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PubMed2002

The nature of the autonomic dysfunction in multiple system atrophy.

The concept that multiple system atrophy (MSA, Shy-Drager syndrome) is a disorder of the autonomic nervous system is several decades old. While there has been renewed interest in the movement disorder associated with MSA, two recent consensus statements confirm the centrality of the autonomic disorder to the diagnosis. Here, we reexamine the autonomic pathophysiology in MSA. Whereas MSA is often thought of as "autonomic failure", new evidence indicates substantial persistence of functioning sympathetic and parasympathetic nerves even in clinically advanced disease. These findings help explain some of the previously poorly understood features of MSA. Recognition that MSA entails persistent, constitutive autonomic tone requires a significant revision of our concepts of its diagnosis and therapy. We will review recent evidence bearing on autonomic tone in MSA and discuss their therapeutic implications, particularly in terms of the possible development of a bionic baroreflex for better control of blood pressure.

Adrenergic Fibers↗
PubMed1996

Alterations in spectral characteristics of heart rate variability as a correlate of cardiac autonomic dysfunction after esophagectomy or pulmonary resection.

BACKGROUND: Both esophagectomy and pulmonary resection are associated with postoperative cardiac complications, partly because of autonomic perturbations involving the heart. This study was undertaken to determine whether heart rate variability (HRV), employed as an index of cardiac autonomic function, changes in patients undergoing esophagectomy or pulmonary resection. METHODS: Electrocardiographic RR intervals were measured in 20 esophagectomized patients, 10 undergoing right and 10 undergoing left pulmonary resection on the preoperative day as baseline data and on postoperative days 1, 3, 5, 7, 14, and 30. Instantaneous heart rate was calculated every 250 ms from 416-s data of RR intervals. Power spectra of HRV for 128 s were computed using a fast Fourier transform and normalized by squared mean heart rate. The average ten sets of normalized HRV power were obtained by integrating the following power spectral bands: the low-, (0.06-0.10 Hz), high- (0.15-0.40 Hz), and total-frequency regions (0.01-0.40 Hz). RESULTS: In the esophagectomy group, mean low-, high-, and total-frequency HRV power decreased after surgery to 17%, 6%, and 15% of their preoperative values, respectively, and these indexes remained suppressed for up to 30 days. After right pulmonary resection, low- and total-frequency HRV power decreased through 30 and 7 postoperative days, respectively. In the left pulmonary resection group, HRV remained unchanged. In the esophagectomy group, mean (+/- SEM) heart rate increased from 78 (+/- 3) bpm to more than 90 bpm throughout the study, and body temperature from 36.5 (+/- 0.1) degrees C to more than 37.0 degrees C through 14 postoperative days. Heart rate and body temperature remained increased for 3 days after pulmonary surgery. Mean arterial pressure remained unchanged in the three surgical groups. CONCLUSIONS: Reductions indicate HRV after esophagectomy or right pulmonary resection indicate a substantial and prolonged surgical injury to the autonomic nervous control of pulse rate.

Aged↗
PubMed1990

[Autonomic dysfunction in diabetics].

The authors examined 120 patients with diabetes mellitus of the first and second types. Vegetative dysfunction was revealed in 84 patients (70%) that was manifested in disorders of the vegetative tone, vegetative reactivity. Different tests for assessment of the vegetative status and method of treatment of vegetative dysfunction are described.

Adolescent↗
PubMed2001

Autonomic dysfunction in patients with mild heart failure and coronary artery disease and the effects of add-on beta-blockade.

