the present study was to determine whether estrogen therapy (ET) reduces alterations of the autonomic control of heart rate (HR) due to hypoestrogenism and aging. Thirteen young (24 +/- 2.6 years), 10 postmenopausal (53 +/- 4.6 years) undergoing ET (PM-ET), and 14 postmenopausal (56 +/- 2.6 years) women not undergoing ET (PM) were studied. ET consisted of 0.625 mg/day conjugated equine estrogen. HR was recorded continuously for 8 min at rest in the supine and sitting positions. HR variability (HRV) was analyzed by time (SDNN and rMSSD indices) and frequency domain methods. Power spectral components are reported as normalized units (nu) at low (LF) and high (HF) frequencies, and as LF/HF ratio. Intergroup comparisons: SDNN index was higher in young (median: supine, 47 ms; sitting, 42 ms) than in PM-ET (33; 29 ms) and PM (31; 29 ms) women (P < 0.05). PM showed lower HFnu, higher LFnu and higher LF/HF ratio (supine: 44, 56, 1.29; sitting: 38, 62, 1.60) than the young group in the supine position (61, 39, 0.63) and the PM-ET group in the sitting position (57, 43, 0.75; P < 0.05). Intragroup comparisons: HR was lower in the supine than in the sitting position for all groups (P < 0.05). The HRV decrease from the supine to the sitting position was significant only in the young group. These results suggest that HRV decreases during aging. ET seems to attenuate this process, promoting a reduction in sympathetic activity on the heart and contributing to the cardioprotective effect of estrogen hormones.

Autonomic modulation of heart rate of young and postmenopausal women undergoing estrogen therapy

The aim of the present study was to determine whether estrogen therapy (ET) reduces alterations of the autonomic control of heart rate (HR) due to hypoestrogenism and aging. Thirteen young (24 ± 2.6 years), 10 postmenopausal (53 ± 4.6 years) undergoing ET (PM-ET), and 14 postmenopausal (56 ± 2.6 years) women not undergoing ET (PM) were studied. ET consisted of 0.625 mg/day conjugated equine estrogen. HR was recorded continuously for 8 min at rest in the supine and sitting positions. HR variability (HRV) was analyzed by time (SDNN and rMSSD indices) and frequency domain methods. Power spectral components are reported as normalized units (nu) at low (LF) and high (HF) frequencies, and as LF/HF ratio. Intergroup comparisons: SDNN index was higher in young (median: supine, 47 ms; sitting, 42 ms) than in PM-ET (33; 29 ms) and PM (31; 29 ms) women (P < 0.05). PM showed lower HFnu, higher LFnu and higher LF/HF ratio (supine: 44, 56, 1.29; sitting: 38, 62, 1.60) than the young group in the supine position (61, 39, 0.63) and the PM-ET group in the sitting position (57, 43, 0.75; P < 0.05). Intragroup comparisons: HR was lower in the supine than in the sitting position for all groups (P < 0.05). The HRV decrease from the supine to the sitting position was significant only in the young group. These results suggest that HRV decreases during aging. ET seems to attenuate this process, promoting a reduction in sympathetic activity on the heart and contributing to the cardioprotective effect of estrogen hormones.

Sympathetic nervous system contributes to the age-related impairment of flow-mediated dilation of the superficial femoral artery

