Rhythm-control strategies were not better than rate-control strategies in atrial fibrillation.
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Improved rate control for electron-beam evaporation and evaluation of optical performance improvements.
A new deposition-rate-control and electron-beam-gun (e-gun) strategy was developed that significantly reduces the growth-rate variations for e-beam-deposited SiO2 coatings. The resulting improvements in optical performance are evaluated for multilayer bandpass filters. The adverse effect of uneven silica-source depletion on coating spectral performances during long deposition runs is discussed.
Journal Article↗
Heart rate variability biofeedback as a behavioral neurocardiac intervention to enhance vagal heart rate control.
BACKGROUND: Patients with coronary heart disease (CHD) who experience depressed mood or psychological stress exhibit decreased vagal control of heart rate (HR), as assessed by spectral analysis of HR variability (HRV). Myocardial infarction and sudden cardiac death are independently associated with depression and stress, as well as impaired vagal HR control. This study examined whether a behavioral neurocardiac intervention to reduce stress or depression can augment cardiovagal modulation in CHD patients. We hypothesized that (1) cognitive-behavioral training with HRV biofeedback would augment vagal recovery from acute stress, and (2) vagal regulation of HR would be inversely associated with stress and depression after treatment. METHODS: This randomized controlled trial enrolled 46 CHD patients from 3 clinics of CHD risk reduction in Toronto and Vancouver, Canada. Subjects were randomized to five 1.5-hour sessions of HRV biofeedback or an active control condition. Outcome was assessed by absolute and normalized high-frequency spectral components (0.15-0.50 Hz) of HRV, and by the Perceived Stress Scale and Centre for Epidemiologic Studies in Depression scale. RESULTS: Both groups reduced symptoms on the Perceived Stress Scale (P = .001) and Centre for Epidemiologic Studies in Depression scale (P = .004). Hierarchical linear regression determined that improved psychological adjustment was significantly associated with the high-frequency index of vagal HR modulation only in the HRV biofeedback group. Adjusted R 2 was as follows: HRV biofeedback group, 0.86 for stress (P = .02) and 0.81 for depression (P = .03); versus the active control group, 0.04 (P = .57) and 0.13 (P = .95), respectively. CONCLUSION: A novel behavioral neurocardiac intervention, HRV biofeedback, can augment vagal HR regulation while facilitating psychological adjustment to CHD.
Biofeedback, Psychology↗
Rate-controlling steps of oxidative phosphorylation in rat liver mitochondria. A synoptic approach of model and experiment.
The contribution of different steps to the control of oxidative phosphorylation in isolated rat liver mitochondria was investigated by a combination of experiments and computer simulations. The parameters of the mathematical model of phosphorylating mitochondria were derived from experimental data. The model correctly described the competition between ATP utilization inside and outside mitochondria for the ATP generated in mitochondria. On the basis of the good agreement between experiments and simulations, the contribution of different steps to the control of respiration was estimated by computing their control strengths, i.e., the influence of their activities on the rate of respiration. The rate-controlling influences vary depending on the load of oxidative phosphorylation. The predominant steps are: in the fully active state (State 3)--the hydrogen supply to the respiratory chain; in the resting state (State 4)--the proton leak of the mitochondrial inner membrane; in states of non-maximum ATP export--the adenine nucleotide translocator. Titrations of respiration with phenylsuccinate, antimycin, oligomycin and carboxyatractyloside completely support these conclusions.
Adenosine Diphosphate↗
Dronedarone: an emerging agent with rhythm- and rate-controlling effects.