AIM: Autonomic impairment is related to the incidence of sudden death in chronic heart failure (CHF). Our objective was to study autonomic profiles in patients with mild CHF due to coronary artery disease, and to investigate the value of add-on beta-blockade. METHODS AND RESULTS: Measures of autonomic function (plasma norepinephrine, heart rate [HR] variability, autonomic function testing), and exercise capacity, were compared between 24 patients with mild CHF, and 24 healthy controls. In this mechanistic study, we assessed the effect of 26 weeks metoprolol treatment in a double-blind, randomized, placebo-controlled design. All patients received metoprolol sustained release (200 mg; n=12) or placebo (n=12). Assessments were made at baseline and after 10 and 26 weeks' treatment. At baseline, norepinephrine levels were elevated, while HR variability parameters were decreased in patients vs. controls (both P<0.05). Autonomic function testing showed only small differences, although significant alterations were observed with deep breathing and head up tilting (both P<0.05). After 26 weeks', metoprolol did not affect exercise capacity or norepinephrine concentrations. In contrast, HR variability was markedly improved in metoprolol-treated patients vs. placebo-treated patients (P<0.05). In particular, a shift toward normal in the sympathovagal balance was observed (P<0.05). Autonomic function testing showed only small, and generally non-significant trends after metoprolol. CONCLUSIONS: Marked autonomic abnormalities are already present in mild CHF, which may be (partially) reversed by metoprolol. These observations support the reported reduction of sudden death by beta-blockade in patients with CHF.

Adrenergic beta-Antagonists↗
PubMed2003

High vibration perception threshold and autonomic dysfunction in hemodialysis patients with intradialysis hypotension.

BACKGROUND: Intradialysis hypotension is a common problem among hemodialysis patients. Some studies have shown that autonomic neuropathy could be a major cause of intradialysis hypotension, whereas others have not. Furthermore, whether there are parallel changes in the autonomic nervous system and somatic nerves remains unclear. METHODS: We investigated the autonomic and peripheral nervous functions of 12 chronic hemodialysis patients who suffered from intradialysis hypotension, and of 12 age- and sex-matched hemodialysis patients who had stable blood pressure during hemodialysis. We used spectral analysis of their heart rate variability and systemic vascular resistance to evaluate autonomic functions. Vibrameter and nerve conduction studies to assess peripheral nervous function were also performed. Low-frequency/high-frequency ratio power index was used as a surrogate of sympathovagal balance. RESULTS: The power index rose progressively in the control group and reached significantly high levels at hour 4 compared to the basal values (3.7 +/- 0.5 vs. 2.1 +/- 0.3; P < 0.05). However in the group prone to hypotension, the power index remained almost unchanged. In addition, their systemic vascular resistance was lower than that in the control group (13.7 +/- 1.8 vs. 22.3 +/- 2.6 Wood units; P < 0.05). The vibration perception thresholds of the index finger and great toe were significantly higher in the group prone to hypotension (4.7 +/- 0.7 vs. 2.2 +/- 0.3 vibration units and 3.1 +/- 0.4 vs. 1.5 +/- 0.2 vibration units, respectively; both P < 0.05). CONCLUSION: We found that more severe damage to autonomic and peripheral nervous system occurred in patients prone to hypotension.

Adult↗
PubMed2003

Ventricular repolarization is prolonged in nondipper hypertensive patients: role of left ventricular hypertrophy and autonomic dysfunction.

OBJECTIVE: The aim of this study was to investigate the influence of circadian behavior of blood pressure, left ventricular hypertrophy, and autonomic function on QTc interval duration in untreated hypertensive patients. DESIGN: Hypertensive patients underwent simultaneous blood pressure and ECG 24-h ambulatory monitoring. Patients were classified into two groups on the basis of a lack of nocturnal fall in blood pressure, as dippers and nondippers. A group of normotensive healthy subjects was studied as controls. METHODS: QT and QTc intervals were automatically computed and spectral analysis was applied to RR interval time series from the same electrocardiogram (ECG) recordings. Left ventricular mass index (LVMI) was computed by echocardiogram. RESULTS: No difference among the three groups was found concerning mean values and circadian pattern of heart rate; by contrast, QTc was significantly longer in nondippers compared to dippers or to normotensive subjects, particularly at night-time, whereas all groups exhibited similar circadian variations in heart rate. Compared to dippers, nondippers showed significantly higher LVMI, which positively correlated with QTc, and parasympathetic withdrawal, which negatively correlated with QTc. CONCLUSIONS: Nondippers show a prolonged ventricular repolarization throughout the 24-h period, absent either in dippers or normotensives. The association of left ventricular hypertrophy and vagal deactivation may lead to prolongation of QTc, potentially facilitating ventricular arrhythmias in nondipper hypertensive patients.

Adult↗