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At least 415 records · Page 23Linked to original sources
PubMed1994

Immunoelectron microscopic localization of HNK-1 in the embryonic rat heart.

To confirm the role of HNK-1 in conduction tissue, the ultrastructural localization of monoclonal antibody HNK-1 was analyzed in developing rat hearts at embryonal day 14.5 by immunoelectron microscopic labeling procedures with post-embedding immunogold staining. Tissue sections in different planes containing the sino-atrial (SA) node, atrio-ventricular (AV) node and His bundle were used to demonstrate HNK-1. Immunogold labeling was detected on the cell surfaces and in the extracellular matrices of cells that had features common to conduction tissue cells. Non-specialized contractile myocytes were not labeled by this antibody. Furthermore, immunogold labeling was more prominent in wide intracellular spaces than in narrow intercellular spaces, and rarely observed in cell-cell contact regions. The cell surfaces and extracellular matrices of mesenchymal cells in the endocardial cushion, which contacts the His bundle, were also positive, suggesting the involvement of tract formation to the AV node. These findings may indicate that HNK-1 plays an important role in cell-cell adhesion processes both temporally and spatially in the developing conduction tissue. It was concluded, therefore, that HNK-1 is a suitable marker of the embryonic heart conduction system and might be useful in analyzing anomalous conduction systems, as in congenital heart disease.

Animals↗
PubMed1996

Effect of HeartMate left ventricular assist device on cardiac autonomic nervous activity.

BACKGROUND: Clinical performance of a left ventricular assist device is assessed via hemodynamic parameters and end-organ function. This study examined effect of a left ventricular assist device on human neurophysiology. METHODS: This study evaluated the time course change of cardiac autonomic activity of 3 patients during support with a left ventricular assist device before cardiac transplantation. Cardiac autonomic activity was determined by power spectral analysis of short-term heart rate variability. The heart rate variability before cardiac transplantation was compared with that on the day before left ventricular assist device implantation. RESULTS: The standard deviation of the mean of the R-R intervals of the electrocardiogram, an index of vagal activity, increased to 27 +/- 7 ms from 8 +/- 0.6 ms. The modulus of power spectral components increased. Low frequency (sympathetic activity) and high frequency power (vagal activity) increased by a mean of 9 and 22 times of each baseline value (low frequency power, 5.2 +/- 3.0 ms2; high frequency power, 2.1 +/- 0.7 ms2). The low over high frequency power ratio decreased substantially, indicating an improvement of cardiac sympatho-vagal balance. CONCLUSIONS: The study results suggest that left ventricular assist device support before cardiac transplantation may exert a favorable effect on cardiac autonomic control in patients with severe heart failure.

Adult↗
PubMed2006

Echocardiography and patient selection for cardiac resynchronization therapy: a critical appraisal.

Echocardiography has been the focus of growing interest for improving patient selection for cardiac resynchronization therapy in order to reduce the number of nonresponders. Various techniques have been described for assessing dyssynchrony, using standard echocardiography (pulsed-wave Doppler and M-mode echocardiography), tissue Doppler imaging, and other imaging modes such as three-dimensional echocardiography. This article provides an overview of the technical and practical aspects of these different techniques and discusses the current evidence for optimizing patient selection by echocardiography.

Cardiac Pacing, Artificial↗
PubMed2002

Mechanisms involved in heart rate turbulence.

Proper understanding of the mechanisms involved in heart rate turbulence (HRT) may offer an explanation of why it is such a potent postinfarction risk stratifier. This article reviews the physiological background of ventriculophasic sinus arrhythmia-a phenomenon which shares some underlying physiological features with HRT including cardiac autonomic regulation. It is now believed that HRT is principally triggered by a transient loss of vagal efferent activity in response to the missed baroreflex afferent input due to ventricular premature beat-induced haemodynamically inefficient ventricular contraction. Studies are summarized which support more or less directly this hypothesis. The physiology of early acceleration and late deceleration of heart rate after a ventricular premature beat is discussed. Qualitatively different but otherwise quantitatively uniform postectopic dynamics of systolic blood pressure after ventricular premature beats is demonstrated in subjects with normal and abnormal left ventricular function. It is concluded that the slope of late deceleration of heart rate after ventricular premature beats can serve as a reasonable surrogate for baroreflex sensitivity.

Arrhythmia, Sinus↗
PubMed2001

Carvedilol: molecular and cellular basis for its multifaceted therapeutic potential.