Of current antiarrhythmic agents, amiodarone is among the most effective with the additional advantage of having little proarrhythmic potential. However, it can cause potentially serious extracardiac side effects, stimulating the search for safer derivatives. Dronedarone, a new antiarrhythmic drug that is structurally related to amiodarone, lacks an iodine moiety and, thus, amiodarone's iodine-related organ toxicity, while its methane sulfonyl group decreases lipophilicity so shortening half-life and decreasing tissue accumulation. Electrophysiological studies show that dronedarone shares amiodarone's multichannel blocking effects, inhibiting transmembrane Na(+), K(+), Ca(2+), and slow L-type calcium channels, as well as its antiadrenergic effects. Unlike amiodarone, it has little effect at thyroid receptors. Possessing both rate- and rhythm-control properties, dronedarone has proved safe and effective in preventing recurrence of atrial fibrillation (AF) in patients with persistent AF in the Dronedarone Atrial Fibrillation Study After Electrical Cardioversion (DAFNE) trial, the first prospective randomized trial to evaluate its efficacy and safety. Dronedarone has since undergone further extensive evaluation in three pivotal phase III trials. In two sister studies, the European Trial in Atrial Fibrillation or Flutter Patients Receiving Dronedarone for the Maintenance of Sinus Rhythm (EURIDIS) and American-Australian-African Trial with Dronedarone in Atrial Fibrillation/Flutter Patients for the Maintenance of Sinus Rhythm (ADONIS), dronedarone 400 mg b.i.d. showed significant efficacy against placebo in prevention of AF recurrence. Additionally, in patients with permanent AF, dronedarone was highly effective at controlling ventricular rate on top of standard rate-controlling therapies in the Efficacy and Safety of Dronedarone for the Control of Ventricular Rate during Atrial Fibrillation (ERATO) study.
Amiodarone↗
Reflex heart rate control in asthma. Evidence of parasympathetic overactivity.
The bronchial hyperreactivity characteristic of asthma may be related to enhanced parasympathetic nervous activity. We postulated that an abnormality in the autonomic control of airway caliber might be reflected by a parallel change in the reflex control of heart rate. We examined the heart-rate variations induced by deep breathing (respiratory sinus arrhythmia), the Valsalva maneuver, and standing up from the recumbent position in asthmatic subjects and nonasthmatic control subjects. The asthmatic patients had evidence of enhanced parasympathetic neural drive to the sinoatrial node, as manifested by a significantly greater magnitude of respiratory sinus arrhythmia, than the controls (p less than 0.0005). We were unable to induce a similar change in normal subjects by resistance breathing. A statistical analysis suggested the presence of a relationship between the magnitude of respiratory sinus arrhythmia and the degree of bronchial hyperreactivity in a group of asthmatic patients. Our results support the hypothesis that enhanced parasympathetic activity is an important factor in the pathogenesis of bronchial asthma.
Adult↗
[Analysis of loco-regional control rate, metastatic remission and survival in 178 breast cancer patients treated by radical modified mastectomy and post-operative irradiation (author's transl)].
178 cases of post-operative irradiation for breast cancer (145 T1, T2, T3 and 33 T4) are analyzed. According to the surgical procedure there are 146 cases of radical modified mastectomy (Patey) and 32 cases of radical mastectomy (Halsted). The axillary status reveals 50% of involved nodes, but radiotherapy has been systematic on chest wall and supra-clavicular, parasternal, axillary lymph nodes areas. Loco-regional failures are only situated on chest wall (3,9%) and in the supraclavicular area (1,7%). The five year actuarial rate of locoregional control is 93% and 98% if we exclude 7 locoregional failures contemporaneous or consecutive to a metastatic evolution. The five year actuarial rate of metastatic remission for patients with negative axillary nodes (N-) is 83% against 55% for N+ (p < 0,001). The five year actuarial survival rate is 92% (N-) and 64% (N+) (p < 0,001). We discuss about indications of selective irradiation of chest wall and parasternal area for patients with negative axillary nodes and also about post-operative immuno-suppression, and chronology of chemotherapy.
Adult↗
Voluntary heart rate control: the role of individual differences.
It is a frequent observation that individuals differ markedly in their success at voluntary heart rate control. Several dispositional variables have now received attention as possible sources of such individual variation. These are critically reviewed under the following headings: resting and stimulus-elicited heart rate characteristics; autonomic and cardiac perception; imagery vividness; locus of control; trait anxiety. It is concluded that the research on individual differences in cardiac control to date is contributing to a clearer understanding of the mechanisms underlying control. However, for this contribution to be sustained, research needs to service explicit hypotheses about mediating processes. The often arbitrary and atheoretical practices that characterize much of the research in the more general context of individual differences in physiological activity must be avoided.
Anxiety↗
Age-dependent pattern of autonomic heart rate control during hypoxia in fetal and newborn lambs.
