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PubMed2001

Limits of clinical tests to screen autonomic function in diabetes type 1.

OBJECTIVES: A precocious detection of cardiac autonomic dysfunction is of major clinical interest that could lead to a more intensive supervision of diabetic patients. However, classical clinical exploration of cardiac autonomic function is not easy to undertake in a reproducible way. Thus, respective interests of autonomic nervous parameters provided by both clinical tests and computerized analysis of resting blood pressure were checked in type 1 diabetic patients without orthostatic hypotension and microalbuminuria. MATERIAL AND METHODS: Thirteen diabetic subjects matched for age and gender to thirteen healthy subjects volunteered to participate to the study. From clinical tests (standing up, deep breathing, Valsalva maneuver, handgrip test), autonomic function was scored according to Ewing's methodology. Analysis of resting beat to beat blood pressure provided autonomic indices of the cardiac function (spectral analysis or Z analysis). RESULTS: 5 of the 13 diabetic patients exhibited a pathological score (more than one pathological response) suggesting the presence of cardiovascular autonomic dysfunction. The most discriminative test was the deep breathing test. However, spectral indices of BP recordings and baro-reflex sensitivity (BRS) of these 5 subjects were similar to those of healthy subjects and of remaining diabetic subjects. CONCLUSION: Alteration in Ewing's score given by clinical tests may not reflect an alteration of cardiac autonomic function in asymptomatic type 1 diabetic patients, because spectral indices of sympathetic and parasympathetic (including BRS) function were within normal range. Our results strongly suggest to confront results provided by both methodologies before concluding to an autonomic cardiac impairment in asymptomatic diabetic patients.

Adult↗
PubMed1998

[Usefulness of heart rate variability for evaluating cardiac autonomic nervous function].

To investigate the effect of gastric ulceration on cardiac autonomic nervous function, 24-hour ambulatory electrocardiograms were recorded in patients with artificial gastric ulcers caused by endoscopic treatment of gastric tumors. Their cardiac autonomic nervous activity was assessed by both time- and frequency-domain analyses of heart rate variability obtained from electrocardiogram recordings. The results were compared with those from patients who had undergone endoscopic treatment of esophageal varices or colorectal tumors, or gastrointestinal endoscopy alone. Parameters of time-domain analysis decreased significantly with the formation of gastric ulcers. Because parameters of frequency-domain analysis did not change in the group with gastric ulcers, this decrease in parameter of time-domain analysis suggests increased activity of cardiac sympathetic nervous system. There were no changes in the parameters of either time- or frequency-domain analysis in other groups. These results suggest that artificial gastric ulceration modifies cardiac sympathovagal balance, favoring cardiac sympathetic activity, while artificial esophageal and colon ulcers have no effect on cardiac autonomic nervous activity. Heart rate variability analysis is a useful method of evaluating possible implications between gastric ulceration and cardiac autonomic nervous function.

Aged↗
PubMed1996

Cardiac autonomic nerve function and insulin sensitivity in obese subjects.

OBJECTIVE: To investigate whether obesity influences cardiac autonomic nerve function. DESIGN: Comparing two groups of subjects with different degrees of obesity to normal weight controls. SUBJECTS: 19 healthy controls (mean age 33 y, BMI 21.7 +/- 0.2 kg/m2) and 17 obese non-diabetic subjects (mean age 39 y, BMI 33.7 +/- 1.8 kg/m2). MEASUREMENTS: Insulin sensitivity was calculated by an oral glucose tolerance test. Autonomic nerve function was evaluated by analysing the variation of the heart frequency at rest (coefficient variation of R-R intervals, REST 1), during deep respiration, at a Valsalva maneuver (longest/shortest R-R interval during inspiration hold) and by the Ewing test (ratio between the 30th and 15th R-R interval after reaching up-right position). RESULTS: The obese showed a lower insulin sensitivity than healthy controls (3.09 vs 4.60 mg x l2/mmol x mU x min, P < 0.001). Their variation in heart frequency was reduced (REST 1: 1.95 vs 2.9, P < 0.01, Valsalva: 1.30 vs 1.52 and Ewing test: 1.03 vs 1.14, P < 0.05). However, patients with moderate (BMI 31.7 kg/m2) or severe obesity (39.0 kg/m2) with identical insulin sensitivity had no significant difference in autonomic nerve function. Except for the Ewing test all measured parameters for the evaluation of cardiac autonomic nerve function correlated with the degree of diminished insulin sensitivity (REST 1: r = 0.475, P < 0.001). CONCLUSION: Moderate obesity with significantly decreased insulin sensitivity is associated with impaired cardiac autonomic nerve function.

