No signs of autonomic nervous system dysfunction in primary Sjörgen's syndrome evaluated by 24 hour heart rate variability.

Objective: Autonomic neuropathy is associated with increased mortality. In patients with primary Sjögren's syndrome (SS), disturbances in the autonomic nervous system have been described using conventional cardiovascular reflex tests. Heart rate variability (HRV) measured from Holter recording has proved to be a reliable and sensitive method in assessing autonomic function and prognosis.

Baroreflex sensitivity and variants of the renin angiotensin system genes.

Objectives: Because the renin-angiotensin-aldosterone system (RAS) modifies cardiovascular autonomic regulation, we studied the possible associations between baroreflex sensitivity (BRS) and polymorphism in the RAS genes.

Background: Wide intersubject variability in BRS is not well explained by cardiovascular risk factors or life style, suggesting a genetic component responsible for the variation of BRS.

Methods: Baroreflex sensitivity as measured from the overshoot phase of the Valsalva maneuver and genetic polymorphisms were examined in a random sample of 161 women and 154 men aged 41 to 61 years and then in an independent random cohort of 29 men and 37 women aged 36 to 37 years.

Measurement of heart rate variability: a clinical tool or a research toy?

The objectives of this review are to discuss the diversity of mechanisms that may explain the association between heart rate (HR) variability and mortality, to appraise the clinical applicability of traditional and new measures of HR variability and to propose future directions in this field of research. There is a large body of data demonstrating that abnormal HR variability measured over a 24-h period provides information on the risk of subsequent death in subjects with and without structural heart disease. However, the mechanisms responsible for this association are not completely established.

Altered complexity and correlation properties of R-R interval dynamics before the spontaneous onset of paroxysmal atrial fibrillation.

Background: Trigger mechanisms for the onset of paroxysmal atrial fibrillation (AF) in patients without structural heart disease are not well established. New analysis methods of heart rate (HR) variability based on nonlinear system theory may reveal features and abnormalities in R-R interval behavior that are not detectable by traditional analysis methods. The purpose of this study was to reveal possible alterations in the dynamics of R-R intervals before the spontaneous onset of paroxysmal AF.

Dynamic behavior and autonomic regulation of ectopic atrial pacemakers.

Background: Heart rate (HR) variability reflects the neural regulation of normal pacemaker tissue, but the autonomic nervous regulation of abnormal atrial foci originating outside the sinus node has not been well characterized. We compared the HR variability of tachycardias originating from the ectopic foci and the sinus node.

Methods And Results: R-R-interval variability was analyzed from 24-hour Holter recordings in 12 patients with incessant ectopic atrial tachycardia (average HR 107+/-14 bpm), 12 subjects with sinus tachycardia (average HR 106+/-9 bpm), and 24 age- and sex-matched subjects with normal sinus rhythm (average HR 72+/-8 bpm).

Autonomic mechanisms and sudden death after abrupt coronary occlusion.

In spite of recent advances in secondary prevention, sudden cardiac death has remained a major public health problem as the majority of fatalities occur in subjects without a history of severe heart disease. Abrupt rupture of a vulnerable plaque resulting in thrombotic occlusion of a coronary artery is a common cause of sudden death in this population. Coronary occlusion does not, however, invariably lead to sudden death but may cause acute myocardial infarction or exacerbation of chest pain.

Heart rate variability and progression of coronary atherosclerosis.

Low heart rate (HR) variability is associated with increased risk of cardiovascular morbidity and mortality, but the causes and mechanisms of this association are not well known. This prospective study was designed to test the hypothesis that reduced HR variability is related to progression of coronary atherosclerosis. Average HR and HR variability were analyzed in 12-hour ambulatory ECG recordings from 265 qualified patients participating in a multicenter study to evaluate the angiographic progression of coronary artery disease in patients with prior coronary artery bypass surgery and low high-density lipoprotein cholesterol concentrations (<1.

Prevalence and natural course of ectopic atrial tachycardia.

Aims: The purpose of this study was to calculate the prevalence of ectopic atrial tachycardia in a population of young asymptomatic males and to assess its natural course both in asymptomatic subjects and in symptomatic hospital patients.

Methods And Results: 12-lead electrocardiograms (ECG) of 3554 consecutive males applying for a pilot's licence were analysed. ECGs of symptomatic arrhythmia patients at two university hospitals were also analysed.

Heart rate variability and occurrence of ventricular arrhythmias during balloon occlusion of a major coronary artery.