Autonomic nervous control of heart rate (HR) during hypoxia was studied longitudinally using 9 chronically catheterized fetal lambs (109 day to term) and 10 newborn lambs (2--28 days old). Changes in heart rate (deltaHR) during hypoxia were age-dependent. Before 120 days of gestation deltaHR was insignificant, but between 120 days to term bradycardia occurred. The newborn response was marked tachycardia. Autonomic influences on HR were quantified using atropine and propranolol blockade. In fetal lambs, antagonistic increases in parasympathetic and sympathetic outflows were evident during hypoxia. In hypoxic lambs 120 days to term, net bradycardia reflected predominant parasympathetic cardio-deceleration; before 120 days of gestation both the parasympathetic and sympathetic outflows increased, but no net deltaHR occurred. In hypoxic newborn lambs, sympathetic and parasympathetic changes contributed synergistically to the net tachycardia. Thus the pattern of autonomic control of HR during hypoxia differs in fetal and newborn lambs. Changes in sympathetic and parasympathetic influences are antagonistic in the fetus, but synergistic in the newborn.
Age Factors↗
Personality correlates of bidirectional heart-rate control.
This study examined the combined effects of personality with instruction and treatment variables in human operant heart-rate conditioning. The Edwards Personal Preference Schedule was administered to 50 subjects tested for bidirectional heart-rate control during no-feedback and analogue auditory feedback conditions. Findings indicated that relative to pre-trial baselines, subjects were able significantly to alter heart rates according to instructed direction of change, but treatment effects for augmented sensory feedback were not reliable. Correlational analyses employing personality variables demonstrated that different traits define successful speeding and reduction performance. Further, post hoc analyses for personality high-low classification X treatment X instructions effects indicated that personality variables of succorance and abasement moderated treatment effects for heart-rate reduction. Questions are raised concerning the efficacy of proportional auditory treatment in biofeedback training.
Adult↗
Novel growth rate control of dam gene expression in Escherichia coli.
Transcription of the dam gene in Escherichia coli is growth rate regulated by a mechanism distinct from that used for ribosomal RNA gene promoters. Single-copy operon fusions to lacZ indicated that the major promoter, P2, is responsible for most or all of the growth rate dependence. Promoter P2 is a typical sigma 70 promoter with 18 bp spacing between the -10 and -35 hexamers. Primer extension analysis was used to show that there was no inhibition of transcription from promoter P2 in cells induced for the stringent response. Beta-galactosidase specific activity from a single-copy dam::lacZ fusion was unaffected by either excess rrnB RNA or the level of Fis protein. Thus growth rate control of dam gene expression differs from that of the rRNA and tRNA genes by its lack of response to stringent control, ribosomal feedback and enhanced transcription by Fis protein. We devised a procedure for selection of mutant cells in which dam gene expression was unregulated. One such mutant (cde-4), obtained by miniTn10 insertion, showed the same level of beta-galactosidase activity at all growth rates tested. In contrast, growth rate-dependent expression of the rrnB gene was unaffected by cde-4 confirming the different modes of regulation. The cde-4::miniTn10 insertion is located close to kilobase 670 on the physical map in or near the lipB gene.
Base Sequence↗
In vitro study of transdermal nicotine delivery: influence of rate-controlling membranes and adhesives.
The objective of this study was to evaluate the influence of a rate-controlling membrane and adhesive on the in vitro permeation of nicotine. The physicochemical properties of the adhesive, including adhesion and rheology (viscosity), were also detected. Higher permeability of nicotine was observed through a hydrophilic membrane than through a hydrophobic membrane. Natural rubber and silicone were used as the adhesive bases, respectively. The silicone adhesive showed the highest adhesion among all adhesive formulations. To increase the adhesion of natural rubber, a tackifier (polyisoprene) and a secondary tackifier (terpene polymer; Px 1150) were incorporated into the formulations to achieve acceptable adhesion. The nicotine permeation through silicone adhesive and three natural rubber adhesives with the secondary tackifier (2%, 4%, and 6% Px 1150) was close to that from a commercially available patch (Habitrol), although the loading amount of nicotine was not the same. A longer lag time during the in vitro permeation study of nicotine was required for the adhesives prepared in our laboratory than for the commercially available patch.
Adhesives↗
Cardiac alpha-1 adrenoceptors are not involved in heart rate control of the anaesthetized dog.