Adult↗
PubMed2003

Cardiac size, autonomic function, and 5-year follow-up of chronic heart failure patients with severe prolongation of ventricular activation.

BACKGROUND: Chronic heart failure is characterized by left ventricular dilation and abnormalities of cardiac autonomic function. Up to 20% of patients with chronic heart failure have QRS prolongation, which can lead to asynchronous left ventricular contraction. We tested the hypotheses that in patients with chronic heart failure, QRS > 150 ms is a risk factor for additional abnormalities of ventricular morphology, heart rate variability, and increased mortality. METHODS AND RESULTS: In 184 patients with left ventricular ejection fraction < 35%, QRS duration was > 150 ms in 53, and </= 150 ms in 131. We evaluated patients with baseline chest radiographs, echocardiograms, and Holter recordings. Patients with QRS duration above and below 150 ms were similar in age, sex, functional class, renal function, serum sodium, and ejection fraction. In patients with QRS > 150 ms, left ventricular end-diastolic and end-systolic diameters were greater than patients with QRS duration </=150 ms (P <.01). Patients with QRS > 150 ms had less low frequency R-R interval spectral power (P <.04). At 5 years 60% of patients with QRS > 150 ms had died compared with 35% of patients with QRS </=150 ms (P <.001). This increase in mortality was predominantly the result of an increase in progressive heart failure. CONCLUSIONS: Chronic heart failure patients with QRS duration > 150 ms have exaggerated disturbance of cardiac autonomic function, and left ventricular remodeling and significantly higher mortality than patients with QRS duration </= 150 ms.

Autonomic Nervous System↗
PubMed1997

Effects of nifedipine and enalapril on cardiac autonomic nervous function during the tilt test in elderly patients with hypertension.

To clarify the effects of nifedipine and enalapril on cardiac autonomic nervous function during postural changes, power spectral analysis of heart rate variability and humoral factors was performed during tilt tests before and after 3 months of drug administration. The study group consisted of 29 elderly patients with hypertension (mean age, 69 yr), who were divided into two groups: 15 patients received nifedipine (group N) and 14 received enalapril (group E). In group N, systolic blood pressure was significantly decreased and the percent changes in low-frequency coefficient of component variance, normalized low-frequency: high-frequency ratio, and plasma norepinephrine concentration were significantly altered by nifedipine administration. Group E, in contrast, showed no significant decrease in SBP, and only the percent change in high-frequency coefficient of component variance increased significantly after enalapril administration. These results suggest that cardiac autonomic nervous function is markedly impaired during the tilt test after long-term treatment with nifedipine, whereas it is well-maintained after long-term treatment with enalapril.

Aged↗
PubMed1985

Effects of sorbinil therapy in diabetic patients with painful peripheral neuropathy and autonomic neuropathy.