Experimental studies suggest that autonomic mechanisms are important in the genesis of ischemia-induced malignant ventricular arrhythmias, but the role of the autonomic nervous system in human arrhythmogenesis is not well known. To assess whether heart rate variability (HRV) predicts the occurrence of ventricular arrhythmias during acute coronary artery occlusion, we performed continuous electrocardiographic, heart rate, and blood pressure recordings before and during a 2-minute balloon occlusion of a stenotic coronary artery in 252 patients with no baseline ventricular premature complexes (VPCs). The ranges of nonspecific responses in heart rate and blood pressure were determined by analyzing a control group of 19 patients with no ischemia during a 2-minute balloon inflation in a totally occluded coronary artery.

Effects of combination antihypertensive therapy on baroreflex sensitivity and heart rate variability in systemic hypertension.

Earlier studies have shown that cardiovascular autonomic regulation is impaired in untreated or poorly controlled systemic hypertension. The purpose of this double-blind, randomized parallel trial was to evaluate whether improved blood pressure (BP) control can reverse this impairment. The study group consisted of 33 patients (age 45 to 63 years) with poor BP control who received randomized metoprolol or enalapril monotherapy.

Arterial baroreflex impairment in patients during acute coronary occlusion.

Objectives: We tested whether acute coronary occlusion interferes with arterial baroreceptor control of heart rate in humans.

Background: Subnormal baroreflex sensitivity (BRS) is an important risk indicator for sudden death. Animal research indicates that both chronic myocardial infarction and acute coronary occlusion impair baroreflex modulation of heart rate.

Vagal cardiac activity in essential hypertension: the effects of metoprolol and ramipril.

Cardiovascular parasympathetic activity is attenuated in essential hypertension. Both beta-adrenoceptor antagonists and angiotensin converting enzyme inhibitors have been reported to increase vagal modulation of heart rate and baroreflex sensitivity, but the relations between the antihypertensive and vagal cardiac effects of these drugs have remained unclear in essential hypertension. In the present study we evaluated the effects of a 4-week crossover monotherapy with metoprolol and ramipril on spectrum analysis indices of heart rate variability in the supine rest and head-up tilted positions, baroreflex sensitivity (phenylephrine method), and 24-h ambulatory blood pressure (BP) in 12 formerly untreated stage 1-2 essential hypertensive patients.

Heart rate variability and baroreflex sensitivity in hypertensive subjects with and without metabolic features of insulin resistance syndrome.

Both abnormal autonomic control of heart rate, assessed by heart rate variability (HRV) and baroreflex sensitivity (BRS), and insulin resistance syndrome are common in hypertensive patients. It is not known, however, whether abnormalities in HRV and BRS in hypertension are related to the insulin-resistance syndrome. Therefore, we compared HRV and BRS in hypertensive subjects with and without metabolic features of the insulin-resistance syndrome.

Power-law relationship of heart rate variability as a predictor of mortality in the elderly.

Background: The prognostic role of heart rate (HR) variability analyzed from 24-hour ECG recordings in the general population is not well known. We studied whether analysis of 24-hour HR behavior is able to predict mortality in a random population of elderly subjects.

Methods And Results: A random sample of 347 subjects of > or =65 years of age (mean, 73+/-6 years) underwent a comprehensive clinical evaluation, laboratory tests, and 24-hour ECG recordings and were subsequently followed up for 10 years.

Ambulatory device for surface EMG recordings.

The principles of electromyographic (EMG) analysis can be divided into the following groups: signal or motor unit shape analysis, amplitude analysis, multi-channel or successive time difference analysis, signal frequency composition analysis, change of frequency time based analysis based on simultaneous amplitude or frequency based analysis or concentric and excentric work based shape and amplitude ratio analysis. The aim of this paper is to present an ambulatory portable device for surface EMG analysing both for integrated EMG and for spectral analysis. The reliability of surface EMG recordings have established.

Heart rate dynamics in patients with stable angina pectoris and utility of fractal and complexity measures.

Dynamic analysis techniques may uncover abnormalities in heart rate (HR) behavior that are not easily detectable with conventional statistical measures. However, the applicability of these new methods for detecting possible abnormalities in HR behavior in various cardiovascular disorders is not well established. Conventional measures of HR variability were compared with short-term (< or = 11 beats, alpha1) and long-term (> 11 beats, alpha2) fractal correlation properties and with approximate entropy of RR interval data in 38 patients with stable angina pectoris without previous myocardial infarction or cardiac medication at the time of the study and 38 age-matched healthy controls.