To study the possible role of cardiac postsynaptic alpha-1 adrenoceptors in heart rate control of the anaesthetized open-chest dog we injected a specific alpha-1 agonist (amidephrine) into the right coronary artery or stimulated electrically the right stellate ganglion. Reflex influences were minimized by bilateral cervical vagotomy and de-afferentiation of both stellate ganglia. Activation of alpha-2, beta- and muscarinic receptors was prevented by intravenous administration of yohimbine, propranolol and atropine, respectively. Since alpha-1 receptor stimulation could affect heart rate indirectly via coronary constriction, a continuous intracoronary infusion of adenosine (0.25 mg/kg/h) was given. Amidephrine did not affect heart rate at the lower dose (1-10 microgram). After the highest dose (100 micrograms) the maximum variation in heart rate was an increase of 2.2 +/- 1.1 bpm at 3 min after injection (mean +/- SEM; P less than 0.05). This slight cardioacceleration was simultaneous with an aortic pressure rise of 13.8 +/- 3.4 mm Hg and it was abolished by alpha-1 blockade with prazosin (1 mg/kg i.v.). After propranolol (1 mg/kg +0.5 mg/kg/h) the residual positive chronotropic effect of sympathetic stimulation (12.2 +/- 4.0 bpm) was not significantly altered (13.8 +/- 5.7 bpm) by prazosin administration. Similar results were recorded without adenosine infusion. We conclude that in the anaesthetized dog chronotropic effects directly mediated by alpha-1 adrenoceptors either do not exist or lack physiological significance.
Adenosine↗
Determinants of sudden cardiac death in patients with persistent atrial fibrillation in the rate control versus electrical cardioversion (RACE) study.
This report evaluated the correlates of sudden cardiac and nonsudden cardiac death in patients with persistent atrial fibrillation randomized to rate or rhythm control in the RAte Control vs Electrical cardioversion (RACE) study. Sudden cardiac death was observed in 16 patients, 8 patients in each group. Previous myocardial infarction resulted in a 4.9-fold increased risk of sudden death (95% confidence interval 1.8 to 13.2). The use of beta blockers showed their protective nature (hazard ratio 0.2, 95% confidence interval 0.05 to 0.9). The randomized treatment strategy, heart rhythm during follow-up, use of antiarrhythmic drugs, and number of stroke risk factors were not associated with sudden cardiac death. In conclusion, the treatment of underlying disease, rather than the heart rhythm, seems essential to prevent mortality.
Adrenergic beta-Antagonists↗
Rhythm or rate control in atrial fibrillation--Pharmacological Intervention in Atrial Fibrillation (PIAF): a randomised trial.
BACKGROUND: Atrial fibrillation is the most commonly encountered sustained cardiac arrhythmia. Restoration and maintenance of sinus rhythm is believed by many physicians to be superior to rate control only. However, there are no prospective data that compare both therapeutic strategies. METHODS: The Pharmacological Intervention in Atrial Fibrillation (PIAF) trial was a randomised trial in 252 patients with atrial fibrillation of between 7 days and 360 days duration, which compared rate (group A, 125 patients) with rhythm control (group B, 127 patients). In group A, diltiazem was used as first-line therapy and amiodarone was used in group B. The primary study endpoint was improvement in symptoms related to atrial fibrillation. FINDINGS: Over the entire observation period of 1 year, a similar proportion of patients reported improvement in symptoms in both groups (76 responders at 12 months in group A vs 70 responders in group B, p=0.317). Amiodarone administration resulted in pharmacological restoration of sinus rhythm in 23% of patients. Walking distance in a 6 min walk test was better in group B compared with group A, but assessment of quality of life showed no differences between groups. The incidence of hospital admission was higher in group B (87 [69%] out of 127 vs 30 [24%] out of 125 in group A, p=0.001). Adverse drug effects more frequently led to a change in therapy in group B (31 [25%] patients compared with 17 [14%] in group A, p=0.036). INTERPRETATION: With respect to symptomatic improvement in patients with atrial fibrillation, the therapeutic strategies of rate versus rhythm control yielded similar clinical results overall. However, exercise tolerance is better with rhythm control, although hospital admission is more frequent. These data may serve as a basis to select therapy in individual patients.
Adult↗
C-reactive protein modulates vagal heart rate control in patients with coronary artery disease.