Clinical investigations with the aldose reductase inhibitor sorbinil in patients with peripheral neuropathy due to diabetes are described. After an improvement in motor and sensory nerve conduction velocities was demonstrated in asymptomatic diabetic patients taking sorbinil (compared with velocities during a placebo period), 11 patients with painful diabetic neuropathy were treated with sorbinil for three weeks without alterations in diabetic management or control. Therapy was placebo-controlled in a single-blind fashion in eight patients. Pain (assessed by or on a zero to 20 rating scale), which had been constant for many months before entry into the study and unresponsive to numerous medications, improved from a mean score of 16 to 8 and returned when the drug was discontinued. Objective improvement in sensation and strength were observed in some cases. Improvements in nerve conduction velocity and cardiac autonomic function were also documented. Cardiac autonomic neuropathy was studied in 36 patients in a double-blind, placebo-controlled, randomized, noncrossover trial. Patients received one 250-mg sorbinil tablet or one placebo tablet daily for six weeks, after a one-week baseline period. Glycemic control did not change during the study period, as indicated by unaltered glycohemoglobin levels. Response was assessed by expiration-inspiration ratios, obtained on electrocardiography during six cycles per minute respiration, and by resting minimal heart rate, both measures of vagal function. In the sorbinil-treated group, expiration-inspiration ratios improved from 1.074 +/- 0.012 to 1.096 +/- 0.020 (p less than 0.03). There was a slight decrease in the ratios in the placebo-treated group, from 1.112 +/- 0.023 to 1.105 +/- 0.023 (not significant). The difference between the Week 0 to Week 6 changes in each group was significant (p less than 0.01). Resting minimal heart rate decreased in the sorbinil-treated group from 76.4 +/- 2.3 to 66.8 +/- 2.8 +/- 2.4 beats per minute (p less than 0.001), with a mean change of 10 +/- 2. In the placebo-treated group, heart rate was unchanged (77.9 +/- 3.9 to 77.5 +/- 3.3 beats per minute). The two-sample t test of the within-group differences was also significant (p less than 0.001). The changes in both expiration-inspiration ratios and resting minimal heart rate are consistent with a sorbinil-related improvement in cardiac parasympathetic nerve function. Several isolated cases of apparent sorbinil-related improvements in autonomic symptoms have been observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1999

The influence of psychotic states on the autonomic nervous system in schizophrenia.

Abnormal autonomic activity in patients with schizophrenia has been reported, but how psychotic states influence the autonomic nervous system (ANS) has remained unclear due to methodological limitations. The influence of psychotic states on ANS activity in patients with schizophrenia was investigated using a recently developed method of analysis based on heart rate variability which assesses cardiac sympathetic and parasympathetic function separately. Cardiac autonomic function (CAF), together with psychotic states, was assessed at the beginning and the end of an 8-week study period in 53 patients with chronic schizophrenia. The CAF in age- and sex-matched control subjects was also examined. There were no significant differences between the patients and the control subjects in the mean R-R interval (RRI) or in the indices of the sympathetic and the parasympathetic function. In the patients who changed in psychotic states, the parasympathetic index was significantly decreased without significant changes in the sympathetic index when their psychotic states were more pronounced, suggesting psychotic states suppressed the parasympathetic function without affecting the sympathetic function. In these patients, the mean RRI was smaller when their psychotic states were more pronounced. Our results demonstrate that psychotic states affect the ANS, suggesting a relationship between cerebral cognitive and peripheral ANS activities, and that this is presumably mediated through the parasympathetic nervous system. These findings are discussed in comparison with previous reports on the CAF in schizophrenia.

Adult↗
PubMed2003

Heart rate variability, left ventricular functions, and cardiac autonomic neuropathy in patients undergoing chronic hemodialysis.

OBJECTIVE: Autonomic neuropathy and impairment of left ventricular functions (LVF) have been frequently encountered in chronic renal failure (CRF). The aim of the present study was to evaluate the relationship of cardiac autonomic modulation impairments, as assessed by means of heart rate variability (HRV), with clinical characteristics, and left ventricular function in the patients with CRF undergoing hemodialysis (HD). METHODS: Twenty control subjects (Group I) and 22 comparable by age and gender patients with CRF undergoing hemodialysis (Group II) were enrolled in the study. After routine clinical and biochemical evaluations, electrocardiography, and 2 Dimensional, M Mode echocardiography were performed in all participants. Frequency domain HRV analysis was studied by using Kardiosis System. The powers (P1 and P2) and the central frequencies (F1 and F2) of low and of high frequency spectral bands were recorded. RESULTS: End systolic (ESV) and end diastolic volumes (EDV) were significantly higher in Group II (59.3 +/- 21.1mL vs. 34.0 +/- 14.3 mL and 131.5 +/- 37.3 mL vs. 96.9 +/- 18.9 mL, p < 0.01, p < 0.05, respectively) when compared to those of Group I. Ejection fraction (EF) and fractional shortening (FS) were significantly lower in Group II than in control subjects (52.3 +/- 2.4% vs. 63.7 +/- 10.1% and 0.29 +/- 0.01 vs. 0.34 +/- 0.07, p < 0.001, p < 0.05, respectively). P and P2 were decreased in Group II than in Group I (136.2 +/- 173.9 m s2 vs. 911.0 +/- 685.5 and 96.5 +/- 149.6 vs. 499.7 +/- 679.5, p < 0.001, p < 0.01, respectively). Significant correlations were found between high frequency spectral power and dialysis duration (DD), ESV, EDV, EF, FS (r = 0.52 p < 0.01, r = 0.68 p < 0.001, r = 0.65 p < 0.002, r = 0.66 p < 0.02, and r = 0.69 p < 0.01). CONCLUSION: As a result, the dependence of cardiac autonomic neuropathy on the disease duration and degree of left ventricular function impairment was shown in the patients undergoing chronic hemodialysis.