The physiological aging process is associated with endothelial dysfunction, as assessed by flow-mediated dilation (FMD). Aging is also characterized by increased sympathetic tone. Therefore, the aim of the present study is to assess whether acute changes in sympathetic activity alter FMD in the leg. For this purpose, the FMD of the superficial femoral artery was determined in 10 healthy young (22 +/- 1 yr) and 8 healthy older (69 +/- 1 yr) men in three different conditions: 1) at baseline, 2) during reduction of sympathetic activity, and 3) during sympathetic stimulation. Reduction of sympathetic activity was achieved by performing a maximal cycling exercise, leading to postexercise attenuation of the sympathetic responsiveness in the exercised limb. A cold pressor test was used to increase sympathetic activity. Nitroglycerin (NTG) was used to assess endothelium-independent vasodilation in all three conditions. Our results showed that, in older men, the FMD and NTG responses were significantly lower compared with young men (P = 0.001 and P = 0.02, respectively). In older men, sympathetic activity significantly affected the FMD response [repeated-measures (RM) ANOVA: P = 0.01], with a negative correlation between the level of sympathetic activity and FMD (R = -0.41, P = 0.049). This was not the case for NTG responses (ANOVA; P = 0.48). FMD and NTG responses in young men did not differ among the three conditions (RM-ANOVA: P = 0.32 and P = 0.31, respectively). In conclusion, in older men, FMD of the femoral artery is impaired. Local attenuation of the sympathetic responsiveness partly restores the FMD in these subjects. In contrast, in young subjects, acute modulation of the sympathetic nervous system activity does not alter flow-mediated vasodilation in the leg.

Mechanism behind Augmentation in Baroreflex Sensitivity after Acute Exercise in Spontaneously Hypertensive Rats

A single bout of dynamic exercise increases baroreflex sensitivity (BRS) in spontaneously hypertensive rats (SHR). We examined whether change in hemodynamics (increases in blood pressure and heart rate) associated with dynamic exercise contribute to the post-exercise modulation of BRS. SHR aged 12 weeks were chronically instrumented with a carotid artery catheter and jugular vein catheter. They were then allocated to three groups submitted to 40 min of 1) running on a treadmill at 12 m/min (Run), 2) concomitant infusion of isoproterenol and a relatively high dose of phenylephrine (Iso+Phe(high)), or 3) concomitant infusion of isoproterenol and a relatively low dose of phenylephrine (Iso+Phe(low)). Arterial pressure and heart rate were continuously recorded throughout the experiments. BRS estimated by heart rate responses to phenylephrine injection and systolic blood pressure-low frequency power amplitude (SBP-LFamp) evaluated by power spectral analysis of SBP, a marker of sympathetic activity, were examined before and after running (Run group), or administration of drugs (Iso+Phe(high) or Iso+Phe(low) groups). BRS increased significantly from 1.4 to 1.9 bpm/mmHg after running, but not after administration of Iso+Phe(high) or Iso+Phe(low). Blood pressure and SBP-LFamp significantly decreased in each of the Run, Iso+Phe(high) and Iso+Phe(low) groups. These results suggest that hemodynamic change alone does not contribute to post-exercise modulation of BRS, while hemodynamic change or sympathetic activation during exercise contributes to post-exercise hypotension associated with a reduction of sympathetic activity.

Cardiorespiratory interactions to external stimuli.

Respiration is a powerful modulator of heart rate variability, and of baro- or chemo-reflex sensitivity. This occurs via a mechanical effect of breathing that synchronizes all cardiovascular variables at the respiratory rhythm, particularly when this occurs at a particular slow rate coincident with the Mayer waves in arterial pressure (approximately 6 cycles/min). Recitation of the rosary prayer (or of most mantras), induces a marked enhancement of these slow rhythms, whereas random verbalization or random breathing does not. This phenomenon in turn increases baroreflex sensitivity and reduces chemoreflex sensitivity, leading to increases in parasympathetic and reductions in sympathetic activity. The opposite can be seen during either verbalization or mental stress tests. Qualitatively similar effects can be obtained even by passive listening to more or less rhythmic auditory stimuli, such as music, and the speed of the rhythm (rather than the style) appears to be one of the main determinants of the cardiovascular and respiratory responses. These findings have clinical relevance. Appropriate modulation of breathing, can improve/restore autonomic control of cardiovascular and respiratory systems in relevant diseases such as hypertension and heart failure, and might therefore help improving exercise tolerance, quality of life, and ultimately, survival.