Gender difference in autonomic and hemodynamic reactions to abrupt coronary occlusion.

Objectives: We sought to determine whether there are gender-related differences in autonomic and hemodynamic responses to abrupt coronary occlusion.

Background: The risk of sudden death before hospital admission is higher in men with an acute myocardial infarction. The reasons for this gender-related difference are not well understood.

Baroreflex sensitivity in drug-treated systemic hypertension.

Baroreflex sensitivity is impaired in patients with systemic hypertension. The persistence of abnormal baroreflex sensitivity despite adequate blood pressure control may be one of the reasons why the effect of antihypertensive therapy on coronary artery disease mortality has been less than expected on the basis of the achieved blood pressure levels.

Dynamic analysis of heart rate may predict subsequent ventricular tachycardia after myocardial infarction.

Dynamics analysis of RR interval behavior and traditional measures of heart rate variability were compared between postinfarction patients with and without vulnerability to ventricular tachyarrhythmias in a case-control study. Short-term fractal correlation of heart rate dynamics was better than traditional measures of heart rate variability in differentiating patients with and without life-threatening arrhythmias.

Cross spectral analysis in assessment of baroreflex gain in patients with coronary artery disease.

Interest in determination of baroreflex sensitivity in clinical practice is growing because of its prognostic information in patients with heart disease. The purpose of the present study was to assess the feasibility of cross spectral analysis in the determination of baroreflex gain from spontaneous RR interval and systolic pressure fluctuations, and to compare the results to the traditional pharmacological method in patients with coronary artery disease. Methods.

Antiarrhythmic effect of repeated coronary occlusion during balloon angioplasty.

Objectives: The purpose of the present study was to assess whether brief, repeated coronary artery occlusions during balloon angioplasty protect against ischemia-induced ventricular ectopy.

Background: Most sudden cardiac deaths are caused by fatal ventricular arrhythmias precipitated by early myocardial ischemia of acute coronary occlusion. In animals, a preceding 3- to 5-min coronary occlusion protects against malignant ventricular arrhythmias during a subsequent prolonged coronary occlusion.

Changes in maternal heart dimensions and plasma atrial natriuretic peptide levels in the early puerperium of normal and pre-eclamptic pregnancies.

Objective: To measure plasma atrial natriuretic peptide (ANP) in relation to maternal haemodynamics and body fluid balance in the early puerperium following uncomplicated pregnancy and pre-eclampsia.

Design: A longitudinal study from late pregnancy and into the early postpartum period (days 1 to 3 and days 4 to 6) compared with nonpregnant controls.

Subjects: Eleven women with uncomplicated pregnancies, 12 women with pre-eclampsia and 12 healthy, nonpregnant women.

Abnormalities in beat to beat complexity of heart rate dynamics in patients with a previous myocardial infarction.

Objectives: The purpose of this research was to study possible abnormalities in the beat to beat complexity of heart rate dynamics in patients with a previous myocardial infarction.

Background: Analysis of approximate entropy of time series data provides information on the complexity of both deterministic and random processes. It has been proposed that regularity or loss of complexity of RR interval dynamics may be related to pathologic states, but this hypothesis has not been well tested in cardiovascular disorders.

Sex-related differences in autonomic modulation of heart rate in middle-aged subjects.

Background: Women have worse outcomes when they experience acute myocardial infarction (MI), but the reasons for this sex-related difference are not well understood. Because cardiovascular neural regulation plays an important role in cardiac mortality, we studied possible sex-related differences in the autonomic modulation of heart rate (HR) in middle-aged subjects without known heart disease.

Methods And Results: Baroreflex sensitivity (BRS) and HR variability were studied in randomly selected, age-matched populations of middle-aged women (n = 186; mean age, 50 +/- 6 years) and men (n = 188; mean age, 50 +/- 6 years) without hypertension, diabetes, or clinical or echocardiographic evidence of heart disease.

Heart rate variability in systemic hypertension.

Low heart rate (HR) variability is a risk factor for cardiac mortality in various patient populations, but it has not been well established whether patients with long-standing hypertension have abnormalities in the autonomic modulation of HR. Time and frequency domain measures of HR variability were compared in randomly selected, age-matched populations of 188 normotensive and 168 hypertensive males (mean age 50 +/- 6 years for both). The standard deviation of the RR intervals was lower in the hypertensive subjects than in the normotensive ones (52 +/- 19 vs 59 +/- 20 mss; p <0.