Carvedilol is a unique cardiovascular drug of multifaceted therapeutic potential. Its major molecular targets recognized to date are membrane adrenoceptors (beta 1, beta 2, and alpha 1), reactive oxygen species, and ion channels (K+ and Ca2+). Carvedilol provides prominent hemodynamic benefits mainly through a balanced adrenoceptor blockade, which causes a reduction in cardiac work in association with peripheral vasodilation. This drug assures remarkable cardiovascular protection through its antiproliferative/atherogenic, antiischemic, antihypertrophic, and antiarrhythmic actions. These actions are a consequence of its potent antioxidant effects, amelioration of glucose/lipid metabolism, modulation of neurohumoral factors, and modulation of cardiac electrophysiologic properties. The usefulness of carvedilol in the treatment of hypertension, ischemic heart disease, and congestive heart failure is based on a combination of hemodynamic benefits and cardiovascular protection.

Adrenergic alpha-Antagonists↗
PubMed1978

Cardiac pacemakers in absence of the SA node: responses to exercise and autonomic blockade.

Surgical excision of the sinoatrial node, verified histologically, is followed by a supraventricular (atrial) rhythm in both resting and exercising dog whether anesthetized or conscious. The ECG is characterized by a definitive P wave and associated atrial electrograms. Waxing and waning in heart rate, generally referred to as sinus arrhythmia continues in the awake animal after complete excision of the SA node. This arrhythmia is responsive to both adrenergic and cholinergic interventions, thus indicating the presence of both sympathetic and parasympathetic regulation of subsidiary atrial pacemaking tissues.

Adrenergic beta-Antagonists↗
PubMed2006

Dynamic clamp analyses of cardiac, endocrine, and neural function.

The dynamic clamp introduces artificial conductances into cells to simulate electrical coupling, votage-dependent, leak, and synaptic conductances. This review describes how the dynamic clamp has been used to address various questions in the cardiac, endocrine, and nervous systems.

Animals↗
PubMed2000

Spectral analysis of heart variability in the newborn infant.

We investigated the relationship between spectral power and both mean heart rate (HR) and heart rate variability (HRV). Spectral power was calculated using digital heart rate recordings from term infants. Regression analysis revealed a positive correlation between low-frequency (LF) sympathetic power and HR, and a negative correlation between high-frequency (HF) parasympathetic power and HR. HRV correlated positively in all regions of the power spectrum. In awake infants, the contribution of HF power to total power (HF/TP) was significantly decreased. LF power tended to be greater, however, this trend was not statistically significant. By following expected autonomic patterns, the findings of this study confirm that spectral analysis provides a noninvasive method for the assessment of autonomic activity influencing the newborn heart. The correlation between spectral power and HRV can serve as an additional tool in the study of autonomic dysfunction.

Autonomic Nervous System↗
PubMedDate not supplied

[Projection of new antihistamines].

The metabolic fate of most antihistamines is not clearly established. The drugs usually appear to be extensively metabolized,mainly in the liver. Some second generation antihistamines are metabolized principally by the cytochrome P-450 microsomal enzyme system, mainly by the isoenzyme 3A4 (CYP3A4), although other isoenzyme,including CYP1A2 and CYP2D6, also may be involved. However,other second generation antihistamines appear to be only minimally metabolized in the liver. Serious cardiac effects (prolongation of the QT interval, arrhythmias, torsades de pointes, ventricular fibrillation, arrest, hypotension, palpitations, syncope, dizziness, and/or death) have been reported rarely in patients receiving terfenadine or astemizole. Cardiotoxic effects ussually were associated with higher than recommended dosages and/or increased plasma concentrations of the drugs and their active metabolites. No clinically important adverse effects or changes in the QT intervals were reported after concomitant administration of ketoconazole with fexofenadine. Patients receiving an azole, antifungal, a macrolide, quinine or grapefruit juice also appear to be at substantial risk of such toxicity, probably secondary to interference with metabolism of the antihistamine. Second-generation H1 receptor antagonist have been studied extensively in the treatment of asthma. Many of these drugs have been reported to inhibit eosinophil and basophil chemotaxis and therefore might have an effect on the inflammatory reactions that characterise this disease. Safe use of antihistamines during pregnancy has not been established; therefore, the drugs should not be used in women who are or may become pregnant unless the potential benefits justify the possible risks to the fetus. Antihistamines should not be administered to premature or full-term neonates. Young children may be more susceptible than adults to the toxic effects of antihistamines.

Adult↗