Adult↗
PubMed1999

Heart rate variability associated with particulate air pollution.

BACKGROUND: Epidemiologic studies have linked fine particulate air pollution with cardiopulmonary mortality, yet underlying biologic mechanisms remain unknown. Changes in heart rate variability (HRV) may reflect changes in cardiac autonomic function and risk of sudden cardiac death. This study evaluated changes in mean heart rate and HRV in human beings associated with changes in exposure to particulate air pollution. METHODS: Repeated ambulatory electrocardiographic monitoring was conducted on 7 subjects for a total of 29 person-days before, during, and after episodes of elevated pollution. Mean HR, the standard deviation of normal-to-normal (NN) intervals (SDNN), the standard deviation of the averages of NN intervals in all 5-minute segments of the recording (SDANN), and the square root of the mean of squared differences between adjacent NN intervals (r-MSSD) were calculated for 24-hour and 6-hour time segments. Associations of HRV with particulate pollution levels were evaluated with fixed-effects regression models. RESULTS: After controlling for differences across patients, elevated particulate levels were associated with (1) increased mean HR, (2) decreased SDNN, a measure of overall HRV, (3) decreased SDANN, a measure that corresponds to ultralow frequency variability, and (4) increased r-MSSD, a measure that corresponds to high-frequency variability. The associations between HRV and particulates were small but persisted even after controlling for mean HR. CONCLUSIONS: This study suggests that changes in cardiac autonomic function reflected by changes in mean HR and HRV may be part of the pathophysiologic mechanisms or pathways linking cardiovascular mortality and particulate air pollution.

Adult↗
PubMed1999

Cardiac autonomic nervous function during long-term nonpulsatile left heart bypass.

We investigated the changes in cardiac autonomic nervous activities during long-term nonpulsatile left heart bypass (NLHB) by analyzing heart rate variability. A pulsatile ventricular assist device was installed in 3 goats, and pulsatile left heart bypass (PLHB) was conducted for 2 weeks. Then, NLHB was maintained for the following 4 weeks. The segmental data of the R-R intervals (R-Rs) was analyzed by maximum entropy spectral analysis. Changes in evaluated parameters from the last week of PLHB to the 4th week of NLHB were as follows: the mean R-Rs increased from 511 ms to 692 ms; the coefficient of variation of R-R increased from 10.2 to 14.1%; the power of the low frequency band (LF) increased from 747 ms2 to 2,855 ms2; the power of the high frequency band (HF) increased from 512 ms2 to 1,270 ms2; and the ratio of LF to HF increased from 2.6 to 6.5. These results indicated that the cardiac autonomic nervous activity, both sympathetic and parasympathetic, increased during long-term NLHB.

Analysis of Variance↗
PubMedDate not supplied

Echocardiographic load-independent indices of contractility in children and adolescents with type I diabetes: effect of metabolic control and insulin on left ventricular performance.