Systemic inflammation is associated with sympathetic cardiac activation and decreased HRV (heart rate variability) in subjects at high risk of CAD (coronary artery disease). In the present study, we examined the influence of systemic inflammation, measured by CRP (C-reactive protein), on vagal HR (heart rate) control during behavioural relaxation in patients with CAD. It was hypothesized that CRP would be associated with decreased vagal HR modulation. Consecutive patients were screened 2 weeks prior to elective PTCA (percutaneous transluminal coronary angioplasty). The study was comprised of 29 subjects who represented the first and fourth quartiles of the CRP distribution: Low (0.47+/-0.07 microg/ml)- and High (8.19+/-1.95 microg/ml)-CRP groups respectively. Vagal HR control was quantified as RR high-frequency spectral power (0.15 to 0.40 Hz), and was assessed in log-transformed absolute units (logHF power). Near-IR particle immunoassay was used to determine high-sensitivity CRP concentration. Assessment entailed 5 min of silent reading and self-guided behavioural relaxation. RR logHF power was decreased in the High-CRP group across both assessment procedures (P=0.032). Behavioural relaxation increased RR logHF power for both the Low- and High-CRP groups (P=0.033). Hierarchical linear regression determined that CRP accounted for 18.9% of the variance in RR logHF power during behavioural relaxation (P=0.03), independent of baseline RR interval, cardiac medication, respiratory logHF power and body mass index. In conclusion, patients with CAD had augmented vagal HR control with behavioural relaxation, but this effect was moderated by the severity of CRP. Therefore it may be advisable to assess systemic inflammation in interventions aimed at improving neurocardiac regulation in patients with CAD.
Behavior Therapy↗
Effects of rhythm regularization and rate control in improving left ventricular function in atrial fibrillation patients undergoing atrioventricular nodal ablation.
OBJECTIVES: To assess the relative contributions of rate control and rhythm regularization to left ventricular function in atrial fibrillation (AF) patients undergoing atrioventricular nodal ablation. This was performed by assessing the effect of ventricular rhythm regularization on left ventricular function during AF, and the effect of varying heart rate on left ventricular function after ablation. PATIENTS AND METHODS: Eleven patients with continuous AF and V/VI-R pacemakers undergoing therapeutic atrioventricular nodal ablation were studied. Preablation patients underwent two 30 min observation periods in a randomized, blinded fashion during which they were either in baseline AF (pacer set to default V/VI 50/min) or being paced using a rhythm stabilizing algorithm (RSA) designed to regularize rhythm without changing baseline ventricular rate. Six weeks after ablation, patients were again observed during the two following 30 min periods: pacing at a low clinically indicated rate (69+/-9 beats/min), and pacing at the rapid, mean preablation rate. During all observation periods, left ventricular function was measured continuously using a nuclear vest that provided validated measures of heart rate, ejection fraction, and normalized end-systolic volume (ESV) and end-diastolic (EDV) volume. RESULTS: Before ablation, RSA successfully regularized rhythm, decreasing the coefficient of variation of interbeat intervals 20+/-5% to 10+/-4% (P<0.001). The heart rate with RSA (105+/-19 beats/min) was not significantly different from the baseline AF rate (102+/-21 beats/min). Increased rhythm regularity achieved by RSA significantly improved left ventricular function, decreasing ESV from 62+/-12 units to 57+/-11 units (P=0.03), and increasing the ejection fraction from 31+/-11% to 36+/-11% (P=0.03). After ablation, at the clinically indicated low pacing rate of 69+/-9 beats/min, a much greater improvement in ejection fraction was observed, increasing to 44+/-13% (P=0.005 compared with preablation). However, rapid regular pacing at the mean preablation rate of 110+/-18 beats/min eradicated this improvement, decreasing the ejection fraction to 31+/-8% (P=0.003), and increasing ESV from 53+/-13 units to 62+/-8 units (P=0.006). CONCLUSIONS: Rhythm regularity achieved by a regularizing pacing algorithm can significantly, albeit modestly, improve left ventricular function in AF. However, more marked improvements in left ventricular function seen after ablation are primarily due to rate reduction alone.
Aged↗
Fertility of frozen-thawed porcine semen following controlled-rate freezing in straws.
A method was developed for freezing large batches of porcine semen in straws at a controlled rate in a liquid nitrogen programmable freezer. The fertilizing potential of spermatozoa frozen by this method was examined by inseminating 220 sows with a mixture of semen from two boars. Estrus was synchronized using one of two regimens and sows were inseminated once at 34 h after human chorionic gonadotropin (hCG) treatment. The average pregnancy rate at 60 d of gestation, farrowing rate and litter size were 60.9%, 51.4% and 8.8, respectively. The fertilizing potential of spermatozoa frozen by this method appeared to be similar to that reported for other methods of freezing porcine semen.
Journal Article↗