Sympathetic overactivity in active ulcerative colitis: effects of clonidine

Previous reports suggest that inflammatory bowel diseases may be accompanied by abnormalities in the neural autonomic profile. We tested the hypotheses that 1) an exaggerated sympathetic activity characterizes active ulcerative colitis (UC) and 2) a reduction of sympathetic activity by clonidine would be associated with clinical changes of UC. In 23 patients with UC and 20 controls, muscle sympathetic nerve activity (MSNA), ECG, blood pressure, and respiration were continuously recorded, and plasma catecholamine was evaluated both at rest and during a 75 degrees head-up tilt. Autonomic profile was assessed by MSNA, norepinephrine, epinephrine, spectral markers of low-frequency (LF) cardiac sympathetic (LF(RR); normalized units) and high-frequency (HF) parasympathetic (HF(RR); normalized units) modulation and sympathetic vasomotor control (LF systolic arterial pressure; LF(SAP)), obtained by spectrum analysis of the R-R interval and systolic pressure variability. Among UC patients, 16 agreed to be randomly assigned to 8-wk transdermal clonidine (15 mg/wk, 9 subjects), or placebo (7 patients). An autonomic profile, Disease Activity Index (DAI), and endoscopic pattern were compared before and after clonidine/placebo. At rest, MSNA, heart rate (HR), LF(RR), LF/HF, and LF(SAP) were higher and HF(RR) was lower in patients than in controls. Tilt decreased HF(RR) and increased MSNA and LF(RR) less in patients than in controls. Clonidine decreased HR, MSNA, epinephrine, LF(RR), and increased HF(RR), whereas placebo had no effects. Changes of the autonomic profile after clonidine were associated with reduction of DAI score. An overall increase of sympathetic activity characterized active UC. Normalization of the autonomic profile by clonidine was accompanied by an improvement of the disease.

Autonomic responses during inhalation of natural fragrance of “Cedrol” in humans

It is well known that odors affect behaviors and autonomic functions. Previous studies reported that some compounds in cedar wood essence induced behavioral changes including sedative effects. In the present study, we analyzed cardiovascular and respiratory functions while subjects were inhaling fumes of pure compound (Cedrol) which was extracted from cedar wood oil. Vaporized Cedrol (14.2±1.7 μg/l, 5 l/min) and blank air (5 l/min) were presented to healthy human subjects ( n=26) via a face mask, while ECGs, heart rate (HR), systolic blood pressure (SBP), diastolic BP (DBP), and respiratory rates (RR) were monitored. Statistical analyses indicated that exposure to Cedrol significantly decreased HR, SBP, and DBP compared to blank air while it increased baroreceptor sensitivity. Furthermore, respiratory rate was reduced during exposure to Cedrol. These results, along with the previous studies reporting close relationship between respiratory and cardiovascular functions, suggest that these changes in respiratory functions were consistent with above cardiovascular alterations. Spectral analysis of HR variability indicated an increase in high frequency (HF) component (index of parasympathetic activity), and a decrease in ratio of low frequency to high frequency components (LF/HF) (index of sympathovagal balance) during Cedrol inhalation. Furthermore, Cedrol inhalation significantly decreased LF components of both SBP and DBP variability, which reflected vasomotor sympathetic activity. Taken together, these patterns of changes in the autonomic parameters indicated that Cedrol inhalation induced an increase in parasympathetic activity and a reduction in sympathetic activity, consistent with the idea of a relaxant effect of Cedrol.

Effects of sevoflurane and isoflurane on the efficacy of rewarming from hypothermic cardiopulmonary bypass

Effects of sevoflurane and isoflurane on the efficacy of rewarming from hypothermic cardiopulmonary bypass

Complete vasomotor collapse: an unusual manifestation of the carotid sinus reflex.

Complete vasomotor collapse: an unusual manifestation of the carotid sinus reflex.