A case-control study was carried out in a tertiary referral teaching hospital to evaluate left ventricular contractility in children and adolescents with type 1 diabetes and to study factors influencing left ventricular contractility. Thirty-four children and young adults with type 1 diabetes (age 10.8-21.8 years) were randomly selected from approximately 400 patients of the same age range in the outpatient department and compared with 16 non-diabetic controls (age 7.3-21.2 years). The relation of end-systolic wall stress to velocity of circumferential fiber shortening as a standard deviation score (SDS) from the normal range described by Colan et al. was used to assess left ventricular contractility. In the diabetic group the effect of age, duration of diabetes, metabolic control, insulin dose, and autonomic function on left ventricular contractility were studied. It was found that the end-systolic wall stress-velocity of circumferential fiber shortening relation was not different between diabetic subjects and controls [+0.52 (SEM 0.21) vs +0.90 (SEM 0.26) SDS, p = 0.3]. In the diabetic subjects, the end-systolic wall stress-velocity of circumferential fiber shortening relation was positively correlated with glycated hemoglobin (r = 0.37, p = 0.03) and insulin dose per kilogram of body weight (r = 0.36, p = 0.04). Those two variables together explained 24% of the variability in the end-systolic wall stress-velocity of circumferential fiber shortening relation. Twenty-eight of the diabetic subjects were also assessed for cardiac autonomic function. Disturbances of cardiac autonomic function were not associated with increased contractility.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2004

Effects of a single bout of exercise on resting heart rate variability.

PURPOSE: Chronic exercise training has been shown to have a positive influence on cardiac autonomic function as assessed by measures of heart rate variability (HRV). Recent evidence indicates that several benefits associated with exercise training (e.g., improved insulin action, reduced blood pressure, improved blood lipid profile) may be realized transiently after a single bout of exercise. As many of these effects of recent exercise are linked to cardiovascular control systems, the purpose of this investigation was to test the hypothesis that a single bout of exercise would result in favorable changes in cardiac autonomic function as assessed by frequency-domain measures of HRV. METHODS: Subjects were 11 healthy male volunteers ages 18-35 yr. Resting HRV measures were obtained during 5 min of paced breathing before and 1, 3, 6, and 22 h after a 60-min bout of cycling exercise at approximately 65% of peak oxygen uptake. Identical measures were obtained in a nonexercise condition based on a randomized crossover design. RESULTS: Exercise resulted in increased high-frequency HRV, decreased low-frequency HRV, and consequently a decrease in the ratio of low-frequency to high-frequency HRV compared with the nonexercise condition. Additionally, a time-domain measure of HRV (pNN50) was markedly higher in the exercise condition as compared to nonexercise. CONCLUSION: The changes in cardiac autonomic function observed are similar to those seen in investigations of long-term training. These changes indicate a shift in autonomic function toward increased parasympathetic nervous system activity and decreased sympathetic nervous system activity, suggesting a more stable autonomic environment for the heart. These results may provide further evidence of the cardioprotective effects of a single bout of submaximal exercise.

Adolescent↗
PubMed2001

Effects of hormone replacement therapy on heart rate variability in postmenopausal women.

BACKGROUND: Hormone replacement therapy (HRT) is associated with reduced cardiovascular risk, but the underlying mechanism(s) are not fully understood. This study investigated the effects of a 6-month course of HRT on cardiac autonomic function parameters assessed by heart rate variability (HRV) in postmenopausal women. METHODS: Forty-six healthy postmenopausal women (age 48 +/- 5, range 40-60) with normal baseline electrocardiogram and negative exercise testing were enrolled. HRT, which was either 0.625 mg/day conjugated equine estrogen (CEE) plus 2.5 mg/day medroxyprogesterone acetate or 0.625 mg/day CEE alone were administered depending on hysterectomy status. Power spectral analysis of HRV was performed to calculate the low frequency component in absolute (LF) and normalized units (LF nu), high frequency component in absolute (HF), and normalized units (HF nu), and the LF/HF ratio. The standard deviation of RR intervals (SDNN) was calculated from the time series of RR intervals. RESULTS: A 6-month course of HRT did not significantly alter resting heart rate (P > 0.05). The LF/HF ratio and LF nu significantly decreased after HRT (P = 0.022 and P = 0.032), whereas a significant increase was noted in the HF component of HRV (P = 0.043), indicating an improvement in cardiac autonomic function. The SDNN value, which was 28.8 +/- 11.8 ms before HRT significantly increased to 35.4 +/- 16.7 ms after 6 months (P = 0.011). CONCLUSION: Our results indicate that a 6-month course of HRT may significantly improve cardiac autonomic function parameters, a finding that could at least partly explain the potential cardioprotective effect(s) of HRT.

Adult↗
PubMed2004

Heart rate variability and turbulence in hyperthyroidism before, during, and after treatment.

Patients with subclinical and treated overt hyperthyroidism have an excess vascular mortality rate. Several symptoms and signs in overt hyperthyroidism suggest abnormality of cardiac autonomic function that may account in part for this excess mortality rate, but few studies have examined cardiac autonomic function in untreated and treated hyperthyroidism. We assessed heart rate turbulence (HRT) and time-domain parameters of heart rate variability in a large, unselected cohort of patients with overt hyperthyroidism referred to our thyroid clinic (n = 259) and compared findings with a group of normal subjects with euthyroidism (n = 440). These measures were also evaluated during antithyroid therapy (when serum-free thyroxine and triiodothyronine concentrations returned to normal but thyrotropin remained suppressed (i.e., subclinical hyperthyroidism, n = 110) and when subjects were rendered clinically and biochemically euthyroid (normal serum thyrotropin, free thyroxine and triiodothyronine concentrations, n = 219). We found that overall measures of heart rate variability and those specific for cardiac vagal modulation were attenuated in patients with overt hyperthyroidism compared with normal subjects; measurements of overall heart rate variability remained low in those with low levels of serum thyrotropin but returned to normal in patients with biochemical euthyroidism. Measurements of HRT (onset and slope) were also decreased in patients with overt hyperthyroidism, but HRT slope returned to normal values with antithyroid treatment. This study is the first to evaluate HRT in overt and treated hyperthyroidism.

Adolescent↗
PubMed1997

Randomized trial of a hospital-based exercise training program after acute myocardial infarction: cardiac autonomic effects.

OBJECTIVES: This study sought to determine whether a moderate intensity supervised exercise training program, performed immediately after an uncomplicated acute myocardial infarction, improves recovery in cardiac autonomic function compared with standard advice about activity at home. BACKGROUND: Exercise training has beneficial effects on cardiac autonomic function and may improve prognosis after acute myocardial infarction. METHODS: Thirty-nine male and 10 female patients, mean (+/-SE) age 57 +/- 1 years, with an uncomplicated acute myocardial infarction were randomized to either a 6-week moderate intensity supervised hospital-based exercise training program (exercise group) or to an unsupervised low intensity home walking program (control group). Outcome measures included changes in baroreflex sensitivity (phenylephrine bolus method) and heart rate variability (24-h Holter monitoring) and the endurance time at 85% of peak oxygen consumption. RESULTS: At baseline, there were no significant differences in left ventricular ejection fraction (57 +/- 2% vs. 53 +/- 2%), frequency of anterior infarction (27% vs. 18%) and peak creatine kinase (1,256 +/- 170 vs. 2,599 +/- 295 IU) between the exercise and control groups. Baroreflex sensitivity (10.5 +/- 1.0 vs. 8.4 +/- 1.2 ms/mm Hg) and time domain measures of heart rate variability were also similar. After completion of the program, the exercise group exercised for a median of 15 min (interquartile range 12 to 25) at a workload of 104 +/- 7 W compared with 7 min (interquartile range 3.5 to 12) at a workload of 89 +/- 8 W in the control group (p < 0.01). There were significant (p < 0.001) improvements in baroreflex sensitivity and heart rate variability for the 49 patients combined but no differences between the exercise and control groups. Baroreflex sensitivity improved by 3.4 +/- 1.0 and 1.7 +/- 1.0 ms/mm Hg and the standard deviation of 24-h RR intervals by 36 +/- 6 and 40 +/- 10 ms, respectively (p > 0.1). CONCLUSIONS: A hospital-based exercise training program increased endurance capacity but did not improve recovery of cardiovascular antonomic function after uncomplicated acute myocardial infarction.

Ambulatory Care↗
PubMed2002

Effects of vital exhaustion on cardiac autononomic nervous functions assessed by heart rate variability at rest in middle-aged male workers.

We investigated the effects of vital exhaustion (VE) on cardiac autonomic functions in relation to working conditions such as overtime and frequent business trips, and to lifestyles such as smoking on 52 healthy middle-aged male workers. VE was evaluated by an abbreviated Maastricht Vital Exhaustion Questionnaire. Cardiac autonomic function at supine rest was assessed by spectral analysis of heart rate variability in an annual health checkup. The mean amplitude of the high frequency (HF: 0.15-0.4 Hz) component was lower in the high-VE group, whereas no significant difference in the ratio of the low frequency (LF: 0.04-0.15 Hz) component power to HF power (the LF/HF ratio) was observed among VE groups. There were significant interactive effects of VE and smoking on HF amplitude, and of VE and frequent business trips on the LF/HF ratio. VE symptoms were related to the suppression of the cardiac para-sympathetic nervous function at rest in middle-aged male workers, but not to the alteration in sympathovagal balance. Smoking and overwork such as frequent business trips may amplify the autonomic dysfunction in relation to VE among workers with a pronounced feeling of VE.

Adult↗
PubMed2001

Acute exposure to environmental tobacco smoke and heart rate variability.

Environmental tobacco smoke (ETS) has been associated with cardiovascular mortality. Pathophysiologic pathways leading from ETS exposure to cardiopulmonary disease are still being explored. Reduced cardiac autonomic function, as measured by heart rate variability (HRV), has been associated with cardiac vulnerability and may represent an important pathophysiologic mechanism linking ETS and risk of cardiac mortality. In this study we evaluated acute ETS exposure in a commercial airport with changes in HRV in 16 adult nonsmokers. We conducted ambulatory electrocardiographic (ECG) monitoring for 8-hr periods while participants alternated 2 hr in nonsmoking and smoking areas. Nicotine and respirable suspended particle concentrations and participants' blood oxygen saturation were also monitored. We calculated time and frequency domain measures of HRV for periods in and out of the smoking area, and we evaluated associations with ETS using comparative statistics and regression modeling. ETS exposure was negatively associated with all measures of HRV. During exposure periods, we observed an average decrement of approximately 12% in the standard deviation of all normal-to-normal heart beat intervals (an estimate of overall HRV). ETS exposures were not associated with mean heart rate or blood oxygen saturation. Altered cardiac autonomic function, assessed by decrements in HRV, is associated with acute exposure to ETS and may be part of the pathophysiologic mechanisms linking ETS exposure and increased cardiac vulnerability.

Adult↗
PubMed2003

Effect of acute carbon monoxide exposure on heart rate variability in patients with coronary artery disease.

Epidemiological studies have shown that air pollution is associated with increased cardiovascular mortality. Although the pathophysiological mechanisms behind this association have remained largely unknown, it has been suggested that changes in cardiac autonomic function may play a role. In this study, we investigated the association between acute carbon monoxide (CO) exposure and cardiac autonomic function as measured by heart rate variability (HRV) in subjects with stable coronary artery disease. Twenty-four hour ambulatory electrocardiographic recording with simultaneous continuous personal CO concentration monitoring was performed in six male patients with angiographically verified coronary artery disease three times with 1-week intervals. Time domain measures of HRV were calculated for 5-min segments before and during the CO exposure periods. For further analysis CO exposures were divided into low (</=2.7 p.p.m.) and high (>2.7 p.p.m.) CO exposure periods. The mean of maximum CO levels during 61 CO exposure periods was 4.6 p.p.m. (SD 5.0 p.p.m.). High CO exposure was associated with an increase in the square root of the mean of the sum of the squares of differences between adjacent RR intervals (r-MSSD) (P = 0.034). Heart rate remained unchanged during the CO exposure. In conclusion, acute CO exposure which represented most likely exposure derived from traffic seems to modify cardiac autonomic control in patients with stable coronary artery disease.

Acute Disease↗